A new species of the large-headed coastal marine turtle Solnhofia (Testudinata, Thalassochelydia) from the Late Jurassic of NW Switzerland

Abstract

Background. The large-headed turtle Solnhofia parsonsi is known by a handful of specimens from the Late Jurassic of Germany and Switzerland (maybe also France). Solnhofia parsonsi is traditionally regarded as a eurysternid Thalassochelydia, a group of small to medium sized, mostly lagoonal or marginal turtles found almost exclusively from the Late Jurassic of Europe. More recently, Solnhofia parsonsi has been proposed to be a close relative of Sandownidae, an enigmatic group of Cretaceous to Paleogene turtles characterized by a derived cranial anatomy and a wider geographical distribution. Sandownids may therefore have evolved from thalassochelydian ancestors such as Solnhofia parsonsi.Methods. We herein describe new material of Solnhofia from the Kimmeridgian (Late Jurassic) of Porrentruy, NW Switzerland. The bulk of the material consists of an association of a cranium and over 180 shell bones found together in a block of marly limestone. A second cranium and a mandible from slightly younger, but nearby localities are also described.Results. We refer the new material to Solnhofia [edited] n. sp. The new species shares with Solnhofia parsonsi a relatively large head, an extensive secondary palate formed primarily by the maxillae, a greatly developed processus trochlearis oticum with a contribution from the parietal and quadratojugal, a large jugal-palatine contact in the floor of the fossa orbitalis, and a posteromedial process of the jugal running on the dorsal surface of the maxilla and pterygoid. Some of these characteristics are also present in sandownids, but our morphological study clearly shows that Solnhofia [edited] is closer to Solnhofia parsonsi than to any sandownids.Discussion. Solnhofia [edited] differs from Solnhofia parsonsi in many aspects, notably: a shortened and broader cranium, a shorter and posteriorly broader upper triturating surface with a slightly sinusoidal lateral margin and without contribution from the palatine, a processus trochlearis oticum more oblique in dorsal or ventral view and less concave in anterior view, choanae that do not extend posteriorly on the pterygoids, a more developed processus pterygoideus externus, a condylus mandibularis situated anterior to the level of the occipital plane, a greater ventral exposure of the parabasisphenoid, a mandible about as wide as long, a relatively short symphysis, a lower triturating surface widened posterolaterally thanks to the presence of large laterally projecting dentary tubercles, a stouter and shorter coronoid process, a splenial positioned more anteriorly along the mandibular ramus, costo-peripheral fontanelles extending more anteriorly and posteriorly along the costal series, and an escutcheon shaped central plastral fontanelle formed mostly by the hypoplastra. In addition to the morphology of the new species, we also briefy discuss about observable ontogenetic variations and possible taphonomic origin of the assemblage.

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

“…This material is too incomplete to warrant a description. Moreover, this turtle group is also represented in the Banné Marls by numerous shell remains and a skull referable to a new species of Solnhofia (Anquetin & Püntener, 2020). This is remarkable, as eurysternids are rarely abundant in plesiochelyid-dominated assemblages (Lapparent de Broin et al, 1996;Anquetin et al, , 2017.…”

“…The turtle fauna of the Banné Marls consists of Tropidemys langii (the dominating taxon; Püntener et al, 2014), Plesiochelys bigleri (Püntener et al, 2017a;Raselli & Anquetin, 2019), and Solnhofia sp. (Anquetin & Püntener, 2020).…”

“…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).…”

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

“…The turtle fauna of the Banné Marls consists of Tropidemys langii (the dominating taxon; Püntener et al, 2014), Plesiochelys bigleri Raselli & Anquetin, 2019), and Solnhofia sp. (Anquetin & Püntener, 2020).…”