, including a short-necked
E.orientalis confronting a
Dryptosaurus Following the description of the
type species,
E. platyurus, a number of other
Elasmosaurus species were described by Cope, Williston, and other authors. However, none of these species are still definitely referable to the genus
Elasmosaurus today, and most of them either have been moved to genera of their own or are considered dubious names,
nomina dubiathat is, with no distinguishing features, and therefore of questionable validity. Accompanying his 1869 description of
E. platyurus, Cope named another species of
Elasmosaurus,
E.orientalis, based on two back vertebrae from New Jersey. He distinguished
E.orientalis from
E.platyurus by the more strongly developed processes known as parapophyses on the vertebrae, in which he considered it to approach closer to
Cimoliasaurus; however, he still assigned it to
Elasmosaurus on account of its large size and angled sides. The first of these vertebrae was used as a doorstop in a
tailor's shop, whereas the other was found in a pit by Samuel Lockwood, a
superintendent. Cope gave the name
orientalis to the new species, on account of it possibly having a more easterly distribution than
E.platyurus. In 1952 Welles considered the species a
nomen dubium, given how fragmentary it was. In an 1870 reply to Leidy, Cope himself stated that the generic placement of
E.orientalis was in doubt, and that he had illustrated it with a short neck due to believing this was the condition of
Cimoliasaurus. If more remains showed
E.orientalis to have had a long neck like
Elasmosaurus, he stated the image may instead represent
Cimoliasaurus better. constrictus
, which Cope assigned to Elasmosaurus'' In the same 1869 publication wherein he named
E. platyurus and
E.orientalis, Cope assigned an additional species,
E.constrictus, Cope recognized this as a natural condition, and considered
constrictus to be "a species of
Elasmosaurus or an ally". Per Ove Persson retained it as valid in 1963, noting the longitudinal ridge on the sides of the centra as an elasmosaurid trait. In 1995 Nathalie Bardet and
Pascal Godefroit also recognized it as an elasmosaurid, albeit indeterminate. originally assigned to
E.serpentinus Cope discovered another elasmosaurid skeleton in 1876. He named it as a new species,
E.serpentinus, in 1877, and differentiated it by the lack of compression in the rear neck vertebrae, the presence of few sessile ribs among the first few dorsals, and the presence of "weak angles" below the front tail vertebrae. Cope had also discovered another large skeleton that bore great resemblance to the known remains of
E.orientalis from the black shale of the "Cretaceous bed No.4"; he excavated it with the help of George B. Cledenning and Capt. Nicholas Buesen. In 1943 Welles removed
E.serpentinus from
Elasmosaurus, and placed it in a new genus,
Hydralmosaurus. Subsequently, all
Hydralmosaurus specimens were moved to
Styxosaurus in 2016, rendering the former a
nomen dubium. Williston published a figure of another
E. serpentinus specimen in 1914;
Elmer Riggs formally described it in 1939. Welles moved this specimen to the new genus and species
Alzadasaurus riggsi in 1943. Subsequently, a series of 19 neck and back vertebrae from the
Big Bend region of the Missouripart of the Pierre Shale formationwere found by John H. Charles. Cope, upon receiving the bones at the Academy of Natural Sciences, considered them yet another species of
Elasmosaurus. The vertebrae were, according to Cope, the shortest among members of the genus (approaching
Cimoliasaurus in this condition), but he still considered them as belonging to
Elasmosaurus due to their compressed form. He named it
E.intermedius in 1894. However, in his 1906 revision of North American plesiosaurs, Williston regarded the vertebrae as "all more or less mutilated", and found no distinct differences between the remains of
E.intermedius and
E.platyurus. however, he proceeded to label it a
nomen dubium in 1962. In 1874 he and Mudge discovered a specimen in Plum Creek, Kansas. 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 the same year, Carpenter assigned both to
Styxosaurus snowii. Several
Russian species, based on poorly preserved vertebral remains, were assigned to
Elasmosaurus by Nikolay N. Bogolubov in 1911. One was
E.helmerseni, which was first described by W.Kiprijanoff in 1882 from Maloje Serdoba,
Saratov, as
Plesiosaurus helmerseni. Some material from
Scania, Sweden, was assigned to
P. helmerseni in 1885 by H.Schröder. Vertebral and limb remains from
Kursk initially assigned by Kiprijanoff to
P.helmerseni were also moved by Bogolubov to the new species
E.kurskensis, which he considered to be "identical with
Elasmosaurus or related to it". He also named
E.orskensis, based on "very large" neck and tail vertebra remains from Konopljanka,
Orenburg; and
E.serdobensis, based on a single neck vertebra from Maloje Serdoba. However, the validity of all these species has been questioned. Welles considered
E.kurskensis as an indeterminate plesiosaur in 1962. In 2000 Storrs, Archangelsky, and Vladimir Efimov concurred with Welles on
E.kurskensis, and labelled
E.orskensis and
E.serdobensis as indeterminate elasmosaurids. this classification was followed by Alexander Averianov and Vasilii Popov in 2005. Then, in 1916,
Pavel A. Pravoslavlev named
E.amalitskii from the
Don River region, based on a specimen containing vertebrae, limb girdles, and limb bones. Persson considered it a valid species, and a relatively large member of the elasmosaurids; In a work published in 1889,
Richard Lydekker assigned this species to
Cimoliasaurus. Wilhelm Deecke moved
chilensis to
Pliosaurus in 1895, a classification which was acknowledged by Pravoslavlev.
Edwin Colbert later assigned the type vertebra in 1949 to a
pliosauroid, and also assigned other assigned remains to indeterminate elasmosauroids; the type vertebra was recognized as potentially belonging to
Aristonectes parvidens by O'Gorman and colleagues in 2013. Another was
E.haasti, originally
Mauisaurus haasti, named by
James Hector in 1874 based on remains found in
New Zealand. Although its validity was supported for a considerable time,
M.haasti is regarded as a
nomen dubium as of 2017. Pravoslavlev recognized another species from New Zealand,
E.hoodii, named by Owen in 1870 as
Plesiosaurus hoodii based on a neck vertebra. Welles recognized it as a
nomen dubium in 1962; In 1949 Welles named a new species of
Elasmosaurus,
E.morgani. It was named from a well-preserved skeleton found in
Dallas County, Texas. However, part of the specimen was accidentally thrown out during the relocation of the
Southern Methodist University's paleontological collections. Despite its reassignment and the loss of its material,
L.morgani is often considered an archetypal elasmosaurid. Data based on these lost elements were unquestionably accepted in subsequent
phylogenetic analyses, until a redescription of the surviving elements was published by Sachs and Benjamin Kear in 2015. Persson assigned another species to
Elasmosaurus alongside his 1959 description of
"E."helmerseni remains from Sweden, namely
E.(?)gigas. It was based on Schröder's
Pliosaurus(?) gigas, named in 1885 from two dorsals; one was found in
Prussia, the other in Scania. While they were incomplete, Persson recognized that their proportions and the shape of their articular ends differed greatly from pliosauroids, and instead agreed well with elasmosaurids. Given that, at the time of Persson's writing, "there [was] nothing to contradict that they are nearest akin to
Elasmosaurus", he assigned them to
Elasmosaurus "with hesitation". Theodor Wagner had previously assigned
gigas to
Plesiosaurus in 1914. Another species from Russia,
E.antiquus, was named by Dubeikovskii and Ochev in 1967 from the Kamsko-Vyatsky
phosphorite quarry, but Pervushov and colleagues in 1999, followed by Storrs and colleagues in 2000, reinterpreted it as an indeterminate elasmosaurid. ==Classification==