To glide or to swim? A reinvestigation of the enigmaticWapitisaurus problematicus(Reptilia) from the Early Triassic of British Columbia, Canada

Abstract

Wapitisaurus problematicus was initially described as a member of the Weigeltisauridae, a clade of Late Permian gliding reptiles from Eurasia and Madagascar. However, the poor preservation of the holotype and only known specimen, from the lower Sulphur Mountain Formation at Ganoid Ridge (British Columbia, Canada), raised doubts about this assignment. Here, we redescribe W. problematicus and reassess its systematic position among diapsid reptiles. Comparison with all known weigeltisaurids, as well as contemporaneous reptiles from the Sulphur Mountain Formation, indicates that the taxon instead represents a thalattosauroid thalattosauriform, with noted similarities to Thalattosaurus and Paralonectes . This reidentification restricts weigeltisaurids to the Late Permian, with no occurrence in North America. Wapitisaurus problematicus potentially represents one of the oldest thalattosauriforms and increases our understanding of their diversity and disparity during the late Early and Middle Triassic. The close morphological similarities with later (thalattosauroid) thalattosauriforms and their high abundance in (shallow) marine settings may indicate an earlier invasion of this realm than previously assumed. This parallels observations in early ichthyopterygians with widespread opportunistic trophic niche diversification occurring relatively rapidly after the end-Permian mass extinction event.

The marine conservation deposits of Monte San Giorgio (Switzerland, Italy): the prototype of Triassic black shale Lagerstätten

“…Our list is not intended to be all inclusive for global Lagerstätten but was assembled with the intention of assessing the characteristics of the Triassic Monte San Giorgio in a global framework. For the Early Triassic, we included the Paris biota (Thaynes Fm) from Idaho, USA (Brayard et al, 2017 ; Doguzhaeva et al, 2018 ), the fauna from Kap Stosch, Greenland (Wordie Creek Fm; Brinkmann et al, 2010 ; Kear et al, 2016 ), the famous fish nodules from the Middle Sakamena Formation of Madagascar (Beltan, 1996 ; Brinkmann et al, 2010 ; Kogan & Romano, 2016 ), the ichthyosaur- and thalattosaur-bearing faunas of the Sulphur Mountain Formation from British Columbia and Alberta, Canada (Bastiaans et al, 2023a , 2023b ; Neuman, 1992 , 2015 ) and of the Vikinghøgda Formation in Svalbard (Hurum et al, 2018 ).…”

“…1 , 2 , 4 ). These comprise, for example, the following vertebrate groups (for a more complete bibliography, see Albisetti & Furrer, 2022 ): The rauisuchian Ticinosuchus (e.g., Krebs, 1965 ; Lautenschlager & Desojo, 2011 ; Nesbitt, 2011 ; Pinna & Arduini, 1978 ); Placodonts (e.g., Kuhn, 1942 ; Kuhn-Schnyder, 1960 ; Neenan et al, 2014 ; Peyer, 1931b , 1931d ; Pinna, 1992 ; Scheyer, 2010 ); Eosauropterygians (e.g., Beardmore & Furrer, 2016 ; Carroll & Gaskill, 1985 ; Cornalia, 1854 ; Hänni, 2004 ; Hugi, 2011 ; Hugi & Scheyer, 2012 ; Hugi et al, 2011 ; Kuhn-Schnyder, 1966 , 1967 , 1987 ; Mariani, 1923 ; Nosotti & Rieppel, 2003 ; Peyer, 1931c ; Renesto, 1993 ; Rieppel, 1989b ; Sander, 1988 , 1989b ); Thalattosaurs (e.g., Bastiaans et al, 2023a , 2023b ; Klein et al, 2023 ; Kuhn, 1946a , 1946b , 1946c ; Kuhn-Schnyder, 1988 ; Müller, 2005 ; Nopcsa, 1925 ; Peyer, 1936a , 1936b ; Rieppel, 1987 ; Rieppel et al, 2005 ); Ichthyosaurs (e.g., Sander, 1989a ; Brinkmann, 1996 , 1998 , 1999 , 2004 ; Dal Sasso & Pinna, 1996 ; Maisch & Matzke, …”

“…Thalattosaurs (e.g., Bastiaans et al, 2023a , 2023b ; Klein et al, 2023 ; Kuhn, 1946a , 1946b , 1946c ; Kuhn-Schnyder, 1988 ; Müller, 2005 ; Nopcsa, 1925 ; Peyer, 1936a , 1936b ; Rieppel, 1987 ; Rieppel et al, 2005 );…”