The first skeletal evidence of an Upper Triassic (Rhaetian) diapsid reptile from the Western Carpathians (Strážov Highlands, Slovakia)

Here we describe the first skeletal evidence of a tetrapod from Rhaetian (Upper Triassic) marine deposits of
the Western Carpathians. The material consists of an isolated left femur and comes from the Úbočka locality near
Čičmany in the Strážov Highlands. Based on morphological, histological, and stratigraphic evidence, we can exclude
affinities of this femur to the most commonly occurring aquatic reptiles: the Eosauropterygia. The histology of a femur
of aff. Pachystropheus from Aust Cliff, Gloucestershire, UK, is also described here for the first time and compared to
the bone from Slovakia. However, a precise taxonomical assignment of the Rhaetian femur from Slovakia is not possible.
The bone shows strong osteosclerosis that points to an inhabitant of a shallow marine environment. On the basis of
morphological and histological characters, affinities to a cyamodontoid placodont, Endennasaurus-like thalattosaur or
a rhynchocephalian are conceivable. The morphology of the Slovak find does not fully exclude choristoderan affinity, but
the rare histological data available for comparison do not support such a statement. For all these reasons, we allocated this
bone as Diapsida indet. The bone described here sheds the first, although limited light on the possible faunal composition
of the Rhaetian tetrapod assemblage in the Western Carpathians. We can assume that the bone, which shows marks of
transport, either represents an allochthonous component in this marine environment, transported postmortem and most
likely from nearby dry land (i.e., in the case of rhynchocephalian affinities), or it belonged to an inhabitant of this shallow
coastal biotope (e.g., cyamodontoid placodont affinities).