Sexual Dimorphism in the Pelvis of <Emphasis Type="Italic">Microcebus</Emphasis> |
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Authors: | Elizabeth M St Clair |
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Institution: | (1) Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794-4364, USA |
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Abstract: | Pelvic sexual dimorphism occurs in many anthropoid species and is often attributed to obstetric selection on female pelvic
morphology. Few studies of pelvic dimorphism have included strepsirrhine taxa, which typically have relatively smaller infants
than those of anthropoids. Because smaller female primates give birth to relatively larger infants, it is possible that the
pelves of Microcebus, the smallest extant primate genus, will show some evidence of selection on obstetric adequacy. A comparison of adult female
and neonatal body masses indicates that individual neonatal Microcebus are relatively large compared to adult female body mass, even though members of the taxon frequently produce twins. I examined
variation in the bony pelvis within a sample of Microcebus. I measured specimens from a single locality, which probably represent 1 population. I measured 8 pelvic and 3 femoral variables
to investigate skeletal size and pelvic size and shape dimorphism. Females significantly exceed males in absolute values of
sacral width, pelvic height, pubic length, and distances from the pubic symphysis to the ischial tuberosity and points on
the sacrum. Measurements of the femur are not significantly greater in females, suggesting that the pelvic differences are
not due to skeletal size dimorphism. Significant pelvic shape or ratio differences, calculated via the geometric mean of 5
variables as the denominator, included greater relative pubic length and sacral width in females. Hence selection for obstetric
adequacy may occur in the extremely small-bodied Microcebus. |
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Keywords: | mouse lemurs neonatal size obstetric adequacy os coxa strepsirrhines |
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