historical geology lecture notes 001

HISTORICAL GEOLOGY LECTURE, PAGE 1

I. Introduction

A. Geology- the study of the Earth

1. Physical Geology- study of the Earth's materials, such as minerals and rocks, and the various physical andchemical changes that occur on its surface and in its interior

2. Historical Geology- history of the planet and its life forms from its origin to the present

B. The Birth of Modern Geology

1. James Hutton (1726 - 1797)- Scottish gentleman farmer and geologist; the "Father of Geology"- formulated concept of "Uniformitarianism"

a. Uniformitarianism- "the present is the key to the past"- the Earth is shaped by daily, mundane processes- the Earth is very old- believed that "great catastrophes" have only minor influence

2. Charles Lyell (1797 - 1875)- English Geologist, wrote Principles of Geology (the first volume appeared in 1830)- his influential popularization of Hutton's principles influenced generations of geologists

3. More recent studies use the concept of Actualism

a. Actualism- apply studies of modern processes to ancient rocks- the processes that now shape the Earth were similar in the geologic past, although the rate ofchange may vary- recognizes that "catastrophes" can have powerful influence on the Earth

4. Geologic Time Scale- the Earth is 4.6 billion years old- the subdivisions of the time scale are based primarily on the predominant life forms livingduring specific times

II. Minerals and Rocks

A. Mineral- naturally occurring, inorganic, homogeneous, crystalline solid; more than 90% of rock-forming


minerals are silicates (contain silicon, oxygen and one or more metals)

1. Chemical Composition of Minerals

a. Elements- fundamental components, cannot be broken down to simpler substances by ordinary chemicalprocesses- there are 88 naturally occurring elements- the 8 most common are Oxygen (O), Silicon (Si), Aluminum (Al), Iron (Fe), Calcium (Ca),Sodium (Na), Potassium (K) and Magnesium (Mg); comprise 98% of the Earth's Crust

b. Atoms- fundamental units of elements

Nucleus - positively charged center of mass; includes protons (with mass and a positive charge)and neutrons (with mass and a neutral charge)

Electrons - with no mass and a negative charge; the number and orientation of electronsdetermines chemical behavior

c. Chemical Reactions- filling of the outer shells of electrons

Ions = charged atoms; atoms with too few or too many electrons; includes cations (positivelycharged) and anions (with negative electrical charges)

2. Physical Properties of Minerals- use color, streak, hardness, crystal form, cleavage, fracture, luster, specific gravity, magnetism,chemical reactivity, radioactivity, fluorescence, etc. to identify minerals- see lab manual

3. Mineral Classification

a. Based on dominant anion present in the Mineral- including silicates, oxides, sulfides, halides, phosphates, carbonates, native elements andhydroxides

b. Silicate Minerals- the most abundant chemical group constitute (about 90% of the Earth's crust)- Silicate Bonding with four oxygen for each silicon; bond directions require a tetrahedralarrangement of the atoms; the tetrahedra may be isolated or form single chains, double chains,sheets, or frameworks

- Important Silicate Minerals Include:


Feldspar - a framework silicate found in almost all rock types; constitutes about 50% of theEarth's crust; includes potassium feldspar and plagioclase feldspar series

Quartz - a very pure framework silicate; common in continental rocks but rare in oceanic andmantle rocks

c2. Nonsilicate Rock-Forming Minerals

Carbonates - with one carbon and three oxygen atoms; Exs. = calcite, dolomite

Sulfates - with one sulfur and four oxygen; Ex. = gypsum

Sulfides - sulfur combines with some other element (not oxygen); Ex. = pyrite, galena

Halides - one or more metals combine with one or more halogen elements (fluorine, chlorine,iodine, bromine); Exs. = halite, fluorite

Oxides - one or more metals combine with oxygen; Exs. = magnetite, hematite, corundum

Phosphates - one or more metals combine with phosphate group (1 phosphorous and 4 oxygenatoms; PO4); Ex. = apatite

Native Elements - mineral consists of a single element; gold, silver, copper, sulfur, graphite,diamond

B. Rocks- naturally-formed, solid materials composed of one or more minerals or mineraloids

C. Igneous Rocks- rocks that solidify from molten material (magma)

1. Melting of magmas- is due to radioactivity, movement of rock masses into high temperature zones, transfer heatupward from deep crust or mantle

2. Magma Composition- ultimate magma composition is especially influenced by type of parent magma (which isprimarily a product of where the magma is formed); mafic magmas (rich in iron and magnesium)are characteristic of oceanic crust, felsic magmas (rich in silica) are characteristic of continentalcrust- magmas change composition primarily through fractionation (remove crystals from magmachamber which alters magma composition)

3. Emplacement of magmas is due to lithostatic ("rock") pressure, pressure due to increased gasvolume, tectonism ("mountain-building"), and stoping (magma surrounds and engulfs crystals or


rocks)

4. Intrusive (Plutonic) Igneous rocks- rocks that solidify beneath the earth's surface- magma cools slowly and rocks form large crystals- Examples = peridotite, gabbro, diorite, and granite

5. Extrusive ("Volcanic") Igneous Rocks- solidify at or near the Earth's surface- forms from lava (magma flows onto Earth's surface) or tephra/pyroclastic material (magma isblown onto Earth's surface)- Examples = basalt, andesite, rhyolite, tuff, agglomerate

D. Metamorphic rocks- rocks formed from pre-existing rocks by solid state transformation in response to change in thephysical or chemical environment

1. Contact Metamorphism- occurs in country rock bordering igneous intrusion- typically created under relatively low pressure, high temperature- types of rocks include marble, quartzite, hornfels and some ore deposits

2. Regional metamorphism- occurs on a regional scale due to orogenies (mountain-building events) triggered by platetectonics- sequence of rocks formed under greater temperature and pressure includes mudstone -> slate ->phyllite -> schist -> gneiss

E. Sedimentary Rocks- rocks formed from consolidation of loose sediment, formed by chemical precipitation, or rocksconsisting of secretions or remains of plants and animals- most important rocks for interpreting Earth history

1. Sedimentary rock is product of :

a. Provenance- pre-existing rocks from which sediment forms and effects of weathering on sedimentarycomposition

b. Process- what happens during transportation, deposition and after deposition

2. Transport of Sediment

a. Agents of transport


- wind, water, ice, gravity

b. Physical Transport

b1. Physical Load- sedimentary particles carried by current- forms Clastic or Detrital Rocks (conglomerates, sandstones, siltstones, mudstones)

b2. Dissolved (Chemical) Load- dissolved ions carried by water; deposited when chemical or physical changes concentratessolutes and cause them to precipitate- form Chemical Rocks such as Carbonates (limestone, dolomite) and Evaporites (halite,gypsum)

3. Sedimentary texture- size, shape and arrangement of grains

a. Sedimentary Grain Size

a1. Wentworth Scale- describes size of sedimentary particles- includes clay, silt, sand and larger size particles- size of particles transported depends on type of transporting agent and energy of transport

b. Sorting- range of particle sizes in a sediment

Well sorted- particles of similar size\

Poorly sorted - wide variety of grain sizes

- Sorting depends on type of sedimentary transport: Gravity and glaciers = poorly sorted; Water =well sorted; Air = most selective sorting

c. Shape

c1. Roundness (Angularity)- degree of curvature of the corners of the particles;- depends on type of parent material and degree of sediment transport

c2. Sphericity- degree to which a particle approximates the shape of a sphere- typically depends upon the degree of sediment transport

4. Sedimentary Structures


- multigrained features formed during or after accumulation of sediment and before lithification

a. Primary Sedimentary Structures- form as sediment is being deposited

a1. Stratification- accumulation of sedimentary particles in horizontal layers

a2. Massive beds- thick and uniform; form under constant conditions or where bedding is destroyed by organismsor dissolution

a3. Graded bedding- grain size increases or decreases from base to top due to changing current velocities

a4. Cross-Bedding- layers are inclined- cross-bedding is used to determine ancient current (paleocurrent) direction

b. Secondary (Postdepositional) Sedimentary Structures- form after sediment deposition, usually due to groundwater interaction with buried sedimentsand rocks

b1. Nodule- irregular, round, flat structure formed by filling voids in sediment

b2. Geodes- hollow, subspherical structures; form around water-filled pocket by crystals growing inward

b3. Concretions- mineral segregations that replace or force aside the surrounding sediment

5. Lithification- transformation of sediment into sedimentary rocks

a. Rocks are composed of:

a1. Particles- clastic rocks are often made of quartz; also feldspar, rock particles- Limestone particles include fossils (most important), pellets (invertebrate feces), oolites (sand-size concentrically-ringed carbonate particles) and intraclasts (carbonate mud "rip-ups")

a2. Matrix- fine-grained material deposited with particles- clay in clastic rocks


- carbonate mud (micrite) in limestones

a3. Cement- transported in solution by groundwater and precipitates between grain particles after they aredeposited- often calcite (termed "sparite" in limestones) or silica (especially quartz)

a4. Pores- void space between sedimentary particles

b. Diagenesis- physical, chemical and biologic changes that occur after deposition and before metamorphism- includes effects of compaction, cementation and recrystallization

III. The Sedimentary Archives

A. Sedimentary Environments- portion of the earth's surface with distinctive physical, chemical and biological characteristics

1. Facies- body of sediment or rocks with distinctive characteristics

2. Environmental Analysis

Determination of Ancient Sedimentary Environments Utilizes:

a. Physical Criteria- including shape of the deposit, rock type (lithology), textures (grain characteristics),sedimentary structures, fining/coarsening upward in sedimentary grain size

b. Geochemical criteria- especially isotopic ratios of elements

c. Biological criteria- fossil content

d. Walther's Law- the vertical sequence of rocks may reflect the horizontal succession of environments/facies

Transgression - relative rise in sea level

Regression - relative drop in sea level

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THE FOLLOWING ARE COMMON NON-MARINE (TERRESTRIAL) SEDIMENTARYENVIRONMENTS:

B. Soils- largely product of biological weathering; with rock debris and humus (= decaying organicmatter)

1. Factors that Influence Soil Formation

a. Type of Parent Rock- influence the type of materials present, amount of fractures, and permeability (ability of fluidsto flow through the system)- granite often produces sand-rich soils; basalts often produce clay-rich soils

b. Time- as time progresses and with more weathering soils often become more alike

c. Climate- affects precipitation and vegetation, which greatly influences soil characteristics

2. Ancient Soils (Paleosols) and Environments:

a. Wetland Paleosols- often gray, organic-rich

b. Tropical Paleosols- often with aluminum-rich bauxites or red laterites

c. Arid paleosols- often red; with shrink-swell clays and mudcracks; often with duricrusts (mineral layers thataccumulate at the soil's upper surface due to capillary action during evaporation, and consist ofsilica, carbonates or iron)

C. Lacustrine (Lake) Environments- landlocked body of water occupying some kind of basin due to faulting, crustal warping, orglaciation- controlled by water circulation, salinity and temperature (climate factors), biological factors andprovenance ("source") of sediments

1. Clastic Lake Deposits- often exhibit a circular morphology, with sand and gravel outside (near the shore) and mud inmiddle of lake facies- lakes typically produce cyclical, often repetitive sedimentary units


2. Carbonate Lake Deposits- are most typical of subtropical to tropical climates- precipitate limestones, dolomites and often contain stromatolites (carbonate algal structures)

3. Playas- broad shallow depressions in desert regions which may be covered by thin sheet of water- often with evaporite deposits such as gypsum and halite

D. Fluvial Environments

Rivers - major transporting and depositional agents for continental sediments

1. Meandering Rivers- with high sinuosity- these are perennial rivers (they typically flow year-round), with substantial base flow (base flowis the water contributed by groundwater)- often produce fining-upward facies with nonmarine fossils; there is often considerablesandstone in the channel, with deposits of shale (and paleosols) on the floodplain

2. Braided Streams- interlaced network of low sinuousity channels- braided streams are due to seasonal "flashy" discharge; often form in temperate mountains, aridregions and areas with monsoon-influenced climates- often create a broad, sheet-like morphology; they are usually coarse-grained and typically withpoorly-sorted sediments; fossils are rare

E. Semiarid Areas (Steppes) and Deserts

1. Desert- areas with less than 25cm rainfall per year- most deserts are situated at 25° - 30° latitude (due to global circulation patterns in thesubtropics producing high-pressure, low-moisture conditions)- often with Interior Drainage (where rivers drain into central desert depressions rather thanflowing to the sea)

2. Semiarid Area (Steppe)- interior continental areas with 25-50 cm rainfall; grassy vegetation

3. Desert Facies Include:

a. Wadis/Arroyos- "dry washes"; often with braided stream-like features

b. Alluvial Fans- cones radiate downslope from the point where streams emerge from rocky highlands


- like braided stream deposits but wedge-shaped and with debris flows

c. Sand Dunes- hill of sand deposited by wind (eolian deposits)- sand dunes consist of well-sorted coarse silt/fine sand; they have a steep slip face and gently-dipping windward face- sand dunes typically form thick, crossbedded quartz sandstones

F. Glaciers

Glacier - system of flowing ice that originates on land through the accumulation andrecrystallization of snow

1. Continental glaciers- Continental glaciers are large, thick, continental- or subcontinental-size glaciers that have been

very important during the Earth's "Ice Ages"- continental glaciers have both depositional facies (form tillites, composed of glacial depositstermed till) and erosional facies (often form unconformity surfaces and glacial striations due tothe weight of the ice eroding the landscape)- continental glaciers are often associated with a combination of fluvial, lacustrine, eolian andshallow marine environments

-------------------------------------------------------------------THE FOLLOWING ARE COMMON MARINE SEDIMENTARY ENVIRONMENTS:

G. Deltas- depositional body of sand, silt and clay formed where a river discharges into a body of standingwater- usually cone-shaped, coarsens upward in grain size, and with cyclothems (repetitivesedimentary sequences alternating from marine- to non-marine deposition)

H. Barrier - Backbarrier Complexes

1. Barrier islands- elongate islands built by large waves- barrier islands are composed of sand, gravel, and/or shell debris- barrier islands are separated from the mainland by lagoons or bays

2. Backbarrier complex- depositional environments situated between a barrier island and the mainland- examples include bays and lagoons

3. Sedimentology of Barrier Facies

a. "Surf-side" of Barriers


- beaches are often sandy; they are typically well sorted, cross-bedded and are quartz-rich- seaward from beaches, facies shift to silt and clay

b. Sheltered Sides of Barriers (Backbarrier Complexes)- wave action is typically insignificant in lagoons and bays- chief influences on backbarrier sediments are tides, organisms and climate- usually organic-rich muds are the prevalent sediment type

I. Tidal-influenced Environments- sea marginal areas subject to effects of tidal fluctuations (tides are due to Moon-Sun gravitationon oceans)- lithology often consists of oolites (sand-size grains of limestone), stromatolites (algal-builtstructures), skeletal debris, coal, and evaporites- sedimentary structures often consist of repetitive fining-upward sequences of sand, silt and clay

J. Organic Reefs- solid but porous limestone structure standing above the surrounding seafloor and constructed byliving organisms (often with skeletal material, especially corals)- with a wide variety of morphologies, from isolated Patch Reefs to continuous Barrier Reefs

K. Marine Shelves

1. Types

a. Continental Shelves- submerged, relatively flat, continental margins (that represent the "true" edges of the continents)- shelf edge averages approximately 130 meters water depth

b. Epeiric (Epicontinental) Platforms- broad, shallow sea over continental area- not common now but was important during periods of major rise in sea level (Example =Cretaceous Period)

2. Terrigenous shelves- with land-derived sediments- sand/gravel nearshore, silt and clay facies offshore- fining upward in grain size (transgressive sequence) or coarsening upward (regressivesequence)

3. Carbonate Shelves- form in tropical/subtropical environments- create thick limestone sequences

L. Continental Slopes- slope seaward of continental shelf


- lower limit 500-5000m- often with turbidites (graded beds deposited when dense, sediment-charged turbidity currentsslow down); carve submarine canyons and deposit deep sea fans

M. Pelagic Deposits- deep marine deposits accumulated due to vertical sedimentation- usually consist of Oozes (with microscopic silica or carbonate shells derived from planktonicorganisms) or clay-rich facies

IV. Stratigraphy- study of rock layers (strata)

Lithostratigraphy and Biostratigraphy have been the major ways in which Relative GeologicTime (sequencing geologic events) has been established

A. Lithostratigraphy (Physical Stratigraphy)- defines rock units on the basis of their physical features (i.e. lithologic features)

1. Stratigraphic Laws

a. Superposition- in series of undisturbed strata, the oldest bed is on the bottom

b. Original Horizontality- sedimentary units are originally deposited in horizontal layers- if the layers are not horizontal, the rocks have been deformed

c. Cross-cutting Relationships- a unit that cuts across another unit is younger than the unit it cuts across

d. Inclusions- a rock included within another unit is older than that unit

2. Formal Rock Units- in decreasing order, includes Supergroup - Group - Subgroup - Formation - Member - Bed- are separated by Contacts (the boundaries between different rock units)

a. Formation- formations are the basic mapping units in stratigraphy- a formation must have mappability (typically mapping is done using air photos) and lithologicconstancy (rocks should be of similar type in a given formation)- Formation names are designated by local geographic names and are capitalized

b. Member


- subdivision of a formation- often only have local significance

c. Beds- smallest rock-stratigraphic unit- beds are informal units, and therefore their names are usually not capitalized- beds may have economic significance (Coal bed, oil sand, etc.) or used in mapping ("key beds"or "marker beds" are used for correlation of strata)

d. Groups- assemblage of 2 or more successive formations- formations lumped together to form groups are related by lithology (rock type) or by positionwith reference to unconformities

