BISC 316 Lecture Notes - Lecture 25: Shuvuuia, Dactyly, Ankle

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 316
• Professor: Joan Sharp

Document Summary

Compare wing support of two taxa of flying archosaurs. Pterosaurs: digit iv elongated, supports membranous skin of wing, digit i, ii, iii present as claws, membrane forms wing surface. Birds: digits fused, some lost, distal portion of wing supported by digit iii, digit ii reduced, iv very reduced feathers form wing surface. Interpret relationships between birds and other dinosaur in figure 19. 25. Features birds share with maniraptor dinosaurs intertarsal ankle joint. Hollow pneumatic bones furcula (wishbone) formed by fusion of clavicles elongate, mobile, s-shaped neck tridactyl foot feathers swilling wrist joints glenoid fossa oriented laterally, not ventrally egg-brooding posture sleeping posture, head tucked under forearm. Evidence that non-avian reptile scales, bird feathers, mammalian fur are homologous all develop from embryonic epidermal placodes. Placodes and set of signalling molecules formed scales in ancestral amniote same developmental genes are expressed in epidermal placodes: edar gene, mediate interacion btwn epidermis dermis, shh gene, provide positional info.