[Photo] Acanthodes bronni, an acanthodian from the Early Permian of Germany, pencil drawing. Source: http://en.wikipedia.org/wiki/File:Acanthodes_BW.jpg

Acanthodes (meaning spiny base or thorny base) is an extinct genus of spiny shark. Fossils have been found in Europe, North America, and Australia.

Compared with other spiny sharks, Acanthodes was relatively large, at 30 centimetres (12 in) long. The genus had no teeth, instead gills. Because of this, it is presumed to have been a filter feeder, filtering plankton from the water. The Acanthodes has been found to have only a couple of skull bones. It was covered in scales that were cubical in shape.

It also had fewer spines than many of its relatives. Each of the paired pectoral and pelvic fins had a spine, as did the single anal and dorsal fins, giving it a total of just six, less than half that of many other species.

Acanthodians to this day are still a subject of great dispute over their scientific classification. This is due to the fact that they share qualities of both bony fish (osteichthyes) and cartilaginous fish (chondrichthyes).

Acanthodes comes from the name Acanthodii which is derived from the Greek word for spine. The oldest known Acanthodian thrived during the late Ordovician period. They reigned supreme during the Devonian period but they died out at the end of the Permian extinction.

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