- Peter Holland
‘Deuterostomes II: the rise of vertebrates’ describes the key features of animals in the Chordata phylum — large size, efficient blood circulation, dynamic skeleton, intricate brain, protective skull, and elaborate sense organs. This phylum is separated into four subphyla; the first is made up of the ‘jawless’ hagfish and lampreys, which separated away from the vertebrates with jaws early in the evolutionary lineage. The jawed vertebrates diversified into three lines, which are the ‘chondrichthyans’ (including sharks with their cartilaginous skeletons), the ‘actinopterygians’ (ray-finned fish), and ‘sarcopterygians’ (lobe-finned vertebrates). The physical characteristics of lampreys, hagfish, sharks, skates, rays, ray-finned fish are noted.