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Reconsideration of a purported historical specimen of a Triassic turtle from Germany as an archosaur metatarsal
(International Palaeontological Association, 2022-11-07) Dróżdż, Dawid; Szczygielski, Tomasz; Słowiak-Morkovina, Justyna; Instytut Paleobiologii, Polska Akademia Nauk
A long-standing truth in vertebrate paleontology is that fragmentary and isolated bones are notoriously difficult to correctly identify and may remain enigmatic even for centuries since their initial description. One of such specimens is SMNS 91559 (Staatliches Museum für Naturkunde, Stuttgart) from the Late Triassic Heslach locality (now part of Stuttgart, Norian Löwenstein Formation) in Germany. The specimen was described and figured in 1865 by Hermann von Meyer who struggled with its identification but noted resemblance to turtle pelvis. Although von Meyer left the taxonomic affiliation of the specimen vague, this could imply that it might belong to Chelytherium– the first historically known turtle from the Triassic of Germany, described by von Meyer from the same locality in 1963. This supposition seems to be confirmed by the original collection tags stored alongside the specimen, which bear the name “Chelytherium sp.”. According to von Meyer, SMNS 91559 was given to him in January 1965. At the time, all the remaining (type) material of Chelytherium obscurum was already purchased by the Natural History Museum in London, but this new specimen remained in the SMNS collection in Stuttgart. Subsequent taxonomic history of Chelytherium obscurum is complex and the taxon itself was considered problematic for most of its history. Recently one of us (TS), however, revised the London material and recognized Chelyterium to be a senior synonym of another German Triassic turtle, Proterochersis robusta (however, due to the obscurity of Chelytherium obscurum, in accord with suggestions of previous authors, a case advocating conservation of the younger, much more popular name was submitted to ICZN: case 3840). Yet, if indeed SMNS 91559 was a pubis of Chelytherium, its unusual anatomy would put the synonymy of both taxa in question. However, our first-hand examination of the specimen revealed that it has no features that would allow for its classification as a pelvic bone (or any other part) of any turtle. As far as we know, since the original description, SMNS 91559 was not revised or mentioned in the literature. However, two other, younger tags attached to it, suggest its phytosaur affinities: either as a pubis of “Belodon?” or ectopterygoid of Phytosauria indet. We agree that the specimen likely belong to a phytosaur, nonetheless, we recognize it to be a part of the pes, a fifth metatarsal, very characteristic for archosauromorphs because of its L-shaped shaft. It seems the most similar to the corresponding bone of the phytosaur genus Pseudopalatus sp. from North America. However, also other possible candidates exist, especially among pseudosuchian archosaurs, such as aetosaurs or rauisuchians. Therefore, this hypothesis is tested with morphometric analysis.
Joint Meeting of the Polish Paleobiologists, and the 95th Annual Meeting of the Paläontologische Gesellschaft (Palges), Warsaw, September 16th–21st, 2024, Book of Abstracts
(Instytut Paleobiologii PAN, 2024-09-16) De Baets, Kenneth; Kaim, Andrzej; Wydział Biologii, Uniwersytet Warszawski; Instytut Paleobiologii, Polska Akademia Nauk

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