Xiphactinus

Xiphactinus is an extinct genus of large predatory bony fish from the Cretaceous. Its fossils are known especially from the Western Interior Seaway of North America.

Teleost: A diverse group of ray-finned fishes that includes most living fish species. Xiphactinus belonged to this major branch of bony fishes.
Fish-within-a-fish fossil: A fossil specimen of Xiphactinus audax preserving the remains of a large, undigested fish in its abdomen. This specimen provides direct evidence of Xiphactinus's predatory feeding.
Predation: An ecological interaction in which one organism kills and consumes another. Xiphactinus was a predator whose feeding is documented by fossil gut contents.
Ichthyodectiformes: An extinct order of mostly predatory bony fishes common in Mesozoic seas. Xiphactinus belonged to this group of large-bodied marine fishes.
Cretaceous: The geologic period from about 145 to 66 million years ago, ending with a mass extinction. Xiphactinus lived in Cretaceous marine environments.
Xiphactinus audax: The best-known species of Xiphactinus, represented by large fossils from Late Cretaceous North America. This species anchors most accounts of the genus's anatomy and ecology.
Jaw: A skeletal structure that supports the mouth and helps seize or process food. Its powerful jaws and teeth suited Xiphactinus to capturing large prey.
Gillicus: An extinct genus of smaller Cretaceous ichthyodectiform fish. Gillicus is both a close ecological neighbor and the prey in a famous Xiphactinus fossil.
Western Interior Seaway: A shallow inland sea that divided North America during much of the Cretaceous. Many famous Xiphactinus fossils come from this seaway's deposits.
Niobrara Formation: A Late Cretaceous rock formation in the central United States, rich in marine fossils. Its chalk and limestone preserve notable Xiphactinus specimens.

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