Lizards and snakes from the earliest Miocene of Saint-Gérand-le-Puy, France: an anatomical and histological approach of some of the oldest Neogene squamates from Europe

Abstract

Background The earliest Miocene (Aquitanian) represents a crucial time interval in the evolution of European squamates (i.e., lizards and snakes), witnessing a high diversity of taxa, including an array of extinct forms but also representatives of extant genera. We here conduct a taxonomical survey along with a histological/microanatomical approach on new squamate remains from the earliest Miocene of Saint-Gérand-le-Puy, France, an area that has been well known for its fossil discoveries since the nineteenth century. Results We document new occurrences of taxa, among which, the lacertid Janosikia and the anguid Ophisaurus holeci, were previously unknown from France. We provide a detailed description of the anatomical structures of the various cranial and postcranial remains of lizards and snakes from Saint-Gérand-le-Puy. By applying micro-CT scanning in the most complete cranial elements of our sample, we decipher previously unknown microanatomical features. We report in detail the subsurface distribution and 3D connectivity of vascular channels in the anguid parietal. The fine meshwork of channels and cavities or sinuses in the parietal of Ophisaurus could indicate some thermoregulatory function, as it has recently been demonstrated for other vertebrate groups, providing implications for the palaeophysiology of this earliest Miocene anguine lizard. Conclusions A combination of anatomical and micro-anatomical/histological approach, aided by micro-CT scanning, enabled the documentation of these new earliest Miocene squamate remains. A distinct geographic expansion is provided for the extinct anguine Ophisaurus holeci and the lacertid Janosikia (the closest relative of the extant insular Gallotia from the Canary Islands).

On Segurasaurus (Squamata: Pythonomorpha), a New Genus of Lizard from the Cenomanian (Upper Cretaceous) of Portugal

“…Within the Squamata, the new vertebra described herein is interpreted as a dorsal vertebra due to the lack of pleurapophyses, which are characteristically present in sacral and proximal caudal vertebrae, and due to the absence of haemapophyses and a chevronshaped haemal arch, typically present in caudal vertebrae, e.g., [28,29]. Moreover, it should occupy a further posterior location in the dorsal section of the spinal column, as it is extremely dorsoventrally depressed and displays a lesser extent of or non-pachyostotic morphology, mainly visible through the paradiapophyses ventral protuberances [2,30].…”

The easternmost record of the largest anguine lizard that has ever lived – Pseudopus pannonicus (Squamata, Anguidae): new fossils from the late Neogene of Eastern Europe

“…The grooves and ridges diverge from the center to the periphery of the bone, becoming longer (note that this is especially prominent, in the anterior portion of the ornamented surface). The sulci, which separate epidermal osteoscutes (i.e., "shield(s)" of other authors, e.g., Klembara et al 2010Klembara et al , 2017Klembara 2012;Čerňanský et al 2020;Georgalis and Scheyer 2021;Vasilyan et al 2022, or "ossicula dermalia", e.g., Fejérváry-Lángh 1923Roček 2019), are less well defined, almost difficult to recognize in some specimens. The incomparably largest osteoscute is the frontal one.…”

Anguimorph lizards from the lower Eocene (MP 10–11) of the Cos locality, Phosphorites du Quercy, France, and the early evolution of Glyptosaurinae in Europe

“…With regard to the virtual microanatomy, microanatomic studies on fossil anguioids (i.e., anguids) have previously been conducted. These published works deal with parietals of Ophisaurus holeci (Georgalis & Scheyer, 2021), Ophisaurus spinari (Syromyatnikova et al, 2022), and Pseudopus pannonicus (Loréal et al, 2023).…”