Theropods 2- the origin of birds

Theropods 2 the - Theropods 2the origin of birds Bird display at the Amherst College Museum of Natural History What does it mean to say that birds

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Theropods 2- the origin of birds Bird display at the Amherst College Museum of Natural History
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What does it mean to say that birds are dinosaurs? It means that they are not just related to dinosaurs, but that they are the direct descendants of a specific group of theropod dinosaurs In a cladistic sense, birds share the diagnostic features of dinosaurs
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Bird relationships They are: Vertebrates Tetrapods Amniotes Diapsids Archosaurs Dinosaurs Theropods http://www.biology-resources.com/drawing-bird-skeleton.html
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Great Auk ACM OS 295 External naris Antorbital fenestrae Orbit
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How do we define birds? At one time, we could define birds as flying animals that had feathers The discovery of dinosaurs with feathers demands that we revise the definition http://wiki.cotch.net/upload/5/50/Microraptor-gui.jpg Microraptor , a theropod dinosaur with feathers on its arms and legs
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Modern birds have a number of unique characters that can be used to define them: absence of teeth Large brains and eyes Modified hand (carpometacarpus) Modified foot with tarsometatarsus Synsacrum Reduced tail
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Great Auk ACM OS 295 No living bird has teeth, instead the beak is covered with a horny ramphotheca Large braincase for brain Large orbits house enlarged eyes
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The hand is highly modified, with three digits being fused onto a single bone Humerus Radius Ulna { Carpometacarpus
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Tarsometatarsus- fused metatarsals and ankle bones Moa, ACM 698
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Reduced tail called a pygostyle Note: some birds loose the tail completely Synsacrum- fused vertebrae in hip region Moa, ACM 698
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Other important bird characters: Keeled sternum Pneumaticized bones Fig. 13.1
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Fig. 13.2
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This note was uploaded on 04/22/2008 for the course GEOL 111 taught by Professor Getty during the Fall '07 term at UConn.

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Theropods 2 the - Theropods 2the origin of birds Bird display at the Amherst College Museum of Natural History What does it mean to say that birds

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