Embed Size (px)
Citation preview
Outline 17:Reptiles and Dinosaurs
Evolution of Reptiles
• The first reptiles appeared in the Mississippian.
• They evolved from amphibians, which first appeared in the Devonian.
• The evolutionary jump was the invention of the amniote egg.
The Amniote Egg
• Requires internal fertilization, unlike amphibians.
• Has a hard, but porous shell.
• Can be laid on dry land. Skips the tadpole stage of amphibians.
• Has a complex series of membranes and a very large yolk.
Amphibian Egg: No Shell
Frog eggs in a Morgantown pond
Typical amniote egg with
an embryonic
reptile.
Crocodiles hatching
from their amniote eggs
Making Lizard Eggs
This is X-rated
Making Dinosaur Eggs
Fossilized embryos still in the shells
Closeup of developing embryo
Searching for sauropod
dinosaur eggs in Patagonia
A single egg laying on an outcrop
Dinosaur developing in the egg
Researcher working on a nest of sauropod dinosaur eggs
Mother and hatchlings in
Patagonia sometime in the
Cretaceous
The fate of many
hatchlings
Dinosaur parent died while sitting on nest with eggs
Recovering the fossil seen in last slide
Dinosaur eggs and reconstructed embryo
Major Reptile Groups
• Anapsids - the stem reptiles, turtles are the only living group.
• Synapsids - the mammal-like reptiles. Mammals evolved from synapsids.
• Diapsids - all modern reptiles except for turtles. Dinosaurs evolved from diapsids.
Pennsylvanian anapsid or stem
reptile
Living anapsid reptile: snapping turtle
Living diapsid reptile: iguana
Living diapsid reptile: crocodile
Permian synapsid reptiles:
Dimetrodon
Triassic synapsid reptiles: Therapsids or mammal-like reptiles
The Mesozoic: The Age of Reptiles
A Nile crocodile. Notice the unspecialized reptilian teeth.
Fossil Crocodile from the Jurassic
Marine crocodiles of the Mesozoic
28 ft. alligator caught in Alabama lake
Sarcosuchus imperator from the Cretaceous of Niger, 45
feet long
www.nationalgeographic.com/supercroc/
Jaw of Sarcosuchus in Cretaceous sandstone of Niger, Sahara Desert
Sereno’s team indicating the
size of Sarcosuchus
Paul Sereno and the
reconstructed jaw of
Sarcosuchus
Skull of a living 6 ft. long crocodile compared to Sarcosuchus
A short-necked Plesiosaur
A Jurassic plesiosaur
A short-necked Plesiosaur
A Mosasaur eating a Cretaceous bird
One species of mosasaur attacking another species
Ichthyosaurs looked like mammalian dolphins
An Ichthyosaur died giving birth
A baby ichthyosaur hiding in a reef
The Flying Reptiles -
Pterosaurs: did they have a high
metabolism?
Pteranodon
Cretaceous pterosaur with 45 ft
wing span
Carnegie Museum, 2009
Evolution of Dinosaurs
• First appeared in late Triassic, 220 MY ago.
• Evolved from thecodont archosaurs (crocodiles are closest living relatives).
• Thecodont ancestor was bipedal and carnivorous.
• First dinosaurs were bipedal and carnivorous.
A Triassic thecodont avoiding a synapsid reptile
Archosaurs
Archosaurs
Evolution of Dinosaurs
• Later dinosaurs that walked on 4 legs were secondarily quadrapedal.
• Herbivorous dinosaurs evolved from carnivorous dinosaurs.
2 Major Groups of Dinosaurs
• Saurischians - theropods and sauropods
• Ornithischians - a variety of herbivores
– Ornithopods
– Pachycephalosaurs
– Stegosaurs
– Ankylosaurs
– Ceratopsians
Dinosaurs are popular with the
public
Jack Horner, Montana State Univ.
Field Work in Montana
Velociraptor was a very active predator
Utahraptor waiting to ambush
Velociraptors hunted in packs
The prey’s view of a pack of Allosaurus
Dinosaur classification
Ornithischians
Saurischians
Dinosaur hips differ between the two major groups
Saurischian hip structure (theropod)
Saurischian hip structure (sauropod)
Ornithiscian hip structure (stegosaur)
Excavating bones at Dinosaur National Monument in Utah
A dinosaur mummy from Mongolia
Dinosaur skin impression from North Dakota
Coelophysis, a late Triassic
theropod
Dinosaur Paleobiology
• Herbivorous dinosaurs - sauropods, the largest animals ever on land, had very small heads. How were they able to eat enough? Gizzards
• In contrast, ornithischians had massive grinding teeth.
