Akmonistion
Akmonistion is an extinct genus of holocephalian that lived in the Early Carboniferous. The genus contains a single species, "A. zangerli". It is distinguished by an unusual enlarged formation of the dorsal fin, called a "spine-brush complex", of unknown function. This is also found in the better known genus "Stethacanthus". Remains have only been found near Bearsden in Scotland. The genus name is derived from the Ancient Greek “"akmon"” (“anvil”) + "“istion"” (“sail”) referring to the appearance of its first dorsal fin.