early mesozoic era - montana state university billings home
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Early Mesozoic
EraJurassic and
Triassic
Mesozoic
Era Age (Myrs) Epoch
0.01Holocene
1.8Pleistocene
5.3Pliocene
23.8Miocene
33.6Oligocene
54.8Eocene
65Paleocene
144
206
248
290
323
354
417
443
490
543
2500
3800
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Eon
Proterozoic
Archean
Hadean
Period
Quaternary
Tertiary
Neogene
Paleocene
Mississippian
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Cretaceous
Jurassic
Age of the Earth 4600 Myrs (4.6 Byrs)Source: Geological Society of America (1999)
Geologic Time Scale
Devonian
Silurian
Ordivician
Cambrian
Triassic
Permian
Pennsylvanian
248-65 Myr
Early Mesozoic:Triassic and Jurassic
145 Million years
202 Million years
251 Million years
Paleogeography• Pangaea began to separate
Paleogeography• Tethys seaway formed
– Site of modern Mediterranean
Major points about the Late Paleozoic
1.Therapsids established as the dominant land animals
2.Gymnosperms are the dominant land plants
3.Two major extinctions in the last few million years of the
Paleozoic, the last being the largest in history
4.Rugose corals and Fusulinids completely wiped out
5.Brachiopods, Bryozoans, Ammonites and Therapsids nearly
wiped out
6.All life on Earth is significantly affected
7.Cause still unknown; Massive flood basalts is the theory du jour
Early Mesozoic • Bounded by mass
extinctions
• Recovery from Permian mass extinction of:– Fusulinids
– Lacy bryozoans
– Rugose corals
– Trilobites
Paleozoic vs. Mesozoic
Rugosa & Tabulate CoralsHexacorals
Reefs - Hexacorals
Early Mesozoic Life
• Reefs
– Hexacorals
– Dominant reef builder
– Some resemble the extinct rugose corals
Paleozoic vs. Mesozoic
Brachiopods Bivalves & Gastropods
Bilateral Symmetry
Inoceramids
Paleozoic vs. Mesozoic
Crinoids Echinoids (Sea Urchins)
Paleozoic vs. Mesozoic
Trilobites Crustaceans
Paleozoic vs. Mesozoic
Large Amphibians Frogs and Salamanders
Paracyclotosaurus
PhytoplanktonErupt
http://www.ucl.ac.uk/GeolSci/micropal/calcnanno.html
Foramifera:
calcareous
(CaCO3)
heterotrophs
http://www.ucl.ac.uk/GeolSci/micropal/calcnanno.html
Diatoms: siliceous
(SiO2)
phytoplankton
(photosynthetic/au
totrophs)
http://www.ucl.ac.uk/GeolSci/micropal/calcnanno.html
Ra
dio
laria
ns
Early Mesozoic Life– Stromatolites
returned temporarily to shallow water
– Ammonoids
• 2 genera diversity to 100
– Mollusks, particularly bivalves abundant
– Sea urchins
Early Mesozoic Life• Fishes continue to flourish
- More modern- Skeletons of cartilage- Peg-like teeth- Scales covered bodies- Simple Jaws
Early Mesozoic Life
– Ammonoids
• Rapid evolution
• 1 million year range
Ammanoids - Parapuzosia
Early Mesozoic Life• Belemnoids
– Squid-like relatives of Ammonoids
New Marine Predators!
Early Mesozoic Life• Marine reptiles
– Placodonts
• Blunt-toothed shell crushers
• Broad armored bodies
Early Mesozoic Life• Marine reptiles
– Nothosaurs
• Early Triassic
• May be first marine reptiles
Marine Reptiles
Pleisiosaur
Early Mesozoic Life• Plesiosaurs
– Evolved from nothosaurs
Plesiosaurs:Elasmosaurus
Mosasaur
Largest-
150 ft long!
MosasaurKronosaurus
Early Mesozoic Life• Ichthyosaurs
– Fish lizards
– Bore live young
Ichthyosaurus
Marine Reptile
Relations
Giant Sea Turtles
Early Mesozoic Life on Land• Tree-forming Gymnosperms
– Cycads
– Cycadeoids
– Ginkgos
Early Mesozoic Life on Land
• Mesozoic forests looked very different from modern forests
The Amniotes
Classified based on skull structure
Diapsids
(Includes lizards,
dinosaurs & birds))
Synapsids (Includes mammals)
Anapsids (Includes turtles)
Mesozoic Reptiles
Synapsids
(Mammals)
Anapsids
(Turtles)Diapsids
Lizards
& Snakes
Crocodiles
Pterosaurs
Marine
Reptiles
Dinosaurs
& Birds
Archosaurs
Anapsids & Diapsids(True Reptiles)
Early Permian - Labidosaurus
Early Mesozoic Life on Land
• Early Mammals
– Mammals evolved from therapsids
• Small
• Thecodonts
– Dinosaur ancestors
– Upper portion of legs extended downward rather than sprawling
Early Mesozoic Life on Land
• Thecodont descendents
– Dinosaurs
• Bipedal
• Different skull
• More highly developed teeth
– Crocodiles
Early Mesozoic Life on Land• Dinosaur evolution
– Bird- hipped• Ornithiscian
• Herbivores
– Lizard-hipped• Saurischian
• Herbivores
• Carnivores
The 2 Major Lines of Dinosaurs
Early Mesozoic Life on Land
• Pterosaurs
– Long wings
–Hollow bones
– Flight
Big Dinosaur Questions
• What are Dinosaurs?