Apatosaurus or Brontosaurus, the classic sauropod
Sauropods, Carnegie Museum, 2008
Sauropods, Carnegie Museum, 2008
Sauropods, Carnegie Museum, 2008
Sauropods, Carnegie Museum, 2008
Sauropods, Carnegie Museum, 2008Looks like your diet is working!
Apatosaurus out for a stroll
A modern view of sauropods
Sauropod trackways showing no evidence of tail dragging.
Diplodocus - a gracile sauropod
Sauropods eating a coniferous forest
The massive digestive system of a sauropod, note the large gizzard
Inside of sauropod gizzard, note the gastroliths for grinding food
Sauropod gastroliths
Plant Debris
Iguanodon, an ornithopod
A Cretaceous ornithopod
Crested hadrosaur or “duck-billed” ornithopod
Duck-billed hadrosaur
Hadrosaur “styles”
What were they for?
Hadrosaur (ornithopod)
grinding teeth
Skull of a pachycephalosaur
Head butting by pachycephalosaurs
Stegosaurus
Stegosaurus at the Carnegie
Stegosaurus
Ankylosaurus
Protoceratops from Mongolia
Triceratops at the Smithsonian Institution
Triceratopsfrom
western USA
Dinosaur Paleobiology
• Posture - all dinosaurs had erect limbs, like mammals and unlike living reptiles.
• Complex behaviors - moved in herds, hunted in packs, had breeding grounds like birds.
Sauropod trackways show evidence of herd behavior.
Theropod tracks in Utah
Warm-Blooded Dinosaurs?Evidence
• Erect posture, particularly bipedal
• Bone histology - extensive vascular canals for production of red blood cells
• Structure of the heart - probably had 4 chambers like birds and mammals, rather than 3 chambers like reptiles.
• Birds evolved from theropods
• Evidence of feathers in some dinosaurs
Abundant vascular canals in dinosaur bone support the warm-blooded theory
Thin section of dinosaur bone
www.bio.fsu.edu/erickson/histological_analysis.php
A four-chambered heart. A three-chambered heart has only one ventricle (pump).
Fossilized heart in an ornithopod. CAT scan shows it has 4 chambers.
The ornithopod Thescelosaurus
LV
RV
Theropods and Birds
Tyrannosaurus rex, the Cretaceous theropod everyone loves to hate
Modern view of a T.rex
Sue Henderson, founder of the T. rex named “Sue”
Sue Henderson, founder of the T. rex named “Sue”
It’s my bone, I found it.
Tyrannosaurus Sue on display in the Chicago Field Museum
What makes it a girl?
Tyrranosaurs, Carnegie Museum, 2009
Mechanical model of T. rex shatters a
large bone
Compsognathus, a chicken-sized theropod
Archaeopteryx, the first bird. Its skeleton is nearly
identical to Compsognathus
Head of Archaeopteryx --note the teeth
Yours truly with Archaeopteryxin Berlin, June
1998
Archaeopteryx carcass in a salty lagoon, 160 MY ago
Reconstruction of Archaeopteryx
Feathered dinosaur from China, 2002
“Dave”, a feathered dinosaur preserved in volcanic ash from China
Birds evolved from
feathered theropods
Sinosauropteryx with colored fuzzy feathers based on preserved melanosomes
http://news.nationalgeographic.com/news/2010/01/100127-dinosaur-feathers-colors-nature/
Feathered dinosaur from China, 1998
Reconstruction of feathered dinosaur
Fossilized gastroliths in feathered dinosaur
How similar are birds of prey to their theropod
ancestors?
Chinese dromaeosaur, 1999
Chinese dromaeosaur skeleton with preserved feathers
Closeup of feathers on Chinese dromaeosaur
Complete skeleton of Chinese dromaeosaur with feathers, tail at the bottom.
Tail of Chinese dromaeosaur showing bundles of bony ligaments for stiffening the
tail, typical of theropods.
Actual fossil birds that are different from feathered dinos
Jurassic Blood-Sucking Fleas Discovered in China http://abcnews.go.com/blogs/technology/2012/03/jurassic-blood-sucking-fleas-discovered-in-northern-china/
A team of researchers has unearthed the fossilized remains of blood-sucking mini-beasts dating back at least 65 million years. They found them to be especially suited for sinking their teeth into dinosaurs. Nearly an inch long, the pesky, prehistoric critters were more than ten times the size of today’s average household flea.
