Outlines of Palæontology

adapted adult ambulacral Amer ammonites ammonoids Amphibia ancestors animals aperture apical appear aquatic attached attained became become bioseries body bones brachiopod branches calcareous Cambrian Carboniferous cartilage cavity cephalon changes character cheek close coiled condition consists coral creodont Cret Cretaceous crinoids Crossopterygii Crustacea cusps Demy 8vo described Devonian digits dorsal earliest early echinoids elongated endoskeleton Eocene evolution exhibited fauna feature fishes food grooves forms fossil gastropods genera genus glabella inner Jurassic later limbs living lobe lower jaw mammals margin median Mesozoic modern modification molars mouth notochord Ordovician organs ossicles outer paired fins Palæozoic Permian plates polype portion posterior present primitive protoconch pygidium radial region represented reptiles resembles rocks scales segments septa shape shell showing Side view Silurian skeleton skull species spines stage Stegocephalia structure surface suture-line tail teeth tendency theca tion Trias Triassic trilobites upper valve ventral vertebrates whilst whorls