"Tylosaurus" subsequently became the near-universally accepted genus for "T. proriger", "T. dyspelor", and "T. micromus". An exception to this adoption was Cope, who refused to accept Marsh's new genus and continued to refer to its species as "Liodon". Cope also insisted that "Rhamphosaurus" was not preoccupied, arguing that while it was indeed used as a genus of lizard, it was subsequently synonymized with other genera before 1872 and was thus a vacant taxon. Cope's persistence can be seen in his 1874 description of the fourth described species of "Tylosaurus", which he named "Liodon nepaeolicus". This type specimen of this species consists of a right lower jaw, a partial upper jaw, a quadrate bone, and a dorsal vertebra and was discovered by geologist Benjamin Franklin Mudge in an unspecified deposit of Cretaceous grey shale about a half-mile south of the Solomon River. The fossils are stored in the American Museum of Natural History under the catalog number AMNH 1565. The specific epithet "nepaeolicus" is in reference to the Nepaholla, the Native American name for the Solomon River. "Liodon nepaeolicus" was formally transferred to the genus "Tylosaurus" in Merriam's 1894 publication.