Triassic turtles ( Testudinata : Proterochersidae and Proganochelyidae ) of Greenland

Abstract Turtles (Testudinata) are a common faunal component throughout most of the Mesozoic and Cenozoic. Particularly, one of their Triassic genera, Proganochelys, was considered exceptionally successful and widespread, inhabiting nearly the whole of northern Pangaea. However, only recently the understanding of the anatomy and taxonomy of Triassic turtles improved, allowing determination of new diagnostic characters and a more granular approach to their taxonomy, revealing a more nuanced distribution than was previously assumed. Herein, two new genera and species of Triassic turtles are described from the Late Triassic (Norian) Fleming Fjord Formation of Greenland. The new taxa represent two of the three known Triassic turtle clades: Proterochersidae and Proganochelyidae. The proterochersid, Cryptochersis paraxene gen. et sp. nov., presents a unique form of the posterior plastral lobe. The proganochelyid, Ypomonetikochelys euryaspis gen. et sp. nov., is now the second known valid representative of its clade. Its generic distinctiveness reveals the solely central Pangaean (modern-day Central European) distribution of the genus Proganochelys. The fossil record indicates that soon after their appearance, the turtles achieved a considerable taxonomic diversity and a widespread distribution, covering most of the northern and a part of the southern hemisphere.