Publication Date: 30 August, 2013
Acanthodians, an exclusively Palaeozoic group of fish, are central to a renewed debate on the origin of modern gnathostomes: jawed vertebrates comprising Chondrichthyes (sharks, rays and ratfish) and Osteichthyes (bony fishes and tetrapods). Moreover, this increasingly detailed picture of early gnathostome evolution highlights ongoing and profound anatomical reorganization of vertebrate crania after the origin of jaws but before the divergence of living clades. An important implication of this study is that the braincase of the last common ancestor of modern gnathostomes was effectively shark-like, of which Acanthodes is a narrow-based (‘tropibasic’) variant.
Samuel P. Davis, John A. Finarelli & Michael I. Coates Nature 486, 247–250 (14 June 2012)