New rodent assemblages from the Eocene Dur At-Talah escarpment (Sahara of central Libya): systematic, biochronological, and palaeobiogeographical implications
Article first published online: 18 AUG 2010
© 2010 The Linnean Society of London
Zoological Journal of the Linnean Society
Volume 160, Issue 1, pages 195–213, September 2010
How to Cite
JAEGER, J.-J., MARIVAUX, L., SALEM, M., BILAL, A. A., BENAMMI, M., CHAIMANEE, Y., DURINGER, P., MARANDAT, B., MÉTAIS, E., SCHUSTER, M., VALENTIN, X. and BRUNET, M. (2010), New rodent assemblages from the Eocene Dur At-Talah escarpment (Sahara of central Libya): systematic, biochronological, and palaeobiogeographical implications. Zoological Journal of the Linnean Society, 160: 195–213. doi: 10.1111/j.1096-3642.2009.00600.x
- Issue published online: 18 AUG 2010
- Article first published online: 18 AUG 2010
- Received 19 November 2008; accepted for publication 12 May 2009
- dental pattern;
- North Africa;
- South Asia
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.