14Mesozoic Diapsids

Mesozoic Diapsids
Goal: To introduce the dinosaurs,
crocodiles and birds
Lepidosaurs
Squamates
Mammalia
Turtles
Tuatara
Lizards Snakes
Archosaurs
Pterosaurs
Crocodiles
Diapsid Phylogeny
Dinosaurs
Birds
Diapsids
Synapsids
Amniotes
Diapsida
Archosauria:
Crocodiles, dinosaurs, birds and numerous extinct
relatives
Extinct early archosaur (~247 million years old) from southern Urals of Russia
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Diapsida
Crocodilia
early crocodilians were
terrestrial
modern species (21)
tropical range
4-chambered heart
range of snout shapes
– alligators and caimans
have wide snouts
– crocodiles can have wide
or very narrow snouts
(fish eaters)
Extant Crocodilians
Alligatoridae
– Alligators (2) and caimans (6)
Crocodylidae
(14 spp)
– Crocodiles
Gavialidae
(1 spp)
– Gharial
Pterosaurs
Size: sparrow to humongous (13m wing span)
Wings not homologous to birds
Parallel evolution with birds
– 4th finger elongated
–
–
–
–
Hollow bones
Large sternum
Large cerebellum
Large eyes
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Diapsida
Dinosauria (includes
Aves)
earliest dinosaurs from
Late Triassic Period
(~228 million years
ago)
Two main groups:
– Ornithischia
– Saurischia
Birds are a group of
saurischian dinosaurs
Dinosaurs: Ornithischian
All
three groups herbivorous
Social behavior
– Parental care
1.Thyreophora
Stegosaurs and Ankylosaurs
Quadrapedal
Plates for thermoregulation?
Ornithischian
2. Ornithipoda:
Hadrosaurs
Bipedal
Complex vocalization?
Anatosaurus
Parasaurolophus
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Ornthischian
3. Marginocephalia
Bony heads
Prenocephale
Protoceratops
Dinosaurs: Saurischian
Two groups
1. Prosauropods
Herbivorous
Long-necked
Largest vertebrates
Diplodocus
Sauropod Biology
Massive
vertebrae to support large size
Cantilevered
Gastroliths
to masticate food in gizzard
Herding
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Saurischian
2. Theropods
Large: Tyrannosaurs
Coelophysis
Saurischian
Small
Theropods
– Carnivorous
– Some group living
Deinonychus
Velociraptor vs Protoceratops
Summary
The reptiles are divided into two major groups, the
Lepidosaurs and Archosaurs.
The Archosaurs include the crocodiles, pterosaurs and
dinosaurs.
The Dinosaurs are divided into two groups based on
their hip bones, Ornithischian and Saurischian.
The Ornithischian include Thyreophora, Ornithopoda,
and Marginocephalia. All were herbivorous.
The Saurisichians include the Prosauropods and
Theropods which comprise the largest herbivores and
carnivores in vertebrate history.
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