Dinosaurs Dinosaur groups Ornithischian Dinosaurs Ornithischian ...
Dinosaurs Dinosaur groups Ornithischian Dinosaurs Ornithischian ...
Dinosaurs Dinosaur groups Ornithischian Dinosaurs Ornithischian ...
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<strong><strong>Dinosaur</strong>s</strong><br />
• The major land animals of the Mesozoic Era<br />
• <strong><strong>Dinosaur</strong>s</strong> occupied all terrestrial top herbivore and predator<br />
niches from the late Triassic to the end of the Cretaceous<br />
• ~225 Ma - 65 Ma<br />
• Descended from Archosaur ancestors, after their split from the<br />
crocodilians and the conventional lizards, snakes<br />
<strong>Dinosaur</strong> <strong>groups</strong><br />
Ornithischia<br />
Prosauropoda<br />
Sauropoda<br />
Theropoda<br />
• NOT Reptiles… more accurate to consider dinosaurs their own<br />
group of animals, as distinct as mammals, reptiles and<br />
amphibians are from each other<br />
<strong>Dinosaur</strong>ia<br />
Eoraptor<br />
<strong>Ornithischian</strong> <strong><strong>Dinosaur</strong>s</strong><br />
• An early offshoot of the main dinosaur lineage<br />
• Mainly herbivores, all known ornithischians are herbivores<br />
• Some early forms may have been omnivorous (insects, etc..)<br />
• Includes an amazing diversity of forms in the Jurassic and<br />
Cretaceous Periods<br />
<strong>Ornithischian</strong> diversity<br />
Pachycephalosaurs<br />
Ceratopsians<br />
Ankylosaurs Stegosaurs<br />
Ornithopods<br />
Marginocephalia<br />
Thyreophora<br />
<strong>Ornithischian</strong>s
Ornithischia: Thyreophora<br />
• Two main <strong>groups</strong>, the Ankylosaurs and the Stegosaurs<br />
• Well-known dinosaurs, abundant skeletons found in Jurassic river<br />
sediments<br />
• Likely moved in small <strong>groups</strong>, rather than large herds.. similar to<br />
modern elephants in this way<br />
• Characterized by heavy armor development, or defensive plates<br />
and spines<br />
• Armor decorations could also have served in mating display<br />
Thyreophora: Ankylosaurs<br />
Euplocephalus<br />
• 5 - 7 m in length<br />
• 3 - 4 tonnes<br />
Thyreophora: Ankylosaurs<br />
Ankylosaurus<br />
• 10 - 11 m in length<br />
• 4 - 6 tonnes<br />
Thyreophora: Stegosaurs<br />
Stegosaurus<br />
• 8 - 9 m in length<br />
• 3 - 4 tonnes
Thyreophora: Stegosaurs<br />
Kentrosaurus<br />
• 3.5 - 5.5 m in length<br />
Ornithischia: Marginocephalia<br />
• Includes the Ceratopsians and the Pachycephalosaurs<br />
• Rose to greatest diversity in the Cretaceous Period<br />
• Took over as most abundant, most diverse land herbivores in the<br />
Cretaceous<br />
• Many species traveled in massive herds… fossil beds of hundreds<br />
of individuals have been found together in river flood deposits<br />
Huayangosaurus<br />
• 4 m in length<br />
Marginocephalia: Pachycephalosaurs<br />
• Two-legged herbivores of the Cretaceous Period<br />
• Share a common trait: all developed massive skulls hosting thick<br />
bony cranial ridges and bulbs<br />
• Not likely defensive structures… most likely used in mating displays<br />
Marginocephalia: Pachycephalosaurs<br />
Stigomoloch<br />
• 2 - 3 m in length<br />
Pachycephalosaurus<br />
• 5 - 8 m in length<br />
Prenocephale<br />
• 2.5 m in length
Marginocephalia: Ceratopsians<br />
• The most abundant dinosaur fossils ever found are the ceratopsians<br />
• Fossil assemblages in the western US include hundreds of<br />
individuals<br />
• Rise to dominance as large land herbivores in the Cretaceous<br />
Period<br />
