Craniofacial Heterochrony and Sexual Dimorphism in the Short-Tailed Opossum (Monodelphis domestica)

Abstract

Craniofacial growth of the short-tailed opossum, Monodelphis domestica , was measured to determine differences in growth between bones of the viscerocranium and of the neuro-cranium and between sexes. Initially, the relative lengths of neurocranial to viscerocranial bones were about the same for both sexes. Viscerocranial bones grew at a faster rate in both sexes, while neurocranial bones grew for a longer period of time at a slower rate. Although females exhibited faster rates of growth, they ultimately had smaller skulls than males, because males were initially larger and grew for a longer period of time. Differences in patterns of growth of the two regions of the skull probably are associated with changes in masticatory function due to weaning and development of the brain.