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New rodent assemblages from the Eocene Dur At-Talah escarpment (Sahara of central Libya): systematic, biochronological, and palaeobiogeographical implications

Authors

  • JEAN-JACQUES JAEGER,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements (IPHEP), UMR-CNRS 6046, Université de Poitiers UFR SFA, 40 avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
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  • LAURENT MARIVAUX,

    Corresponding author
    1. Département de Paléontologie, Institut des Sciences de l'Évolution (ISE-M), UMR-CNRS 5554, Université Montpellier 2, CC64, Place Eugène Bataillon, F-34095-Montpellier Cedex 05, France
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  • MUSTAPHA SALEM,

    1. Geology Department, University of El Fateh, Tripoli, Libya
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  • AWAD ABOLHASSAN BILAL,

    1. Geology Department, Garyounis University, Bengahzi, Libya
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  • MOULOUD BENAMMI,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements (IPHEP), UMR-CNRS 6046, Université de Poitiers UFR SFA, 40 avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
    2. Laboratorio de Paleomagnetismo, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, 04510 Mexico DF, Mexico
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  • YAOWALAK CHAIMANEE,

    1. Paleontology Section, Department of Mineral Resources, Rama VI road, Bangkok-10400, Thailand
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  • PHILIPPE DURINGER,

    1. Université Louis Pasteur, EOST –École et Observatoire des Sciences de la Terre, CGS – Centre de Géochimie de la Surface, UMR-CNRS 7517, 1 rue Blessig, F-67084 Strasbourg Cedex, France
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  • BERNARD MARANDAT,

    1. Département de Paléontologie, Institut des Sciences de l'Évolution (ISE-M), UMR-CNRS 5554, Université Montpellier 2, CC64, Place Eugène Bataillon, F-34095-Montpellier Cedex 05, France
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  • EDDY MÉTAIS,

    1. TOTAL E & P – Libye Tower 3, Dhat el Imad Complexe, Tripoli, Libya
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  • MATHIEU SCHUSTER,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements (IPHEP), UMR-CNRS 6046, Université de Poitiers UFR SFA, 40 avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
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  • XAVIER VALENTIN,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements (IPHEP), UMR-CNRS 6046, Université de Poitiers UFR SFA, 40 avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
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  • MICHEL BRUNET

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements (IPHEP), UMR-CNRS 6046, Université de Poitiers UFR SFA, 40 avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
    2. Chaire de Paléontologie Humaine, Collège de France, Place Marcellin-Berthelot, F-75005-Paris Cedex 05, France
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E-mail: laurent.marivaux@univ-montp2.fr

Abstract

In this paper, we describe four fossil rodent taxa from two new localities situated in the Idam Unit (‘Bioturbated Unit’) of the Dur At-Talah escarpment in central Libya. These rodents belong to the family Phiomyidae (Hystricognathi) and are distributed amongst three genera (Phiomys, Protophiomys, and Talahphiomys gen. nov.) that include three new species (Phiomys hammudai sp. nov., Protophiomys durattalahensis sp. nov., and Talahphiomys libycus sp. nov.). Although some of these new species are morphologically close to certain phiomyids from the latest Eocene and Oligocene of the Jebel el-Qatrani Formation of the Fayum in Egypt, the Idam rodent faunas lack the abundant and somewhat morphologically derived Fayum phiomyids (such as: Metaphiomys, Gaudeamus, Paraphiomys, Phiocricetomys), thereby excluding a similar age for the Dur At-Talah rodent assemblages. More resemblance is shared with the phiomyid (Protophiomys algeriensis) of the Nementcha locality in Algeria, for which a late middle Eocene age is presently admitted. Protophiomys is a primitive representative of the phiomyid African radiation and it is represented at Dur At-Talah by a slightly more derived species (Pr. durattalahensis) than that of Nementcha, thereby suggesting a younger age for Dur At-Talah. As a result, the new rodent assemblages suggest a late middle Eocene age for the Idam (‘Bioturbated’) deposits of the Dur At-Talah escarpment. This age hypothesis is substantiated by other mammals (especially Proboscidea), which occur in the same sedimentological unit. Interestingly, the dental pattern of Protophiomys and that of Talahphiomys have somewhat stronger affinities with South Asian hystricognath baluchimyines than with Fayum phiomyids. It is clear that baluchimyines and phiomyids have a common ancestry, and that dispersal occurred between Asia and Africa during the middle of the Palaeogene. However, it is not clear if both groups can be strictly separated in two distinct natural groups inasmuch as some baluchimyines (e.g. Lophibaluchia, Bugtimys, Hodsahibia) appear to be phiomyid-like, and some early members of phiomyids (e.g. Protophiomys, Talahphiomys) are baluchimyine-like. South Asia and North Africa represent two centres of adaptive radiation of early hystricognathous rodents. The strong dental resemblances between early Asian and African forms are perhaps the result of subsequent convergent evolution after an initial dispersal from Asia. Otherwise, the systematics of these rodents has to be entirely revised, or we must consider that their historical biogeography is much more complex.

© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160, 195–213.

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