Williston regarded the vertebrae as "all more or less mutilated", and found no distinct differences between the remains of E.intermedius and E.platyurus. In 1952 Welles opined that, if E.intermedius was valid, "it must be referred to a pliosaurian genus"; however, he proceeded to label it a nomen dubium in 1962. Three shorter vertebrae found alongside E.intermedius, assigned by Cope to the new genus and species Embaphias circulosus, were also considered by Welles to be a nomen dubium in 1962. Williston named a number of other new Elasmosaurus species in his 1906 revision. In 1874 he and Mudge discovered a specimen in Plum Creek, Kansas. While he initially assigned it in 1890 to a new species of Cimoliasaurus, C.snowii, he subsequently recognized the elasmosaurid nature of its humerus and coracoids. Thus, he renamed the species E.snowii. A second specimen, discovered by Elias West in 1890, was also assigned by him to E.snowii. In 1943 Welles moved E.snowii to its own genus, Styxosaurus, where the species has remained. However, the West specimen was assigned to Thalassiosaurus ischiadicus (see below) by Welles in 1952; Carpenter returned it to S.snowii in 1999. Williston also reassigned the species E.ischiadicus from the genus Polycotylus, where he had initially placed it when he named it in 1903. The type remains were discovered by him in the same 1874 expedition with Mudge. Williston assigned another specimen discovered by Mudge and H.A. Brous in 1876. In 1943 both specimens were assigned to the new genus Thalassiosaurus by Welles, who then assigned the latter to the new genus and species Alzadasaurus kansasensis in 1952. Glenn Storrs considered both to be indeterminate elasmosaurids in 1999; in the same year, Carpenter assigned both to Styxosaurus snowii. An elasmosaurid specimen was found by Handel Martin in Logan County, Kansas in 1889. Williston named this as a new species, E.(?)marshii. He bore reservations about its referral to the genus, and he recognized that it possibly pertained to another genus. In 1943 Welles moved E.(?)marshii to a genus of its own, Thalassonomosaurus; however, Carpenter sunk T.marshii into Styxosaurus snowii in 1999. Another species, E.nobilis, was named by Williston from very large remains discovered by Mudge in 1874 in Jewell County, Kansas. Welles named E.nobilis as a species of Thalassonomosaurus, T.nobilis, in 1943, but it too was considered to be part of S.snowii by Carpenter. Finally, two exceptionally large dorsal vertebrae collected by Charles Sternberg in