Dinosaurs

Dinosaurs - Birds: SDC: planar feathers w/...

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Birds: SDC: planar feathers w/ asymmetrically-positioned shafts, keeled sternum, pygostyle (reduced tail), toothless opposable big toe, modified shoulder for upstroke, tarsometatarus (bone used for maneuverability), alula (feather used to break turbulence), carpometacarpus (fused wrist and hand used to reduce flexion), furcula (wishbone), hollow air-filled bones. Birds closely related to dromaeosaurs (raptors). Oldest bird dated back to late Jurassic found in Germany: Archaeopteryx. Characteristics: Bird- expanded braincase, asymmetric feathers, keeled sternum, pneumatic bones. Dinosaurs- teeth, 3 fingers w/ claw, long tail, raptor-like pelvis. Feathers on Dinosaurs : Not symmetrical (not able to help in flight. Lack of feathers and short arms also proves not used to fly). Used for insulation, display, insect-catching, increased speed/lift. Evidence used against raptor descendancy: dinos w/ feathers are flightless birds that evolve into dino characteristics, 1 st true feathers appear in late Triassic along with 1 st real bird, archaeopteryx appears Jurassic; raptors appear cretaceous. Aviales: last common ancestor of Archaeopteryx and living birds SDC: asymmetric feathers (flight), keeled sternum, pneumatic bones, opposable big toe? Pygostylia : e.g., Confuciusornis. SDC: pygostyle, large corocoid bone between arm and sternum Ornithothoraces: two groups with the following SDCs: carpometacarpus, flexible wishbone- furcula, modified backstroke shoulder Enantiornithes: dominant birds of Mesozoic Ornithurines , SDC: full backward rotation of pubis, synsacrum, tarsometatarsus Aves (also called Neornithes): modern birds, dominant after the K-T extinction,
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