Today – 4/12Today – 4/12

• Critter on the T-shirt

• Ornithischia

• Pterosaurs, marine reptiles, crocodiles

• Geodaze

Last time

Evolutionary convergence

Sauropodomorpha – Prosauropoda (Plateosaurus) and Sauropoda (Apatosaurus, Brachiosaurus, and Alamosaurus). Lifestyles and social behavior

Sauropod nesting grounds in Argentina

Test 4/24

Review 4/23, 5:45-7, right here

15% from ch. 8-14 of BotF

Clade Ornithischia

Pisanosaurus – oldest known ornithischian

228 Ma – Ischigualasto Formation

Clade Ornithischia

Shared evolutionary novelties include pelvic structure, ossified tendons on the vertebral column, and the predentary bone

Ancestral ornithischian – Pisanosaurus, 228 Ma form the same Ischigualasto Formation as Eoraptor and Herrerasaurus

Contains three clades: Thyreophora, Ornithopoda, and Marginocephalia

Scutellosaurus – ancestral thyreophoran, 200 Ma in N AZ

Clade Thyreophora

Healthy animals, from 200 Ma up to the end

No egg fossils, few tracks, mostly isolated individuals except for groups of juvenile ankylosaurs from China so no evidence for social behavior except maybe for herding of young, quadrupedal low-grazing herbivores

Scutellosaurus – 200 Ma N AZ, 4 ft long, 18” tall at hips, 22 lbs, ancestral thyreophoran

More Thyreophora

“Armored dinosaurs”, up to 30 feet long, 4.5 tons, scissoring side spikes , osteoderms, two clades – ankylosaurs (tail clubs), nodosaurs (no tail clubs)Stegosauria – two rows of alternating plates or spikes running down back, four tail spikes. Thermoregulation, defense, species recognition? Mainly Jurassic, but held on to the end, no “second brain”, up to 30 feet long, 3 tons

Duckbill jaws

Clade Ornithopoda

Early Jurassic to the end, chewers, some signs of diseases and healed wounds

Iguanodon – 130 Ma, lots of trackways: slow! and social, 30 ft long, 16 ft tall, 4.5 tons, thumb spike, bipedal

Duckbills – late Cretaceous, big: up to 40 feet long, two clades – hadrosaurs (no head crest, dewlap) and lambeosaurs (head crests for display and sound, sexual dimorphism)

More duckbills

On the menu for tyrannosaurs – Edmontosaurus found with healed bite in vertebra, another with tyrannosaur tooth embedded in healed rib! Found in coprolites.

Maiasaura – colonial nesting grounds, nests evenly spaced about 22 feet apart (size of an adult), site fidelity, 10-footers still in nest!, grew fast, herd of 10,000 killed in Montana volcanic eruption

Dome-headed dinosaur, or

pachycephalosaur

Triceratops

Clade Marginocephalia

Cretaceous only, two clades, only found in NA, Asia, and EuropeDome-headed dinosaurs – skulls up to 10 in thick!, display (?) head-butting (?) ramming (?) defense (?), poor fossil record, 25 ft long, 1.5 tonsHorned-dinosaurs (ceratopsians) – 27 feet long, 8 tons, up to 10 foot long skulls!, intraspecific combat, many bone beds (social), pathologies related to weight (torn tendons, stress fractures)

Deinosuchus – alligator of death, 40 (?) feet long