Revision of the Triassic European turtles Proterochersis and Murrhardtia (Reptilia, Testudinata, Proterochersidae), with the description of new taxa from Poland and Germany TOMASZ SZCZYGIELSKI* and TOMASZ SULEJ Institute of Palaeobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warsaw, Poland Received 4 May 2015; revised 7 September 2015; accepted for publication 1 November 2015 A recently discovered Norian outcrop in Poreba, Poland, has yielded numerous well-preserved turtle remains. These, together with historical materials from Germany, enabled the identification of two new proterochersid taxa: Proterochersis porebensis sp. nov. from Poland and Keuperotesta limendorsa gen. et sp. nov. from Germany. Moreover, two problematic taxa, Proterochersis intermedia Fraas, 1913; and Murrhardtia staeschei Karl & Tichy, 2000; are shown to be conspecific with Proterochersis robusta Fraas, 1913. New diagnoses for the family Proterochersidae Nopcsa, 1923 and all included taxa are provided. Proterochersids are of great importance to turtle phylogeny because of their age (they comprise the oldest fully shelled turtle species known to date) and their still- debated phylogenetic position (classically they are considered the basalmost Pleurodira, but in some analyses they are placed on the stem of Testudinata). Newly discovered plesiomorphic aspects of the anatomy of these three species included in the phylogenetic analysis demonstrate that they are not only the oldest, but are also the most basal fully shelled turtles. The unique features of their shell (e.g. the first thoracic rib unreduced and costal-bearing, and the osseous contact between the carapace and sacral vertebra) are of special significance for future research of the earliest stages of turtle shell evolution. This is the first contribution focused solely on the new, phylogenetically informative, and important characters of this group since the initial description of P. robusta more than 100 years ago. © 2016 The Linnean Society of London, Zoological Journal of the Linnean Society, 2016, 177, 395–427 doi: 10.1111/zoj.12374 ADDITIONAL KEYWORDS: L€ owenstein Formation – Norian – origin of turtles – Stubensandstein – Upper Triassic – vertebrate phylogeny – Zbaszynek Beds. INTRODUCTION The origin and early evolution of turtles (Testudinata) remain unclear, despite constant, intensive research and increasing palaeontological data. The position of turtles on the phylogenetic tree used to change a lot during the 19th and 20th centuries (for a short, histor- ical review of hypothesized turtle relationships, see Mlynarski, 1956), and even today three main hypothe- ses, supported by different data sets, are being dis- cussed (for a brief but comprehensive review of the modern research on turtle origins, see Joyce, 2015). The early evolution and diversifications of turtles (beginning from the Middle Triassic) are slightly better understood. Pappochelys rosinae Schoch & Sues, 2015; from the Ladinian of Germany, is unam- biguously the oldest and most basal stem turtle known to date. Odontochelys semitestacea Li et al., 2008 from the Carnian of China, is the oldest amniote with a turtle-like plastron. During the Norian the turtle lineage spread worldwide, as shown by fossils from Germany (e.g. Baur, 1887; Fraas, 1913; Karl & Tichy, 2000), Thailand (de Broin et al., 1982; de Broin, 1984), Argentina (Rou- gier, de la Fuente & Arcucci, 1995; Sterli, de la Fuente & Rougier, 2007), Greenland (Jenkins et al., 1994), and Poland (Sulej, Nied zwiedzki & Bronow- icz, 2012). For a long time the German Progano- chelys quenstedti Baur, 1887 was recognized as the most basal fully shelled turtle. An older turtle found in strata lying directly below those yielding *Corresponding author. E-mail: t.szczygielski@twarda.pan.pl 395 © 2016 The Linnean Society of London, Zoological Journal of the Linnean Society, 2016, 177, 395–427 Zoological Journal of the Linnean Society, 2016, 177, 395–427. With 11 figures Downloaded from https://academic.oup.com/zoolinnean/article/177/2/395/2452387 by guest on 12 March 2022