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''Aenigmastropheus'' is an extinct genus of protorosaurid archosauromorph reptile known from the middle Late Permian Usili Formation of Songea District, southern Tanzania. It contains a single species, ''Aenigmastropheus parringtoni'', known solely from UMZC T836, a partial postcranial skeleton of a mature individual. It was collected in 1933, and first described in 1956, as a "problematic reptile" due to its unique morphology. Therefore, a binomial name was erected for this specimen in 2014. ''Aenigmastropheus'' was probably fully terrestrial, and represents the only known Late Permian protorosaur from the southern hemisphere. ==Discovery== Fossils of ''Aenigmastropheus'' were first described by the British paleontologist Dr. Francis Rex Parrington in 1956, in an article titled as "A problematic reptile from the Upper Permian". Parrington reported collecting these remains in the Ruhuhu Valley in the Songea District of southern Tanzania in 1933, and considered them to come from a single individual. This specimen, UMZC T836, in currently housed at the University Museum of Zoology, in Cambridge, UK. UMZC T836 consists of a partial postcranial skeleton including five posterior cervical and anterior dorsal vertebrae, the distal half of the right humerus, a fragment of probable left humeral shaft, the proximal end of the right ulna, and three indeterminate fragments of bone, one of which may represent a partial radius.〔 In his article, Parrington (1956) highlighted the apparent contrast between the primitive appearance of the forelimb bones and the more derived appearance of the vertebrae, resembling those of archosaurs. Thus, he concluded that the specimen did not bear close resemblances to any known synapsid, including the ones collected at the same locality, and suggested possible close affinities with archosaurs due to the vertebral morphology and the presence of hollow limb bones and an ectepicondylar groove on the humerus. Hughes (1963) subsequently noted similar vertebral morphology in some "pelycosaurian" synapsids and concluded that, as the combination of a derived vertebral column and a primitive limb structure occurs in proterosuchian archosauromorphs, UMZC T836 might possibly be a proterosuchian ancestor. Subsequent studies came to a similar conclusion, listing the specimen as a possible member of Proterosuchidae, however Gower and Sennikov (2000) noted that it still could possibly be archosaurian. Ezcurra, Butler and Gower (2013) indicated that UMZC T836 is an archosauromorph likely not referable to Archosauriformes, and thus not proterosuchian. ''Aenigmastropheus'' was first erected for UMZC T836 by Martín D. Ezcurra, Torsten M. Scheyer and Richard J. Butler in 2014 and the type species is ''Aenigmastropheus parringtoni'', following a re-description of this "problematic reptile". The generic name is derived from ''aenigma'', "enigmatic" in Latin, and ''stropheus'', "vertebra" in Greek, in allusion to the problematic taxonomic history of the holotype and only known specimen. The specific name, ''parringtoni'', honors Dr. Francis Rex Parrington for the discovery and initial description of UMZC T836, and for his contribution to the understanding of Permo-Triassic amniotes.〔 UMZC T836 was collected in fossil-bearing levels that correspond to locality B35 of Stockley (1932), which is located close to the road near the town of Ruanda in the Songea District, part of the “Lower Bone Bed” corresponding to his K6 horizon of the Songea Series. This outcrop is currently assigned to the upper part of the Usili Formation, formerly known as the Kawinga Formation, of the Songea Group of the Ruhuhu Basin. Recent studies have described this formation as a 260 meters thick fluviolacustrine succession made up of a lowermost conglomeratic interval that is approximately 5 meters thick, grading up into a trough cross-bedded, coarse-grained, sandstone-dominated interval that is 25–40 meters thick, overlain by massive nodular siltstone and laminated mudstone beds with minor ribbon sandstones forming the bulk of the succession. Sidor ''et al.'' (2010) recognized only one tetrapod faunal assemblage in the Usili Formation, which includes, in addition to ''Aenigmastropheus'', temnospondyls, pareiasaurs, gorgonopsians, therocephalians, cynodonts, and dicynodonts. Based on UMZC catalogue and unpublished field notes of Parrington in UMZC collections, an isolated maxilla of a dicynodont listed as ''cf. "Esoterodon" uniseries'' (UMZC T969, now ''Endothiodon''), as well as other dicynodont (UMZC T779, T1170) and gorgonopsid (UMZC T882, T883) remains, were collected at locality B35, along with UMZC T836.〔 Based on the possible presence of ''Endothiodon'', and the more recently described presence of the dicynodonts ''Dicynodon huenei'' and possibly ''Katumbia parringtoni'', the faunistic associations of Usili Formation appear to directly correlated with these of the Zambian Upper Madumabisa Mudstone. The well-supported correlation of the later with the rocks of the ''Cistecephalus'' Assemblage Zone in the South African Karoo Basin implies that the Usili Formation can be considered a lateral equivalent of this assemblage zone. Therefore, the Usili Formation spans the middle–late Wuchiapingian stage of the middle Late Permian, approximately 260–255 million years ago.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aenigmastropheus」の詳細全文を読む スポンサード リンク
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