Amphibian and reptilian fauna from the early Miocene of Echzell, Germany

Abstract

The present study describes a rich amphibian and reptilian assemblage from the early Miocene locality Echzell, Germany. It consists of one allocaudate, five salamander, five frog, one gecko, chamaeleonids, anguine lizards, one lacertid, one skink and five snake taxa. The entire herpetofauna of Echzell is represented by genera and/or families very broadly known from the early Miocene of Europe. Contrary to other early Miocene herpetofaunas, the Echzell assemblage includes surprisingly only one form of crocodile-newts (Chelotriton). The Echzell Palaeobatrachus robustus represents the youngest record of the species and extends its stratigraphic range to the late early Miocene. Regarding chameleons, the frontal is partly preserved, but represents the first described frontal of the extinct species Chamaeleo andrusovi. The only anguine lizard that can be identified in the assemblage is represented by a new genus and species Smithosaurus echzellensis. Our phylogenetic analyses consistently recovered it as the sister taxon to either [Ophisauriscus quadrupes + Ophisaurus holeci] + [Anguis + Ophisaurus] (in the first analysis) or [Anguis + Ophisaurus] (in the second analysis). However, the results are based on limited fossil material – the parietal – and the support for the clade is very low. Thus, the interpretation of the Smithosaurus relationship among anguines needs to be taken with caution and has to be tested in further studies. Among snakes, Natrix longivertebrata represents the oldest record of the species and extends the stratigraphic range of this fossil snake back to the early Miocene. In addition, we provide here a broader comparison of the Echzell amphibian and reptilian assemblage with their European records for the MN3 and MN4 biostratigraphical units. Besides that, the entire herpetofauna of Echzell includes very broadly known early Miocene European forms. Remains of other groups of the same period such as Bufonidae, Hylidae, Pelodytidae, Amphisbaenia, Varanidae, Cordylidae, Pseudopus, are not found in the material available to us. We also conclude that the amphibian and reptilian fossil record across MN3–MN4 is significantly biased by taphonomic and/or environmental conditions. The amphibian and reptilian assemblage of Echzell is rich in forms living in humid and warm environments with forested areas, permanent water bodies and also some open habitats. The following climatic parameters can be reconstructed based on the herpetofauna: a mean annual temperature of 17.4–28.8 °C, minimal warm month temperature 18–28.3 °C, minimal cold month temperature 8–22.2 °C, and mean annual precipitation with a value of 791±254 mm.

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

“…Here, we attribute the caudal vertebrae from our material to the genus Pseudopus because none are showing an autotomic split, a feature that is present and well-visible in either Anguis or Ophisaurus (Hoffstetter and Gasc 1969;Čerňanský et al 2019). This condition is, however, currently unknown in either Ragesaurus and Smithosaurus based on the material available (Bailon and Augé 2012;Vasilyan et al 2022). We refer the vertebrae described here to the species P. pannonicus due to the fact that this species is the sole (with the exception of the recently described and rare occurrences of Ophisaurus from Lucheshty and Etulia; Syromyatnikova et al 2022) and most abundant representant of anguines in the localities studied here as evidenced by the additional cranial material described here.…”

“…However, some doubts concerning the distinguishing of Pseudopus pannonicus and recent P. apodus still exist. In phylogenetic analyses, the two were recovered as sister-taxa and, together with P. laurillardi and P. ahnikoviensis, formed the clade Pseudopus (see Klembara et al 2019;Vasilyan et al 2022). The taxonomic allocation of the various elements studied here from different localities to P. pannonicus is based not only on the generally large size that characterized this taxon, but also on the presence of several diagnostic features.…”

“…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.…”

“…Here, in the case of our material, we argue that the features displayed by these osteoderms exclude an Anguis identification, thus leaving Ophisaurus, Pseudopus, Ragesaurus, and Smithosaurus as the remaining anguine taxa that these osteoderms could be attributed to. The osteoderms of either Ragesaurus or Smithosaurus are still unknown as these taxa are known only by limited material respectively from the Quaternary of Spain (Bailon and Augé 2012), and from the Early and Middle Miocene of Germany and Austria (Vasilyan et al 2022). The larger size and robustness of these elements seems to be more congruent with Pseudopus.…”

“…This taxon is known by only a subcomplete dentary and is restricted to one locality on Islas Medas (Catalonia, Spain) (Bailon and Augé 2012). Recently, a fifth taxon -Smithosaurus Vasilyan, Čerňanský, Szyndlar & Mörs, 2022 was described from the Early and Middle Miocene of Germany and Austria (Vasilyan et al 2022). Today, Pseudopus is represented only by a single extant species Pseudopus apodus.…”