Physical appearance and biologyEdit
Xiphactinus was one of the fastest and most agile creatures in the Cretaceous seas. Not only that, it was also one of the most grotesque. Its ugly appearance has earned it the nickname "bulldog fish". With all that aside, Xiphactinus was a swift and powerful carnivore. It had a streamlined body and a broad and muscular tail, allowing it to reach speeds of 60kph. At this speed, it could outrun nearly all the fish around it.
Behaviour and traitsEdit
Xiphactinus spent most of its time cruising the surface waters of the shallow seas hunting fish. Its lower jaw was specially hinged so that its mouth could be opened particularly wide. Xiphactinus would pursue its prey and swallow it whole. Its diet wasn't exclusively fish, it also hunted seabirds like Hesperornis and even possibly pterosaurs.
Xiphactinus had the ability to jump clear of the water like modern dolphins. This was probably done to dislodge any loose scales or attached parasites. However, Xiphactinus was vulnerable to attack. Larger predators like Tylosaurus could easily kill it.
In a feeding frenzy, two Xiphactinus attacked several Hesperornis. One managed to eat a Hesperornis whole. As the remaining Hesperornis swam away, the Xiphactinus did the same. Later, as some Pteranodon swam close to the water's surface, a Xiphactinus nearly caught one.