Pycnodontiformes

Pycnodontiformes (sometimes included inside a larger superorder, Pycnodontomorpha) is an extinct order of primarily marine bony fish. The group first appeared during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America.

They were small to middle-sized fish, generally with laterally-compressed deep bodies, some with almost circular outlines, adapted for manoeuvrability in reef-like environments, though the group was morphologically diverse. Most, but not all members of the groups had jaws with round and flattened teeth, well adapted to crush food items (durophagy), such as echinoderms, crustaceans and molluscs. Some pycnodontiformes developed piranha like teeth used for eating flesh. Most species inhabited shallow marine reef environments, while a handful of species lived in freshwater or brackish conditions.