Hylaeochelys belli? ( Mantell, 1844 )

Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique & Bailly, Gilles, 2022, Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J / K boundary, Geodiversitas 44 (25), pp. 683-752 : 701

Hylaeochelys belli? ( Mantell, 1844) ( Fig. 12 C-H)

DESCRIPTION

The third turtle taxon is represented by many isolated plates and one incomplete specimen discovered in 2018, consisting of parts of the plastron, some peripherals and both humeri ( Fig. 12 C-H). The shell bone surface is nearly smooth with shallow grooves, which clearly distinguishes this taxon from the two others previously described. The shell bones are relatively thin. The vertebral scutes are very wide and cover more than half of the costals laterally. The neurals are narrow and elongated, especially in the mid-posterior part of the carapace. The plastron bears a central plastral fontanelle. The mesoplastron is absent. The humerus shape is unremarkable and similar to that recently described in Late Jurassic thalassochelydians (e.g., Püntener et al. 2014, 2017). Based on the available characters, this form is possibly closely related to the Early Cretaceous (Purbeck and Wealden of the United Kingdom) thalassochelydian Hylaeochelys belli ( Lydekker 1889; Hirayama et al. 2000; Pérez-García 2012; Pérez-García & Ortega 2014; Anquetin & André 2020).

Hylaeochelys belli is generally considered to be a freshwater turtle based on the sedimentary contexts of the localities in which it occurs ( Milner et al. 2012; Pérez-García & Ortega 2014; Anquetin & André 2020). Most of the Angeac-Charente material represents juveniles or sub-adults, which may suggest that the swampy environment was a rookery for this turtle.

Figures

FIG. 12. — Helochelydrid and thalassochelydian turtle remains from Angeac-Charente: A, peripheral plate of Helochelydridae indet. in dorsal view;B, pleural plate of Helochelydridae indet. in dorsal view; C, D, right hyoplastron of Hylaeochelys belli? (Mantell, 1844) (ANG18-5915) in ventral (C) and dorsal (D) views; E, left humerus of Hylaeochelys? belli? (ANG18-5937) in ventral view; F, right humerus (ANG18-5938) in dorsal view;; G, H, Peripheral of Hylaeochelys? belli? (ANG 18-5993) in dorsal (G) and ventral (H) views. Scale bar: A, 1 cm; E-H, 2 cm; B, 3 cm; C, D, 4 cm.