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Archaeopteryx

Archaeopteryx. One of first bird fossils described (1861) Still the earliest known bird Lived 145 MYA “Missing link” between birds and reptiles, prominent in early debates about evolution (Origin of Species published 1859). Avian Features. Feathers (asymmetric) Wing-like forelimb Hallux

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Archaeopteryx

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  1. Archaeopteryx • One of first bird fossils described (1861) • Still the earliest known bird • Lived 145 MYA • “Missing link” between birds and reptiles, prominent in early debates about evolution (Origin of Species published 1859)

  2. Avian Features • Feathers (asymmetric) • Wing-like forelimb • Hallux • Furcula

  3. Reptilian Features • Teeth instead of bill (not as critical as one might think) • Claws on forelimb • Tail with vertebrae • No keel • No reinforced ribs

  4. Archaeopteryx lived in the middle of the age of dinosaurs, before Tyrannosaurus rex, before flowering plants

  5. 4 Lines of Reptilian Evolution • Turtles • Aquatic reptiles (extinct) • Mammal line • Lizards/snakes + thecodonts

  6. Thecodont radiation • Armored dinosaurs (Ornithischia) (extinct) • Flying reptiles (Pterosaurs) (extinct) • Crocodiles • Sauropods (extinct) • Theropods (extinct) • Carnosaurs • Coelurosaurs

  7. Classic theory – birds evolved from thecodonts • Crocodile link rejected • Long period with no fossil forms (80 MY) • Arboreal origin flight • Leaping • Parachuting • Gliding • Feathers – flight first, insulation second

  8. Ostrom theory – birds evolved from coelurosaurs • Group appeared 155 MYA (too late?) • Extreme convergence of skeletal features • Cursorial origin of flight • Balance • maneouver • Feathers – insulation first, flight second • Dinosaurs as endotherms

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