Elasmosaurus

Elasmosaurus is a plesiosaur genus from the Late Cretaceous, specifically the Campanian stage, that lived in North America roughly 80.6 to 77 million years ago. It gives its name to the family Elasmosauridae, a group known for their long necks. The animal’s neck alone stretched about 7.1 meters (23 feet), contributing to a total body length of around 10.3 meters (34 feet).

The first specimen turned up in 1867 near Fort Wallace, Kansas, discovered by army surgeon Theophilus Hunt Turner and scout William "Medicine Bill" Comstock. Turner, despite lacking paleontological training, recognized the bones as belonging to an "extinct monster." He gave three vertebrae to scientist John LeConte, who passed them to paleontologist Edward Drinker Cope at the Academy of Natural Sciences of Philadelphia. Cope identified them as plesiosaur remains, larger than any he had seen in Europe, and asked Turner to send the rest. In December 1867, Turner and others dug out much of the vertebral column and concretions containing other bones—about 360 kilograms (800 pounds) of material—from the Pierre Shale formation. They shipped it to Philadelphia, where Cope named it *Elasmosaurus platyurus* in March 1868. The genus name combines Greek words for "metal plate" and "lizard," referencing the plate-like bones in the chest and pelvis, though it is often translated as "thin-plate reptile." The species name means "flat-tailed," referring to the compressed vertebrae in what Cope mistakenly thought was the tail.

Cope originally reconstructed the skeleton with the skull at the wrong end—attached to the tail. This error was mocked by rival paleontologist Othniel Charles Marsh and became a famous episode in their "Bone Wars." Only one incomplete skeleton of *Elasmosaurus* is definitely known today, including a partial skull, the spine, and now-lost pectoral and pelvic girdles. A single species is recognized; others have been reassigned or deemed invalid. A fragmentary specimen from Germany may also belong to this genus.

The skull was slender and triangular, with large, fang-like teeth at the front and smaller ones toward the back. The upper jaw had six teeth in each premaxilla, possibly 14 in the maxilla, and the lower jaw had 19 in the dentary. Most neck vertebrae were compressed sideways and had a longitudinal crest or keel along their sides. The neck contained 72 vertebrae, at least three fewer than its relative *Albertonectes*, making *Elasmosaurus* one of the longest-necked animals ever.

Elasmosaurids were well adapted for water, using flippers to swim. Despite older depictions, their necks were not very flexible and could not be held high above the surface. The function of the long neck is unknown, but it may have helped with feeding. These animals likely ate small fish and marine invertebrates, seizing prey with their long teeth, and possibly used gastroliths (stomach stones) to aid digestion. *Elasmosaurus* is known from the Pierre Shale, which preserves marine deposits from the Western Interior Seaway.

Turner continued searching for more bones, sending additional fossils in 1868. He died unexpectedly at Fort Wallace in July 1869, before seeing the work completed. Cope, unaware of his death, kept writing to him until 1870. Turner’s role in the discovery remained unknown until his letters were published in 1987. *Elasmosaurus* was the first major fossil find in Kansas and the largest from the area at the time, sparking a rush that sent thousands of fossils to East Coast museums. It was also one of the few plesiosaurs known from the New World and the first recognized member of the long-necked elasmosaurid family.