An exceptional Dimetropus pes imprint with scalation pattern from the lower Permian of Lodève and its broader implications for early synapsid palaeobiogeography and skin evolution
Antoine Logghe, Valentin Buffa, and Lorenzo Marchetti
Dimetropus is one of the most widespread tetrapod ichnogenera of the Permian, known from several Cisuralian units of Euramerica and North Africa. Generally attributed to pelycosaur-grade synapsid trackmakers, two ichnospecies are currently considered valid: D. leisnerianus and D. osageorum. A revision of a well-preserved Dimetropus pes footprint from the lower Permian (upper Artinskian) Rabéjac Formation of the Lodève Basin highlights the first definitive presence of D. osageorum from the Variscan Belt. A synapomorphy-based track–trackmaker correlation suggests ophiacodontids, such as Ophiacodon, as potential tracemakers of D. osageorum. Therefore, this potentially extends the palaeobiogeographic distribution of ophiacodontids in the upper Cisuralian in both North American and European basins. Moreover, the presence of well-preserved epidermal scale imprints on the D. osageorum pes of Lodève precises the evolution of epidermal scalation in pelycosaur-grade synapsids and suggests the presence of both dermal and epidermal scales in ophiacodontids. This occurrence is time-equivalent with the Artinskian Warming Event, strengthening the scenario of epidermal scale evolution in light of palaeoclimatic changes in the Variscan Belt, from everwet-adapted biotas to seasonal drought-adapted biotas.
Key words: Ophiacodontidae, Dimetropus osageorum , epidermal scales, track-trackmaker correlation, Artinskian Warming Event.
Antoine Logghe [antoine.logghe1@mnhn.fr; ORCID: https://orcid.org/0000-0002-2854-7716], Centre de Recherche en Paléontologie–Paris, Muséum national d’Histoire Naturelle, CP38, 8 rue Buffon, 75005 Paris, France. Valentin Buffa [valentin.buffa@wits.ac.za; ORCID: https://orcid.org/0000-0002-4255-7822], Department of Paleontology, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland; Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, WITS, 2050, Johannesburg, South Africa. Lorenzo Marchetti [lorenzo.marchetti85@gmail.com; ORCID: https://orcid.org/0000-0002-1047-7887], Museum für Naturkunde, Leibnitz-Institut für Evolutions-und Biodiversitätsfoschung, Invalidenstrasse 43, 10115 Berlin, Germany.
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