The comparative osteology ofPlesiochelys biglerin. sp., a new coastal marine turtle from the Late Jurassic of Porrentruy (Switzerland)

Abstract

BackgroundDuring the Late Jurassic, several groups of eucryptodiran turtles inhabited the shallow epicontinental seas of Western Europe. Plesiochelyidae are an important part of this first radiation of crown-group turtles into coastal marine ecosystems. Fossils of Plesiochelyidae occur in many European localities, and are especially abundant in the Kimmeridgian layers of the Swiss Jura Mountains (Solothurn and Porrentruy). In the mid-19th century, the quarries of Solothurn (NW Switzerland) already provided a large amount of fossil turtles, most notably Plesiochelys etalloni, the best-known plesiochelyid species. Recent excavations in the Porrentruy area (NW Switzerland) revealed new fossils of Plesiochelys, including numerous well-preserved shells with associated cranial and postcranial material.Methods/resultsOut of 80 shells referred to Plesiochelys, 41 are assigned to a new species, Plesiochelys bigleri n. sp., including a skull–shell association. We furthermore refer 15 shells to Plesiochelys etalloni, and 24 shells to Plesiochelys sp. Anatomical comparisons show that Plesiochelys bigleri can clearly be differentiated from Plesiochelys etalloni by cranial features. The shell anatomy and the appendicular skeleton of Plesiochelys bigleri and Plesiochelys etalloni are very similar. However, a statistical analysis demonstrates that the thickness of neural bones allows to separate the two species based on incomplete material. This study furthermore illustrates the extent of intraspecific variation in the shell anatomy of Plesiochelys bigleri and Plesiochelys etalloni.

A re-description ofSandownia harrisi(Testudinata: Sandownidae) from the Aptian of the Isle of Wight based on computed tomography scans

“…harrisi has a medial process that braces the lateral skull surface against the palate (figures 3b and 4a). This process is absent in protostegids [6,8,20,21] and plesiochelyids [6,22,23], both of which are groups with which sandownids have been proposed to be closely related (e.g. [12]).…”

“…A maxilla-pterygoid contact is also present in Solnhofia parsonsi, but not in protostegids [8] or plesiochelyids (e.g. Plesiochelys etalloni: [28]; Plesiochelys bigleri: [23]; Plesiochelys planiceps: [6]), with the exception of Portlandemys mcdowelli [28].…”

“…However, studies finding the latter placement did not include information that was published in a series of papers around the same time or later, which helped clarify the anatomy of at least plesiochelyids within thalassochelydians (e.g. [9,23,29,38,[43][44][45][46][47][48]). These papers established some anatomical features thought to be unique to thalassochelydians, such as the infolding ridge on the quadrate [9], that have since also been observed in sandownids as well [6].…”

Peculiar tooth renewal in a Jurassic ray‐finned fish (Lepisosteiformes, †Scheenstia sp.)

“…; Püntener et al . , ), crocodilians (Schaefer et al . ), pterosaurs (Marty & Billon‐Bruyat ), chondrichthyans (Leuzinger et al .…”

New material of “Eurysternidae” (Thalassochelydia, Pan-Cryptodira) from the Kimmeridgian of the Swiss Jura Mountains

“…They were discovered in the frame of the Paleontology A16 project (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018) that aimed to rescue the paleontological material discovered during the construction of the A16 highway. These excavations brought to light a rich and diverse fossil turtle assemblage that is dominated by "Plesiochelyidae" (e.g., Püntener et al, 2014;Anquetin et al, 2015;Püntener et al, 2017a). The most complete eurysternid material from the Porrentruy area is an assemblage of disarticulated shell elements and a skull that can be attributed to a new species of Solnhofia (Püntener et al, 2017b;Anquetin & Püntener, 2020).…”