Basilemys morrinensis: A new species of Nanhsiungchelyid Turtle from the Late Cretaceous Horseshoe Canyon Formation of Alberta, Canada.

Nanhsiungchelyid Turtles are a curious group of possibly terrestrial Turtles from the Cretaceous. They had thick, heavily-ornamented shells and powerful limbs, with a well-developed plastron (underside of the shell) and limb armour, all traits seen in terrestrial Tortoises. However, the interpretation of these animals as terrestrial is not universally accepted, particularly for members of the genus Basilemys, which were large (generally over a metre), Nanhsiungchelyid Turtles with flattened shells from the Late Cretaceous of North America. Flattened shells are common in Turtles, and help to make them streamlined for swimming. They are also known in some Tortoises, typically species which hide in crevices or under dense vegetation, but such strategies are unlikely in an animal over a metre in length.

In a paper published in the Journal of Vertebrate Paleontology on 5 April 2018, Jordan Mallon of Palaeobiology at the Canadian Museum of Nature, and Donald Brinkman of the Royal Tyrrell Museum of Palaeontology, describe a new species of Basilemys from the Late Cretaceous Horseshoe Canyon Formation of Alberta, Canada.

The new species is named Basilemys morrinensis, meaning ‘from Morrin’, in reference to a village close to the site where the single known specimen of this species was found. The specimen is an almost complete shell, first located by a boy called Elmer Hiller in 1924, and later excavated by the palaeontologist Charles Sternberg. It comprises an almost complete Turtle shell 798 mm in length, and compressed on the left side.

 

Basilemys morrinensis, shell, in (A) dorsal, (B) ventral, (C) right lateral, and (D) anterior views Mallon & Brinkman (2018). 

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