PCB 4674C Lecture Notes - Lecture 21: Feathered Dinosaur, Mesozoic, Thecodontia
Document Summary
145 million years ago to return to the dinosaurs: these well-adapted forms dominated the terrestrial landscape during the jurassic and cretaceous. Dinosaurs are typically thought to have gone extinct at the end of the. Cretaceous, but this is the result of grade thinking. 66 million years ago - while the dinosaurs reigned, little furry animals watched in the background. With the final extinction of the dinosaurs (archosaurs minus birds), these little furry creatures (the mammals) underwent explosive diversification: these little creatures were descendants of one branch of the synapsids or mammal-like reptiles, the therapsids. By the eocene period, 40 million years ago, the mammalian radiation really got underway. Note the distinction between the time of radiation and the time of origination. The radiation of mammals is possibly due to ecological release following extinction of dinosaurs. 5 million years ago - african deposits of pliocene age yield fossils of hominids, primarily australopithecines, the lineage giving rise ultimately to.
