Xiphactinus vetus LEIDY, 1856

Xiphactinus vetus was originally described as the new genus Polygonodon by Joseph Leidy in 1856, several years before the genus Xiphactinus was named from the Santonian-early Campanian of Kansas. Polygonodon was misidentified as a mosasaur in the original description and in some later publications before being recognized as a fish by Dale Russell in his 1967 publication on North American mosasaur. Although currently referred to Xiphactinus (Schwimmer et al. 1997 noted the widespread use of Xiphactinus in most literature on prehistoric bony fish compared to Polygonodon), the known material for X. vetus is very sparse, consisting only of teeth and vertebrae, and given its younger age compared to X. audax, and new material from the Maastrichtian of New Jersey probably lead to Polygonodon being revalidated for X. vetus and Xiphactinus being restricted to the type species X. audax. DeMar and Breithaupt (2006) and Schwimmer et al. (1997) refer material from the Mesaverde Group of Colorado and middle-late Campanian age deposits in the Gulf Coast Plain to X. vetus, but the type horizon of X. vetus is much older than some middle Campanian deposits that have yielded vetus-like teeth, so it is likely that more than one species of Xiphactinus-like fish existed in middle Campanian-Maastrichtian deposits in the eastern US.   

DeMar, D.G.,  and Breithaupt, B.H., 2006. The nonmammalian vertebrate microfossil assemblages of the Mesaverde Formation (Upper Cretaceous, Campanian) of the Wind River and Bighorn Basins, Wyoming. In S. G. Lucas and R. M. Sullivan (eds.), Late Cretaceous Vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35:33-54

Leidy, J., 1856. Notices of remains of extinct vertebrated animals of New Jersey, collected by Prof. Cook of the State Geological Survey under the direction of Dr. W. Kitchell.  Proceedings of the Academy of Natural Sciences of Philadelphia 8: 220-221.

Schwimmer, D. R., Stewart, J.D., and Williams, G.D., 1997. Xiphactinus vetus and the distribution of Xiphactinus species in the eastern United States. Journal of Vertebrate Paleontology 17 (3): 610-615.