Middle Devonian cartilaginous fish

Cheiracanthus (from , 'hand' and , 'spine') is an extinct genus of a group of fish called Acanthodii (or "spiny sharks"). It was a deep-bodied acanthodian about 12 in. (30 cm) in length. It had a blunt head, upturned tail, and fins protected by spines. Unlike many other acanthodians, it had one, solitary dorsal fin. Cheiracanthus swam at mid-depth in lakes and rivers, seizing small prey in its gaping jaws. Whole fossils of this fish occur only in Mid-Devonian rocks in Scotland, but its distinctive small, ornamented scales crop up around the world, as far south as Antarctica. thumb|Life re

Diplacanthus is an extinct genus of Mid to Late Devonian fish in the class Acanthodii, known as spiny sharks.

Mesacanthus ('middle spine') is an extinct genus of acanthodian fish from Devonian Scotland. It is among the more primitive of the Devonian acanthodians.

Phoebodus is an extinct genus of phoebodontiform total group elasmobranch, known from over a dozen species found worldwide spanning the middle to late Devonian, making it one of the oldest known total group elasmobranchs. Most species are only known from their isolated tricuspid teeth, but one species, Phoebodus saidselachus from the Late Devonian of Morocco, is known from a complete skeleton, estimated to have been in total length in life, which shows that it had a slender body superficially similar to that of the living frilled shark. The teeth of Phoebodus and frilled sharks are also morpho