Outline 17: and of Reptiles

• The first reptiles appeared in the Mississippian. • They evolved from , which first appeared in the . • The evolutionary jump was the invention of the . The Amniote Egg

• Requires , 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 . Egg: No Shell in a Morgantown pond Typical amniote egg with an embryonic . hatching from their amniote eggs Eggs Fossilized still in the shells Searching for sauropod dinosaur eggs in 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 The fate of many hatchlings Dinosaur parent died while sitting on nest with eggs Major Reptile Groups

- the stem reptiles, are the only living group. • - the -like reptiles. evolved from synapsids. • - all modern reptiles except for turtles. Dinosaurs evolved from diapsids.

Pennsylvanian or stem reptile Living anapsid reptile: snapping Living reptile: reptiles:

Triassic synapsid reptiles: or mammal-like reptiles The : A Nile . Notice the unspecialized reptilian teeth. Crocodile from the 28 ft. caught in Alabama A short-necked Plesiosaur A Jurassic plesiosaur A eating a Cretaceous looked like mammalian dolphins An died giving birth The Flying Reptiles - : did they have a high ? Evolution of Dinosaurs

• First appeared in late , 220 MY ago. • Evolved from thecodont (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 – Ornithopods – Pachycephalosaurs – Stegosaurs – Ankylosaurs – Ceratopsians Dinosaurs are popular with the public Jack Horner, State Univ.

Dr. Alan Grant, was a very active predator waiting to ambush The prey’s view of a pack of Dinosaur classification


Ornithischians Dinosaur hips differ between the two major groups

Saurischian hip structure (theropod) Saurischian hip structure (sauropod) Ornithiscian hip structure (stegosaur) A dinosaur mummy from Mongolia , a late Triassic theropod Dinosaur Paleobiology

• Herbivorous dinosaurs - sauropods, the largest ever on land, had very small heads. How were they able to eat enough? Gizzards • In contrast, ornithischians had massive grinding teeth. or Brontosaurus, the classic sauropod Apatosaurus out for a stroll A modern view of sauropods Sauropods, Carnegie Museum, 2008 Sauropods, Carnegie Museum, 2008 Sauropods, Carnegie Museum, 2008 Sauropod femur of a found in in 2014. Sauropod trackways showing no evidence of dragging. Sauropods eating a coniferous The massive digestive system of a sauropod, note the large gizzard Inside of sauropod gizzard, note the for grinding Sauropod gastroliths

Plant Debris , an ornithopod Duck-billed hadrosaur Crested hadrosaur or “duck-billed” ornithopod Hadrosaur (ornithopod) grinding teeth of a pachycephalosaur Head butting by pachycephalosaurs Stegosaurus at the Carnegie Stegosaurus Protoceratops from Mongolia at the Smithsonian Institution 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 . 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 - probably had 4 chambers like birds and mammals, rather than 3 chambers like reptiles. • Birds evolved from theropods • Evidence of 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 (pump). Theropods and Birds Jurassic Park 3D https://www.youtube.com/watch?v=5y4PTsFI2v8 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? Stan

Sue Tyrranosaurs, Carnegie Museum, 2009 , a chicken-sized theropod , the first bird. Its skeleton is nearly identical to Compsognathus

Head of Archaeopteryx -- note the teeth Combination of bird and theropod features Archaeopteryx carcass in a salty lagoon, 160 MY ago Reconstruction of Archaeopteryx

Feathered dinosaur from , 2002 ,a preserved in volcanic ash from China Birds evolved from feathered theropods with colored fuzzy feathers based on preserved

http://news.nationalgeographic.c om/news/2010/01/100127- dinosaur-feathers--/ Feathered dinosaur from China, 1998 Reconstruction of feathered dinosaur, Caudipteryx Fossilized gastroliths in feathered dinosaur

Actual fossil birds that are different from feathered dinos