História evolucionária e biogeográfica antiga de roedores histricognatos

terça-feira, setembro 29, 2009

Fossil and molecular evidence constrain scenarios for the early evolutionary and biogeographic history of hystricognathous rodents

Hesham M. Sallama,1, Erik R. Seiffertb, Michael E. Steiperc,d and Elwyn L. Simonse,1

+ Author Affiliations

aDepartment of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, United Kingdom;

bDepartment of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794;

cDepartment of Anthropology, Hunter College of the City University of New York, 695 Park Avenue, NY 10065;

dDepartments of Anthropology and Biology, Graduate Center of the City University of New York, 365 Fifth Avenue, NY 10016; and

eDivision of Fossil Primates, Duke Lemur Center, 1013 Broad Street, Durham, NC 27705

Contributed by Elwyn L. Simons, Duke Lemur Center, Durham, NC, August 11, 2009 (received for review July 12, 2009)


The early evolutionary and paleobiogeographic history of the diverse rodent clade Hystricognathi, which contains Hystricidae (Old World porcupines), Caviomorpha (the endemic South American rodents), and African Phiomorpha (cane rats, dassie rats, and blesmols) is of great interest to students of mammalian evolution, but remains poorly understood because of a poor early fossil record. Here we describe the oldest well-dated hystricognathous rodents from an earliest late Eocene (≈37 Ma) fossil locality in the Fayum Depression of northern Egypt. These taxa exhibit a combination of primitive and derived features, the former shared with Asian “baluchimyine” rodents, and the latter shared with Oligocene phiomorphs and caviomorphs. Phylogenetic analysis incorporating morphological, temporal, geographic, and molecular information places the new taxa as successive sister groups of crown Hystricognathi, and supports an Asian origin for stem Hystricognathi and an Afro-Arabian origin for crown Hystricognathi, stem Hystricidae, and stem Caviomorpha. Molecular dating of early divergences within Hystricognathi, using a Bayesian “relaxed clock” approach and multiple fossil calibrations, suggests that the split between Hystricidae and the phiomorph-caviomorph clade occurred ≈39 Ma, and that phiomorphs and caviomorphs diverged ≈36 Ma. These results are remarkably congruent with our phylogenetic results and the fossil record of hystricognathous rodent evolution in Afro-Arabia and South America.

Caviomorpha Eocene Hystricidae Oligocene Phiomorpha

1To whom correspondence may be addressed. E-mail: sallam@mans.edu.eg or esimons@duke.edu

Author contributions: H.M.S., E.R.S., and M.E.S. designed research; H.M.S., E.R.S., M.E.S., and E.L.S. performed research; H.M.S., E.R.S., and M.E.S. analyzed data; and H.M.S., E.R.S., and M.E.S. wrote the paper.

The authors declare no conflict of interest.

This article contains supporting information online at www.pnas.org/cgi/content/full/0908702106/DCSupplemental.


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