Cheiracanthus Acanthodian Devonian Fossil Fish from Scotland

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 massive spines formed of dentine support all fins other than the caudal fins. Indeed, the name Acanthodii is derived from the Greek word for spine. The oldest acanthodian lived during the late Ordovicain. 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 Cheiracanthus; the genus died out in the upper Devonian. As is typical, the most prominent feature to be seen here are the diagnostic spines. This has some distortion to the anterior due to post-mortem bloating.