Xiphactinus

Xiphactinus was one of the largest bony fish of the Cretaceous seas, and of all time! Nicknamed, the “bulldog fish,” Xiphactinus had a prominent underbite with large fangs. They were pelagic, open water predators.

There are two species of Xiphactinus: X. audax, and X. vetus.

X. audax teeth have a smooth crown, while X. vetus are faceted, and can have either one or two carinae (cutting edges). The facets are an evolutionary “derived” trait, and serve to strengthen the tooth. Since X. vetus (with the faceted teeth) evolved from X. audax (smooth crown), intermediate teeth are also found and are described as X. audax vetus.

Xiphactinus audax vetus from the Demopolis Formation:

Xiphactinus audax vetus from the Eutaw Formation:

Xiphactinus sp. vertebrae from the Eutaw Formation: