EDWARD'S LECTURE NOTES:
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C O U R S E
Dinosaur Paleobiology
Philip John Currie, University of Alberta
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C O U R S E L E C T U R E Ornithischians Notes taken on January 14, 2016 by Edward Tanguay |
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two key traits that distinguish ornithischians and saurischians
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1. ornithischians have a hip with a pubic bone which points backwards
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sometimes it has a projection that points forward, but they are usually short
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resembles those of birds
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this is an evolutionary convergence
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birds belong among saurischian dinosaurs
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plants are hard to digest
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the backward-pointing public bone gave the ornithischians room for a large digestive track
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2. a special bone in the lower jaw
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predentary bone
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no other animals have one
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the predentary [pree-DEN-taree] is an extra bone in the front of the lower jaw, which extends the dentary (the main lower jaw bone), and coincides with the premaxilla in the upper jaw
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together they form a beak-like apparatus used to clip off plant material
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ornithischians were herbivores
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gave ornithischians tool for slicing off plant stems
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five main lineages
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1. Hadrosaurs
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duck-billed
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Ornithopods started out as bipeds but Hadrosaurs probably walked on all four legs most of the time
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Hadrosaurs
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had hand encased in a mitten of skin
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crests on top of heads and flat heads
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Iguanodons
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spikey thumb
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2. Ceratopsia
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Tricerotops
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four-legged dinosaurs
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relatively short tails
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Casmosauraus
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an extreme form of skull bones coming out the back of the head
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some had horns over their eyes
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unlike duck-billed dinosaurs, had very narrow skulls
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more like a parrot's beak
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teeth had elaborated banks of teeth for sheering and crushing plant material
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older forms don't have so many frills and horns as newer forms, but they still have a beak
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Pachyrhinosaurus
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Albert and Alaska
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bony mass called a boss
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nasal
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above eyes
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3. Pachycephalosauria
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dome-headed
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intelligent-looking because they have high-domed skulls
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unfortunately, brain was not very large
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most of the skull was solid bone
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heads may have been used as battering rams
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don't have long legs, so probably not that fast
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skeleton is frail so not many exist
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1920 a skeleton of Pachycephalosauria was found
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4. Stegosauria
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walked on all four legs
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front legs shorter
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skull small compared to rest of body
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teeth were leaf-shaped and had narrow beak
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plates or spikes along the back
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bone that forms in the skin: osteoderm
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earlier forms had spikes
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later forms had plates
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but even later forms had spikes at end of tail
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5. Ankylosauria
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armored dinosaurs
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had osteoderms
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walked on four legs
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skulls were blocky
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teeth were small
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on some, the end of the tail had a bone which was used as a kind of club
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two main branches of the dinosaur family tree
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1. Saurischian Hips ("lizard hip dinosaur")
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a. Sauropods ("long neck dinosaurs")
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Brontosaurus
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b. Theropods
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Tyrannosaurus
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common birds
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2. Ornithischia Hips
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a. Hadrosaurs
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duck-billed
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b. Ceratopsians
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Triceratops
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c. Pachycephalosauria
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dome-headed
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d. Stegosauria
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Stegosaurus
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e. Ankylosauria
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armored dinosaurs