Original articleSystematics and diversity of the giant soft-shelled turtles (Cryptodira,Trionychidae) from the earliest Eocene of Belgium

In 1909, the famous paleontologist Louis Dollo identified two putative new species of giant soft-shelled turtles from the lowest Eocene record of Belgium, ‘Trionyx erquelinnensis’ and ‘Trionyx levalensis’, from Erquelinnes and Leval, respectively. However, these proposals did not meet the requirements of the International Code of Zoological Nomenclature, so they were considered as nomina nuda. The information on these specimens or about any other specimen of this lineage of giant turtles from the Belgian record is currently extremely limited. Relatively scarce material from giant trionychids has been described for the lower Eocene record of other European regions. Considering the available information, all the European material has recently been recognized as belonging to the genus Axestemys, which has a North American origin, and possibly attributable to a single species, Axestemys vittata, which currently lacks a diagnosis. Numerous and well-preserved Belgian specimens are deposited in the Royal Belgian Institute of Natural Sciences. In addition to the cited individuals from Erquelinnes and Leval, additional specimens from both localities, as well as others from Orp-le-Grand, are part of this collection. These specimens, found between the decades of 1910 and 1930, have been recently restored, and their study is carried out here. The presence of Axestemys vittata in Belgium (in Leval and Orp-le-Grand) is confirmed. Knowledge about this species is significantly improved, and a diagnosis is proposed. However, the hypothesis proposed by Dollo is here confirmed, this species being not the only identified in the Belgian record. So, Axestemys erquelinnensis nov. sp. is defined based on the carapace from Erquelinnes known by Dollo, suggesting that the genus probably reached Europe during the Paleocene Eocene Thermal Maximum.

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Article history: Received 22 April 2020 Revised 10 July 2020 Accepted 24 July 2020 Available online 2 December 2020