page_title: Xiphactinus
section_title: Paleobiology
hierarchical_section_title: Xiphactinus / Paleobiology
caption_attribution_description: English: Fossils of Xiphactinus audax with a Gillicus arcuatus within its stomach. The fossils were recovered from Gove County, Kansas in 1952 by George F. Sternberg (1883–1969). The fossils are on display at the Sternberg Museum of Natural History in Hays, Kansas and described as "probably the most photographed fossil specimen in the world."
context_page_description: Xiphactinus is an extinct genus of large predatory marine bony fish that lived during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon. The species Portheus molossus described by Cope is a junior synonym of X. audax. Skeletal remains of Xiphactinus have come from the Carlile Shale and Greenhorn Limestone of Kansas, and Cretaceous formations all over the East Coast in the United States, as well as Europe, Australia, the Kanguk and Ashville Formations of Canada, La Luna Formation of Venezuela and the Salamanca Formation in Argentina.
context_section_description: Species of Xiphactinus were voracious predatory fish. At least a dozen specimens of X. audax have been collected with 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 owing to the smaller prey's 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.
  Like many other species in the Late Cretaceous oceans, a dead or injured individual 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 the 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.
  The species and all other ichthyodectids became extinct near the end of the Late Cretaceous – see Cretaceous–Paleogene 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 Šachov next to Borohrádek city, by then 16-year-old student Michal Matějka.
  In July 2010 the bones of a Xiphactinus were discovered near Morden, Manitoba, Canada. The specimen was about 6 metres (20 ft) long and was found with the flipper of a mosasaur between its jaws.
caption: Gillicus arcuatus within the stomach of Xiphactinus audax, George F. Sternberg's most famous fossil find.
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