| Elasmosaurus serpentinus: In Cope, 1877; Williston, 1903; Williston, 1906. |
| Elasmosaurus sergentinus: In Watson, 1924. |
| Hydralmosaurus serpentinus: In Welles, 1943; Welles, 1949; Welles, 1952;Welles, 1962; Welles & Bump, 1949; Persson, 1960; Persson, 1963; Kuhn, 1964; Carpenter, 1999. |