Gyracanthides
Gyracanthides had a body shape similar to that of modern-day sharks, with a skull anywhere from 0.22m to 1.2m long. The had and abdomen were broadly flattened dorsoventrally and were attached to a laterally compressed heterocercal caudal fin. They possessed a long, sharp pectoral spine on their ventral side, as well as a somewhat forked caudal fin. They also had paired spines on their fins. Their entire body, from head to tail and including fin webs, was decorated with small rhomboid polyodontodia. These scales are thin, rhomboid in nature, and slightly concave, with a central pore.
Morphology
They are mainly known for their long pectoral spine.