Xiphactinus

Xiphactinus audax (from Latin and Greek for "sword-ray") was a large, 4.5 to 5 m (15 to 20 feet) long predatory bony fish that lived in the Western Interior Sea, over what is now the middle of North America, during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon (to which it was, however, not related). Portheus molossus Cope is a junior synonym of the species. Skeletal remains of Xiphactinus have come from Kansas, Alabama, and Georgia; Europe and Australia.

Paleobiology
Xiphactinus audax was a vora

cious predator fish. At least dozen specimens have been collected the remains of large, undigested or partially digested prey in their stomachs. In particular, one 13 feet (4.0 m) fossil specimen was collected by George F. Sternberg with another, nearly perfectly preserved 6 feet (1.8 m) long ichthyodectid Gillicus arcuatus, inside of it. The larger fish apparently died soon after eating its prey, most likely due to the smaller fish prey struggling and rupturing an organ as it was being swallowed. This fossil can be seen at the Sternberg Museum of Natural History in Hays Kansas.[2]

Like many other species in the Late Cretaceous oceans, a dead or injured X. audax was likely to be scavenged by sharks (Cretoxyrhina and Squalicorax). The remains of a Xiphactinus were found within a large specimen of Cretoxyrhina collected by Charles H. Sternberg. The

specimen is on display at the University of Kansas Museum of Natural History.

Virtually nothing is known about their larval or juvenile stages. The smallest fossil specimen of X. audax consists of a tooth bearing premaxilla and lower jaws of an individual estimated to be about 12 inches (30 cm) long. [2]

The species went extinct near the end of the Late Cretaceous as the Western Interior Sea began to recede from the middle of North America along with all the other ichthyodectids - see Cretaceous-Tertiary extinction event.

An incomplete skull of what may be a new species of Xiphactinus was found in 2002 in the Czech Republic, in a small town called Sachov next Borohradek city, by student Michal Matejka.