Conodonts

Conodonts, minute fossil tooth-like bodies, about a line in length, generally with acute denticles or serrated edge and mainly calcareous in composition, which occur in Cambro-Silurian and Devonian rocks in England, Russia, and North America. They differ from the minute jaws of annelids in being calcareous rather than horny, and are considered with some certainty to be the teeth of cyclostomatous or lamprey-like fishes.