Ichthyodectes ctenodon (meaning fish biter with comb teeth) large ichthyodectid growing to more than 10 feet long that lived in the U.S. Western Interior Seaway during the late Cretaceous Period. This Cretaceous seaway was filled with many fierce predators, and, as its name implies, ctenodon was clearly one of them.

The skeleton of this fish fossil consists of 90% real bone and weighs some 150 pounds. The skull is 100% complete, with substantial depth and vertical relief. All four jaws are present and contain 88 teeth. The large cranial crest, which is characteristic of Ichthyodectids, is well-defined and three-dimensional. The left upper jaw displays a healed injury. Complete skeletons of large fossil fish from the Niobrara Formation are exceedingly rare because of scavenging by the many large sharks and other scavengers present in this Cretaceous seaway. The FAMILY Ichthyodectidae contains another impressive fossil fish, Xiphactinus audax, the Xiphactinus audax, the largest bony fish of the Late Cretaceous that grew to lengths near 18 feet.

Ichthyodectes is a member of Infraclass Teleostei, one of three infraclasses in class Actinopterygii, the ray-finned fishes. The Teleostei comprise a diverse group that arose in the Triassic period descending to some 20,000 extant species across some 40 orders. Found at all depths, Teleostei contain many well known fishes, including eels, salmon, trou, catfish, tarpon, tuna, halibut, flounder and cod. By the end of the Cretaceous Period, the teleosts had become the dominant fishes in both the marine and freshwater environments. Teleosts are primarily differentiated by a fully movable maxilla and premaxilla that form the biting surface of the upper jaw. The upper jaw is movable, enabling them to protrude their jaws when feeding.