Eocene Western European endemic genus Thaumastosaurus: new insights into the question “Are the Ranidae known prior to the Oligocene?”

Abstract

BackgroundAmphibians, due to their ecophysiological peculiarities, have a physiology dependent on environmental conditions and sensitively respond to their changes. Here, the oldest record of the genus Thaumastosaurus is described, whose fossil record known exclusively from Western Europe is discussed in the scope of the climatic changes of 33.5–40.5 Ma.ResultsIn the present paper, the fossil remains of the genus from three localities in Switzerland (11 samples overall) have been studied and referred to the species Thaumastosaurus bottii. Its stratigraphic distribution has been revised and summarised. The studied localities present the stratigraphically oldest and the most eastern occurrences of the genus Thaumastosaurus. Eocene probable ranids (Ranidae indet./Rana sp./? Rana sp.) from Europe could be referred to Thaumastosaurus.DiscussionTheir first occurrence of ranids most likely coincides with a warm phase of the global climate at 40 Ma, as tropical conditions were prevailing in Europe. As a result of the gradual cooling of the global climate, the tropical conditions in Europe were replaced by drier open habitats towards the latest Eocene at 34 Ma, when the latest occurrence of the European endemic genus Thaumastosaurus is known. Taking the fossil record and the climate evolution of that time into account, it can be concluded that Thaumastosaurus represents one of the groups among the vertebrates that disappeared during the large extinction event at the Eo–Oligocene transition, known as the Grande Coupure. The fossil finds of the genus from the studied localities allow to refer the previously suggested Eocene true frogs to the genus Thaumastosaurus, hereby stating the arrival of the true frog family Ranidae by the genus Pelophylax in Europe from the east at the earliest Oligocene.

From Toad to Frog, a CT-based Reconsideration of Bufo servatus , an Eocene Anuran mummy from Quercy (France)

“…6E). This notch was also observed in non-articulated maxillae in Thaumastosaurus (Roček and Lamaud, 1995;Vasilyan, 2018). On the medial surface of the maxilla, the lamina horizontalis broadens, and a groove for the palatoquadrate bar is present dorsally to the lamina (Fig.…”

“…Some hyobranchial bones are preserved, along with most of the postcranial bones, except the limbs and pelvic girdle. An isolated ilium (PRR 2002) collected in 1984 (Rage, 1984a) was recently attributed to Thaumastosaurus (Vasilyan, 2018). As the postcranial of the two species of Thaumastosaurus described in the Quercy, T. gezei Rage & Roček, 2007 and T;botti De Stefano, 1903, is very similar (Vasilyan, 2018), we used this specimen for the scoring of T. servatus in the dataset for phylogenetic analysis.…”

“…Stratigraphic range-The genus Thaumastosaurus (to which two of the mummies have been attributed so far) is known from various localities in Western Europe (Vasilyan, 2018). The earliest remains of Thaumastosaurus are from the MP16 (Late Middle Eocene ~39.5 Ma) from two Swiss localities, and the genus is present throughout the Late Eocene, with most of the localities located in the Quercy phosphorites.…”

Fish, amphibian and reptilian faunas from latest Oligocene to middle Miocene localities from Central Turkey

“…localities Grafenmühle 10, Möhren 12 and 13; Böhme and Ilg 2003). Their appearance in Europe coincides with the Grande Coupure event, during which the vertebrate fauna of Europe has been replaced by new arrivals including large and small mammals (Legendre 1989;Hooker 2010), as well as amphibians and reptiles (Rage 2012;Vasilyan 2018). Whether Latonia invaded Europe (e.g.…”

Fish, amphibian and reptilian assemblage from the middle Miocene locality Gračanica—Bugojno palaeolake, Bosnia and Herzegovina

“…Therefore, further comparisons can be confined to the families Alytidae (genus Latonia) and Pelobatidae, which have ornamented frontoparietals and are present in the fossil record of Europe. The genus Thaumastosaurus can be excluded from the comparison since it disappeared from Europe at the Eo-Oligocene boundary (Vasilyan 2018). The comparison with the family Pelobatidae shows that the most important character of the genera Pelobates and Eopelobates, the presence of the tripartite composition of the frontoparietal, cannot be observed in the available material (Roček and Wuttke 2010).…”