Tatenectes is a genus of cryptoclidid plesiosaur known from the Upper Jurassic of Wyoming, United States. Its remains were recovered from the Redwater Shale Member of the Sundance Formation, and initially described as a new species of Cimoliosaurus by Wilbur Clinton Knight in 1900. It was reassigned to Tricleidus by Maurice G. Mehl in 1912 before being given its own genus by O'Keefe and Wahl in 2003. Tatenectes laramiensis is the type and only species of Tatenectes. While the original specimen was lost, subsequent discoveries have revealed that Tatenectes was a very unusual plesiosaur. Its torso had a flattened, boxy cross-section and its gastralia (belly ribs) exhibit pachyostosis (thickening). The total length of Tatenectes has been estimated at 2–3 meters (6.6–9.8 ft). Tatenectes is related to Kimmerosaurus, although their taxonomic placement has varied. They were once considered to be close relatives of Aristonectes in the family Cimoliasauridae or Aristonectidae, but later assigned to Cryptoclididae. The unusual body shape and pachyostotic gastralia of Tatenectes would have helped to make it more stable and resistant to turbulence. Based on stomach contents, Tatenectes fed on cephalopods and fish. It would have lived in the shallow waters of the Sundance Sea, an epicontinental sea covering much of North America during part of the Jurassic. Tatenectes shared its habitat with invertebrates, fish, ichthyosaurs, and other plesiosaurs, including another cryptoclidid, Pantosaurus, and the large pliosaurid Megalneusaurus.
History of study
All known specimens of Tatenectes come from the Redwater Shale Member in the upper part of the Sundance Formation. This formation is located in Wyoming, in the Eastern Rocky Mountains. An incomplete plesiosaur skeleton preserving multitudinous vertebrae and a nearly complete forelimb from the Sundance Formation was described by Wilbur C. Knight in 1900. With this specimen as a holotype, which was never assigned a specimen number, he named a new species of Cimoliosaurus, C. laramiensis. In 1912, Maurice G. Mehl questioned the assignment of C. laramiensis to Cimoliosaurus, noting that Cimoliosaurus was a catch-all, and that since this genus was named based on vertebrae, the vertebrae of C. laramiensis would have to be similar to those of the type species, C. magnus. He was unable to find such similarities, and provisionally reclassified C. laramiensis as a species of Tricleidus, due to the anatomy of its forelimbs. Although the holotype specimen of T. laramiensis has since been lost, Knight's description of the specimen was sufficient to determine that T. laramiensis is a valid species. In 2003, F. Robin O'Keefe and William Wahl, JR. referred another specimen housed at the Tate Geological Museum to this species. This specimen, listed under the specimen numbers UW 15943 and UW 24801, consists of vertebrae, ribs, a shoulder girdle, a partial forelimb, and a fragmentary skull and was assigned as a neotype. Additionally, O'Keefe and Wahl noted that the shoulder girdle of this species was quite different from that of Tricleidus, so they named a new genus, Tatenectes, to include T. laramiensis. The name Tatenectes honours Marion and Inez Tate, founders of the Tate Museum in Casper, Wyoming in 1980 and combines this with the Greek word nektes, meaning "diver." O'Keefe and Hallie P. Street assigned more material to Tatenectes laramiensis in 2009, including UW 24215, a partial skeleton including further cranial, vertebral, pectoral, and phalangeal elements. Another skeleton, USNM 536976, was assigned to this species by O'Keefe and colleagues in 2011. This specimen preserved 22 vertebrae, ribs, gastralia, and complete pelves.
Description
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