Thadeosaurus
| Thadeosaurus Temporal range: Late Permian,
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| Speculative life restoration | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Diapsida |
| Clade: | Neodiapsida |
| Family: | †Younginidae |
| Genus: | †Thadeosaurus Carroll, 1981 |
| Type species | |
| †Thadeosaurus colcanapi Carroll, 1981
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Thadeosaurus is an extinct genus of diapsid reptiles from the late Permian Lower Sakamena Formation (Sakamena Group) of Madagascar. The genus contains a single species, Thadeosaurus colcanapi, known from several specimens preserved as natural molds.
Discovery and naming
[edit]The generic name, Thadeosaurus, is an anagram of "Datheosaurus", a synapsid genus to which fossils of the former were initially referred. The specific name, colcanapi, honors J.-M. Colcanap, a French infantry captain and the discoverer of the holotype specimen.[1][2]
Description
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Thadeosaurus was a superficially lizard-like reptile, with a remarkably long tail that comprised about two-thirds of the animal's total length of 60 centimetres (24 in). It had long toes, especially on the hind legs, and a strong breast bone.[1][3][2]
Classification
[edit]The relationships of Thadeosaurus have been debated since its 1981 description. Prior to receiving a name, the fossil material was provisionally referred to Broomia (now recognized as a millerettid[4]), Tangasaurus, and Datheosaurus (now recognized as a caseid synapsid). In his 1981 publication naming Thadeosaurus and Claudiosaurus, Carroll noted similarities between Thadeosaurus and Youngina, but opted to describe it as a 'primitive' sauropterygian—an 'ancestral taxon' to nothosaurs and plesiosaurs.[1]
In the description of the early Permian reptile Orovenator, the phylogenetic results of Reisz et al. (2011) suggested a close relationship between Thadeosaurus and Youngina, united in the family Younginidae. These results are displayed in the cladogram below:[5]
In 2025, Valentin Buffa and colleagues thoroughly redescribed the fossil material assigned to Thadeosaurus, and reassessed its phylogenetic position. They identified it as a member of the neodiapsid family Tangasauridae, as the sister taxon to the clade formed by Hovasaurus and Tangasaurus, a position also supported by Philip J. Currie in a publication redescribing Tangasaurus.[6] The results of the strict consensus phylogenetic results of Buffa et al. (2025) are displayed in the cladogram below:[2]
References
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- ^ a b c Carroll, Robert L. (1981). "Plesiosaur ancestors from the Upper Permian of Madagascar". Philosophical Transactions of the Royal Society. B. 293 (1066): 315–383. Bibcode:1981RSPTB.293..315C. doi:10.1098/rstb.1981.0079.
- ^ a b c Buffa, Valentin; Jalil, Nour‐Eddine; Falconnet, Jocelyn; Vincent, Peggy (2025-03-23). "The neodiapsid Thadeosaurus colcanapi from the upper Permian of Madagascar". Papers in Palaeontology. 11 (2). doi:10.1002/spp2.70008. ISSN 2056-2799.
- ^ Currie, Philip J.; Carroll, Robert L. (September 1984). "Ontogenetic changes in the eosuchian reptile Thadeosaurus". Journal of Vertebrate Paleontology. 4 (1): 68–84. doi:10.1080/02724634.1984.10011987. ISSN 0272-4634.
- ^ Jenkins, Xavier A; Benson, Roger B J; Elliott, Maya; Jeppson, Gabriel; Dollman, Kathleen; Fernandez, Vincent; Browning, Claire; Ford, David P; Choiniere, Jonah; Peecook, Brandon R (2025-03-03). "New information on the anatomically derived millerettid Milleretta rubidgei from the latest Permian based on µCT data". Zoological Journal of the Linnean Society. 203 (3). doi:10.1093/zoolinnean/zlaf004. ISSN 0024-4082.
- ^ Robert R. Reisz; Sean P. Modesto; Diane M. Scott (2011). "A new Early Permian reptile and its significance in early diapsid evolution". Proceedings of the Royal Society B. 278 (1725): 3731–3737. doi:10.1098/rspb.2011.0439. PMC 3203498. PMID 21525061.
- ^ Currie, P. J.; Currie, P. J. (1982). "The osteology and relationships of Tangasaurus mennelli Haughton". Annals of the South African Museum. Annale van die Suid-Afrikaanse Museum. 86: 247–265.
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