3. Defining Formal Rock Units

a. Conformities- contacts between rocks which exhibit continuous depositional histories- contacts are typically defined at the boundaries between differing lithologies or textures

b. Unconformities- unconformities are gaps in the rock record due to erosion or nondeposition; unconformitiesoften form contacts between groups or formations

b1. Angular Unconformity- surface separating tilted or folded strata from overlying undisturbed strata

b2. Disconformity- unconformity between essentially parallel strata

b3. Paraconformity- unrecognizable in outcrop without the use of fossils, absolute dating, etc.

b4. Nonconformity- erosion surface between sedimentary and igneous/metamorphic rocks

4. Correlation- matching stratigraphic sections of the same age

B. Biostratigraphy ("Stratigraphic Paleontology")

1. Biostratigraphic Unit- body of rocks delimited from adjacent rocks by their fossil content- fossils are often used for Correlation


a. Biozone- basic unit of biostratigraphic classification- based on the distribution of Index Fossils (fossils characteristic of key formations; should haveshort time span, wide geographic range, independent as possible of facies, abundant, rapidlychanging and with distinctive morphology)

b. Range Zones- plot stratigraphic range of fossil(s)

Taxon Range Zone – represents the total horizontal and vertical range of a taxon

Concurrent range zone - overlapping ranges of specified taxa

- Taxon and Concurrent Range Zones are the major types of biozones

2. Major Fossils used in Biostratigraphy- best are pelagic [planktonic (floating) or nektonic (swimming)] forms

V. Geologic Time

A. Absolute (Actual) Dating Techniques- dates geologic events in terms of years before present

1. Methods that Depend on Radioactive Decay of one element to another

a. Radioactivity

a1. Isotopes- forms of an element (with the same number of protons), but they have a different number ofneutrons

a2. Radioactive Decay- atoms change to another element by releasing subatomic particles and energy; parent isotopedecays to daughter isotope at a constant rate

a3. Radiometric Dating- measure amount of parent materials relative to their daughter products

Half Life - time required for isotope to decay to half its original amount

a4. Notation

Kiloannum (plural = Kiloannum; kilo an) = Ka = thousands of years in the radioisotopic timescale


Megannum (plural = Meganna; mega an) = Ma = millions of years in the radioisotopic timescale; M.Y. (or m.y) = millions of years, without reference to the radioisotopic time scale

Gigannum (plural = Giganna; giga an) = Ga = billions of years in the radioisotopic time scale

a5. Common Isotopes Used for Radiometric Dating

Carbon-14/Nitrogen-14 = Half Life of 5.73 Ka; used to date organic materials; typicallyrestricted to objects less than 50 Ka

Uranium-238/Lead-206 = Half Life of 4.47 Ga; mostly used to date zircon grains in igneous andmetamorphic rocks

Potassium-40/Argon-40 = Half Life of 1.25 Ga; often used to date volcanic igneous rocks

b. Fission Track Dating- when uranium 238 decays it emits subatomic particles at a constant rate; this damages thesurrounding crystals, producing fission tracks- determine track density to date (usually for sites greater than 100,000 years)

2. Methods that require calibration by radioactive or chemical means

a. Magnetic Stratigraphy

a1. The Earth's Magnetic Field is due to the motion of the liquid, iron-rich outer core (itbehaves like a bar magnet to form a north and south magnetic pole)

a2. Magnetic Reversal- reversal of polarity in Earth's magnetic field; is recorded in iron-rich igneous and sedimentaryrocks

Normal Interval = polarity same as today

Reversed Polarity = polarity opposite to todays

a3. have constructed Paleomagnetic Polarity Scale based on magnetic reversals and "tied" withabsolute dates

b. Changing ratios of Isotopes (Strontium, Sulfur, Carbon, Oxygen) in rocks and shells ofmarine fossils- are tied to absolute dates

c. Thermoluminescence (TL)- measures the number of electrons caught up in defects in the crystal structure of minerals;


measures time elapsed since electrons were last "drained" from the "traps" (due to burning,exposure to sunlight, etc.)- rocks heated in the past release energy (light) when reheated; the more light that is releasedduring reheating, the older the rock

VI. Geologic Time Scale

A. Chronostratigraphy- subdivision of rocks considered solely as the record of a specific interval of geologic time

1. Ranks of Time-Stratigraphic Units (Time-Rock Units)

a. Eonothem- highest ranking chronostratigraphic unit- includes the Phanerozoic and Precambrian (Proterozoic and Archean) Eonothems

b. Erathem- subdivisions of an eonothem- commonly consist of several adjacent systems

c. System- fundamental unit of worldwide Time-Stratigraphic classification- usually based on local section and then correlated world-wide on basis of fossils- the names of systems have diverse origins and all types of endings (Cambrian, Cretaceous,Jurassic, Tertiary)

d. Series- next in rank below system- some of worldwide extent, others provinces- commonly known by geographic names (Comanchean, Gulfian) OR Upper, Middle, Lower(Lower Cretaceous, Upper Cretaceous)

e. Stage- next in rank below series; groupings of biozones- names often based on rock-stratigraphic units; often divided into substages

2. Time Units Versus Chronostratigraphic Units

Time Unit Chronostratigraphic UnitEon EonathemEra ErathemPeriod SystemEpoch SeriesAge Stage


B. Geologic Time Scale

- Learn the Geologic Time Scale Provided!

VII. Life on Earth

A. Paleontology- study of ancient life

Fossil = any evidence of prehistoric life

1. Paleozoology- study of fossil animals

a. Invertebrate paleontology- study of fossil invertebrates (animals without a vertebral column)

b. Vertebrate paleontology- study of fossil vertebrates (animals with a vertebral column)

2. Paleobotany- study of fossil plants

a. Palynology- study of pollen and spores- often also include study of marine one celled "plants"; i.e. acritarchs, dinoflagellates, diatoms,calcareous nannoplankton/coccoliths, etc.

3. Micropaleontology- study of small fossils- includes many groups mentioned under palynology and also foraminifera, radiolaria,chitinozoa, graptolites, pteropods (gastropods), ostracods (crustaceans), conodonts

4. Paleoecology- study of ancient environments and how ancient creatures relate to their environment and otherorganisms

B. Prerequisites/Preferred Conditions for fossilization:

1. Relatively abundant organisms

2. Presence of hard parts


3. Avoid chemical and physical destruction- rapid burial, typically within a relatively low energy depositional environment- preservation often depends on oxidation/reduction (Eh) and acidity/alkalinity (pH)characteristics in the environment; plants are often preserved within acidic and reducingconditions; calcareous shells and bones are typically preserved in non-acidic environments

C. Types of Fossil Preservation

1. Unaltered Fossil Preservation

a. Unaltered Soft Parts- unstable organic compounds are preserved such as carbon, hydrogen and oxygen- rarely preserved; sometimes within permafrost (Ex. = mammoths) or glaciers, mummificationin dry caves (ground sloths), tanning by humic acids in peat (Ex. = "bog people"), withinanaerobic aqueous environments (such as the "limnic stagnation deposits" in the Eocene German"brown coal" at Messel), within oil seeps, and in amber

b. Unaltered Hard parts (Durapartic Preservation)- preserve original calcium carbonate or calcium phosphate "hard parts" such as bone (ex. = LaBrea tar pits, California), shells, "coralline" algae; durapartic preservation is relatively rare

2. Altered Hard Parts- this includes the most common fossil preservation types

a. Petrification includes:

a1. Cellular Permineralization (Impregnation)- percolating groundwater introduces minerals (ex. = silicates, carbonates, iron compounds,phosphates) into the pore spaces (especially permineralize calcareous shells with calcite; alsowood and bone often permineralized)

a2. Recrystallization- change form and/or size of original crystal structure; Ex. = conversion of the calcium carbonatemineral aragonite to calcite (calcite has the same composition as aragonite, but a differentcrystalline structure); recrystallization often destroys fossil detail

a3. Replacement- percolating groundwater dissolves hard parts and replaces them with different minerals;Minerals involved include carbonates, silicates, iron oxides such as hematite and "limonite",pyrite, and collophane

b. Carbonization- volatile components (hydrogen, oxygen, nitrogen) decrease and the outline of the animals ispreserved as a carbon film; often combines with petrification


3. Traces of Animals

a. Molds and casts

Mold - impression of skeletal (or skin) remains in an adjoining rock

External mold - impression of outer side

Internal mold (steinkern) - impression shows form or markings of inner surface

Cast - original skeletal material dissolves and cavity (mold) fills with material

b. Ichnology- study of trace fossils (Ichnofossils = tracks, trails and burrows of organisms)

- are very useful since trace fossils were created when the organism was alive (therefore, tracefossils reflect ancient ecologies and habits of organisms)

- trace fossils are often used to determine rate of deposition and the original characteristics of thesedimentary environment in which the organism lived

Bioturbation Texture - sedimentary texture due to disturbance of sediments by organisms(bioturbation); often consists of dense, contorted, truncated or interpenetrating burrows or othertraces of indistinct form

- the major use of trace fossils is for determining ancient water depths (Paleobathymetry)

c. Coprolites- fossil excrement of animals; may contain undigested remains of food

D. Groups, Names and Relationships

Taxonomy - process of classification and naming organisms; typical classification of organismsis by their relationship to one another (= "natural" classification)

- the classification of organisms has traditionally used the Linnaean System, formulated byCarolus Linnaeus in the 1700's (Many biologists and paleontologist are now abandoning theLinnaean System, due to the influence of Cladistic Taxonomy, which groups animals on the basisof their shared derived characteristics)

1. Taxa (classification categories; singular = taxon) in the Linnaean System

a. Domain- in some recent classifications, constitutes the highest taxonomic category- often include the Domains Archaea/Archaebacteria, Bacteria/Eubacteria, and Eucarya


b. Kingdom- in many classifications is the highest taxonomic category- there are typically 5 to 6 recognized kingdoms [Monera (often classified as Domain orKingdom Archaea/Archaebacteria and Domain or Kingdom Bacteria/Eubacteria); DomainEucarya includes the Kingdoms Protoctista (Protista), Fungi, Animalia (Metazoa), and Plantae(Metaphyta)]

c. Phylum

d. Class

e. Order

f. Family

g. Genus- group of interrelated species; plural = genera

h. Species- fundamental unit of taxonomy- a species is considered to represent a population of individuals that can interbreed and produceviable offspring- because paleontologists typically do not know what individuals interbred in the fossil record,most fossil species are based on their morphology (form)

E. Chemical Cycles in Earth System History

Chemical Reservoirs - bodies of key elements and compounds in the Earth system that shrink orexpand as fluxes between them change- these reservoirs are influenced by the following:

1. Photosynthesis and Respiration

Photosynthesis - process by which plants use the energy of sunlight to produce sugars fromcarbon dioxide and water; oxygen is a by-product of this process

Respiration - opposite chemical reaction versus photosynthesis; organisms oxidize sugars inorder to release their energy

2. Carbon Dioxide and Oxygen Cycles- if no dead plant tissue is buried, it decomposes and carbon dioxide returns to the atmosphere- if dead plant tissue is buried (such as in swamps or anoxic marine environments), it upsets thebalance between photosynthesis and respiration (with the amount of carbon dioxide in theatmosphere shrinking and with increase in oxygen levels)


- weathering of minerals removes carbon dioxide from the atmosphere (enhanced by mountainbuilding, warm climates, high rates of precipitation, and more vegetation)- the initial spread of forests during the Devonian intensified weathering, depleted theatmospheric reservoir of carbon dioxide; this reduced greenhouse warming and probablycontributed to the cooler climate conditions and formation of the Late Paleozoic "Ice Age"

3. Methane Cycles- methane is a powerful greenhouse gas- when global warming melts masses of methane hydrate on the seafloor, the addition of methaneto the atmosphere produces further global warming

4. Negative Feedback in Carbon Dioxide and Global Warming Cycles- when climate warms, chemical weathering accelerates (extracting carbon dioxide from theatmosphere) and the amount of evaporation increases on the ocean (which further acceleratesweathering on land, extracting more carbon dioxide from the atmosphere)

5. Submarine Volcanism versus Seawater Chemistry, Mineralogy and Types of Organisms- seawater circulating around mid-oceanic ridges transfers calcium to the seawater; magnesium isextracted from the water and becomes locked in the rocks [therefore with more seafloorspreading there is a rise in sea level (because more rocks are produced that displace the water)and a decrease in the magnesium/calcium ratio (more magnesium is extracted from seawater)]- with increased marine volcanism, the low magnesium/calcite ratios produce "Calcite Seas", inwhich calcite forms oolites and marine cements and organisms with calcite skeletons becomesuccessful reef builders (the lowest magnesium/calcite ratio of the Phanerozoic was during theCretaceous, which contains much more "chalk" than any other system)- when the total volume of volcanics at mid-oceanic ridges is low, aragonite and high-magnesiumcalcite is more abundant; "modern" types of corals, with aragonite skeletons, are more abundantduring these periods of Earth history

VIII. Evolution and Extinction

Evolution = (1) historical changes in structure, function and adaptation (2) genetic changes andprocesses of selection and population dynamics

Adaptations - specialized features of organisms that provide useful functions (adaptationinvolves the “remodeling” of old organs); adaptations are how organisms cope with changingenvironmental conditions, invade new environments, and function more efficiently in a givenenvironment

A. History of Evolutionary Theory

1. Jean Baptiste de Lamarck (1744-1829)- French naturalist; developed theory now known as Lamarckism (theory of inheritance ofacquired characteristics)


2. Thomas Malthus (1766-1834)- English clergyman and economist; wrote "Essay on the Principle of Population"; introducedconcept that population exhibits exponential growth, whereas food production exhibits lineargrowth; population expands to limits set by famine, war and disease

3. Alfred Wallace (1823-1913)- codiscoverer of the theory of natural selection independent of Darwin; also a prominentzoogeographer

4. Charles Darwin (1809-1882)- most naturalists of his time were "special creationists"; as ship's naturalist on the H.M.S. Beagle(1831-1836) developed the foundation of his theory of evolution; Read Malthus' Essay onPopulation; Wrote "The Origin of Species by Means of Natural Selection" in 1859

Darwin's facts and deductions include:- organisms tend to increase in numbers exponentially- in spite of the tendency to progressive increase, the number of individuals within a species tendto remain approximately constant.- Deduction: Since more young are produced than can survive there must be a competition forsurvival ("Struggle for Existence")- all organisms vary; some variations are inherited- some individuals fail to survive, others live to reproduce (Natural Selection)

Summary of Darwinian Evolutionary Theory: New species arise from preexisting ones as aresult of natural selection acting on inherited variations

B. Evidence for Evolution

1. Geographic distribution of organisms- different animals are found in similar environments worldwide- isolated environments (especially islands) with similar animals with diverse form and habits

2. Anatomy

a. vertebrate embryos are very similar, especially during their early stages of development

b. Homology- organs in different animals with the same origin but different function

c. Vestigial Organs- organs with no function (resemble working organs in other creatures)- examples include the pelves of whales and boa snakes, the "dewclaws" of dogs, and the "extratoes" of horses


3. Artificial Selection- domestic breeders preserve certain biological features and eliminate others- similar to Natural Selection

4. Genetics- study of mechanisms of inheritance- founded by Gregor Mendel (1822-1884)

a. Particulate Inheritance- presence of hereditary factors (genes) that retain their identity while being passed on fromparent to offspring- Genes are segments of DNA (they are concentrated in chromosomes in the cell nucleus)

b. Mutations- chemical changes in genetic features- provide most variability on which natural selection operates

c. Sexual Reproduction- sex cells (gametes = egg and sperm) unite to form a zygote (this process is termed SexualRecombination)- this yields new combinations of chromosomes/genes and greater variation

Populations = groups of interbreeding individuals

Gene Pool = total genetic components of populations

- origin of new species (Speciation) is probably by isolating a population

d. Genetic Paleontology- almost all molecular paleontology studies have been performed using DNA from mitochondria(mtDNA), cell structures that supply energy for metabolism- the extracted DNA is compared to other DNA sequences (from a relative, a particularpopulation, or a species) to identify an individual or the population the sample came from- these studies have been used to determine the genetic similarity (and evolutionary relationshipsof species)- random mutations substitute various amino acids in molecules or nucleotide sequences forDNA that is more or less directly proportional to time (therefore there may be "MolecularClocks", which have proven useful in determining the timing of evolutionary divergence inorganisms)

5. Paleontology- studies of fossils reveal phylogenies (evolutionary histories and relationships)

C. Evolutionary Theories Concerning Rate of Change


1. Phyletic Gradualism- rates of evolution are regular- is Darwinian Evolutionary Theory

2. Punctuated Equilibrium- first proposed by Niles Eldredge and Stephen Gould during the 1970's- says that evolution occurs in fits and spurts separated by long periods of little change- problem in testing (sudden appearances in fossil record may be due to immigration rather thanrapid speciation)- problem in classification [no classification system can show intermediate forms (only"species")]

D. Adaptive Radiation- rapid origin of many species from a single ancestral group- often follows immediately after origin of group (with adaptive breakthroughs) or after a massextinction

E. Social Darwinism- proponents used writings of Charles Darwin, and especially Herbert Spencer, to urge laissez-faire economic policies to weed out the "unfit, inefficient, and incompetent"

1. Herbert Spencer- English author and philosopher (1820-1903)- believed that "rational men" should not interfere with the laws of evolution, and poorer classesshould be "eliminated" by their "unfitness"- his views were popular among conservative politicians, millionaires, etc.

