TheThe EarlyEarly PaleozoPaleozoic Worldic WorldLateLate CambrianCambrian andand EarlyEarly

OrdovicianOrdovician development of development of Life and LandLife and Land

Jarðsaga 1

-Saga Lífs og Lands –

Ólafur Ingólfsson

RoleRole of of oxygenoxygen inin CaCambrian evolutionmbrian evolutionOxygen priorities:Low oxygen levels: respiration & tissue synthesis

High oxygen levels: oxygen can be usedfor lower priority things - skeletons, shells, etc.

Oxygen reached critical threshold inCambrian, eliminating the need for priorities.

Evidence: modern low O2 environmentshave only small, soft-bodied forms.

TheThe LateLate CambriaCambrian Globen Globe

TheThe LateLate CambrianCambrian ClimateClimate

Fossil Assemblages of the Proterozoic -Cambrian boundary

Windows into the Past:Chengjiang Lagerstatten

Chengjiang Lagerstatten

Sinoburiuslunaris

Xandarellaspectaculum

Squamacula clypeta

LateLate CambrianCambrian developdevelopment of lifement of lifeTrilobites, brachiopods, and othertypical Cambrian groups continued to flourish. Molluscs diversified.

During this time grazing increased. Mat scratchers and mat miners migrated upwards towards littoral zone and downwards to deeper water

Trace fossils made by animals showthat the animals of the Cambrian weredeveloping new ecological niches andstrategies - such as active hunting, burrowing deeply into sediment, and making complex branching burrows.

AlmostAlmost everyevery metazoanmetazoan phylumphylum arrivarrived on ed on the Cambrian scene...the Cambrian scene...

Almost every metazoan phylum with hard parts, and many that lackhard parts, made their first appearance in the Cambrian. The only modern phylum to appear after the Cambrian was the phylum Bryozoa (mosadýr), which is not known before the early Ordovician.

PLANTSANIMALS

PROTISTANS

FUNGI

MONERANS

flowering plants

cycads

ferns

horsetailslycophytes

whisk ferns

conifers

ginkgo

gnetophytes

mosses, liverworts, hornworts

club fungi

sac fungi

zygomycetes

eubacteria

chemical origin of life

archaebacteria

arthropodsannelidsmollusks

roundwormsrotifers

sponges

chordates

echinoderms

ribbon wormsflatworms

cnidarianscomb jellies

Trichoplax

chytrids

red algae

green algae

brown algae

diatoms

dinoflagellates chrysophytes

ciliated protozoans

euglenoids

water molds

slime molds

flagellated protozoanssporozoans

amoeboid protozoans

The Early Cambrian Radiation

With abundant oxygen, phyla underwent adaptive radiation, but many early phyla didnot stand up to competition

Metazoan Diversification: Molluscs

Metazoan diversification: The Echinoderms (Skrápdýr)

TheThe ConodonConodontstsThe conodonts first appearduring the Late Cambrian. These were probably fast swimming micro-predators, soft-bodied animals, nowconsidered to be among thefirst vertebrates, withflattened elongate eel-like bodies. They are known almost entirely from their hard (calcium phosphate) tooth-like elements, but a few instances of soft tissue preservation revealed their physical form.

The wide variety in conodont teethsuggest that even at this earlystage in the evolution of life, they were part of a com-plex ecosystem of predator and prey

Cephalochordates: Primitive, Fish-Like Forms(appear by at least Middle Cambrian)

Amphioxus

conodonts conodont animal

Cartilaginous fishes

Bony Fishes

PrimitiveFishes

TheThe fishesfishes start start toto evolve...evolve...The first fishes, and amongthe first vertebrates, werethe ostracoderms (bryn-fiskar), which appeared inthe Late Cambrian Period, about 510 million years ago, and became extinct at the end of the Devonian, about 350 million years ago. The internal skeletons of these jawless creatures are rarely preserved.

PoorPoorswimmswimmers

Ostracoderms hadbony external shieldsthat covered the headand most of the trunk. From 9-30 cm long, ostracoderms hadrather thick, flattened bodies withonly a pair of side flaps to help in steering. They probably swam clumsily just above the sea floor. The mouth served to obtain oxygen and to retain bits of food.

ers

Early Paleozoic Ostracoderms (Jawless fishes)

RecurringRecurring extinctionsextinctions duringduring the the Cambrian PeriodCambrian Period

The Cambrian extinction first of a numberof such events through Earth’s history

The very end of the Cambrian saw a mass extinction that killed off a number of unique taxa, including:

• the last archaeocyathids

• the anomalocarids

• many lobopods (worms)

• many trilobites

• basal arachnomorphs (fjölfætlur)

• several orders of early nautiloids (kuggar)• a number of primitive echinoderms

A A majormajor extinctionextinction byby thethe end end of the Cambrian. Why?of the Cambrian. Why?

