Early Mesozoic Era - Montana State University Billings Home

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