A marine, swordfish-like fish, Protosphyraena thrived worldwide during the Upper Cretaceous Period. Fossil remains have been found in America, Asia and Europe, although the best known specimen is that found in Kansas (see photo on right). It was quite a large fish, with an average length of 2–3 metres, and shared the Cretaceous oceans with many other aquatic reptiles and predatory fish. Initially, scientists thought that Protosphyraena was the ancestor of modern-day barracudas, which is why its name in Greek means "early barracuda". Recent study has revealed that Protosphyraena was not related to the true swordfish family, but was actually a member of the now extinct family Pachycormidae. Protosphyraena became extinct at the end of the Mesozoic period, roughly 66 million years ago.
Protosphyraena resembled a modern
sailfish, though it was smaller and less hydrodynamic, and adults had large blade-like teeth. Complete skeletons are rare, and skull portions are often found separately to the rest of the skeleton. This is most likely due to the fact that predators could easily tear it apart, scattering the various areas of its body in the process.