WhatWhat doesdoes itit taketake to survive...?to survive...?During the Cambrium and most of the Ordovician, sealevels were high. On the continental shelves, marineorganisms engage in evolutionary experiments. The number of families of known marine invertebrates increases from about 200 at the end of the Cambrian to around 500 in the early Ordovician.

Pikaina

EvolutionaryEvolutionaryexperimentsexperiments: :

Strange animals...Haplophrentis carinatus

Strange animals...

Hallucigenia sparsaMarrella splendens

Wiwaxia corrugata

Opabinia regalis Amiskwia sagittiformis

FewFew questionsquestions onon extinctioextinctions and survivalns and survival

• Were victims of early extinctionsbiologically inferior to the groups that survived?

• Were they less effective in competing withother taxa or in avoiding predators?

• Can extinctions of whole groups be blamed on predators?

• Were they maybe simply the unlucky victimsof catastrophic extinctions that struck species regardless of their ecological abilities?

• Did groups go extinct because they failed to diversify rapidly?

Stephen Jay Gould – Radical ThinkerCould some Burgess Shale organisms belong to extinct phyla ?Is it possible that a phylum could be represented by few or

single species ?

If so, suggests that the Cambrian Explosion produced more phyla than are present today

extinction

Gould’s View:Sudden appearance of phyla,removal of many by mass extinction

Conventional view:Gradual increase in numberof phyla through time

CauseCause(s) of (s) of CambrianCambrian extintextintion(s) not ion(s) not known...known...

During the Late Cambrian alone, there werethree distinct bio-stratigraphic intervals intrilobite distribution, each marked by a mass-extinction. The cause(s) of the late Cambrian extinction(s) are not known, but it seems almost certain that a change in sea level occurred at this time, changing the habitat to which many of these early animals were adapted, and driving them to extinction. Pherhaps climate change as well...?

OrdoviciumOrdovicium PeriodPeriod (495(495--443 MY) 443 MY) –– a period of great diversificationa period of great diversification

• The Ordovician was named by the British geologistCharles Lapworth in 1879. He took the name from an ancient Celtic tribe, the Ordovices, renowned for its resistance to Roman domination.

• The boundary between the Cambrian and the Ordovicianis marked by the appearance of certain planktic graptolites

TheThe OrdovicianOrdovician (495(495--443 MY)443 MY)Particularly good examples of Ordovician sequences

are found in:

• China, Western Australia, Argentina, the United States and Canada.

• Ordovician rocks over much of these areas aretypified by considerable thickness of lime andother carbonate rocks that accumulated in shallow subtidal and intertidal environments.

• Rocks formed from sediments deposited on themargins of Ordovician shelves are commonly dark, organic-rich mudstones which bear the remains of graptolites and may have thin seams of iron sulfide.

• Graptolites are the most common fossils found in the mudstones.

MiddleMiddle OrdovicianOrdovician continentalcontinental plate configurationplate configuration

The Ordovician Period - great radiation of life

• Life in sedimentsdeveloped – witnessedby increased biotur-bation of sediments. Mostly bivalves and trilobites.

• Life on the sea floordeveloped rapidly –intense grazing, scavenging, predation and reef building. Starfishes arrive.

Ordovician strata arecharacterized by numerousand diverse trilobites andconodonts found in sequencesof shale, limestone, dolostone, and sandstone. In addition, bryozoans, corals, crinoids, as well as many kinds of brachiopods, snails, clams, and cephalopods appeared for the first time in the geologic record in tropical Ordovician environments.

NewNew groupsgroups of of animanimals als arrivearrive

The Graptolites appear. For a long time noone was sure what kind of animals theywere. Most fossil graptolites look likenothing so much as tiny sawblades. Well-preserved graptolites can be seen to betubular in cross-section. Graptolites are thought to have been planktonic, floating or slowly sinking through the water. The spiral shape of some was probably an adaptation to slow sinking. Other graptolites may have been connected to gas-filled sacs, keeping them buoyant.

Very important stratigraphic markers due to rapid evolution.

GRAPTOLITES

In structure they were stick like organisms with an organic skeleton. In shape they could either be straight or curved, or possibly even spiral. Their preservation is quite often poorand usually just a carbonaceous film remain (hence their namgraptho: greek= write, lite: from greek, lithos= rock).

Kingdom Kingdom AnimaliaAnimalia,,Phylum Phylum ProtochordataProtochordata•• GraptolithiniaGraptolithinia ––

Graptolites Graptolites ––plankticplanktic or benthicor benthic–– Appear as “pencilAppear as “pencil--

like” marks on shalelike” marks on shale

CoralsCorals firstfirst appearedappeared in Lower Ordoviciumin Lower Ordovicium

Sea anemones (sæfíflar) are closely related to Paleozoiccorals, while jellyfish are distant relatives. Coral is a veryprimitive animal consisting almost exclusively of a large stomach with an opening that serves both as mouth and anus. Corals dwell on the floor of shallow tropical seas.

