Skeletal morphology of the forefoot in shrews (Mammalia: Soricidae) of the genus Cryptotis, as revealed by digital X-rays

Authors

  • Neal Woodman,

    Corresponding author
    1. USGS Patuxent Wildlife Research Center, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013
    • USGS Patuxent Wildlife Research Center, National Museum of Natural History, MRC 111, Smithsonian Institution, PO Box 37012, Washington, DC 20013-7012
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  • James J.P. Morgan

    1. Fort Valley State University, Fort Valley, Georgia 31030
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  • This article is a US Government work and, as such, is in the public domain in the United States of America.

Abstract

Variation in the forefoot skeleton of small-eared shrews (family Soricidae, genus Cryptotis) has been previously documented, but the paucity of available skeletons for most taxa makes assessment of the degrees of intraspecific and interspecific variation difficult. We used a digital X-ray system to extract images of the forefoot skeleton from 101 dried skins of eight taxa (seven species, including two subspecies of one species) of these shrews. Lengths and widths of each of the four bones of digit III were measured directly from the digital images, and we used these data to quantify variation within and among taxa. Analysis of the images and measurements showed that interspecific variation exceeds intraspecific variation. In fact, most taxa could be distinguished in multivariate and some bivariate plots. Our quantitative data helped us define a number of specific forefoot characters that we subsequently used to hypothesize evolutionary relationships among the taxa using the exhaustive search option in PAUP, a computer program for phylogenetic analysis. The resulting trees generally concur with previously published evolutionary hypotheses for small-eared shrews. Cryptotis meridensis, a taxon not previously examined in recent phylogenies, is rooted at the base of the branch leading to the C. mexicana group of species. The position of this species suggests that the mostly South American C. thomasi group shares an early ancestor with the C. mexicana group. J. Morphol. Published 2005 Wiley-Liss, Inc.

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