A new species of the large-headed coastal marine turtleSolnhofia(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 in 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 brachyrhyncha 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 brachyrhyncha is closer to Solnhofia parsonsi than to any sandownids. Discussion Solnhofia brachyrhyncha 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 briefly discuss about observable ontogenetic variations and possible taphonomic origin of the assemblage.

Ontogenetic development of the European basal aquatic turtle <i>Pleurosternon bullockii</i> (Paracryptodira, Pleurosternidae)

“…The presence of these structures is also evidenced by the absence of a serrated border on the distal margin of the costals, this region being unmineralized in the first stages of the ontogeny after hatching (Bona and Alcalde, 2009). Shell fontanelles are commonly identified as a juvenile feature and as an approach to know whether the individual has reached maturity both in extinct and extant turtle species belonging to clades in which adults lack these structures (Zangerl, 1939;de Broin, 1977;Gaffney, 1996;Bever, 2009;Jansen and Klein, 2014;Farke and Distler, 2015;Joyce, 2017;Shao et al, 2017Shao et al, , 2018Limaverde et al, 2018;Anquetin and Püntener, 2020). Likewise, another character related to skeletogenesis that reveals the juvenile condition of the individuals studied here is the presence of a median suture strongly interdigitated between several plastral plates (e.g.…”

A new specimen of Solnhofia parsonsi from the Upper Jurassic (Kimmeridgian) Plattenkalk deposits of Painten (Bavaria, Germany) and comments on the relationship between limb taphonomy and habitat ecology in fossil turtles

“…Solnhofia parsonsi Gaffney, 1975 [ 12 ] and Solnhofia brachyrhyncha Anquetin and Püntener, 2020 [ 4 ].…”

“…No other sutures are discernible on the dorsal and lateral aspects of the skull. Nasals, reported for SM 137 [ 12 ], JM SCHA 70 [ 13 ] and MJSN BAN001-2.1 [ 4 ], are not discernible.…”

“…Recent phylogenetic analyses have consistently placed Solnhofia in the Thalassochelydia [ 6 , 17 , 18 ], a group of predominantly coastal marine turtles from the Upper Jurassic and Lower Cretaceous of Europe and South America [ 2 ]. Moreover, based on morphological comparisons, Solnhofia has also been suggested to belong to the Sandownidae [ 19 ], a group that is likely part of Thalassochelydia [ 4 , 6 , 17 , 19 ].…”

Les vertébrés du Kimméridgien supérieur de Fumel (Lot-et-Garonne, France) dans la collection Jacques-Ludomir Combes (1824-1892)

“…sochelydia kimméridgien comme Craspedochelys, Thalassemys ou Jurassichelon(Anquetin et al 2014 ;Püntener et al 2017b). Il existe d'ailleurs une grande variabilité intra-spécifique des neurales chez les Thalassochelydia et une identification même générique sur la base d'un élément isolé reste hasardeux(Anquetin & Püntener 2020). C'est pourquoi, cette neurale sera assignée à un Thalassochelydia indet.…”