Xiphactinus is an extinct genus of large, 4.5 to 6 m long predatory marine bony fish that lived during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon. The species Portheus molossus described by Cope is a junior synonym of X. audax. Skeletal remains of Xiphactinus have come from Kansas, Alabama, and Georgia in the United States, as well as Europe, Australia, Canada and Venezuela. This particular fossil was unearthed in Collin County just north of Dallas, TX.

These series of pictures are taken from Texas Memorial Museum, http://www.utexas.edu/tmm/exhibits/