Sexual dimorphism in the mandible of the armadillo Chaetophractus villosus (Desmarest, 1804) (Dasypodidae) from northern Patagonia, Argentina

Sm Squarcia,R Camina,Eb Casanave,Ns Sidorkewicj

doi:10.1590/s1519-69842009000200016

Abstract

The aim of this study was to study the sexual dimorphism in adult Chaetophractus villosus (Desmarest, 1804), from northern Patagonia, Argentina. Eight mandibular traits were measured in 37 males and 34 females. Univariate and multivariate morphometric analysis were applied to the data set. Results showed that C. villosus was sexually dimorphic, with higher absolute values corresponding to females. The total length of the mandible was the most important variable to discriminate sexes, followed by the height at the level of the last tooth and body length. The percentages of sex discrimination were high, as they were when a new sample (17 males, 13 females) was tested. Females have larger mandibles than males independently of their larger cranial size. They also showed a higher degree of correlation between variables, suggesting a more stable shape for the mandible than in males.

Highlights

Dasypodidae (Xenarthra) is a family of fossorial mammals, commonly known as armadillos, that originated in South America and radiated to Central and North America during the late Pliocene as the Panamanian land bridge neared completion (Webb, 1985)
These data showed that C. villosus is sexually dimorphic in every trait measured, with higher absolute values corresponding to females
The variables selected according to their discriminant power were, sequentially: total length (TL), height at the level of the last tooth (HLT) and body length (BL)

Summary

Introduction

Dasypodidae (Xenarthra) is a family of fossorial mammals, commonly known as armadillos, that originated in South America and radiated to Central and North America during the late Pliocene as the Panamanian land bridge neared completion (Webb, 1985). Eight living genera with twenty one probable species are known (Gardner, 2005), the majority of which are distributed in South America, in Argentina, constituting an important part of the native fauna of the continent. They constitute a very interesting taxon from a scientific point of view, owing to peculiar characteristics concerning their anatomy It is strictly confined to South America, being distributed from the Chaco of Paraguay and Argentina to the south-east of Chile and Argentina (Atalah, 1975; Wetzel, 1985; Deferrari et al, 2002)

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