2. Ernst Haeckel- German zoologist and evolutionist (1834-1919)- believed that Darwin's theory of evolution was the answer to all questions of science,philosophy, ethics, religion and politics (the Monist Philosophy)- was considered a national hero in Germany for his influential views that the German "masterrace" must "outcompete inferior peoples"- Adolf Hitler in Mein Kampf ("My Struggle"), published in 1925, took the title of his book fromDarwin's phase "the struggle for existence" as translated by Haeckel

3. Francis Galton- English scientist and philosopher (1822-1911)- founded the Eugenics Movement (sought to bring about social improvement through selectivebreeding of humans)- adopted by the Nazis in their Lebensborn ("Fountain of Life") Movement, an attempt byHeinrich Himmler and the German S. S. to create a "master race" of "Aryans", and "clear" vastareas of land inhabited by "inferior peoples" to provide a place for "Aryan" habitation

F. Extinction


- total disappearance of a taxon- most likely in species with small populations and those that live in limited geographic areas(population size related to trophic level and body size with carnivores most likely to becomeextinct and small herbivores least likely)

1. Types of Extinction

a. Background Extinction- probability of extinction is approximately constant through the life of a particular group butrates vary from group to group- therefore there is a "normal background rate" of extinction

b. Mass Extinction- there are about half a dozen Phanerozoic episodes of major extinction

Theories for Mass Extinction Include:

Environmental Deterioration - climate changes (Exs. = cooling trends, drop in sea level, oxygen-depleted deep ocean water rises onto continental shelves, violent volcanism) cause massextinctions

Stochastic Processes- says that origin and extinction of organisms is probabilistic (like a "flip of a coin")- computer programs randomly generating "artificial" phylogenies are much like "natural" clades- an example of a stochastic event would be extinction by a bolide impact (no matter howperfectly adapted the organism is to its environment, it will still die as a result of this catastrophicevent)

Man – has impacted ecosystems for the past 11,000 years (?)

IX. Continental Drift and Plate Tectonics

A. Continental Drift

1. Alfred Wegener- German meteorologist and polar explorer (1880-1930)- in 1915 wrote The Origin of Continents and Oceans- proposed that all continents were part of a huge supercontinent (Pangaea)- Pangaea "broke up" 200 million years ago to form Laurasia (North America and Eurasia) andGondwana (South America, Africa, Antarctica, India)

2. Wegener's Evidence Included:

a. Fit of Continents


- continental coastlines form a puzzle-like fit (later geoscientists found that edges of continentalshelves form an even better fit)

b. Fossil Evidence- distribution of the fossil plant Glossopteris and the reptile Mesosaurus on the Gondwanacontinents indicates that they were once joined

c. Paleoclimatology- distribution of glacial deposits (tillites), ancient deserts and reefs, and coal deposits indicate thecontinents were one joined and were at different paleolatitudes

d. Geologic Evidence- matching of rock types between modern continents indicate that the continents were oncejoined

3. The Demise of Continental Drift Theory- Wegener believed that the continents were like "boats" (plowing through the ocean basins) or"sleds" (sliding on top of oceanic rocks), with the continental crust moving upon the mantle- there is no evidence that the continents moved through or over the ocean basins; the crust anduppermost mantle are joined together as a rigid unit

B. Plate Tectonic Theory- theory that Earth's crust is divided into a series of large lithospheric plates

1. Lithosphere- brittle material forming the large plates; consists of Earth's crust and upper portion of mantle- lithosphere rides on the moving asthenosphere (ductile material separating the lithosphere fromthe lower mantle)

2. Types of lithospheric plates

a. Oceanic (Simatic) Plates- formed from basalt being produced along Rift Zones at mid-oceanic ridges; have high specificgravity and therefore form basin areas

b. Continental (Sialic) Plates- granitic composition and form continental areas

3. Evidence for plate tectonics

a. fit of continents

b. climatic criteria

c. paleontologic support


d. petrologic (rock) evidence

e. measurements from space - indicate that plate movement averages 2-9 cm/yr

f. Paleomagnetism

Seafloor Spreading - the process through which plates diverge and new lithosphere is created atmidoceanic ridges- youngest rocks are nearest to the midoceanic ridges- during seafloor spreading the polarity of the Earth's magnetic field alternates, which ispreserved as bands of normal and reversed polarity "stripes" in the magnetized basaltic crust

"Polar Wandering Curves" - due to movement of lithospheric plates the magnetic poles appear tochange in position; used to reconstruct the ancient positions of the continents

5. Plate Movements

a. Craton - tectonically passive part of a continent

b. Continental Divergent Boundaries- the mantle material rises as a Thermal Plume, the crust cracks and forms a “Triple Junction";two of the "arms" form a Rift Valley; the "failed arm" that does not open forms a large trough(Aulacogen) which receives sediments- rifting produces basalt and igneous rocks of mixed composition; weathering of the surroundingcontinental granitic rocks produces feldspar-rich arkosic sandstones (arkoses) which are shed intothe rift valley

c. Rift valley opens wider and forms a Proto-Oceanic Gulf- with restricted water circulation; in arid climates evaporites may form in these basins (such asthe Jurassic-age Louann Salt deposits of the Gulf of Mexico)

d. Further Rifting creates Ocean Basins- age of the ocean floor is determined by radiometric dating of basalt, study of microfossils, andcorrelation of magnetic "stripes"; oldest ocean rocks are about 200 million years old- continued continental divergence often creates a passive continental margin (with widecontinental shelves upon which wedges of land-derived terrigenous sediments are deposited andcarbonate platforms build)

- Oceanic sedimentation is controlled by:

Nearness of tectonism - volcanism tends to be most dominant along plate boundaries

Carbonate compensation depth (CCD) - depth at which carbonate dissolution equals carbonateproduction, due to acidic water in deeper parts of oceans; below the CCD within ocean basins,


mostly clay and chert is deposited as carbonate sediments dissolve

e. Convergent boundaries- lithospheric plates collide- tectonically active boundaries, typically with relatively narrow continental shelves

e1. Suture Belts- usually formed due to collision of continental lithospheric plates; creates sedimentary basinsand/or huge mountain ranges (Exs = Himalayas, Urals)

e2. Ophiolite Suites- series of rocks exposed when plates are Obducted (oceanic plate overrides continental oranother oceanic plate); provides a cross-section of the Earth's crust and upper mantle

e3. Subduction- Convergent plate junctions where oceanic plate "dives" beneath a continental plate and isdestroyed- often contain Melanges (large bodies of broken and sheared rock)- Subduction zones are located by study of deep-seated earthquakes (Benioff Zones; up to 700km depth) that are caused by the shattering of the subducted plate

f. Transform (Shear) boundaries- boundaries in which plates slide past one another (Ex. = San Andreas Fault, California)- transform faults offset mid-oceanic ridges at perpendicular angles; develop due to differentrates of seafloor spreading and due to fracturing of a round object (the Earth's surface)

6. Hot Spots and Mantle Plumes- chains of seamounts and volcanic islands are often formed by lithospheric plates moving over"fixed" mantle plumes or hot spots- "weight" of the islands produced by hot spots causes isostatic sinking and the ultimateformation of coral atolls and flat-topped submarine guyots- hot spot traces may show the direction of plate movement (Example = the orientation of theHawaiian Islands indicate that the Pacific Plate is moving toward the northwest)- hotspots/mantle plumes may also form under continents (Ex.= Yellowstone National Park)

7. Microcontinents- small pieces of continental crust that have fragmented and moved by sea-floor spreading- a modern example is the island of Madagascar, located east of Africa

8. Exotic Terranes- microcontinents that collide and become attached to larger continental margins (Ex.= parts ofWestern North America and Appalachia)

X. Origin of the Universe and the Archean Eon


A. Origin of The Universe- the universe is believed to be approximately 10 - 20 billion years old

Age Estimation is Based Upon:

1. Star Observations- observation of star clusters and interpretation of nucleosynthesis (study of element formation,especially in massive stars) estimates that age of universe is from about 15 to 20 billion years old

2. Hubble's Law (Law of Redshifts)- the velocities at which galaxies move away from us are proportional to their distance from us;more and more remote galaxies will have greater and greater speeds of recession- based on the Law of Redshifts, it is believed that the universe is 10 to 20 billion years old(recent studies indicate possibly 13.7 billion years old)

a. According to Hubble's Law, the universe is expanding

b. At the "beginning of time" all energy and matter in the universe was crowded together at asingle point

c. The Big Bang - the event that created the Universe; it generated the expanding motion thatwe observe today- the first stars and galaxies began forming within one billion years after the Big Bang

B. Solar Nebula Hypothesis- Solar System probably began as a slowly rotating cloud of gas and dust- gases and dust condensed and clumped to form planetesimals; planetesimals aggregated to formplanets and their satellites (moons); dates of oldest rocks on the Earth's Moon and the oldestMeteorites cluster at about 4.5 Ga- rocky and metallic material condensed to form planets in the hot inner portion of the SolarSystem; lighter gases and ice condensed in the cold outer portions of the Solar Nebula to formhuge planets- late impact of planetesimals cratered the surfaces of the planets and moons, and may have tiltedthe rotational axes of some planets- some planetesimals survive to this day as asteroids and comets

C. The Planets

1. The Terrestrial Planets- small, dense "rocky" planets including Mercury, Venus, Earth and Mars- lie in inner part of Solar System- not much hydrogen and helium; Moons absent or few

2. The Jovian Planets


- giant planets consisting primarily of hydrogen, helium, methane and ammonia gases and liquids(and water)- include Jupiter, Saturn, Uranus and Neptune- low density; ring systems and many moons present

3. Pluto and the "Minor Planets"- Pluto completes its highly elliptical orbit (which is out of the ecliptic plane) in approximately248 years; axis of rotation nearly lies in it's orbital plane- made of rock mixed with ices (water, nitrogen, methane)- Pluto and it's "moon" Charon are now considered to be "Minor Planets"; they are probablyremnant planetesimals from the birth of the Solar System

D. Other Solar System Features

1. Comets- icy bodies (mostly water and carbon dioxide/carbon monoxide ice) less than 10 kilometersacross- the comet nucleus consists of ice and gases; as comets approach the Sun they begin to vaporizeto form a Coma (cloud of gases) and a tail

2. Asteroids- irregular-shaped rocky or metallic bodies with diameters from a few meters to 1000 kilometers- most orbit Sun within the Asteroid Belt between Mars and Jupiter

3. Meteorites- iron, stony (silica-rich), or stony-iron particles that hit the Earth’s surface; most formed frombroken-up asteroids/planetesimals or material left over from formation of the Solar System

4. Bolides- a meteorite, asteroid or comet that hits the Earth- there were many bolide impacts in the early history of the Solar System; this is shown by theheavy cratering of the Moon (and other Solar System satellites) and "geologically dead planets"like Mercury- an asteroid may have struck Earth at the end of the Cretaceous Period (approximately 65million years ago), stirred up dust and created fires, initiated a "nuclear winter" and caused massextinctions (including the dinosaurs)

E. Origin of the Earth's Moon- probably formed when a Mars-sized body collided with the Earth, splashing material into orbit- the Moon is not a chunk of Earth; it formed almost entirely from the mantle of the impactingbody (which accounts for the differing proportions of iron and magnesium versus the Earth)- this material coalesced to form the Moon (which has a feldspar-rich outer layer and very smallmetallic core)- the core material of the impacting planet combined with the Earth's core


F. Origin of the Earth

1. Initial Earth Differentiation into Layers- heat from bolide impacts and radioactive decay produced a molten planet, in which the most

dense material sank toward the center and the least dense rose toward the surface (produced aniron core and a silicate-rich mantle)- the less dense silicates floated to the surface, forming a "magma ocean", which cooled to form asilicate-rich crust (this was a precursor to the oceanic crust of the modern world)

2. Crustal Origin

a. Primitive Crust- was of mafic composition (with abundant ferromagnesian minerals; the crust was derived fromultramafic mantle material)

b. Continental Crust- formed at least 4.1-4.2 Ga, and was produced by partial melting of the primitive mafic crust- during the Archean the Earth had higher heat flow and abundant "hot spots"- igneous processes associated with hot spot activity produced felsic crust by partially melting themafic parent material (a similar process is occurring now in Iceland, where felsic volcanics formalong the Mid-Atlantic Ridge)- small Archean continents (Protocontinents) formed; weathering and metamorphism generatedadditional felsic crystalline rocks- the oldest crustal rocks from Canada are dated at approx. 4.04 Ga; metamorphosed sediments inwestern Australia have zircon grains dated at 4.4 billion years old; this is the official beginningof the Archean, which includes about 45% of Earth History

c. No large continents in the Archean- broad blocks of crust older than 3 billion years are absent in Preccambrian Shields (strong heatflow from below prevented protocontinents from coalescing to form large continents)

G. Precambrian Tectonics

1. PreCambrian Shields- igneous and metamorphic cratons form the nuclei of continents; these are surrounded byyounger rocks- rocks of similar age occupy distinct orogenic belts- there is at least one PreCambrian Shield area on every continent (ex.= Canadian Shield)

2. Archean Rocks

a. Types of rocks present

Greenstones - belts of low-grade metamorphic rocks with chlorite, epidote and green amphibole;probably formed by metamorphism of volcanic belts along margins of small continents/ ocean


basins

Granulites - quartz- and feldspar-rich, high-temperature metamorphic rocks; occur betweengreenstone belts; most formed during the Kenoran Orogeny at 2.5 Ga

Deep-water sedimentary rocks - graywackes (clay- and feldspar-rich sandstones) and deep marinemudstones are common; metamorphosed turbidites are common (deposited in forearc basin andother environments along subduction zones); nonmarine and continental shelf deposits are rare(therefore there were evidently no large continents during the Early Archean)

Oldest Banded Iron Formations (ex. = Isua, southern Greenland) dated at approx. 3.65-3.8 Ga;alternating iron oxides and quartz (originally chert) layers; silica probably derived fromsubmarine volcanoes; fomation of iron may have been influenced by the presence of bacteria

b. Formation of Large Cratons began during late Archean- heat flow from the Earth's interior diminished and allowed protocontinents to coalesce- in Southern Africa there is evidence of a large craton at 3.1 - 2.7 Ga (with a thick sequence ofsedimentary rocks, the Witwatersrand strata, containing placer gold- and uranium-bearingbraided stream deposits; glacial tillites are found in the Pongola Basin at 2.9 Ga)

H. The Atmosphere was Formed By:

1. Degassing of the Earth's Interior- an initial atmosphere was probably formed during differentiation, then "swept away" when theearly Solar System was cleared of debris by a strong "Solar Wind" (charged particles movingaway from the Sun)- volcanic activity then produced a second atmosphere of water vapor, hydrogen, hydrogenchloride, nitrogen, carbon dioxide, carbon monoxide (and secondary chemical reactions in theatmosphere produced methane and ammonia)

2. From Comets/"Space Ice"- comet-like material supplied ammonia, methane, water vapor, etc. to partially create theatmosphere

3. Photosynthesis- early photosynthetic organisms, such as blue-green algae (cyanobacteria), created oxygen- but there was evidently little "free" oxygen present in the Precambrian

I. The Oceans- the Earth's interior degassed, gases condensed in the atmosphere during Earth cooling, andprecipitation formed and fell to Earth to form oceans- the salinity of the Ocean was created by weathering rocks on land- seawater has varied little in salinity since the Early Archean (although the relative proportionsof dissolved ions has varied significantly)- the Early Archean ocean was probably much warmer than that of today due to the presence of


abundant radioactive elements in the Earth's crust and the "Greenhouse Effect"

I. Origins of the Biosphere

1. Organisms- ordered (i.e. with cellular organization) living creatures- "life" is a series of chemical reactions, using carbon-based molecules, by which matter is takeninto a system and used to assist the system's growth and reproduction, with waste products beingexpelled- life forms pass on their organized structure when they reproduce

2. Origins of Life

a. The Earth During the Archean Eon- equable conditions for prebiotic evolution could have existed on Earth as long ago as 4.4 Ga- Archean Earth was dominated by oceanic lithosphere with volcanic islands and smallmicrocontinents- large amounts of CO2 may have led to a Greenhouse Effect, with atmospheric temperatures upto 100°C or more (therefore there were no polar icecaps; with permanently stratified stagnantiron-rich deep ocean waters and with wind-mixed iron-poor surface waters)- hot springs, submarine hydrothermal systems, and heated wind-mixed layers of the oceans mayhave been areas where prebiotic evolution occurred

b. Origins of Life

b1. Depends upon the synthesis of Carbon- once carbon is synthesized, all other biogenic molecules may be formed (Organic Molecules arecomplex, carbon-based molecules)- elements most prominent in organic molecules are carbon, hydrogen, oxygen and nitrogen

b2. Cellular Structure

b2a. Cell- a "container" filled with organic and inorganic molecules (= Protoplasm); the cell contains:

b2b. Proteins- built from amino acids; proteins are used as "building materials" and for chemical reactions

b2c. Nucleic Acids- includes Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA); provide information for

the structure of the organism and the means to pass on this information in reproduction

- DNA carries the genetic code of an organism, providing information for its growth andmetabolism; it has the ability to replicate itself in order to pass this information on tosubsequent generations


