page_title: Tatenectes
section_title: Paleoenvironment
hierarchical_section_title: Tatenectes / Paleoenvironment
caption_attribution_description: Pachyteuthis densus (Meek &amp; Hayden, 1858) - fossil belemnite from the Jurassic of Montana, USA. (~4.05 centimeters long) Belemnites are an extinct group of marine organisms. They were squids that had a solid, calcareous, bullet-shaped, internal skeleton called a guard. Classification: Animalia, Mollusca, Cephalopoda, Coleoidea, Belemnitida Stratigraphy: Swift Formation, upper Callovian STage to Oxfordian Stage, uppermost Middle Jurassic to lower Upper Jurassic Locality: unrecorded/undisclosed site in Carbon County, southern Montana, USA See info. at: &lt;a href="https://en.wikipedia.org/wiki/Belemnitida" rel="noreferrer nofollow"&gt;en.wikipedia.org/wiki/Belemnitida&lt;/a&gt; and &lt;a href="https://en.wikipedia.org/wiki/Belemnoidea" rel="noreferrer nofollow"&gt;en.wikipedia.org/wiki/Belemnoidea&lt;/a&gt;
context_page_description: Tatenectes is a genus of cryptoclidid plesiosaur known from the Upper Jurassic of Wyoming. Its remains were recovered from the Redwater Shale Member of the Sundance Formation, and initially described as a new species of Cimoliosaurus by Wilbur C. 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 exhibit pachyostosis. The total length of Tatenectes has been estimated at 2–3 meters.
  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.
context_section_description: Tatenectes comes from the Oxfordian-aged (Upper Jurassic) rocks of the Redwater Shale Member of the Sundance Formation. This member is about 30–60 meters (98–197 ft) thick. While mainly composed of grayish green shale, it also has layers of yellow limestone and sandstone, the former layers containing plentiful fossils of marine life. The Sundance Formation represents a shallow epicontinental sea known as the Sundance Sea. From the Yukon and Northwest Territories of Canada, where it was connected to the open ocean, this sea spanned inland southwards to New Mexico and eastward to the Dakotas. When Tatenectes was alive, most of the Sundance Sea was less than 40 meters (130 ft) deep. Based on δ¹⁸O isotope ratios in belemnite fossils, the temperature in the Sundance Sea would have been 13–17 °C (55–63 °F) below and 16–20 °C (61–68 °F) above the thermocline.
  The paleobiota of the Sundance Formation includes foraminiferans and algae, in addition to a variety of animals. Many invertebrates are known from the Sundance Formation, represented by crinoids, echinoids, serpulid worms, ostracods, malacostracans, and mollusks. The mollusks include cephalopods such as ammonites and belemnites, bivalves such as oysters and scallops, and gastropods. Fish from the formation are represented by hybodont and neoselachian chondrichthyans as well as teleosts (including Pholidophorus). Marine reptiles are uncommon, but are represented by four species. Plesiosaurs, in addition to Tatenectes, include another cryptoclidid, Pantosaurus striatus, as well as the large pliosaurid Megalneusaurus rex. Besides plesiosaurs, marine reptiles are also represented by the ichthyosaur Ophthalmosaurus (or, possibly, Baptanodon) natans, the most abundant marine reptile of the Sundance Formation.
caption: Belemnites like this Pachyteuthis would have been an important food source for the marine reptiles of the Sundance Formation[17]
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