BIOL-3030 Lecture Notes - Lecture 18: Sclerotic Ring, Diapsid, Cephalopod Limb
Document Summary
Major groups of distinguished by holes in skill. Shared features from common ancestry and ectothermy. Unique features (shell, venom) allow for different lifestyles. Warmer climate, no ice caps, more ocean. Who (positions of fossils lineages in diapsid phylogeny) Marine reptiles (not actually sister taxa in diagram pp18) Pterosaurs, dinos, crocs are all archosaurs - crocs closest living relative (except birds which are dinosaurs) Classic nessie shape, but diverse variations on this theme. Long propulsive tail; feet modified to paddles for steering. Pelvis poorly attached to spine - not weight-supporting. Many also increase number of digits hyperdactyly. Young born tail first, embryos oriented this way, gut contents include fish scales and cephalopod arm hooks. Eyes are very close to their nostrils. They probably kept that portion of skull above water to breathe. Calcaneum small - ankle now a simple hinge. Suggests feet pointed forwards in upright limb posture. Aids fast forward running (some dinos) or roosting with feet (pterosaurs)
