Genus: Tylosaurus MARSH, 1872
Etymology:

Species: proriger (COPE, 1869) MARSH, 1872

Referred material:

STERNBERG, 1918, EVERHART, 2004

Locality: South side of (Twin) Butte Creek, 15 miles southeast of Russell Springs, Logan County, Kansas.

Horizon: Smoky Hill Chalk Member, Niobrara Chalk Formation.

Biostratigraphy:

Age: Late Santonian to Early Campanian Stage, Middle Senonian Subepoch, Uppermiddle Gulf Epoch, Late Cretaceous.

Material:

USNM 8898: Nearly complete specimen.
Note: With stomach contents of partially digested plesiosaur bones.
Note: Gastroliths were found.