''Plesioelasmosaurus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

elasmosaurid Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

from the Late Cretaceous (middle

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

)

Greenhorn Limestone The Greenhorn Limestone or Greenhorn Formation is a geologic formation in the Great Plains Region of the United States, dating to the Cenomanian and Turonian ages of the Late Cretaceous period. The formation gives its name to the Greenhorn cycle ...

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The genus contains a single species, ''P. walkeri'', known from a partial skeleton.

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, UNSM 50134, was discovered by Joe Purzer, an oil field geologist, in 1931 near the town of Holyrood, Kansas. He notified George F. Sternberg and Myrl Vincent Walker, and the excavation of the specimen commenced later in the year. It was collected over a period of ten days in October 1931. The specimen became known as the 'Holyrood elasmosaur' and was eventually sold to the

University of Nebraska State Museum The University of Nebraska State Museum, also known as Morrill Hall, founded in 1871, is a natural history museum featuring Nebraska biodiversity, paleontology, and cultural diversity, located on the University of Nebraska–Lincoln City Campus n ...

in 1935, where it was prepared and placed into storage. Everhart (2007) noted that Harold Ehler used photographs of the holotype to identify the type locality, but no further remains of ''Plesioelasmosaurus'' resulted from Ehler's discovery. The holotype consists of both ilia, partial hind

paddles A paddle is a handheld tool with an elongated handle and a flat, widened end (the ''blade'') used as a lever to apply force onto the bladed end. It most commonly describes a completely handheld tool used to propel a human-powered watercraft by p ...

, a nearly complete fore paddle, vertebrae from all sections of the vertebral column ( cervical, 'pectoral',

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

, sacral, and

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into th ...

ribs The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great vessels ...

and

gastralia Gastralia (: gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In these reptil ...

, two teeth, and more than two hundred

gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...

, all from a single individual. One of these front paddles is still on display at the UNSM today. In 2022, ''Plesioelasmosaurus walkeri'' was described as a new genus and species of elasmosaurid plesiosaur by Schumacher & Everhart based on these remains.The generic name, "''Plesioelasmosaurus''", is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

words "plesios", meaning "near to", "elasmos" meaning "metal plate", and "sauros", meaning "lizard". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, "''walkeri''", honors paleontologist Myrl Walker, one of the collectors of the holotype.

Description

A photograph of a front flipper of ''Plesioelasmosaurus'', taken in the 1930s by George F. Sternberg, was captioned as belonging to "a large plesiosaur, which would have measured from 40 to 60 feet in length" (12.2 to 18.3 m). According to Everhart (2007), ''Plesioelasmosaurus'' was a "large ..elasmosaur", but no further size estimates were given.

Classification

Schumacher & Everhart (2022) confidently identified ''Plesioelasmosaurus'' as a basal member of the

Elasmosauridae Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

References

{{Taxonbar, from=Q115163268 Late Cretaceous plesiosaurs of North America Fossil taxa described in 2022 Elasmosauridae Sauropterygian genera