- RNA has several functions (carries genetic message of DNA to sites; assembles amino acidsinto proteins; acts as a catalyst for chemical reactions), and because of this versatility wasprobably the nucleic acid present within the earliest life forms (this earliest ecosystem is oftentermed the "RNA World"); but RNA was eventually replaced by DNA as the genetic code (asDNA is a more stable molecule)

b2d. Organic Phosphorous Compounds- found in small amounts; transform light or chemical fuel into energy

c. The Formation of Proteins

c1. Amino Acids- mixture of methane, ammonia, hydrogen and water vapor (or nitrogen, carbon dioxide andwater vapor) in the presence of electricity or ultraviolet light leads to the production of aminoacids- some meteorites also contain amino acids- production of amino acids must take place in an anaerobic (devoid of free oxygen) environment

c2. Proteins- removing water from amino acids yields Polypeptides (protein-like chains)- when polypeptides cool they form Microspheres (cell-like structures)

3. Kinds of Organisms

a. Prokaryotes- single-celled organisms with their DNA loosely organized within the cell, are not bounded by amembrane into a nucleus and they lack chromosomes- meiosis is absent (see discussion under Eukaryotes below)- range from 0.3 to 20 microns in size- are often termed Monerans- often divided into two Domains (or Kingdoms):

a1. Domain/Kingdom Archaea/Archaebacteria- superficially similar to Eubacteria but differ greatly in their molecular (especially RNA)sequences- include the methanogens (tend to be found in highly saline environments), sulfur-metabolizingbacteria and sulfate-reducing bacteria (found around hydrothermal vents)- probably included the oldest life forms, which were probably thermophilic ("heat-loving")autotrophs (used molecular hydrogen, carbon dioxide and sulfur compounds to produce energy,with optimal growth at temperatures from 70° to 110°C); possible environments of origininclude hot springs, heated ocean waters, and hydrothermal vents

a2. Domain/Kingdom Bacteria/Eubacteria- contain the most commonly recognized or "true" bacteria and cyanobacteria


- evolved both thermophilic autotrophs in heated environments and photoautotrophs in shallowmarine environments

- life originated at least as early as 3.5 Ga ago, as indicated by (mostly) Eubacteria

Evidence Includes:

a2a. Megascopic Stromatolites- Stromatolites are laminated structures formed by blue-green algae (cyanobacteria)- the earliest Stromatolites come from South Africa and Australia (dated about 3.0 to 3.45 Ga)

a2b. Permineralized Microfossils- filamentous kerogen-rich microfossils similar to cyanobacteria occur in Australian cherts datedat about 3.5 Ga

a2c. Biologically Produced Organic Matter- organic carbon-13 values from the 3.0 to 3.55 Ga-old South African and Australian sedimentsare similar to those of modern cyanobacteria and photosynthetic bacteria

XI. The Proterozoic Eon (Late Precambrian)

A. Proterozoic Eon Tectonics (2.5 Ga - 543 Ma)

1. Development of the First Cratons- the first cratons of modern proportions formed about 3 Ga (see discussion in Archean sectionabove)

2. Plate Tectonics Begins

a. Plate Convergence and Tectonism- 2 Ga ago with earliest evidence of plate tectonism- The Wopmay System of Canada is a body of deformed rocks that represent the formation of thefirst mountain system (the Wopmay Orogen); consists of a fold-and-thrust belt of sedimentaryrocks (representing non-marine to deep marine clastics and carbonates), a metamorphic belt andbelt of igneous intrusions

b. Continental Accretion- continental accretion and growth occurs during mountain-building (orogenesis) by suturing anisland arc or microcontinent to a large craton along a marginal subduction zone OR bycompression and metamorphism of sediments that have accumulated along continental margins(Orogenic Stabilization)- the Wopmay System may have enlarged the Slave Craton by both suturing of a small plate andorogenic stabilization- Orogenic Processes and regional metamorphism may alter preexisting rocks beyond recognition


and resets their radiometric clocks so that the age of the crust can not be determined (this processis termed Remobilization); this has been a problem in studying the earliest tectonic events onEarth

- following continental accretion, the first extensive carbonate platforms and shallow-waterterrigenous deposits appeared

c. Plate Rifting in the Proterozoic- continents can decrease size by erosion (not very significant since it is relatively slow), bysubduction (also not very significant since continents are light-weight and resist being pulled intosubduction zones), or by continental rifting (very important)- first evidence of continental rifting appeared in what is now eastern North America at about 1.0to 1.2 Ga, with basaltic lavas extruding along the Great Lakes Region (the KeweenawanSupergroup; also with alluvial fan conglomerates deposited within down-thrown fault blocks, orgrabens) and extended into the central U. S. (the Mid-Continent Rift); rifting ceased, but notbefore the rift belt grew to 1500 kms (900 miles) long and 100 kms (60 miles) wide

d. Creation of Larger Continents Worldwide

- The core area of Laurentia (primarily North America) sutured to the microcontinents of Baltica(a portion of Europe), northern South America, West Africa, Southern Africa, Eastern Antarcticaand Australia at 1.95 to 1.85 billion years ago and formed a larger craton

- Between about 1 billion and 800 million years ago the landmasses that would later becomeGondwanaland encircled and tectonically sutured to Laurentia (forming a supercontinentsometimes termed Rodinia)

- the Grenville Orogeny was occurring along the east coast of North America (from easternCanada through the Llano Uplift region of Central Texas) at about 1.1 Ga; this was caused by thecollision of eastern North America with what would later become northern South America

e. Rodinia Rifts- between 800 and 700 million years ago Rodinia rifted apart to form the Pacific Ocean (there aremany failed rifts from Northern Canada to Arizona, including the Belt Supergroup in thenorthern United States, that represents this divergence)

f. A Second Supercontinent Forms?- another supercontinent may have formed by about 550 million years ago, beginning with thesuturing of the microcontinents that would become Gondwanaland (this event is often termed thePan-African Orogeny)- there is some controversy as to whether the supercontinent was fully formed - if not, most of theEarth's continental crust were certainly clustered close together at this time

B. Proterozoic Climate


1. Early Proterozoic- Early Proterozoic with widespread glaciation (an example is the Gowganda Formation ofsouthern Canada, consisting of varved mudstones, tillites and glacial dropstones); also glaciers ofsimilar age in Wyoming, Finland, southern Africa and India

2. The Vendian Period (610-550 Ma ago) or Neoproterozoic- the beginning of Vendian Period exhibits the most extensive glaciation in Earth history (theVaranger/Varangian or Marinoan Glaciation)- later Vendian with relatively warm global climate, with major marine transgression anddevelopment of extensive shallow marine environments, which led to a greater diversity oforganisms

C. Life in the Proterozoic

1. Prokaryotes- beginning about 2.2 GA, stromatolites become increasingly abundant (probably because ofincreased size of continental shelves)

2. Domain Eucarya

Eukaryotes = single- or multi-celled organisms with chromosomes made of DNA, RNA andproteins contained within a membrane-bound nucleus

a. Characteristics- cells range from 3 microns to several millimeters- with specialized structures (vacuoles, mitochondria, many with chloroplasts) that providemetabolic functions for the cells- oxidize sugars as a source of energy- meiosis present = with two consecutive cell divisions by which the chromosomes are reducedfrom the diploid number of somatic cells to the haploid number (half) characteristic of gametesand spores- sexual reproduction provides more variation that may potentially enable the species to bettersurvive environmental changes- the Domain Eucarya includes the Kingdoms Protista (Protoctista), Fungi, Plantae (Metaphyta)and Animalia (Metazoa)

b. Origin of Eukaryotes- the nuclear membrane probably formed by invagination (folding inward) of the cell membrane- specialized structures (chloroplasts and mitochondria) probably developed from endosymbioticprokaryotes living within the cell membrane of archaebacterial prokaryotes

c. The Oldest Eukaryotes- as oxygen built up in the Early Proterozoic atmosphere, due to the presence of photosyntheticprokaryotes, the concentration of dissolved oxygen increased in the upper ocean; as a result morenitrogen was oxidized to form nitrate (NO3-), which is an important nutrient for eukaryotic algae


[Cyanobacteria don't need nitrates, as they can use pure nitrogen (N2) for their metabolism]- oldest known probable eukaryote is the corkscrew-shaped, cylindrical megascopic colonial algaGrypania, from a 2.1 Ga-old banded iron formation in Michigan- organic-walled microfossils of eukaryotic photoautotrophic plankton ("acritarchs") occur inrocks slightly younger than those containing Grypania

D. Atmospheric Oxygen- increased dramatically between 2.2 and 1.9 Ga-ago; evidence includes the presence of paleosolsand redbeds, the decrease in uraninite deposits (uraninite is unstable in free oxygen), and increasein uranium and molybdenum in marine shales (they weathered from the land in the presence ofoxygen and were washed into the oceans)- increase in atmospheric oxygen was very important for the development of more complex lifeforms

1. Banded Iron Formations- consist of alternating chert and hematite/magnetite layers- therefore oxidized (ferric) iron formed in marine basins (although there is some debate as to theoriginal oxygen content in BIF's)- but Banded Iron Formations disappeared about 1.9 Ga-ago when oxygen content was supposedto be increasing (BIF's may also be influenced by ocean stratification and therefore this may bethe source of conflicting data, or they may not have contained as much oxygen as somegeologists have claimed)

2. The Ozone Shield- development of ozone (O3) prevented lethal radiation from reaching the Earth and was of majorimportance in the development of life

E. Origin and Diversification of the Metazoa

1. Metazoa (Animalia)- with specialized cells forming tissues (= metazoan organization)- tissues are united into organs (except in simplest invertebrates)

2. Vendian Body Fossils and Trace Fossils

a. Tracks and Burrows- oldest undisputed metazoan traces found in Late Proterozoic rocks (approx. 560 Ma)- Vendian trace fossil assemblages include feeding burrows, dwelling burrows, crawling andgrazing trails; differ from later Phanerozoic types with Vendian trace fossils smaller and withshallow penetration into the sediment (i.e, no deep burrowers were present during theProterozoic)

b. Ediacara Fauna- approximately 580-542 Ma; originally from the Pound Quartzite of South Australia; later foundin approximately 25 Late Proterozoic localities worldwide


- Vendian fossil record consists of moderately large, soft bodied invertebrates preserved in well-aerated shallow marine environments (it is unusual to preserve in this environment during laterPhanerozoic times; Ediacaran preservation is probably mostly due to the absence of predators,scavengers, deposit feeders, etc. during Vendian times)- the structure and relationships of Vendian Fossils is greatly debated; hypotheses of theirrelationships state that most Ediacara fossils can be placed in modern groups such as jellyfish,various worm phyla, and arthropods OR the Ediacara fauna have a unique “pancake-like”organization with a quilted construction to increase surface area; this allowed absorption ofoxygen and organic matter that were dissolved in the water to diffuse through the body wall; ifthis is true, Ediacara animals did not have a mouth, digestive system, or respiratory organs

XII. Paleozoic Plate Tectonics and Paleogeography

A. The Proterozoic-Cambrian Transition- in the late Proterozoic the continents may have been sutured together to form a hugesupercontinent- during the Late Proterozoic and Early Cambrian most of the Earth's cratons were exposed abovesealevel (with only a few shallow-water limestones at their margins)

B. Cambrian- by late Cambrian time Gondwana and three smaller landmasses existed, with major portions ofthe continents at low latitudes- Cambrian with progressive flooding of continents by marine transgressions, with land-derivedterrigenous sediments surrounded by shallow-water carbonates and deeper marine deposits

C. Ordovician- Gondwanaland was situated over the South Pole, with accumulation of large glaciers (and witha drop in global sealevel, cooling of seas, and a major extinction event at the end of theOrdovician)- Laurentia and Baltica were situated closer to the Paleoequator, with accumulation of limestonedeposits (similar to those seen today in the Bahamas)

Taconic Orogeny - Ordovician mountain-building event in eastern North America due to thesuturing of Laurentia with several large islands; this resulted in a shift from carbonate depositionto deep marine ("flysch" or turbidite) deposition along a subduction zone that was created by thisconvergence; the suturing of these "exotic terranes" resulted in the introduction of "foreign" lateCambrian-early Ordovician fossils into eastern North America

- in western Laurentia there was a passive margin from Cambrian through Ordovician time (withaccumulation of thick clastic and carbonate rock sequences; an example is the Burgess Shale ofBritish Columbia, Canada (famous for it's fossils - see below)

D. Silurian- Taconic Orogeny subsides, where erosion of the eastern mountains produced clastic (and later


carbonate) deposits; in the Michigan Basin region large coral-strome reefs dotted shallowepicontinental seas (and was surrounded by large barrier reefs); by Late Silurian times restrictedflow in the basin led to accumulation of huge amounts of evaporite minerals

Acadian Orogeny - Laurentia collides with Baltica (to the north) and the microcontinentAvalonia in the south; began in the north during Mid-Silurian time and extended down throughthe eastern United States (to form the Carolina Terrane)

E. Devonian- Gondwanaland is formed, with a large portion of it situated over the South Pole- Laurentia and Baltica converge by the Late Devonian and form highlands between them;sediments were shed off the mountains to form the Catskill Clastic Wedge (ranging from non-marine redbeds, through braided and meandering streams to coastal deltas); there was a mud-floored seaway to the west of the coastal mountains with limestones, reefs and evaporites beyond- an island arc developed along the western margin of Laurentia, which later collided with thecontinental margin (to produce the Antler Orogeny); this was the first important episode ofmountain-building during the Phaneozoic in western North America- sealevel declined in the late Devonian

F. Mississippian (Early Carboniferous)- continents were tightly clusered- sealevel rose, with warm shallow seas spread across broad continental regions within lowlatitudes; many limestones were formed

G. Pennsylvanian (Late Carboniferous)- Gondwanaland moves northward to collide with Euramerica; this creates a mountain range insouthern Europe (the Hercynides) and northwestern Africa (this is called the Hercynian orVariscan Orogeny) and in North America (the Alleghenian Orogeny, which is in effect acontinuation of the Acadian Orogeny)- the Alleghenian Orogeny created the Appalachian Mountains, with mountain-building alsoextending from Mississippi through Oklahoma and Texas to create the Ouachita Mountains,Wichita Mountains, Amarillo Mountains and Marathon Uplift; it also resulted in the formation ofthe Midland and Delaware Basins in western Texas and New Mexico- in the southwestern U. S. the region became transformed into a series of uplifts and basinsbounded by faults; examples include the Front Range and Uncompahre Uplifts (often referred toas the "Ancestral Rocky Mountains"), and the Paradox Basin to the west (which is filled withevaporites, due to the rain-shadow influence of the "Ancestral Rockies")- the formation of Pangaea transforms climate, with cooler conditions resulting in the greatest iceage of Phanerozoic time- there were extreme temperature differences between the poles (where continental glacierspushed within 30 degrees of the equator on Gondwanaland) and the subtropics (where coalswamps flourished in North America and western Europe, resulting in the most important coalresources in the Northern Hemisphere; these coal deposits were formed within cyclothems(repetitive sedimentary cycles associated with deltas)


H. Permian- Siberia sutured to eastern Europe, nearly completing the assembly of Pangaea (southeast Asiawas the only landmass not included, which would become attached in the Early Mesozoic)- suturing created numerous mountain ranges; the result of this mountain-building and the factthat much of Pangaea was far from moisture-providing oceans led to dry conditions with theformation of huge dune deposits, extensive red-beds, and evaporites- the huge Capitan Reef (centered in the Guadalupe Mountains region of west Texas and NewMexico) grew upward in the shallow seas of the Delaware Basin; the Midland Basin to the eastbecame infilled with sediment; eventually the Delaware Basin became restricted, resulting in thedeposition of thick evaporite deposits (including the economically-important potash mines nearCarlsbad, New Mexico)- the drying Permian climate resulted in diminishing coal deposits (except in China andAustralia, which has large Permian coal reserves)- from Late Permian through Early Triassic time, an orogenic episode centered around Nevada(the Sonoma Orogeny), with active volcanoes in the island arc area around California

XIII. Life of the Paleozoic

A. The Tommotian Fauna- often classified as the base of the Cambrian- first fossils of the "Cambrian Explosion"; first abundant record of hard parts, with thousands oftaxa represented- the Tommotian Fauna includes "small shelly fossils", or tommotiids, that consisted of distinctchain mail-like sclerites of calcium carbonate or calcium phosphate that evidently articulated toform an exoskeleton; there are also mollusc-like shells, sponge spicules, soft corals(?),fragmentary arthropods, sponge-like archaeocyathans, and shells of brachiopods and brachiopod-like animals

B. The Causes of Metazoan Diversification (the "Cambrian Explosion")

1. Environmental Factors

- end of late Precambrian (Varanginian) glaciation

- development of extensive continental shelf areas and epicontinental seas

- Oxygen increases to 6-10% of present atmospheric levels; development of the ozone layerallows organisms to leave restricted environments

2. Biological Factors

- microorganisms increase in number and therefore with increase in filter-feeders

- organisms create habitats for other organisms


- secretion of skeletons- development of hard skeletons of organic or biomineralized (silica, carbonate, phosphatic)materials- skeletons were useful for protection, support above the substrate, muscle attachment, guides forfeeding currents, and as supplies of calcium and phosphate nutrients- calcium carbonate skeletons could not be secreted until oxygen reached approximately 10% ofmodern levels (about 2% total atmospheric gases)

C. Development of the First Reefs- reefs originate in Early Cambrian (dominated by the sponge-like archaeocyathids andcyanobacteria-formed stromatolites)- at the end of the Cambrian almost all archaeocyathids became extinct

