EARTH 7 Lecture Notes - Lecture 8: Saurischia, Digitigrade, Quadrupedalism
Document Summary
The end permian mass extinction and an overview of dinosaurs. Landmark study that first gave us an indication of significant, focused extinction events. ~80% marine species and ~70% terrestrial vertebrate species went extinct. 10-30 million years for recovery of global diversity. Ornithodira novelties: mesotarsal ankle, rotates in just one plane, good for running, digitigrade stance, ankle is above the ground, stand on the tips of their toes. Two groups of dinosaurs: saurischia, (cid:862)lizard-hipped(cid:863, forward pubis, does(cid:374)"t defi(cid:374)e the group (cid:271)e(cid:272)ause it"s a(cid:374) a(cid:374)(cid:272)estral (cid:272)hara(cid:272)ter, extant (birds, ornithischian, (cid:862)(cid:271)ird-hipped(cid:863, reverse pubis, evolved convergently within saurischians, extinct. Initially small-bodied bipeds: later, evolved large, quadrupedal bodies. Quadrupedal evolved within dinosaurs many times independently. Growth rates indicated by dinosaur bones suggest that they may have been mesothermic or endothermic: also several other lines of evidence indicating that dinosaurs maintained elevated body temperatures. Dinosaurs appear to have evolved in southern pangaea and spread from there.
