Basilemys

Basilemys is a large, terrestrial trionychoid turtle that was from the Upper Cretaceous time period.[1] In Greek, the "Basil (name)" means royal or kingly and the word "Emys" means turtle. Therefore, Basilemys means King Turtle. The stratigraphic subdivisions of the Upper Cretaceous include Cenomanian, Turonian, Coniacian, Santonian, Campanian, and Maastrichtian. Basilemys was mostly from the Campanian and Maastrichtian subdivisions of the Cretaceous time period and is considered to be the largest terrestrial turtle of its time.[2] This extinct genus of land turtles belongs to the family Nanhsiungchelyidae.[2] Occurrences of Basilemys have largely been reported in the North America region.[3] It is interesting to note that the family Nanhsiungchelyidae made its first appearance in the Lower Cretaceous in Asia and we know from Basilemys that this family appeared in the Upper Cretaceous in North America.[4] The North American populations of Basilemys are considered to be immigrants from Asia through the Beringia during the Upper Cretaceous.[4] In an analysis made by Sukhanov et al. on a new Nansiunghelyid turtle from the Upper Cretaceous of Mongolia, it was demonstrated that Asian nanhsiungchelyids gave rise to the North American nanhsiungchelyids.[5] One genus from the family Nanhsiungchelyidae, Zangerlia, is similar to Basilemys in terms of skull proportions.[6] However, Basilemys has a more complex triturating surface that includes well-defined pockets on the dentary.[6] Basilemys also has tooth-like projections on the triturating surface of the maxilla.[6] From the turtle species, Basilemys is described to be most similar to tortoises.[3] Many paleontologists have described the behaviors of Basilemys to be similar to tortoises due to living in terrestrial habitats and the consumption of tough plants.[3] Moreover, the complex triturating surface that is a feature of Basilemys, indicates that they are similar to tortoises in being terrestrial and herbivores.[6] Basilemys is easily identifiable due to how thick its shell is, the intricate sculpture of rows of triangular tubercles separated by pits, and reduced inframarginal scales.[2] The fossil record is abundant with shell and appendicular material for Basilemys, but cranial and cervical material is quite rare.[1]