D. Chengjiang Fauna- The Chengjiang Fauna (approx. 525-520 Ma) is found in the middle portion of the EarlyCambrian in Yunnan, China- contains many well-preserved remains of soft-bodied organisms including jellyfish and othercnidarians, segmented and priapulid worms, arthropods (including the fearsome 6 foot-longcarnivorous Anomalocarids), as well as the earliest fishes

E. The Middle Cambrian Burgess Shale Fauna (ca. 515 Ma)- Burgess Shale of British Columbia, Canada is dominated by arthropods and several phyla of"worms", but also many weird forms with no living kin

F. The Late Cambrian Extinction- there are three periods of trilobite mass extinction in Late Cambrian- these were probably due to cooling periods

G. The Ordovician Adaptive Radiaton- all major modern phyla are present by the end of the Ordovician

1. The Ordovician Biota

a. The Ordovician Benthos- stromatolites (algal structures) decline due to marine herbivores- trilobites suffered a major extinction at the end of the Cambrian, but became the most abundantmarine invertebrates of the Early Ordovician- articulate brachiopods, rugose corals (especially horn corals), tabulate corals andstromatoporoid sponges form calcite reefs (Coral-Strome Reefs)

b. Ordovician Plankton and Nekton- graptolites became major components of the Ordovician zooplankton- huge, straight-shelled nautaloid cephalopods, some over 10 feet long, become the top predatorsof Ordovician Seas


2. The Ordovician Ecosystem becomes "Filled"- "ecological crowding", where all the marine niches become filled, prevented furtherevolutionary diversification near the end of the Ordovician and the number of species "levelledoff"

3. Mass Extinctions at the End of the Ordovician- oxygen isotopes indicate a major cooling period (glaciation) and extinction lasting from 0.5 to 1million years at the end of the Ordovician- Gondwanaland was over the South Pole, and carbon isotopes also indicate a decrease ingreenhouse gases- two pulses of extinction occurred; the first event killed off tropical species as the seas cooled;this was followed by a second event, where cool-water species that took over the seas was killedby a warming event

H. Life of the Silurian and Devonian

1. Reef Communities- Coral-Strome Reefs diversified, and some became much larger than their Cambrian-Ordoviciancounterparts- Reef communities were formed in the same types of habitats, and exhibited similar ecologicevolution (Ecological Succession) as their modern analogues

2. New Swimming Carnivores Evolve

a. Ammonoids- coiled cephalopod molluscs diversified rapidly within marine environments

b. Eurypterids- scorpion-like large predators that inhabited brackish and freshwater environments

c. Huge Fish Evolve- placoderms were the top vertebrate predators of the Devonian (see discussion below)

3. Late Devonian Extinction

a. Glaciation- tillites show that glaciers were widespread over southern Gondwanaland- the cooling may have been caused by the great expansion of forest ecosystems in the Devonian;these may have depleted carbon dioxide in the atmosphere, causing cooler temperatures

b. Extinction of the Coral-Strome Reefs- most reef-building organisms die out at the end of the Devonian (tabulate corals andstromatoporoid sponges will never again be important reef-formers)


c. Extinction of Land Plants- the Late Devonian also had extensive extinction among land plants

I. Late Paleozoic Marine Ecosystems

1. Shift in Reef Ecosystems- marine ecosystems were very much like those seen in the Late Devonian, butMagnesium/Calcium ratios rose early in the Carboniferous, with "Aragonite Seas" replacing"Calcite Seas"- the shift in ocean chemistry saw the replacement of the old "Coral-Strome Reefs" with reefsconsisting mostly of aragonite-secreting algae and fusulinid foraminiferans; sponges witharagonite skeletons became imporant Permian reef-builders

2. Life on the Carbonate Sea Floor- crinoids ("sea lilies") and lacy bryozoans became very important during the earlyCarboniferous, extending and filter-feeding above the muddy carbonate seafloor

3. Switch of Top Predators- the heavy placoderm fishes and huge nautiloid cephalopods were replaced by more mobileammonoid cephalopods, sharks and ray-finned fishes

J. Chordates

1. Characteristics- possess a notochord, a dorsal hollow nerve cord with a shared developmental pattern, anendostyle organ (equivalent to the thyroid gland of vertebrates), and a tail for swimming (a tail isa distinct region developed behind the anus)

2. Origin of the Chordates- chordates may have been derived from hemichordates (both have ciliated gill slits and giantnerve cells not seen in echinoderms) or another similar echinoderm group OR fromcalcichordates (based on interpretation of fossils; calcichordates were a strange echinoderm-likegroup with an exoskeleton composed of large plates and had a stem- or tail-like structure)

K. The Vertebrates

1. Characteristics of Vertebrates- bilaterally symmetrical, usually with a fusiform ("streamlined") shape- tendency to concentrate sensory organs on the anterior ("front" or “head”) end; a skull is presentwhich articulates with the vertebral column- a notochord is present (a long, rod-shaped anti-telescoping structure below the nerve tube)- vertebrates have a skeletal system made of cartilage (flexible material capable of growth) orbone (strong material made of irregular, branching cell spaces); the skeleton consists of an AxialSkeleton (the "backbone") and Appendicular Skeleton (consisting of limb girdles, unpaired fins[the dorsal, anal, and caudal (tail) fins], and paired fins (the pectoral fins are in front, pelvic fins


behind)

2. The Record of the earliest Vertebrates

a. Middle Early Cambrian (525-520 Ma)- the Chengjiang Fossil Site, Yunnan Province, southwest China has mostly arthropods but alsothe first fishes

b. Late Cambrian Vertebrates- conodonts (eel-like animals) were the earliest vertebrates with hard tissues (consisting of tooth-like structures)- another group of vertebrates is indicated by isolated pieces of dermal armor from Wyoming andGreenland (this dermal armor is made from apatite, which is characteristic of vertebrates)

3. Agnathans- jawless vertebrates; paired fins are absent or poorly developed

The Major Types of Paleozoic Agnathans are:

a. Pteraspidomorphs- include a couple of poorly-known Ordovician groups represented by pieces of dermal armor,and the heterostracans

Heterostracans - Ordovician to Upper Devonian jawless fish with partially-developed headshields and with long, narrow oral ("mouth") plates for capturing prey; these are the earliestundisputed vertebrates

b. Cephalaspidomorphs- include the Osteostracans, and a couple of other lesser-known Paleozoic jawless fish

Osteostracans (include the Cephalaspids) are the most common cephalaspidomorphs; UpperSilurian to Upper Devonian; usually small fish with an undivided bony shield which extendeddown the body; the head was dorsoventrally compressed; the eyes were dorsally-placed and withdorsal and lateral fields ("electric" or pressure-sensitive "sensory" organs?) on top of the head;they are believed to have been bottom dwellers and "mud grubbers"

4. Evolution of Jaws and Fins

a. Origin of Jaws- Older theories state that jaws may have been derived from gill arch supports (but embryologicalstudies indicate some problems with this theory)- Modern embryological studies indicate that once bones around eyes are formed, a series ofconnector genes may have begun making a lower jaw cartilage, perhaps to strengthen the existingmouthparts


b. Origin of Paired Fins

Fin-Spine Theory – the theory that the primitive fin developed around a movable spine

Fin-fold Theory – the theory that fins originated as lateral folds along the body walls; pectoraland pelvic fins originated by subdivision of this fold; this is the most widely accepted theory butfin origins may be a combination of "fin spines" and "fin folds"

5. Placoderms- typically dorsoventrally compressed Devonian- to Mississippian-age fish with head and trunkshields (in advanced types the shields were connected by a ball-and-socket articulation)- placoderms include the large carnivorous Arthrodires and the "arthropod-like" mud-grubbingAntiarchs

6. Acanthodians- small fusiform fish from the Ordovician through Lower Permian; all fins except caudal withspines on anterior edge; upper lobe of tail larger than lower lobe (heterocercal tail)

7. Chondrichthyans- sharklike fishes- sharks have cartilaginous skeletons; the skin is covered with dermal denticles including placoidscales, teeth, claspers and fin spines

Major Types of Paleozoic Sharks include:

a. Symmoriids- best known Paleozoic sharks (Devonian – Pennsylvanian); with multicusped teeth, a short blunt"snout"; some species had wierd dorsal fin brushes (for sexual display?)

b. Eugeneodonts (Edestid and Helicoprionid Sharks)- Upper Devonian to Triassic sharks in which the front teeth tended to form strange whorl-shaped cutting devices; the rear teeth usually formed crushing surfaces

c. Xenacanths (pleuracanths)- primarily freshwater sharks from the Upper Devonian to Upper Triassic; they had a straight(diphycercal) tail and the teeth usually had two or three pointed cusps

8. Actinopterygians- bony fish (Osteichthyes) that differ from sarcopterygians in the presence of fin rays (bony, rod-like fin supports)- found in both freshwater and marine environments from the Devonian to Recent- possibly originated from the acanthodians- major evolutionary changes in the skeleton of ray-finned fish include a change in tail (caudal)fin morphology from an asymmetrical (heterocercal) to symmetrical (homocercal) tail and a shiftin the position of the paired fins where the pelvic fins move forward and the pectoral fins shift to


a higher position on the lateral body wall (this is good for intricate manuevering)- in primitive ray-finned fish the skull bones are oriented obliquely, with many skull bonespresent; the major tooth-bearing bone was the maxilla; primitive ray-finned fish were "biters"- in more derived fish the jaw becomes more nearly vertical, there are fewer skull bones, and theanterior-most bone in the upper jaw (the premaxilla) becomes hinged and is pushed forward bythe now-toothless maxilla (this allows the jaws to open wide, and open fast to consume largerprey and for “suction feeding”)

9. Sarcopterygian Fishes- bony fish (Osteichthyes) with fleshy lobe fins and cosmoid scales (these scales have sensorycanal systems withing them)

Types of Sarcopterygian Fish Include:

a. Dipnoans- the lungfish are Devonian to Recent lobe-finned fish in which the teeth typically form crushingtoothplates; the tails are typically straight (diphycercal)- modern species of lungfish are found in freshwater but extinct types inhabited a wide variety ofenvironments- lungfish burrows (for aestivation during dry seasons, where they can survive in a semi-inanimate state) are found from the Devonian to Recent

b. Coelacanths- coelacanths are predominantly predatory fish whose fossils are found in Devonian throughCretaceous-age rocks, where they lived in both marine and freshwater environments; there is nowonly 2 living coelacanth species known (both are marine)

c. Osteolepiforms ("Rhipidistians", in part)- important fish since they (or a closely related group) gave rise to the amphibians- osteolepiforms are large, voracious fish that lived from the Middle Devonian to Lower Permian- the skull bones of osteolepiforms are largely homologous to those of primitive tetrapods; theyalso had labyrinthodont teeth (with infolded plicidentine) and had a similar limb and vertebralstructure to early amphibians

L. Land Plants (Kingdom Plantae)

- evolved from the Chlorophyta (grass-green algae)- possibly represented by plant tissue and spores in Mid- to Late Ordovician (probably lived onlyin moist habitats at that time)- began to become abundant during the Devonian

1. Subkingdom Tracheophyta- vascular plants [with conducting cells (xylem and phloem) for transporting water andnutrients]; usually possess roots, stems and leaves


The most important divisions are:

a. Division Rhyniophyta (Rhyniopsida) and Psilopsida (Psilophyta)- oldest-known vascular plants (Middle Silurian); the best fossils are from the Rhynie Chert(Lower Devonian, Scotland)- no leaves or roots (therefore with photosynthesis occurring in the outer cells of the stem); withstems capped by spore-bearing cases

b. Division Lycophyta (Lycopodophyta, Lycopsida)- includes the modern club mosses and quillworts; also include the arborescent (tree-like)lycopods that dominated the Carboniferous coal swamps- the leaves were often strap-like; there were also leaves present in pits on the trunk;- Examples = Lepidodendron, Lepidophloios, Sigillaria (stems/trunks), Stigmaria (roots),Lepidophylloides (leaves)

c. Division Sphenophyta (Sphenopsida)- include the modern horsetails and several extinct groups (Devonian- Recent)- with scale-like, small leaves arranged in whorls around an above-ground, bamboo-like jointedphotosynthetic stem- are typically found in swamps, moist woodlands, and along lake edges- common fossils include Calamites (a Pennsylvanian-age arborescent sphenopsid; somemembers were up to 15 meters or more in height) and Annularia (leaf whorls)

d. Division Filicinophyta (Filicopsida, Pteridophyta)- include ferns and their allies (Upper Devonian - Recent)- immature fronds unroll (circinate) in most members; usually the leaves are pinnately compound(the leaves are opposite one another) with spore cases on the leaf undersides- Tree ferns were large, arborescent ferns (Mississippian - Permian) found in coals swamps (Exs.= Psaronius, Pecopteris)- arborescent lycopods, sphenopsids and tree ferns became extinct when the Late Paleozoic coalswamp environment declined, probably due to climate changes resulting from the formation ofPangaea

e. "Gymnosperms"- probably not a "natural" classification group-"modern" cone-bearing types and glossopterids spread in Permian (probably due to greaterseasonality/aridity)- gymnosperms (and angiosperms) are characterized by seeds; typically formed by fusion of eggand sperm nuclei; then develop into ripened ovules (= seeds)- gymnosperms have no flowers and seeds are not fully enclosed (gymnosperm means "nakedseed")- the Pteridosperms, or "Seed Ferns" (Devonian – Jurassic) had fern-like compound leaves butgymnosperm-like seeds and wood; examples include Alethopteris, Neuropteris, and possiblyGlossopteris


M. Land Invertebrates- earliest fossilized land animals were arthropods

1. Late Silurian (approx. 415 Ma)- the oldest undisputed arthropods are centipedes and millipedes

2. Middle Devonian of Gilboa, New York (approx. 380-375 Ma)- represent soil- and leaf litter-dwellers- most common are spider-like trigonotarbids; also earliest true spiders, oldest terrestrial(?)scorpions, fungus- and worm-eating mites, first insects (flightless bristletails)

3. Pennsylvanian (approximately 315 Ma)- with abundant flying insects and first evidence of insects that ate living vascular plants(indicated by mouthparts and gut contents)

N. Evolution of Land Vertebrates

Tetrapods = "four-footed" vertebrates

1. Origin of the Tetrapods- may have left aquatic environments due to low oxygen content in the water, populationpressures (seeking food, competition for space, breeding sites, and to escape from predators oregg-eaters)

2. "Amphibians"- the earliest tetrapods (four-footed creatures) are from Upper Devonian rocks

Types of Paleozoic "Amphibians" include:

a. Ichthyostegids- earliest tetrapods but not ancestral to other groups; Upper Devonian to Lower Mississippian- some of the early tetrapods have as many as 8 toes (Ichthyostega had 7) that were developedinto paddle-like appendages; ichthyostegids were probably largely aquatic and could not fullysupport their weight on land

b. "Temnospondyls"- Mississippian- to Cretaceous-age labyrinthodont amphibians that evolved from osteolepiformfishes; primitive features inherited from these fish include labyrinthine infolding of dentine,palatal fanged teeth, vertebrae composed of several centra elements- often with large, flat heads; examples include the aquatic eryopoids and trimerorhacids; theterrestrial, armored dissorophids and the metoposaurs (large-skulled aquatic amphibians)]

c. Lepospondyls- usually small, Mississippian to Permian-age amphibians; may have evolved from earlylabyrinthodonts (but with no labyrinthine infolding, no palatal fangs and pits, and no otic notch at


the back of the skull)- characterized by lepospondylous vertebrae (spool-shaped bony cylinder surrounding thenotochord)- includes the snake-like aistopods and lysorophids, the eel-like nectridians [Diplocaulus andDiploceraspis had “boomerang-heads”], and the lizard-like terrestrial "microsaurs"

d. Seymouriamorphs- have a combination of reptile and amphibian features, and gave rise to reptiles

O. Reptiles

1. Characters of Reptiles:

a. Development of amniote egg- has a large yolk, a shell, and extraembryonic membranes which protect the egg, supplynourishment and for gas exchange

Amniotes - probably a monophyletic group; probably originated in the Mississippian

b. Changes in the Skull- lose several bones in the skull; decrease the size of the bones in the back of the skull, andlengthen the ones in front

c. Changes in the Skeleton- develop a more efficient and flexible vertebral column, and an improved limb and anklestructure

2. Reptile Classification and Radiation

- often based on patterns of openings of the skull roof (termed temporal openings), whichdeveloped behind the orbits

a. Anapsid condition- no temporal opening; Exs. = captorhinids, turtles

b. Synapsid condition- lower opening with postorbital and squamosal meeting above; Ex. = mammal-like reptiles

c. Diapsid condition- two temporal openings present; Exs. = dinosaurs, pterosaurs and ancestral condition of allmodern reptiles except turtles

d. Euryapsid (Parapsid) condition- upper opening with postorbital and squamosal meeting below; Exs. = plesiosaurs, ichthyosaurs- derived from the diapsid condition through loss of the lower temporal fenestra


3. Important Paleozoic "Reptile" Groups

a. The Anapsids- most primitive forms which are unquestionably reptilian; consists of small lizard-like"parareptiles" (such as the captorhinids and procolophonids) and the large Permian-age knobby-skulled herbivorous pareiasaurs

b. Mesosaurs- aquatic parareptiles of Permian age from Africa and South America; probably restricted to onelimited ocean basin and was used as evidence of continental drift- up to one meter long, slender; with long, laterally-compressed tail and neck and paddle-likefeet; the marginal teeth were long and slender (for straining microplankton?)

