Mesacanthus

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

==Description== thumb|250px|Mesacanthus peachi fossil from the Sandwick Fish Beds of [[Quoyloo, Scotland.]] Mesacanthus body fossils have pectoral, pelvic, anal and dorsal fin spines, as well as a pair of prepelvic spines, which are intermediate between the pectoral and pelvic fin spines. They also have small, unornamented, diamond shaped scales. According to Agassiz, the genus also has a distinct tail in which the upper lobe extends to a sharp point and the lower lobe forms a small triangle. Overall the genus is small (average length = 30mm) and fairly conservative, anatomically speaking, for acanthodians.