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The ‘Grande Coupure’ in the Hampshire Basin, UK: taxonomy and stratigraphy of the mammals on either side of this major Palaeogene faunal turnover

By
J. J. Hooker
J. J. Hooker
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK (email: j.hooker@nhm.ac.uk)
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Published:
January 01, 2010

Abstract

Mammals from strata immediately underlying and overlying the Grande Coupure in the Hampshire Basin, UK, are described or reviewed. Precise superposed mammaliferous horizons are documented and the stratigraphy of older less precise records is assessed. The following species group taxa are described for the first time in the UK: Amphiperatherium minutum, A. exile, Peratherium cf. perrierense, Bransatoglis planus, Butseloglis micio, Theridomys bonduelli, Isoptychus margaritae, Pseudoltinomys cuvieri, Tetracus aff. nanus, Myxomygale cf. antiqua, Hyaenodon cf. dubius, Amphicynodon? sp., Plagiolophus major and Ronzotherium cf. romani.

The main systematic innovations are as follows. The post-Grande Coupure record of Perather-ium cf. perrierense shows this species to range into the Oligocene, later than its supposed descendant P. cayluxi, with which it is tentatively concluded instead to have a sister relationship. Pre-Grande Coupure Glamys fordi represents the earliest record of the species; its morphology shows no increased similarity to its primitive sister species G. devoogdi, supporting the clado-genetic model for Glamys species. Intraspecific variation and the previously unknown upper fourth deciduous premolar are documented in the rodent Theridomys bonduelli, thanks to the discovery of the first substantial assemblage of the species. A first lower premolar is tentatively recognized for the mole Myxomygale, which if correctly associated suggests placement in the tribe Scaptonychini rather than Urotrichini, where it is usually classified. If the tentative identification to M. antiqua is correct, upper teeth are recorded for the first time in this species. An ulna is tentatively attributed to the oldest known mole Eotalpa. The occurrence of Leptadapis in the upper Hamstead Member is the first post-Grande Coupure adapid and the youngest member of the family Adapidae in Europe.

The recent synonymy of Elomeryx porcinus with E. crispus is discounted and the former species resurrected. Diplopus is once more considered closely related to Elomeryx and returned from the Choeropotamidae to the Anthracotheriidae. In addition to the established dental differences, the subspecies Palaeotherium muehlbergi muehlbergi is shown to be distinguished from P. m. thaleri by having a shallower narial incision. The dimensions of Plagiolophus minor from the lower Hamstead Member imply a more complex pattern of relationships with its immediate relatives than the single-lineage model so far proposed. Plagiolophus major is distinguished from P. fraasi on proportional dimensions of M3 and tentatively on crown height and position of the preorbital fossa.

Implications for European Paleogene biostratigraphy are as follows. Reference level MP20 is difficult to identify without the terminal subspecies of Palaeotherium medium and P. curtum. The upper limit of the Palaeotherium curtumfrohnstettense–P. medium suevicum Biozone in the UK is raised to a position within the Hamstead Member. A significant and eventful timespan is concluded to be represented by the lowest European reference level above the Grande Coupure (MP21), which would be best resolved by conventional biostratigraphic subdivision. The distancing of Elomeryx crispus from E. porcinus means that the former may not be an early herald of the Grande Coupure.

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Contents

The Micropalaeontological Society, Special Publications

Micropalaeontology, Sedimentary Environments and Stratigraphy: a Tribute to Dennis Curry (1912–2001)

Geological Society of London
Volume
4
ISBN electronic:
9781862396227
Publication date:
January 01, 2010

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