• Occupied the ecological niche of buffalo, except each individual<br />
weighed over 5 tonnes<br />
• Important point: no grasses had yet evolved in the Mesozoic<br />
Era…<br />
• <strong>Dinosaur</strong> herds would have lived on fast-growing herbaceous<br />
shrubs, or ferns<br />
Marginocephalia: Ceratopsians<br />
• Jurassic forms such as Archaeoceratops are smaller animals, but<br />
still herbivorous<br />
• Common feature is a sharp beak, inside the mouth were rows of<br />
grinding molars for thoroughly chewing tough vegetation<br />
• By Cretaceous, had developed into large grazers, with characteristic<br />
wide, bony head plates…<br />
• Oxygen isotope data indicates that porous bones in plates were<br />
warmer than the rest of the animal… were used as heat radiators<br />
Archaeoceratops<br />
• 1 m in length<br />
Marginocephalia: Ceratopsians<br />
Triceratops<br />
• 5 - 9 m in length<br />
Marginocephalia: Ceratopsians<br />
Centrosaurus<br />
• 6 m in length<br />
Torosaurus<br />
• 6 - 8 m in length<br />
Arrhinoceratops<br />
• 5 m in length<br />
Monoclonius<br />
• 5 - 6 m in length
Marginocephalia: Ceratopsians<br />
Styracosaurus<br />
• 5 - 8 m in length<br />
Ornithischia: Ornithopods<br />
• “Duck-billed” dinosaurs<br />
• Although they didn’t really have a duck’s bill, they were very birdlike<br />
in behavior<br />
• More is known about the behavior of ornithopods (hadrosaurs) than<br />
about any other dinosaurs<br />
• Became a dominant form of herbivore in North America, Asia and<br />
Europe by the middle Cretaceous<br />
• Moved in herds of hundreds of individuals<br />
• Numbers of skeletons found together in river flood deposits<br />
• Appear to have been migratory<br />
• Trackways have been found, showing repeated directional<br />
movement over time<br />
• Practiced colony-breeding<br />
• Colonial nesting sites have been found, with eggs and young<br />
Ornithopods: Hadrosaurs, Lambeosaurs<br />
• Two similar <strong>groups</strong>… lambeosaurs had more elaborate head crests<br />
• Walked using four legs, could stand on two legs… probably used<br />
two legs in running<br />
• Jaws had hundreds of grinding teeth designed for chewing tough<br />
vegetation… teeth constantly grew back, unlike in modern mammals<br />
Lambeosaurs<br />
• Head crest is thought to have been used as a resonating chamber<br />
for loud calls, communication<br />
Parasaurolophus<br />
• 10 m in length<br />
Maiasaura<br />
• 9 m in length
Hadrosaur nesting behavior<br />
• In Western US and Canada, Hadrosaur nesting sites have been found<br />
• Fossil nests of sediment, plant material, mounded up on river floodplains<br />
• 2 m wide, about 0.75 m deep circular mounds<br />
• Some contained fossilized eggs<br />
• Some fossilized eggs contain embryonic hadrosaur chicks<br />
• Fossil chicks range from pre-hatched to young hatchlings<br />
Maiasaura<br />
• Described from Montana fossils, nesting sites<br />
• Name means “good mother lizard”<br />
• Nests contained up to 11 hatchlings, eggs<br />
• Nests were positioned about one adult body-length apart… similar<br />
spacing as that used today by colony-nesting birds<br />
• Vegetation in nest suggests compost incubation… technique is used<br />
today by some birds, crocodiles<br />
• Hatchlings were from 30 cm to 1 m in length… indicates young did not<br />
leave the nest immediately… parental care<br />
• Youngest hatchlings had incomplete leg-bone development.. chicks<br />
could not walk, had to be tended, fed by adults<br />
Maiasaura chicks<br />
Body length ~ 1 m
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