Tuesday, 4 October 2016

Paiutemys tibert: A new species of Bothremydid Turtle from the Late Cretaceous of Utah.

Bothremydids are an extinct group of Side-necked Turtles (i.e. Turtles  that could not withdraw their heads back into their shells, bt had to fold it sideways instead) that arose in the Early Cretaceous and persisted till the Eocene. The earliest members of the group are thought to have been Freshwater Turtles living in the Gondwanan interior, but members of the group evolved to colonize first brackish and then fully saline waters, enabling them to spread around the margins of the Atlantic. Bothremydids were an ecologically diverse group, producing a variety of forms, including species interpreted as adapted to specializing in feeding on Molluscs, others with a piscavorous (Fish-eating) diet, and more generalist forms.

In a paper published in the journal PeerJ on 26 September 2016, WalterJoyce of the Departement für Geowissenschaften at the Universität Freiburg, Tyler Lyson of the Department of Earth Sciences at the Denver Museum of Nature and Science and James Kirkland of the UtahGeological Survey describe a new species of Bothremydid Turtle from the Late Cretaceous Naturita Formation of MacFarlane Mine in southwest Utah.

The specimen was excavate in the early 1960s and has since resided unprepared in the collection of Zion National Park, prior to being rediscovered by James Kirkland and Don DeBlieux of the Utah Geological Survey and moved to the Natural History Museum of Utah. Since the time of its discovery the MacFarlane Mine site has been buried by a major landslide, and is no longer accessible, however the specimen was preserved in a block that also contained numerous Molluscs and other invertebrates, enabling a detailed diagnosis of both its stratigraphic and palaeoenvironmental context. These suggest that the Turtle was buried in a brackish water environment, such as an estuary or lagoon with freshwater input, and that it lived in the latest Cenomanian, i.e. about 94 million years ago.

The specimen is described as Paiutemys tibert, where 'Paiutemys' refers to the Southern Paiute people who inhabit the area where the specimen was found (-mys is a commonly used suffix for Turtles), and 'tibert' honours Neil Tibert, who established the stratigraphy (rock dating sequence) for the area where the specimen was found. The specimen is largely complete and undistorted, being s shell 16.5 cm in length, estimated to have been about 18 cm long in life.

Paiutemys tibert, Late Cretaceous (Cenomanian) of Utah, USA. Photographs and illustrations of shell in (A) dorsal and (B) ventral view. Abbreviations: Ab, abdominal scute; An, anal scute; co, costal; EG, extragular scute; ent, entoplastron; epi, epiplastron; Fe, femoral scute; Gu, gular scute; Hu, humeral scute; hyo, hyoplastron; hypo, hypoplastron; Ma, marginal scute; mes, mesoplastron; ne, neural; nu, nuchal; Pe, pectoral scute; per, peripheral; Pl, pleural scute; SP, supernumerary pleural scute; SN, supernumerary nuchal scute; spy, suprapygal; Ve, vertebral scute; xi, xiphiplastron. Joyce et al. (2016).

See also...

http://sciencythoughts.blogspot.co.uk/2015/12/xiaochelys-ningchengensis-sinemydid.htmlXiaochelys ningchengensis: A Sinemydid Turtle from the Jehol Biota.                 Sinemydid Turtles are a group of extinct Turtles known from the Middle Jurassic to the Early Cretaceous of Asia. They have traditionally been thought to be stem-group Cryptodires (i.e. more closely related to...
http://sciencythoughts.blogspot.co.uk/2015/11/turtle-remains-from-late-miocene-to.htmlTurtle remains from the Late Miocene to Early Pliocene Black Rock Sandstone of Victoria, Australia.                                          Australia has a diverse assemblage of Sea Turtles today, with six of the seven living Sea Turtle species found in Australian waters and one found nowhere else. The continent also has an extensive...
http://sciencythoughts.blogspot.co.uk/2015/10/turtle-eggs-from-late-cretaceous-of.htmlTurtle eggs from the Late Cretaceous of Madagascar.                                               Turtles are unique among living Amniotes (Vertebrates that can lay...
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