Patterns of Sexual Dimorphism, Static Allometry, and Modularity in the Skull of the Ethiopian White-Footed Mouse, Stenocephalemys albipes (Rodentia: Muridae).

Sexual differences are commonly described as male-biased sexual dimorphism, female-biased dimorphism, and monomorphism. Nevertheless, detailed patterns of sexual dimorphism have only been explored in a few rodent species. We used geometric morphometrics to investigate patterns of sexual dimorphism, static allometry, and modularity in the skull of the Ethiopian white-footed mouse (Stenocephalemys albipes). Procrustes analysis of variance showed nonsignificant sexual dimorphism for the size and shape of the cranium. Significant sexual differences were detected in the mandibular size but not in the mandibular shape. Discriminant analysis indicated nonsignificant differences between sexes in the Procrustes distance of the cranium and mandible. Additionally, scatter allometric plots demonstrated similar patterns of allometry in both sexes. Allometric variation showed an elongation of the rostrum, widening of the zygomatic bones, and narrowing of the braincase. We also observed an expanding of the ascending ramus and shortening of the alveolar part for the mandible. These may indicate the existence of modularity in the skull, which was supported by modularity analysis. Although these trends have been thought to be a growth-related phenomenon of the mammalian skull, functional requirements may also have an effect. In conclusion, our results indicate sexual monomorphism in the skull of S. albipes, which may have no effect on allometric variation and modularity patterns.