Xiphactinus

• Name: Xiphactinus (combination Latin and Greek for "sword ray"); pronounced zih-FACK-tih-nuss
• Habitat: Shallow waters of North America, Western Europe, and Australia
• Historical Period: Late Cretaceous (90-65 million years ago)
• Size and Weight: About 20 feet long and 500-1,000 pounds
• Diet: Fish
• Distinguishing Characteristics: Large size; slender body; prominent teeth with distinctive underbite

About Xiphactinus

At 20 feet long and up to half a ton, Xiphactinus was the largest bony fish of the Cretaceous period, but it was far from the top predator of its North American ecosystem--as we can tell from the fact that specimens of the prehistoric sharks Squalicorax and Cretoxyrhina have been discovered containing Xiphactinus remains. It was a fish-eat-fish world back in the Mesozoic Era, though, so you shouldn't be surprised to learn that numerous Xiphactinus fossils have been discovered containing the partially digested remains of smaller fish. (Finding a fish inside a fish inside a shark would be a true fossil trifecta.)

One of the most famous Xiphactinus fossils contains the almost-intact remains of an obscure, 10-foot-long Cretaceous fish called Gillicus. Paleontologists speculate that the Xiphactinus died right after swallowing the fish, possibly because its still-living prey managed to puncture its stomach in a desperate attempt at escape, like the grisly extraterrestrial in the movie Alien. If this is really what happened, Xiphactinus would be the first fish known to have died from acute indigestion.

One of the odd things about Xiphactinus is that its fossils have been discovered in just about the last place you'd expect, the landlocked state of Kansas. In fact, during the late Cretaceous period, much of the American midwest was submerged under a shallow body of water, the Western Interior Sea. For this reason, Kansas has been a rich fossil source of all sorts of marine animals from the Mesozoic Era, not only giant fish like Xiphactinus but various marine reptiles as well, including plesiosaurs, pliosaurs, ichthyosaurs, and mosasaurs.