c. Synapsids- early synapsids had a single, lower lateral temporal opening- they have often been termed "mammal-like reptiles", but synapsids are now typically consideredto be a group distinct from "true reptiles"; the Synapsida often includes pelycosaurs, therapsids,and true mammals

c1. Pelycosaurs- Pennsylvanian-Permian synapsids- important Paleozoic groups include the Sphenacodonts (highly predaceous forms such asDimetrodon; many with elongate neural spines forming "sails"), and the Edaphosaurs(herbivores; usually with elongate neural spines with crossbars)

c2. Therapsids- therapsid jaw structure was improved over the pelycosaurs, with reduction of canine teeth toone per jaw half; the skeleton had improved locomotion versus earlier "reptiles"- Therapsids include the Dinocephalians (very large Permian carnivores and herbivores);Anomodonts (Permian to Triassic; herbivorous; most successful mammal-like reptiles; includethe tusked dicynodonts); Cynodonts (Permian to Jurassic; advanced mammal-like reptilesrepresenting transitional stages in the development of mammalian characteristics)

P. The Late Paleozoic (Permian) Extinction Events

1. The Middle Permian (Guadalupian) Extinction Event- at about 7 to 8 million years before the end of the Permian, a mass extinction killed about 70percent of all marine species- the reef communities were destroyed, and three-fourths of the genera of fusulinidforaminiferans became extinct- sedimentary evidence indicates that anoxic (oxygen-poor) waters from the Permian "stratifiedseas" began to ascend upon the Middle Permian marine shelves, with devastating results

2. The End-Permian Extinction Event


- this was the greatest Phanerozoic extinction event, with some 80 to 85 percent of all speciesbecoming extinct- all of the tabulate corals and trilobites became extinct, and only a few ammonoids, crinoids andbryozoans survived the extinction event- terrestrial forests were replaced by patches of small, non-woody lycopods; the huge numbers offungal remains in shallow marine environments indicate that fungi flourished due to the deathand decay of the forests- the End-Permian extinction was the first major extinction of terrestrial animals, with mostfamilies of therapsids becoming extinct- Permian extinctions may have been caused by upwelling anoxic waters onto the continentalshelves (such as in the Guadalupian Event), by stratification of the Permian Seas (which wouldlead to stagnation of deep-ocean waters, as well as to dramatic warming and drying of climates),by the formation of Pangaea (which led to less marine shelf area for organisms, and more aridityin the continental interiors), or from volcanism [huge volcanic deposits in China match the dateof the Guadalupian Event; the "Siberian Traps" of northeast Asia match the date of the End-Permian Event; carbon dioxide from the volcanism caused by this single, moving mantleplume/hotspot would increase global warming and may have triggered the melting of methanehydrates on the ocean floor, with an enhanced greenhouse effect)

XIV. Mesozoic Plate Tectonics and Paleogeography

A. Early Triassic- all land masses become united as the supercontinent Pangaea- sea level rose slightly, but most landmasses were above sealevel- during the Early and Middle Triassic, erosion subdued the Appalachian Mountains (which werelocated near the center of Pangaea)

B. Late Triassic - Jurassic

1. The Breakup of Pangaea- the Tethys Seaway (situated around the paleoequator in the Mediterranean region) began tolengthen due to rifting between southern Europe and Africa; this rifting spread westward toultimately separate North and South America- North America began to rift from Africa in the Middle Jurassic, forming a series of triplejunctions- the Atlantic Ocean began to form, dividing Pangaea into a series of basins throughout easternNorth America (the Newark Supergroup); these rift basins contained a series of large lakes andwith mafic magmas intruding the fault block basins (basaltic sills from the Palisades, along theHudson River near New York City, represent a part of this rift system)

2. Formation of the Gulf of Mexico- the Gulf of Mexico began forming during the Middle and Late Jurassic; the initial riftingformed an evaporite basin within which great thicknesses of evaporites (Ex. = Louann Salt, GulfCoast of Texas) were precipitated; because of their low density, these salts have moved up


through younger-aged sediments as salt domes (diapirs), which are associated with the greatpetroleum reservoirs and sulfur deposits of the Gulf Coast

3. Jurassic Paleogeography- there was a general rise in sealevel through the Middle and Late Jurassic- there was a southern, tropical province (the Tethyan Realm; with warm-adapted molluscs, coralreefs, and with the production of carbonates) and the Boreal Realm (to the north, with cooler-adapted species)

4. Tectonism in Western North America

a. Paleozoic - Triassic Tectonism and Sedimentation- after the Late Paleozoic Antler Orogeny, the Golconda Arc sutured onto the Pacific coast ofNorth America (the Sonoma Orogeny), adding a series of terranes (Sonomia) in the region ofsoutheastern Oregon and northern California and Nevada- in Middle Triassic time a subduction zone extended from Alaska to Chile, creating a series ofAndes-type mountains; subduction of the oceanic plate beneath North America created extensiveintrusions (such as the Jurassic-age intrusives of the Sierra Nevada range of California); thesubduction zone is indicated by deposition of the Franciscan Sequence of California (consistingof a series of turbidite deposits and accretionary wedges); this tectonic event is termed theNevadan Orogeny- western North America had primarily non-marine deposition through most of the Triassic;climate was primarily arid, although at certain times there was enough moisture for the growth oflarge forests (an example is at Petrified Forest in Arizona, with the spectacular "Painted Desert"redbeds representing ancient soil zones deposited in seasonally wet-dry climates)

b. Jurassic Tectonism and Sedimentation- during the Jurassic a large exotic terrane (consisting of a composite block of several smallerterranes) collided in the region of Washington to southern Alaska, substantially adding to thenorthwestern North American Craton- sealevel rose in a series of four transgressions in the Middle and Late Jurassic, eventuallyforming the Sundance Sea (centered around Wyoming, and extending into the surroundingstates); this marine basin was created because the eastward thrusting and folding due to westcoast tectonism formed a large foreland basin- great volumes of sediment were shed from the fold-and-thrust belt towards the east, eventuallyfilling in much of the Sundance Sea by Late Jurassic times; this created a series of river, lake andswamp deposits representing the Morrison Formation (famous for the presence of largedinosaurs, such as at Dinosaur National Monument in Utah)- during the Jurassic a couple of periods of aridity are indicated, represented by ancient sand dunedeposits of the Wingate Sandstone and Navajo Sandstone

C. Cretaceous Tectonism and Paleoclimate

1. Plate Tectonics


- by Late Cretaceous time, Gondwanaland rifted to form South America, Africa and India(Antarctica and Australia remained connected to one another); the separation of continentscaused the oceans to widen

2. Cretaceous Ocean Circulation and Sedimentation- global sealevel rose due to the expansion of the total volume of mid-oceanic ridges and mantleplumes (sealevel was as high as any time during the Phanerozoic, depositing large volumes ofsediment on the continental cratons - in North America this is termed the Zuni Sequence)- the Tethys Seaway was a dominant feature of the Cretaceous, along which were prominentcarbonate banks and rudist bivalve reefs- during the Middle Cretaceous anoxic waters accumulated within deeper ocean waters(indicating poor vertical circulation within the warm seas); this resulted in accumulation oforganic-rich muds to form black shales- warm temperatures spread to higher latitudes by Middle Cretaceous time (as indicated by thepresence of fossils of warm-adapted plants in northern Alaska, Greenland and Antarctica;dinosaurs lived within about 15 degrees of the Cretaceous South Pole); this is possibly due toupwelling of hypersaline warm waters around the poles- oxygen isotope data indicates a decline in oceanic temperatures during the Late Cretaceous;ocean circulation changed, wherein cool, high-latitude waters sank into the deep ocean (theGlobal Conveyer Belt Model), bringing oxygen with them (and therefore with a decline in theamount of black shales seen in latest Cretaceous marine deposits); reef-forming rudist bivalvesbecame extinct

XV. Mesozoic Life

A. Marine Invertebrates

1. Triassic-Jurassic Marine Invertebrates

a. Benthos- molluscs (bivalves, gastropods), sea urchins and scleractinian corals (hexacorals) becomeabundant- by latest Triassic and Early Jurassic time hexacorals form large reefs

b. Phytoplankton- microscopic photosynthetic "plants" floating near the Ocean's surface became very important- include dinoflagellates and coccolith "algae" (calcareous nannoplankton), which are autotrophicorganisms that formed the base of the food chain

c. Large Nektonic Predators- especially cephalopods such as ammonites (with coiled shells, that constitute important indexfossils throughout the Permian and Mesozoic) and the cigar-shaped squid-like belemnites

d. Two periods of extinction occurred during the Triassic


- dinosaurs became the dominant reptile group after the first, or "end-Carnian Extinction Event"during the Upper Triassic- about half of all marine animals became extinct during the End-Triassic extinction event (all ofthe conodonts and the placodont reptiles became extinct, and most species of bivalves,ammonoids, plesiosaurs and icthyosaurs became extinct)- on land, most species of seed plants became extinct (the ferns briefly underwent an abruptexpansion at this time)- almost all of the therapsids became extinct; dinosaurs survived the extinction event, andunderwent an adaptive radiation in the Jurassic- the extinction was probably due to a sudden period of greenhouse warming at theTriassic/Jurassic boundary, probably due to the intense volcanism associated with the breakup ofPangaea

2. Cretaceous Invertebrates

- there was a combination of "modern" and "ancient" forms

a. Plankton- "modern" dinoflagellates, diatoms; coccoliths (calcareous nannoplankton) and planktonicforaminiferans form extensive chalks (Exs. = Austin Chalk of Texas; Chalk Cliffs of Dover,England)

b. Nekton- ammonoids are very important index fossils; many forms had complex suture patterns and witha great diversity of shell morphology

c. Benthos- "modern" groups of foraminiferans, bryozoans, bivalves, gastropods, crabs; rudist bivalvesdominate reef environments; brachiopods and stalked crinoids decline

B. Marine Vertebrates

1. Mesozoic Fishes

a. Teleost Ray-Finned Fishes- ray-finned fish develop better jaws and evolve swim bladders; Teleost ray-finned fish firstappear during the Late Mesozoic (these "modern" fish have symmetrical tails, round and thinscales, specialized paired fins, and short jaws that can open wide and fast for "suction feeding")

b. Chondrichthyans- sharks (especially the shell-crushing hybodonts) are abundant

2. Marine Reptiles become Top Predators

a. Turtles


- develop shells; most vertebrae and ribs are fused to shell; limbs and limb girdles modified forsprawling posture- anapsid skull; teeth rudimentary or absent- during the Cretaceous marine turtles grew to huge proportions

b. Ichthyosaurs- Dolphin-, tuna- and shark-like neodiapsid reptiles of the Mesozoic- skull highly modified for aquatic life, with a euryapsid skull pattern- tendency through time to develop a hypocercal tail (with the vertebral column bending into thelower lobe of the tail fin); limbs reduced to steering paddles- reproduction probably took place in water and with live birth (some females have skeletons ofyoung ichthyosaurs inside them)

c. Sauropterygians- lepidosauromorph neodiapsids that include the nothosaurs, pachypleurosaurs, plesiosaurs, andpossibly the placodonts; aquatic reptiles with euryapsid temporal openings

- Nothosaurs (Triassic; the limbs of nothosaurs were relatively normal) and Plesiosaurs (Jurassic-Cretaceous; plesiosaurs developed paddles by adding toe joints; their nostrils migrated far backon the skull; the ventral ribs formed a basket-like structure; the ventral portion of the limb girdleswere expanded into plate-like structures)

- Placodonts were wierd Triassic, aquatic mollusc-eating neodiapsids (but with euryapsidtemporal opening); most with "pavement teeth"; placodonts were kin to the "Sauroptergyia" andare now often placed within that group

d. Crocodilians- crocodiles, alligators and their relatives; belong to the archosaurs (see discussion below)- Skull elongate, flattened, massive; evolutionary trend in posterior extension of the palatal bonesto form a secondary palate (for aquatic mode of life or to support the elongate snout?)- with dermal armor; with a semi-improved gait [hind legs longer than front legs; improvedankle joint]- some Mesozoic crocodilians were fully marine in their habits

C. Important Land Plants of the Mesozoic

1. "Gymnosperms"

a. Conifers- include pines, spruces, firs, hemlocks, junipers, cypresses, redwoods; Triassic-Recent- woody trees and shrubs with needlelike or scalelike leaves; most are evergreens (shed leavesthroughout year but retain enough of them to distinguish them from deciduous trees); conifershave Cones (cone-shaped clusters of modified leaves that house the reproductive organs); seedsdevelop on the shelf-like scales of the female cones


b. Cycads and Cycadeoids- cycads (Permian-Recent) and cycadeoids (Triassic-Cretaceous) are often difficult to distinguishas fossils (both often form shrubby or tree-like plants with pinnate, strap-like, palm-like leavesand similar wood)

2. Angiosperms- flowering plants (Triassic??; Cretaceous- Recent); include the majority of recent plants- with pollen-producing flowers (flowers developed from modified leaves); the wind-carried orinsect-borne pollen lands on the stigma (the end portion of the female element); the pollen tubegrows to the ovules for the transport of sperm; one portion of the sperm fertilizes the egg andanother portion unites with a second portion of the ovule (which generally forms a structurewhich provides nutrients for the growing embryo; this is termed "double fertilization"); a seeddevelops that is totally encased inside a fruit- angiosperms became the dominant land plants in the Late Cretaceous (they are rapid colonizers)

D. "Lissamphibians" Evolve in the Mesozoic- include frogs and toads (Triassic-Recent), the long-bodied aquatic salamanders (Jurassic-Recent) and the worm-like caecilians (Jurassic-Recent)

Frogs and Toads - greatly derived (most features are related to jumping): only 5 to 9 trunkvertebrae; no ribs; pelvis modified for jumping; long legs with arm and lower leg bones fused;skull forms "open" structure

E. Diapsids become the Dominant Land Vertebrates- diapsids have two temporal openings; includes all modern reptile groups except turtles; alsoinclude dinosaurs, pterosaurs, plesiosaurs and several other ancient groups

1. Lepidosauromorphs- include sphenodontids, lizards, snakes, and the extinct aquatic placodonts, nothosaurs, andplesiosaurs- differentiated from archosauromorphs by retention of sprawling posture

- Sphenodontids, represented today by the Tuatara from New Zealand, were very common smalllizard-like reptiles during the Triassic and Jurassic

- Lizards (Triassic - Recent) have a tendency towards streptostyly (loosening of the skull to eatlarger prey)- Cretaceous marine lizards, especially the mosasaurs, became very important large predators inthe oceans

Snakes (Upper Cretaceous - Recent) have extreme streptostyly, their ancestors lost their limbsduring the Cretaceous

2. Primitive Archosauromorphs- most important structure uniting archosauromorphs is ankle and foot structure (related to


upright posture)

Most Important Groups of Primitive Archosauromorphs are:

a. Trilophosaurids- small to medium-sized, Triassic-age, lizard-like "herbivorous" reptiles (teeth typically withthree cusps); postcranial skeleton like primitive archosaurs; Ex. = Trilophosaurus

b. Rhynchosaurs- heavily-built Triassic herbivorous lepidosaurians; advanced types with upper jaw with broadcrushing toothplates and a parrot-like toothless beak

2. Archosaurs- the "ruling reptiles" including the dinosaurs, crocodiles, pterosaurs and many primitive groups(the thecodonts)- Skull with diapsid condition (two temporal openings) and may evolve one or more other skullopenings; there is a thecodont dentition (the teeth are placed in sockets)- skeleton with hind limb much better developed than the forelimb; tendency towards bipedalpose involves change in hip and femur (“thighbone”) structure

Important Early Mesozoic Archosaurs Include:

a. Rauisuchians ("Poposaurs")- large, fierce Middle and Upper Triassic carnivorous archosaurs (up to 6 meters long) with hugecarnivorous dinosaur-like skulls

b. Aetosaurs- relatively large herbivorous quadrupeds of Late Triassic age; body covered by armor plates

c. Phytosaurs- very abundant, crocodile-like, Upper Triassic thecodonts

3. Dinosaurs- dinosaurs originated in the Middle Triassic and became extinct at the end of the Cretaceous- Over 800 species of dinosaurs are known- limbs brought under the body and moved in a fore-and-aft direction [femur inturned; the pelvis"socket" (acetabulum) is wide-open (perforate); improved ankle joint; digits form the mainsurface that contacts the ground (digitigrade posture)]- dinosaurs became the dominant reptile group after the "end-Carnian Extinction Event" duringthe Upper Triassic, which cleared ecospace for the dinosaurs to take over

Types of Dinosaurs Include:

a. Saurischians- with a primitive "triradiate" pelvis structure; digits of hand and foot reduced; teeth occupied the


rims of the jaws; large openings reduced the weight of the skull- saurischians dominated during the early Mesozoic but were outnumbered by the ornithischiansduring the upper Mesozoic

- The most Important Saurischians are:

a1. Theropods- include all of the bipedal carnivorous dinosaurs (Late Triassic - Cretaceous)- neck is generally short; lower portion of hind limb is longer than the upper part; hands bearsharp claws and there are two or three fingers only; feet with three clawed toes (the fifth isalways reduced and the first or big toe is shortened and turned backwards)- include many groups such as the Ceratosaurs, Carnosaurs (spinosaurs and allosaurs),Coelurosaurs (including the ornithomimid "ostrich dinosaurs"), tyrannosaurids, anddeinonychosaurs ("raptors")]

a2. Sauropodomorphs- typically heavily built quadrupedal dinosaurs with small heads and long necks; most withpeglike teeth; Upper Triassic-Upper Cretaceous

