page_title: Elasmosaurus
section_title: Known and possible fossil elements
hierarchical_section_title: Elasmosaurus / History of study / Known and possible fossil elements
caption_attribution_description: Pectoral and pelvic bones of Elasmosaurus, which are now lost
context_page_description: Elasmosaurus is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, and was sent to the American paleontologist Edward Drinker Cope, who named it E. platyurus in 1868. The generic name means "thin-plate reptile", and the specific name means "flat-tailed". Cope originally reconstructed the skeleton of Elasmosaurus with the skull at the end of the tail, an error which was made light of by the paleontologist Othniel Charles Marsh, and became part of their "Bone Wars" rivalry. Only one incomplete Elasmosaurus skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera.
  Measuring 10.3 meters long, Elasmosaurus would have had a streamlined body with paddle-like limbs, a short tail, a small head, and an extremely long neck. The neck alone was around 7.1 meters long.
context_section_description: Today, the incomplete holotype specimen, catalogued as ANSP 10081, is the only definite specimen of Elasmosaurus. It was long exhibited, but is now stored in a cabinet with other assigned fragments. The specimen consists of the premaxillae, part of the hind-section of the right maxilla, two maxilla fragments with teeth, the front part of the dentaries, three more jaw fragments, two cranial fragments of indeterminable identity, 72 neck vertebrae, including the atlas and axis, 3 pectoral vertebrae, 6 back vertebrae, 4 sacral vertebrae, 18 tail vertebrae, as well as rib fragments. In 2013 an incomplete neck vertebra centrum of the holotype that had been mentioned by Cope but thought to have been lost was rediscovered in storage by Sachs, and the neck vertebra count was revised from 71 to 72. In 1986 a three-dimensional reconstruction of the holotype skeleton was completed and is now displayed at the ANSP. This cast was later copied by the company Triebold Paleontology Incorporated, and replicas were provided to other museums. One of these measures about 12.8 meters (42 ft) in length.
  Though Cope described and figured the pectoral and pelvic girdles of Elasmosaurus in 1869 and 1875, these elements were noted as missing from the collection by the American paleontologist Samuel Wendell Williston in 1906. Cope had loaned these elements to the English sculptor Benjamin Waterhouse Hawkins to help prepare them out of their surrounding concretions. At the time, Hawkins was working on a "Paleozoic Museum" in New York's Central Park, where a reconstruction of Elasmosaurus was to appear, an American equivalent to his life-sized Crystal Palace Dinosaurs in London. In May 1871 much of the exhibit material in Hawkins' workshop was destroyed by vandals (working for the New York politician William M. "Boss" Tweed) and their fragments buried; it is possible that the girdle elements of Elasmosaurus were at the workshop and were likewise destroyed. Nothing was subsequently mentioned about their loss by Hawkins or Cope. In 2018, Davidson and Everhart documented the events leading up to the disappearance of these fossils, and suggested that a photo and drawing of Waterhouse's workshop from 1869 appear to show concretions on the floor that may have been the unprepared girdles of Elasmosaurus. They also noted that conceptual sketches of the Palaeozoic Museum show that the model Elasmosaurus was originally envisioned with a long "tail", though later updated with a long neck. Davidson and Everhart concluded that the girdle fossils were most likely destroyed in Hawkins' workshop.
  Fossils that may have belonged to the holotype were found by the American geologist Benjamin Franklin Mudge in 1871, but have probably been lost since. Additional plesiosaur fossils were recovered near the original locality in 1954, 1991, 1994, and 1998, including back vertebrae, ribs, gastralia (belly ribs), and gastroliths. As none of these elements overlap with those of the holotype specimen, in 2005 the American paleontologist Michael J. Everhart concluded they belonged to the same individual, and that the parts had been separated before burial of the carcass. He also noted that a small stone wedged in the neural canal of one of the tail vertebrae of the holotype may be a gastrolith, based on its polished appearance. In 2007 the Colombian paleontologists Leslie Noè and Marcela Gómez-Pérez expressed doubt that the additional elements belonged to the type specimen, or even to Elasmosaurus, due to lack of evidence. They explained that elements missing from the holotype may have been lost to weathering or simply not collected, and that parts may have been lost or damaged during transportation or preparation. Gastroliths may also not have been recognized as such during collection, since such stones were not reported from a plesiosaur until ten years after.
  In 2017 Sachs and Joachim Ladwig suggested that a fragmentary elasmosaurid skeleton from the upper Campanian of Kronsmoor in Schleswig-Holstein, Germany, and housed in the Naturkunde-Museum Bielefeld, may have belonged to 
caption: Cope's 1869 figures of the now lost pectoral (left) and pelvic (right) girdles of the holotype; the generic name refers to these "plate" bones
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