A re-examination of the enigmatic Russian tetrapod Phreatophasma aenigmaticum and its evolutionary implications

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dc.citation.doi10.5194/fr-20-87-2017en_ZA
dc.citation.issue1en_ZA
dc.contributor.authorBrocklehurst, N.
dc.contributor.authorFröbisch, J.
dc.date.accessioned2017-10-23T14:33:16Z
dc.date.available2017-10-23T14:33:16Z
dc.date.issued2017-02
dc.description.abstractPhreatophasma aenigmaticum is a mysterious tetrapod from the earliest middle Permian of Russia, represented by a single femur. At various times since its original description it has been considered a therapsid synapsid, a pelycosaurian-grade synapsid from the family Caseidae, and most recently a seymouriamorph amphibian. Using up-to-date knowledge of the postcranial morphology and evolution of early synapsids, the specimen is re-evaluated and subjected to cladistic analysis. Seymouriamorph and therapsid affinities are rejected, and a caseid affinity is supported based on the deep intertrochanteric fossa; the widely spaced distal condyles; the short, robust femoral shaft; and the lack of a longitudinal ridge enclosing the posterior margin of the intertrochanteric fossa. When included in two cladistic matrices, the first a global analysis of basal synapsids and the second devoted to caseids, Phreatophasma is found to occupy a basal position within caseids, retaining plesiomorphic characters such as the lack of compression of the anterior condyle of the femur and the almost identical distal extent of the two condyles. The recognition of Phreatophasma as a basal caseid has great implications for the evolution and biogeography of this family. This is only the second example of a caseid from the palaeo-temperate region of Russia, and it is not closely related to the first (Ennatosaurus tecton), implying at least two distinct dispersal events from the palaeoequatorial to temperate latitudes. It also implies that a number of plesiomorphic characteristics of caseids, including small body size and a relatively long femur, were retained as late as the middle Permian, a time when caseids were otherwise represented by large herbivorous taxa.en_ZA
dc.description.librarianEM2017en_ZA
dc.identifier.issn2193-0066 (Print)
dc.identifier.issn2193-0074 (Online)
dc.identifier.urihttp://hdl.handle.net/10539/23324
dc.journal.titleFOSSIL RECORDen_ZA
dc.journal.volume20en_ZA
dc.language.isoenen_ZA
dc.publisherCopernicus GmbHen_ZA
dc.rights© Author(s) 2017. CC Attribution 3.0 Licenseen_ZA
dc.subjectTetrapoden_ZA
dc.subjectPostcranial morphologyen_ZA
dc.subjectEvolutionen_ZA
dc.subjectRussiaen_ZA
dc.subjectSOUTH-AFRICAen_ZA
dc.subjectRECORDen_ZA
dc.subjectEXTINCTIONen_ZA
dc.subjectPhreatophasma aenigmaticumen_ZA
dc.subjectPhreatophasmaen_ZA
dc.subjectpermianen_ZA
dc.titleA re-examination of the enigmatic Russian tetrapod Phreatophasma aenigmaticum and its evolutionary implicationsen_ZA
dc.typeArticleen_ZA
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