3454chapter27 - Birds, Ch. 27 I. Class Avesbirds; 9,600+...

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Birds, Ch. 27 I. Class Aves—birds; 9,600+ species of feathered, often flying, endothermic, diapsid dinosaurs A. Common to all extant birds: feathers, wings, bill, oviparous B. Evolved from theropod dinosaurs sometime in the Jurassic period (maybe 175 mya)
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1. Archaeopteryx is about 147 my old 2. protoavis 75 my older. .. 3. T.H. Huxley said glorified reptiles
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4. Alternately, they may have evolved earlier from other diapsids called thecodonts (paraphyletic) a) Dinosaurs and birds may have evolved independently from thecodonts b) Both theories have support 5. currently classified as therapods
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6. coelurosauria -- contains tyrannosaurs, oviraptor, velociraptor, birds a) maniraptora (1) oviraptorosauria
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(2) dromaeosauridae (velociraptor, etc.) (3) troodontidae (4) aves
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(a) archaeopteryx (b) confuciusornithidae (c) enantiornithes (d) euornithes (true birds) i) patagopteryx ii) hesperornithiformes iii) ichthyornithiformes
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neornithes (modern birds) B. Feathers—first evolved for flight? or insulation? or social
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3454chapter27 - Birds, Ch. 27 I. Class Avesbirds; 9,600+...

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