• How do we understand Dinosaur behavior?
• Where dinosaurs warm-blooded (endotherms) or cold-blooded (ectotherms)?
• Did birds evolve from dinosaurs?
• What caused the extinction of the dinosaurs?
Dinosaurs vs. “Reptiles”
1. Upright posture
Legs beneath the body rather than
to the side
2. Unique arrangement of ankle hinge
(and other skeletal differences)
Early Mesozoic Life on Land• Sauropods
– Largest of all dinosaurs
• Jurassic Morrison Formation
Ornithischia“Bird-Hipped Dinosaurs”
1. Stegosaurs
2. Hadrosaurs
3. Ankylosaurs
4. Pachycephalosaurs
5. Ceratopsids
All Herbivores
Hadrosaurs - “Duck-billed Dinosaurs”
Ouranosaurus
Hadrosaurs
Parasauralophus
Hadrosaurs
Maiasaurus
Laellynasaura
Dinosaurs
• Maiosaurahatchling
– 50 cm long
Stegosaurs
Stegosaurus
Ankylosaurids - Natures Tanks
Euoplocephalus
Ankylosaurids
ankylosaurus
Pachycephalosaurs - “Bone Heads”
Pachycephalosaurus
Ceratopsids“Horned Dinos”
Torosaurus
Ceratopsids
Triceratops
Saurischia“Reptile-Hipped Dinosaurs”
1. Sauropods (Herbivores)
2. Theropods and Coelurosaurs (Carnosaurs)
• Aves (Birds)
Herbivores and Carnivores
Generally more mobile, pubis facing forward teeth on
the rims of the jaws, two-legged and four-legged,
dominated Early Mesozoic
Sauropods
Seismosaurus
Up to 90 feet
long and 10
tons, ‘lizard-
feet’ (five
toes like a
reptile,
nostrils
sometimes on
top, small
brain (size of
a kitten’s),
used
gastroliths for
digestion,
herding
animals
X 20
Sauropods
Barapasaurus
Sauropods
apatosaurus
Theropods
Tyrannosaurus: up to 30 feet in length, several tons, size of a large elephant, Slow rambling gait?, large mouth for swallowing
Early Mesozoic Life on Land
• Allosaurus
–Largest carnivore!
http://www.youtube.com/watch?v=3D4AA_l6c3w&feature=related
Velociraptor
Theropods
allosaurus
Theropods
Small Theropods:coelurosaurs
Compsognathus
How do we know about Dinosaur Behavior?
Dino Nests
Dinosaur Trackways
How do we know about Dinosaur Color and Soft
“Stuff”?
Skin Imprints
Triceratops
Feathers
Brain Casts & Gizzard Stones
Emphasizes smell and senses, not planning
gastroliths
Color?
Ceratosaurus
Horner (2001) Dinosaurs under the Big Sky
Warm vs. Cold Blood(Endotherms vs. Ectotherms)
http://www.youtube.com/watch?v=iaLpzhOpjTA
http://www.youtube.com/watch?v=Fo-yFw6VOyw&feature=related
Predator/Prey Ratios
What limits
how many
animals can
exist on a
patch of
ground or
seafloor?
Upright Posture & Fast Speeds
Problems - Food & Heat Loss & blood pressure
Fossilized dinosaur heart4-chambered
Bone Structure
Bottom Line
Some dinosaurs were endotherms
(small theropods) and others were
ectotherms (large sauropods)
Early Mesozoic Life on Land
• Archaeopteryx
• Missing link
– Feathered
– Breastbone
Paleogeography• Pangaea began to separate
Paleogeography• Tethys seaway formed
– Site of modern Mediterranean
Paleogeography
• Rifting began first in north, then spread south
Paleogeography• Salt domes
– Thick evaporites built up in modern Gulf of Mexico
– Formed salt domes
• Petroleum reserves
Triassic Mass Extinction• Global warming
– Volcanic activity released high volumes of CO2
– Number of leaf stomates increased• Cells that utilize CO2
Tectonic Events in Western U.S.
• Petrified Forest
–Chinle formation
–Utah and Arizona
Tectonic Events in Western U.S.• Sundance Sea
– Global sea level rose
– Pacific flooded western U.S.
Tectonic Events in Western U.S.
• Grew by accretion of exotic terrane
– Island arc terranes• Accreted Golconda Arc
– Microplates• Accreted Sonomia
– Southeastern Oregon
– Northern California and Nevada
Tectonic Events in Western U.S.
• Accretion
– Golconda Arc
– Sonomia
Tectonic Events in Western U.S.
• Additional accretion
– Accretionary wedge
– Franciscan rocks
– Great Valley turbidites
Tectonic Events in Western U.S.
• Subduction led to intrusions
– Sierra Nevada batholiths
MesozoicBatholiths
Tectonic Events in Western U.S.• Sundance Sea
– Retreated as it filled with sediments• Morrison Formation
• Reddish river sediments. Famous for the dinosaur fossils
Dinosaurs
• Oviraptor
– Egg stealer
– small at 0.7 m in size
Dinosaurs• Protoarchtopterix
– Precursor of feathers
– 60 cm in size
Dinosaurs• Protoarchaeopteryx
– Fossilized tail feathers
MesozoicSeas
Transgression Regression
Low
High
Sedimentary Sequences of NA
Blue = No deposition
Cretaceous Seaway