CoralCoral reefsreefsCoral reefs are complex, enduring, magnificent and dynamicliving structures of geologic proportion. They are amongour planet’s most prolific and intricately interrelated ecosystems. They are also the planet’s oldest natural com-munity. Today’s reefs are simply the most recent link in a lengthy genetic chain.

TheThe nautiloidsnautiloids (Álfasmokkar)(Álfasmokkar)

The nautiloids, predecessors of present day squids andoctopuses, evolve during the latest Cambrian and early Ordovician. They were highly successful predators

SomeSome factsfacts onon cephalopodscephalopods((hausfætlur, smokkar hausfætlur, smokkar ))

• All are active marine predators, able to swim swiftly, and easily competing with fish in the marine habitat.

• There are 650 living species, but more than 7,500 fossil forms are known.

• Cephalopods are quite large by molluscan standards (6-70 cm), with the modern day Architeuthis, the giant squid, with a body length of up to 16 m

• the Ordovician nautiloid Cameroceras had a straightshell up to 10 metres in length and and the Cretaceous ammonoid Pachydiscus seppenradensis, with a coiled shell 3 metres in diameter

• The cephalopods are the largest invertebrates ever to live, with weights of one to two tons.

CephalopodsCephalopods: a : a majormajor step step towards more intelligent life...towards more intelligent life...

• The tremendous evolutionary radiation of nautiloidcephalopods meant an increase in the level of intelligence in Paleozoic oceans.

• Cephalopods are the most intelligent of allinvertebrates, owing to the development of elaborate manipulative organs (tentacles for touching and grasping).

• One researcher described the common octopus as like a sort of aquatic dog or cat. Although Ordovician cephalopods were probably not equal to modern forms in intelligence, they were certainly superior to that of contemporary (non-cephalopod) life-forms.

OrdovicianOrdovician sea floorsea floor

ReferencesReferences, , webweb resources etcresources etc• Stanley, Earth System History, chapter 12• Fortey, R. Life – A natural History of the first four billion years

of life on Earth. New York, Vintage Books, 346 pp.• Fortey, R. Trilobate – Eywitness to Evolution. London, Flamingo,

246 pp.• http://www.ucmp.berkeley.edu/cambrian/camb.html• http://jan.ucc.nau.edu/~rcb7/global_history.html• http://www.gps.caltech.edu/~devans/iitpw/science.html• http://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm• http://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm• http://www.peripatus.gen.nz/Books/WonLif.html• http://www.toyen.uio.no/palmus/galleri/blader/blad_x03.htm• http://www.fossilmuseum.net/Paleobiology/Paleozoic_paleobiolog

y.htm#Ordovician• http://www.ucmp.berkeley.edu/ordovician/ordovician.html

•• StanleyStanley, , EarthEarth SystemSystem HistoryHistory, chapter 12, chapter 12• Fortey, R. Life – A natural History of the first four billion years

of life on Earth. New York, Vintage Books, 346 pp.•• ForteyFortey, R. , R. TrilobateTrilobate –– EywitnessEywitness toto EvEvolutionolution. London, Flamingo, . London, Flamingo,

246 pp.246 pp.•• httphttp://://wwwwww..ucmpucmp..berkeleyberkeley.edu/cambrian/camb.html.edu/cambrian/camb.html•• httphttp://jan.://jan.uccucc..naunau..eduedu/~/~rcbrcb7/global_history.html7/global_history.html•• httphttp://://wwwwww..gpsgps..caltechcaltech..eduedu/~devans/iitpw/science.html/~devans/iitpw/science.html•• httphttp://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm•• httphttp://://wwwwww..palaeospalaeos..comcom//PaleozoicPaleozoic/Ordovician/Ordovician.htm/Ordovician/Ordovician.htm•• http://www.peripatus.gen.nz/Books/WonLif.htmlhttp://www.peripatus.gen.nz/Books/WonLif.html•• httphttp://://wwwwww..toyentoyen..uiouio..nono//palmuspalmus/galleri/blader/blad_x03.htm/galleri/blader/blad_x03.htm•• httphttp://://wwwwww..fossilmuseumfossilmuseum.net/.net/PaleobiologyPaleobiology/Paleozoic_paleobiolog/Paleozoic_paleobiolog

y.htm#Ordoviciany.htm#Ordovician•• httphttp://://wwwwww..ucmpucmp..berkeleyberkeley..eduedu/ordovician/ordovician.html/ordovician/ordovician.html