Description: The Acanthodians are jaw-bearing fish who still are the subject of dispute over their systematic position. They possess highly advanced, spindle-shaped bodies thought to have made them swift swimmers. The body was covered in small mosaic-like scales. They possessed small teeth that were typically confined to the lower jaw; some were toothless. The feature they all share in common is the fact that all fins other than the caudal are supported by massive spines formed of dentine. Indeed, the name Acanthodii is derived from the Greek word for spine. The oldest acanthodian lived during the late Ordovician. They reached their peak during the Devonian, and became extinct during the Great Dying of the end-Permian extinction. This well-preserved example is known as Acanthodes bridgei, the patronymic genus. The genus died out in the lower Permian. As is typical, the most prominent feature to be seen here are the diagnostic spines. This is one of the few taxa known from an ontogenic series from juvenile to adult that has demonstrated that scales developed fisrt on the caudal peduncle and then on the anterior flanks next to the lateral line.

Also see: Paleozoic Fish Fossils