- "Prosauropods" - small- to large-sized; possible ancestors of sauropods; carnivorous,herbivorous and perhaps omnivorous forms

- Sauropods were huge Jurassic/Cretaceous herbivores with quadrupedal pose, powerful limbs,long tail, long neck and small head; the jaws were short and weak with small peglike orspoonshaped teeth; the front legs were shorter than the hind legs; include the largest land animalsof all time (the Brachiosaurs)

b. Ornithischians- pubis points backward (bird-hipped); with single median bone at the tip of the lower jaw (thepredentary); jaw with beak, posterior to which is a grinding dention; most with concave cheekregion (therefore most with muscular cheeks); tendency for internal nostrils to be displacedposteriorly

The Groups of Ornithischians are:

b1. Ornithopods- had bird-like feet with blunt claws or hooves; examples include the Hypsilophodontids,Iguanodontids (Cretaceous) and Hadrosaurids ("duck-billed" dinosaurs)

b2. Pachycephalosaurs- small group of Late Cretaceous "bone-headed" dinosaurs (with unusually thick skull roofs,probably used for "butting contests" between males)

b3. Ceratopsians- small to large dinosaurs with skulls ranging from relatively large to gigantic, often with horns


and large shields of bone; snout beaklike; almost exclusively quadrupedal; one of the lastevolved (Cretaceous) and most abundant groups of dinosaurs

b4. Stegosaurs- Jurassic-Cretaceous armored quadrupedal ornithischians- relatively large; with small skull, front legs short; back arched high over long hind limbs; withseries of plates and spines arranged in a row down the neck, trunk and tail

b5. Ankylosaurs- Jurassic-Cretaceous stocky dinosaurs with short, broad feet; with extensive development ofbony, armored carapace, often with tail club

4. Were Dinosaurs Warm-Blooded?

- Evidence cited that dinosaurs were endotherms includes the following:

a. Erect posture- limbs held vertically (with metabolism like birds and mammals)

b. Bone structure- dinosaurs have haversian canal systems in their bones like those of mammals (indicates morerapid metabolic processes; but these seem to be present in large animals in general and are absentin small animals)- but dinosaurs did not have determinant growth and continued to increase in size throughout life(unlike birds and mammals)

c. Population Studies/ Community Structure- carnivorous dinosaur numbers (versus herbivores) are more like that of mammals than reptiles

d. Long-necked dinosaurs would have to have a more efficient heart in order to pump blood upto their brains

e. A few dinosaurs were at least as intelligent as birds

f. Dinosaurs show social behavior (such as herding and "nurseries") that is unknown amongother reptiles

g. Dinosaurs have been discovered in Mesozoic "polar regions"

h. Some dinosaur fossils have feathers

i. Growth Rates- reptiles grow slowly, dinosaurs grew quickly like birds and mammals

j. Oxygen Isotopes


- ratios are influenced by temperature; oxygen isotopes from dinosaur bones indicate moresimilarity to modern endotherms (warm-blooded animals) than ectotherms (cold-bloodedanimals)

However, dinosaurs would probably maintain a relatively constant internal temperature due totheir small surface area versus volume. Also, if dinosaurs were such great endotherms why all ofthe plates, frills, spikes and nasal cavities that probably served as heat exchangers, helping towarm and cool their bodies?

5. Pterosaurs- active flying diapsid reptiles from the Upper Triassic through Upper Cretaceous- most from shallow marine environments- Active Flight in pterosaurs is indicated by their hollow bones, keeled sternum (breastbone) forattachment of flight muscles, the shoulder girdle and upper wing bone are modified to form apulley-like structure; the first three fingers are short, and the fourth finger is greatly elongate tosupport the wing membrane, the fifth finger is absent- the earliest pterosaurs, the rhamphorynchoids, had a long tail- the pterodactyloids lost the tail, many had bony extensions at the back of their skulls, andseveral types were of enormous proportions (Quetzalcoatlus, from the Big Bend region of Texas,had a 40 foot wingspan)

F. Birds

1. Characteristics- highest metabolic rate of any modern vertebrate- bones are pneumatic (with extensive air-sac system for respiration); compact skeleton withwing and leg bones reduced in number and many elements fused [including hand, foot, sacralvertebrae, tail vertebrae, and clavicles (the "wishbone"); the sternum ("breast bone") has a largekeel that provides a broad base for the flight muscles- skull bones are typically fused; modern birds are toothless with the beak covered by a horny bill

2. Origin of flight

a. Arboreal theory- four-footed, ground-dwelling reptile became bipedal, then climbing, then began leaping fromtree to tree. Later it began parachuting, gliding and finally included active, powered flight(probably the most popular theory for flight origins)

b. Cursorial theory- feathers developed as thermoregulatory devices for insulation; then used for trapping insects;then provided lift during running and leaping; then flight

3. Important Groups of Mesozoic Birds

a. Archaeopterygids


- includes Archaeopteryx, the earliest known undisputed bird (pigeon-size), from the UpperJurassic- there are no unique features in the bony skeleton to differentiate them from dinosaurs- the skull of Archaeopteryx is birdlike, but with thecodont teeth; tail dinosaur-like; hind legsand pelvis similar to saurischian dinosaurs; clavicles joined to form a bird-like furcula("wishbone") but no keeled sternum

b.Hesperornithiformes- loon-like aquatic, flightless, toothed Cretaceous birds

G. Mammals

1. Characteristics

a. Soft Anatomy- have hair and specialized mammary glands for suckling their young- different reproductive modes distinguish the major groups of living mammals [platypus andechidnas are egg-laying monotremes; marsupials have a marsupium (a pouch in which mostembryonic development takes place); placentals have development taking place in the uterus andthe embryo is nourished by tissues of the placenta (the tissues shed following a birth)- mammals are intelligent with complex behavioral patterns- mammals are endothermic ("warm-blooded) and usually have high metabolic rates

b. Bones and Teeth- the skeleton of mammals is modified for upright posture- the most widely accepted paleontological definition of a mammal is articulation of the dentary(jaw bone) with the squamosal of the skull (reptiles with articular-quadrate articulation)- the articular and quadrate were modified in mammals to form two of their three earbones!- molar teeth are often useful for identifying fossil mammals

2. Mesozoic Mammals- mammals originated in the Late Triassic- nearly all early mammals were very small

Some of the Most Important Mesozoic Mammals Groups were:

a. Triconodonts and Symmetrodonts- Late Triassic to Late Cretaceous small mammals with multicuped molar teeth

b. Multituberculates- multituberculates (Jurassic-Oligocene) were the most diverse and numerous Mesozoicmammals- they were rodent-like; they had a pair of large incisors, and with low, many-cusped molar teeth

c. Marsupials


- Late Cretaceous to Recent- the didelphid marsupials were the most primitive marsupials and probably ancestral to othertypes; they include the American oppossum

d. Placentals- the oldest undisputed eutherian is a well-preserved shrew-sized placental from the EarlyCretaceous of Mongolia, which proves that there were true placental mammals by this time

H. The End-Mesozoic Extinction Event

- several groups (including dinosaurs and ammonites) became extinct at the end of theCretaceous (Cretaceous/Tertiary, K/T, or Maastrichtian/Danian Boundary; approximately 65 Ma)

1. Catastrophic Theories

a. Extraterrestrial Causes- large asteroid (10 to 20 kilometers across) hit the earth, creating a cloud of dust and somethingsimilar to "nuclear winter"; decrease in photosynthesis, increase in carbon dioxide, increase inacidity of oceans and a short-term "greenhouse effect"?- evidence includes the iridium layer at the Cretaceous/Tertiary boundary (probably depositedover a period no more than a few thousand years), the presence of glassy spherules (tektites),microscopic diamonds, and "tsunami beds" at the K/T boundary- the impact structure may be represented by the Chicxulub Crater, on the Yucatan Peninsula inMexico- possible conflicting data concerns the apparent extinction of most dinosaurs prior to the K/Tboundary

b. Vulcanology models- geochemical data in boundary rocks indicate major volcanic eruptions (e.g., The Deccan Trapsof India) at the end of the Cretaceous- volcanic eruptions would produce greenhouse gases that would trigger rapid climate change

b. Hypothesis of Gradual Change- the stratified ocean of the Middle Cretaceous gave way to more modern ocean circulation (the"Global Conveyer Belt Model), which brought colder waters to the tropics and changed climate- the end of the Cretaceous is marked by a major regression and drying up of epicontinental seas- tectonic activity and mountain building led to a major change in climate and seasonality- Western North America may have seen a gradual decrease in temperature between the lateCretaceous and Paleocene of 10°C ; evidence includes gradual extinction and replacement ofdinosaurs and other groups (including plesiosaurs, pterosaurs, ostracods, bryozoans, ammonitesand bivalves, all with low diversity at the end of the Cretaceous)

XVI. The Cenozoic Era


A. Paleogene Plate Tectonics and Climate

1. General Plate Configurations and Climate

a. Paleocene- during the Early Paleogene, continents were arranged much like today but were bunched closertogether- average global temperature increased dramatically within the late Paleocene (probably due toglobal warming and the melting of frozen methane hydrates along the continental slopes); thisled to a shift in marine and terrestrial faunas

b. Eocene Plate Tectonics and Climate

b1. Early Eocene- during the Early Eocene climates were warm (with tropical floras and faunas in England andeven extending well within the Arctic Circle!); this warming may have been due to largeamounts of water vapor in the air (water vapor is a greenhouse gas)

b2. Late Eocene- by late Eocene times climate was cooler and drier, with expansion of glaciers over Antarcticaby the Eocene-Oligocene transition; Australia separated from Antarctica and forms the coldcircumpolar current; the psychrosphere formed (deep, cold ocean currents) and climatedeteriorated (colder and/or drier)

2. Paleogeography and Sedimentation in the Gulf of Mexico and Atlantic Coast

a. Gulf of Mexico- during Paleogene time, marine waters still occupied the Mississippi Embayment (an inlandextension of the Gulf of Mexico), where thick Paleocene-Eocene sediment sequencesaccumulated; there was a regression of waters in the Oligocene, followed by a brief Oligocenetransgression

b. Bolide Impacts in the Atlantic- in the Chesapeake Bay region of the middle Atlantic coast of the U. S., a 3 to 5 kilometer wideasteroid struck the Earth (as indicated by the remains of a huge impact structure, and by shockedquartz); other equivalent structures are found in the Atlantic east of New Jersey, which indicatesthat a multiple bolide impact occurred about 36 Ma during the Late Eocene; tsunami ("tidalwave") deposits from this impact are present from New Jersey to North Carolina

3. Paleogene Tectonism in the Western United States- in latest Cretaceous through Paleogene time a region of fold-and-thrust belts and uplifts (theLaramide Orogeny) extended from Mexico, West Texas, and northward into Canada; largeblocks of Precambrian-age rocks were uplifted, the largest of these centered around Colorado(forming the Ancestral Rocky Mountains); the Laramide Orogeny may have been due to a low-angle subduction zone, melting and sending magma into the overlying crust and creating a series


of uplifts and basins

- the formation of basins and uplifts is reflected in the formation of giant lake basins representedby the Green River Formation (Eocene) of Utah, Colorado and Wyoming, by hot-spot volcanismin the Absaroka Mountains (where Yellowstone National Park is situated; the burial of fossilforests in Yellowstone by volcanic tuffs is a result of this activity), and by the uplift of the BlackHills of South Dakota

B. Neogene Plate Tectonics and Climate

1. Ocean Circulation and Climates Change

a. Formation of Cold Ocean Circulation- Miocene-age ice-rafted boulders from Antarctica indicates the expansion of continental glaciersonto the Antarctic continental shelves; this is due to the deepening and widening of the AntarcticCircumpolar Current with the continued movement of Australia away from Antarctica- Greenland/northern Europe rifting opened the Arctic Ocean (this helped form thepsychrosphere)

b. Warming during the Early Pliocene

- Early Pliocene climates (approx. 5 Ma) were relatively warm, sea levels rose, and marinedeposits are found inland in North America and countries bordering the North Sea andMediterranean

c. Beginning of the Ice Ages- at approximately 3.2 Ma the modern Ice Age began; details of the timing and geographicdistribution of continental glaciation is indicated by erratic boulders (deposited far from theirpoint of origin), by ice-deposited glacial till (Tillites), by isostatic depression of the land due toglacial weight, by glacial scouring, by lowering of sea level (at the glacial maxium sea level wasapproximately 100 meters lower than today, or about 330 feet), and by distribution (andmigration) of plant and animal species- oxygen isotope ratios indicate that by 2.5 Ma the Northern Hemisphere had moved fully into theIce Age; many regions became drier as cooler seas released less water vapor into the atmosphere

2. Formation of the Caribbean Sea and Isthmus of Panama

a. Caribbean Sea- during the Cretaceous the Caribbean was a small segment of the Pacific Plate that was pushingtoward the Atlantic; during the Cenozoic it became a distinct plate due to a new subduction zoneappearing along the west coast of Central America

b. Isthmus of Panama- the Isthmus of Panama was emplaced by plate movements between 3.5 to 3 Ma, at about thetime the Ice Age in the Northern Hemisphere began


3. Plate Tectonics in Eurasia and Africa- a series of mountain chains stretching from Spain and North Africa to southeast Asia werecreated due to remnants of Gondwanaland moving northward into Eurasia- the Alps and other Cenozoic mountains of the Mediterranean region were created when theAfrican Plate moved northward into the Eurasian Plate- India was an island continent that split from Antarctica during the Cretaceous (about 80 Ma); itmoved northward and began to wedge beneath the southern margin of Tibet about 20 Ma; acouple of huge thrust faults were created, with even greater crustal wedging and thickening; theseunderthrust slices of crust built the Himalayas into the World's tallest mountain chain (about 5.5miles high)- the collision of the African Plate with India and Eurasia destroyed the remnants of the TethysSeaway; during the Miocene the Mediterranean shrank, forming a huge evaporite basin (withdeposition of large amounts of salt); at about 5 Ma the natural barrier at Gibralter was breached,refilling the Mediterranean with Atlantic seawater

4. Circum-Pacific Orogenies- plate subduction in the circum-Pacific Belt gives rise to orogenies in the Philippines, Japan, theAleutian Islands, and North, Central and South America

5. Development of Modern Physiographic Provinces in the Western United States:

a. Rocky Mountains- during the Oliogocene, most of the Laramide Uplifts had been leveled, depositing a veneer ofsediments around them (an example are the terrestrial deposits of the Badlands of South Dakota,which yields a spectacular fossil mammal fauna)- Uplift of the Rockies began during the Early Miocene, and accelerated about 5 Ma; total upliftis 1 to 2 miles; sediments from the uplifting rockies spread eastward during the Late Miocene,resulting in the deposition of the Ogallala Formation (abundant caliche nodules in ancientOgallala soils indicates seasonally arid climates; the buried Ogallala Formation forms the famousand very important Ogallala Aquifer, the major source of groundwater on the High Plains)

b. Colorado Plateau- situated in the "Four Corners" of New Mexico, Colorado, Utah and Arizona; relatively flat-lying strata that has been uplifted about 1 mile above sealevel; uplift began about 10 to 8 Ma,with uplift accelerating about 5 Ma (at the same time as major uplifting occurred in the Rockies);uplift of the Colorado Plateau was accompanied by downcutting of the Colorado River, creatingthe Grand Canyon; swelling of the Earth's mantle and isostatic adjustment probably created themodern Rockies and Colorado Plateau

c. Basin-and-Range Province- centered around Nevada, forming the Great Basin; consists of fault block basins (Grabens)separated by upfaulted blocks forming ridges (Horsts); crustal thickness is about 20-30kilometers (versus about 35-50 kilometers in the Colorado Plateau), which indicates crustalextension in the Basin-and-Range Province; this faulting began in the Early Miocene


d. The Great Valley and Coast Ranges- the Great Valley is an elongate basin in California situated between the Sierra Nevada Rangeand the uplift area of the California Coast Ranges; faulting and deformation from the Pliocene(about 5 Ma) to the present has moved coastal California northward by about 100 kms (60Miles); uplift since the Pliocene converted the Central Valley from a marine basin to anagriculturally-rich (and oil-rich) terrestrial basin; the Great Valley and Basin and Rangeprovinces were probably created by crustal shearing adjacent to the transform strike-slip faults ofthe Pacific coast

e. Columbia Plateau and Snake River Plain- centered in Oregon; consists of thick sequences of flood basalts created by the YellowstoneHotspot, which has shifted eastward through time

f. Cascade Ranges- volcanic belt in the Pacific Northwest; subduction of the Pacific/Juan de Fuca plate beneath theNorth American Plate created a series of volcanic mountains, most of which have formed withinthe past 2 million years

6. Catastrophic Events at the End of the Ice Age- a huge lake (Glacial Lake Missoula) was created in the northwestern United States by glacialice pushing down from Canada; when this ice dam broke sometime between 11 and 20Ka,catastrophic flooding carved the landscape into the Channeled Scablands of the PacificNorthwest, and with deposition of giant ripples to the west (this process repeated itself about 40times during the Pleistocene)

