Symposium: Ancestry and origin of birds (original) (raw)
1994, Journal of Ornithology
A skeletal model constructed from casts of the London Archaeopteryx gives a unique threedimensional look at a Jurassic bird. The acetabulum of the pelvis has the articular region restricted to the anterior margin. This is unlike modern birds where the articular area is posterior and supplemented by an antitrochanter; nor is it like dinosaurs that have their articular surface on the dorsal rim of the acetabulum. When the leg is articulated to the pelvis, the only posture possible is erect, and primate-like. A vertical posture along with elongated manus phalanges, highly recurved manus claws, and laterally facing glenoids provide an ideal morphology for climbing tree trunks. They also support suggestions that flight may have originated from vertical clinging and leaping. When on the ground, Archaeopteryx would have been clumsy and vulnerable to predators. Because of the lack of a triosseai pulley system it is unlikely that it could take off directly from the ground. This capacity is the signal feature of more modernized birds with a horizontal posture, antitrochanter, upward facing glenoid, keeled sternum, triosseal canal, loss of manal claws and phalanges.
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