Compared with other spiny sharks, Acanthodes was relatively relatively large, at Template:Convert/cm long. The genus had no teeth, instead having tooth-like spikes on its gills. Because of this, it is presumed to have been a filter feeder, filtering plankton from the water.
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.