XVII. Cenozoic Life

A. Marine Life

1. Marine Benthos- groups surviving the Cretaceous extinction (benthic foraminifera, sea urchins, cheilostomebryozoans, crabs, snails) had an adaptive radiation in the Paleogene- there are few corals in the Paleocene and Eocene, but increasing Magnesium/Calcium ratios inmarine waters triggered the growth of large reefs during the Oligocene

2. Marine Plankton- calcareous nannoplankton (coccoliths) and planktonic foraminifera almost became extinct at theend of the Cretaceous, but the few species surviving experienced a very large adaptive radiationduring the Tertiary- diatoms and dinoflagellates were not as greatly affected by K/T extinction, but also diversifiedduring the Cenozoic

3. Marine Nektonic Carnivores


- new types of sharks, whales, pinnipeds (seals, sea lions, walruses) and penguins evolved anddiversified during the Paleogene

a. Sharks- improvements in locomotion and jaw structure led to an adaptive radiation of modern sharkgroups- some Miocene sharks, which probably fed on the new gigantic whales, were of enormousproportions

b.Whales- mesonychids (the largest land mammal carnivores of all times), whales, artiodactyls (cattle,antelopes, pigs, etc.) and perissodactyls (horses, rhinos and tapirs) are related and often placedwithin the same "superorder"- whales are specialized for aquatic life with a streamlined body; the tail forms a horizontal flukefor propulsion; hind limb absent; fore limb forms a short flipper for steering; brains large andcomplex; primarily carnivores (feed on squid, fish or plankton)- the Archeocetes [earliest whales; Eocene - Oligocene, Miocene(?)] were derived from land-dwelling mesonychids or artiodactyls; includes the long-snouted, toothed "zeuglodonts")- the Odontocetes (Miocene - Present) are toothed whales, which includes dolphins, porpoises,sperm and killer whales- the Mysticetes (Miocene - Present) include the plankton-straining baleen whales; these are thelargest animals that ever lived

c. "Pinnipeds"- seals, sealions and walruses are often lumped together, but genetic and paleontological studiesindicate that sealions and fur seals probably came from dog-like ancestors, whereas true sealswere probably derived from otter-like ancestors

B. Flowering Plants (Angiosperms) Become Dominant

1. Types of Angiosperms

a. Monocotyledons ("Monocots")- include grasses, lilies, sedges, palms, pineapples and orchids; Jurassic(?); Cretaceous-Recent- leaves usually parallel veined and usually with only one cotyledon (the "seed leaf" of theembryo)

b. Dicotyledons ("Dicots")- include herbs and woody plants, cacti, and water lilies; Cretaceous-Recent- usually leaves are net veined and their embryos have two cotyledons ("seed leaves")

2. Changing Cenozoic Climates Lead to Changing Vegetation

a. Broad-leaved evergreen "gymnosperms" became extinct at the Cretaceous/Tertiary boundary,to be replaced by deciduous dicots


b. Paleocene to Early Eocene global climate became warmer and precipitation increased, withexpansion of tropical forests to about 50° to 60° North latitude

c. Upper Eocene with decline in temperature and drier climates, and with spread of broadleafdeciduous forests

d. During Miocene with drier climates and development of widespread grasslands (grasseshave continuously-growing leaves and can withstand heavy grazing), and with adaptive radiationof "weeds" (the Compositae, mostly annual or perennial herbs capable of rapid development andcolonizing disturbed habitats)

e. During the Pliocene the climate of northwestern Europe and North Africa changeddramatically, with loss of subtropical forests in Europe (due to cooler temperatures), and thespread of the Sahara Desert (due to increased aridity in North Africa)

C. The Adaptive Radiation of Birds

1. Flightless Birds- If there is no continual selection for the maintenance of flight apparatus (as is the case onislands or island continents), birds tend to become flightless- bird groups that developed flightless members include the Gruiformes (cranes, rails, and thegiant phorusrhacids), Diatrymiformes and "Ratites" [include moas (New Zealand; some overthree meters tall), elephantbirds (up to 500 kilograms), ostriches, rheas, cassowaries, emus,tinomous and kiwis]

2. The Passeriform Birds Flourish- the most important group of birds are the Passerines (Order Passeriformes), or songbirds- there are over 5000 modern species (three-fifths of all living birds), and are placed in from 50 to70 families- flowering plants, rodents and birds "co-evolved", with the evolution of angiosperms greatlyinfluencing the evolution of rodents and birds

D. Plate Tectonics and Changing Climates Influence the Types of Birds and Mammals on theContinents

1. The Island Continents of South America and Australia Evolve Unique Animals

a. South America- Phorusrhacids were giant flightless Early Tertiary carnivorous birds that were at the top of theterrestrial food chain- marsupials were very successful in South America during the Tertiary, including Didelphidoppossums, mole-like and rodent-like marsupials, dog-like marsupials (the borhyaenids), andeven "sabre-toothed cat"-like marsupials (the thylacosmilids)- "Edentates" were also important within South America, including giant armadillos and the


Volkswagen-sized armadillo-like glyptodonts, and giant ground sloths (some as large aselephants)- beginning in the Oligocene, there was a unique radiation of placental herbivores in SouthAmerica including the Litopterns (with rabbit-like groups, the horse-like Prototheriids, and theweird camel-like, trunk-bearing Macraucheniids) and the Notoungulates (with rodent-likespecies, the rhino-like toxodonts and astrapotheres, and the tapir-like pyrotheres)- the "Great Faunal Interchange" occurred during the Pliocene-Pleistocene with faunas migratingnorth and south across Central America; all of the large marsupial carnivores and odd placentalherbivores in South American became extinct

b. Australia- several "ratite" bird groups evolved in Australia including the cassowaries, emus and the extinctdromornithids (the largest dromornithid was 3 meters high and weighed about 500 kilograms!)- marsupials dominated the faunas in Australia with oppossum-like groups, carnivorousmarsupials (like the Tasmanian Devil, the dog-like Thylacine, and the lion-like thylacoleonids),mole-like and rodent-like groups, and a wide variety of large herbivores (including kangaroosand the rhino-sized diprotodontids)

3. The Placental (Eutherian) Mammals Radiate

a. Rodents- rodents include squirrels, rats, mice and guinea pigs- the skull and teeth are much modified for gnawing; with one pair of continuously-growingincisor teeth- rodents include approximately 40% of all known modern mammalian species (over 2,000 livingspecies); approximately 50 families evolved in the Cenozoic

b. Carnivorous Mammals

b1. "Creodonts" ("Order Creodonta")- probably polyphyletic, but some members were ancestral to the "true carnivores"- dominant Tertiary carnivores; found on all continents except Australia and South America

b2. "True Carnivores" (Order Carnivora)- true carnivores were a relatively minor part of faunas in the Paleocene and early Eocene; duringthe Middle Eocene cat-like and dog-like lineages evolved, which became very successful groupsof predators

c. Early Rooters and Browsers- the earliest herbivores lived mostly during the Paleocene and Eocene; they were from rabbit- toelephant-sized; probably most were rooters or feeders on tubers (with clawed feet, large caninesand broad, low crowned cheek teeth; they typically had a complete dentition with no diastema)- includes the pig-like Taeniodonts, semiaquatic Pantodonts, massive herbivorous Dinocerata(the "Uintatheres"), the large clawed-footed Tillodonts, the rhino-sized Embrithopods, and the"Condylarths" (ancestral to all other herbivorous groups)


d. The Elephants (Proboscideans)- Eocene - Recent; elephants are "Tethytheres" [and are kin to the rodent-like hyraxes and themarine dugongs and manatees (Sirenians)]- overall evolutionary trends in elephants include increase in size, enlarged cheek teeth,enlargement of the second incisor teeth to form tusks, and development of a proboscis (theelephant "trunk"; with the nasal opening in the skull becoming posteriorly-placed)- the most important groups of proboscideans are the Deinotheres (with downturned andbackwardly curved tusks), the Gomphotheres ("shovel-tuskers") and the Elephantidae ("true"elephants and mammoths)]

e. Perissodactyls- "odd toed" ungulates including tapirs, rhinoceroses, horses, brontotheres and chalicotheres- derived from condylarths; first appear in the Eocene (also peaked in the Eocene); good fossilrecord in North America and Eurasia and later members are found in Africa and South America- the axis of weight-bearing in the leg passes through the middle or third digit; most members arethree-toed but later horses eliminated the lateral digits to become one-toed- astragalus (ankle bone) with a single "pulley"; developed plant-crushing molar teeth with aloop-like enamel pattern

Major Perissodactyl Groups include the:

e1. Tapirs and Rhinoceroses- include the largest land mammals known (Inthricotherines were rhinos up to 5.4 meters at theshoulder)

e2. Chalicotheres- Eocene-Pleistocene of North America, Eurasia and Africa- Moropus (Miocene, North America) was a horse-sized clawed bipedal browser

e3. Horses- Eocene to Recent- evolutionary trends include increase in size and height, increased complexity of enamel patternon cheek teeth, elongation of legs, reduction of toes to one

e4. Brontotheres- titanotheres (brontotheres) were medium- to very large-sized herbivores of the early Tertiary ofNorth America and eastern Asia

f. Artiodactyls- "even toed" ungulates; includes pigs, camels, giraffes, deer, antelope, goats, sheep, cattle andother extinct and modern groups; derived from the condylarths- foot axis between the third and fourth digits; astragalus (ankle bone) forms a double-pulleystructure- primitive stocks (Ex.= pigs) with complete dentition and often with enlarged canine tusks; later


stocks with upper incisors reduced or lost, with a diastema (an anterior gap in the toothrow),premolars become molar-like and the molar tooth cusps are crescent- or half-moon shaped- with origin in the Paleocene; first radiation in early Eocene gave rise to many pig-like stocks(forest and woodland rooters and browsers); second radiation in late Eocene and early Oligocenegave rise to early ruminants (large herbivores); in Miocene ruminants diversified to exploit thesavannahs and grasslands and they remain the dominant herbivores there today [includingcamels, giraffes, deer, cattle, antelopes, sheep, goats and extinct groups such as the oreodonts (avery successful sheep-like artiodactyl group) and the protoceratids (a deer-like group with somemembers having weird "nose horns")]

XVIII. Human Origins

A. Primates (Order Primates)- it is possible that primates and rodents share a common ancestor in the late Cretaceous- usually scansorial ("scurrying"), small- to medium-sized forest-dwelling herbivores oromnivores

1. General Characteristics- Skeleton - retain a primitive, generalized skeleton, with five fingers and toes on the hands andfeet; trend toward increasing the mobility of the thumb and big toe; orthograde (upright) posture;typically cling or sit vertically when resting; locomotion generally quadrupedal- Skull - facial part of skull is reduced in more advanced primates; nasal apparatus generallyreduced; eyes face forward on skull; brain relatively large; molars often form a "square" cusppattern

B. Primitive Primates and Primate-Like Groups- there are a number of primitive groups of primates and primate-like mammals, oftendifferentiated on the basis of skull shape, tooth and ear morphology

1. Plesiadapiforms- Late Cretaceous-Eocene; previously placed within the Primates (and still considered torepresent a sister group to them); Plesiadapids had a rodent-like dentition with a long diastema("gap") between the procumbent incisors and grinding molar teeth (probably herbivorous diet)

2. Lemurs- Lemurs are found in the Old World tropics; they are typically small, arboreal, nocturnal, furry,with a fox-like face

C. Anthropoid Primates- monkeys, apes and man (late Eocene - Recent)- with derived features of the skull; molar cusps usually form a "square" pattern; braincaseexpanded with the skull opening for the attachment of the vertebral column placed under theskull (therefore the face is turned forward almost at a right angle to the backbone)- substantial changes in global climates during the Miocene were due to the northward movement


of the African plate (created the Antarctic Circumpolar Current , and semi-arid savannahenvironments became dominant); the Old World "catarrhine" monkeys did well in this climate,other primates didn't

1. Origin of the Hominoids- based primarily on DNA evidence, it has been theorized that at approximately 5-6 Ma gorillas,chimps and hominids (man's family) diverged when climate became cooler, drier and moreseasonal (termed the Messinian Climate Crisis)

a. Australopithecines- the first "humans"

- Ardipithecus species were the earliest known australopithecines, including Ardipithecuskadabba (ca. 5.7 Ma?) and Ardipithecus ramidus (ca. 4.5-4.3 Ma) from Ethiopia, Africa; consistof gracile (lightly-built) australopithecines with chimp-sized brains that inhabited woodlands- Ardipithecus was bipedal (as indicated by the pelvis and leg structure) but the “big toe” on thefoot was divergent (the foot could be used for “grasping”), suggesting Ardipithecus may havenested and fed in trees

- Australopithecus species (ca. 4-2 Ma) were gracile (lightly-built) hominids; fully bipedal(determined by hips, thigh bones and fossil footprints at Laetoli); very apelike in most of skeletonwith long arms and fingers; the brain is chimp-size (400-500 milliliters); moderate to markedsexual dimorphism (males larger than females); height from 1.0 to 1.5 meters (3' 3" to 4' 11") andweight from 30 to 70 kilograms (66 to 154 pounds); a "gracile" australopithecine probably leadto Homo

- Paranthropus species (2.6-1.2 Ma) were robust (heavily-built) australopithecines; relativelylong arms; height 1.1 to 1.4 meters (3' 7" to 4' 7") and weight 40 to 80 kilograms (88 to 176pounds); marked sexual dimorphism; prominent crests on top and back of skull; very long, broad,flattish face; strong facial buttressing; very thick jaws; small incisors and canines; large, molar-like premolars; very large molars; brain size 410 to 530 milliliters

b. Homo- the genus containing modern man

b1. Early Homo Species- Homo rudolfensis (ca. 2.5 - 1.9 Ma) and Homo habilis (ca. 2.1 - 1.5 Ma) were similar toAustralopithecus but brain size increased to about 650-750 ml

The Oldowan Culture- first tool culture; although the Oldowan Culture has considered to be a "pebble tool" culture,their primary use appears to have been as choppers, scrapers and pounders; the Oldowan Culturewas probably due to Australopithecus gahri, Homo rudolfensis, H.habilis and early H. ergaster- dates at 2.5 - 1.5 Ma; early humans used these tools for "expanding their niche" - cutting,crushing, digging, projectiles and carrying; it appears that the hominids had no preconceived


shape of the tool during manufacture (i.e., no "mental template")

- early Homo species may have lived in multi-male and multi-female groups; males competed foraccess to females- no evidence of intentional burials, grave goods, art, etc.; no clear evidence of architecturalfeatures

b2. Homo ergaster- approximately 1.9 to 1.5 Ma in eastern Africa- may be ancestral to all subsequent Homo species- the slender-bodied, long-legged "Turkana Boy" skeleton is essentially modern and with a highlyefficient striding structure; adults probably 1.8 meters tall (6') or more; brain size 800- 1050 ml- oldest H. ergaster made Oldowan tools; at approximately 1.65 Ma developed Acheulianindustry (with large hand-held stone axes); may have been first to use fire at 1.7 Ma (fireprovides warmth, used in hunting, protection against predators, remove toxins from food)

b3. Homo erectus- Asiatic form [ca. 1.5 Ma to 225 Ka] with a relatively large brain (850 -1150 ml), flat skull, largebrow ridges, sloped forehead, nuchal crest on back of skull, almost no chin; probably did not giverise to later Homo species

b4. Origin of Homo sapiens- probably evolved from H. ergaster-like species- by 500 - 200 Ka with forms intermediate between H. ergaster/"erectus" and H. sapiens

Origin Theories for Homo sapiens include:- Multi-Regional Hypothesis - evolution from several "stocks" of migrated Homo ergaster /"erectus" (especially Africa and eastern Asia)- Out-of-Africa Hypothesis - evolution from a single stock of H. ergaster / "erectus" that latermigrated (most popular theory) and replaced older groups

- Homo floresiensis, a tiny (adults 42 inches high!) island species from Indonesia, is similar toHomo ergaster ; it may have lived as late as 18,000 years ago (if true, this greatly changes ourideas of the diversity and distribution of ancient hominids)

b5. Homo neanderthalensis- “early pre-Neandertals” at 400 Ka; Homo neanderthalensis at 150 Ka to 27 Ka; mostly lived inEurope and western Asia- often massive brow ridges; large cheek bones; protruding face; no chin; "bun"-shaped skull;large cranial capacity (often greater than modern man); short (1.5 meters; 5 ft.) but very powerful- probably not ancestral to Homo sapiens (with distinct DNA)

- hand axes decline, flake tradition becomes dominant

Mousterian Tradition- usually attributed to Homo neanderthalensis


- strike flake from underside of a prepared "tortoise-shell" core to create many tool types; manyof these were Composite Tools (artifacts made from more than one component)

b8. Homo sapiens sapiens- Homo sapiens sapiens evolved from archaic H. sapiens in Africa and then replacedneanderthals in Eurasia?- there may have been an early dispersal of anatomically modern-looking Homo sapiens fromAfrica at about 100 Ka; there may have been a substantial “bottleneck” of population after that,with numbers dropping to as low as 10,000 individuals

- Homo sapiens sapiens developed the Upper Paleolithic tool technology (35 to 9 Ka); oftentypified by "punch-struck" blade industries (a blade is a long flake); these were "specialized"hunter-gatherers (concentrate on a few resources) that often hunted herd animals

Religion - Burials with ceremonial burials and grave goods

Upper Paleolithic Art - first widespread production of true art was by modern Homo sapiens (Ex.= cave paintings), probably with a religious significance

historical geology lecture notes 001

Documents

highest taxonomic

historical

antarctic

dead plant

marked sexual

western united

fault block

radioisotopic