Hypsocormus was a fast-swimming predatory fish about 1 metre (3.3 ft) long, with a half moon-shaped caudal fin similar to that of a modern mackerel. It had a single dorsal fin, elongated pectoral fins and tiny pelvic fins about halfway down the body. An early teleost, Hypsocormus was still primitive, possessing primitive traits such as armored scales. These were, however, small compared with those of earlier fish, allowing greater flexibility. Its jaws were muscular and highly developed, giving it a powerful bite.