Cheiracanthus

Cheiracanthus ("hand 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.