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

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.Keywords: Xenarthra, gender differences, jaw, morphometry, discriminant analysis. Dimorfismo sexual da mandíbula do tatu Chaetophractus villosus (Desmarest, 1804) (Dasypodidae) do norte da Patagônia ArgentinaResumo O presente estudo examinou o dimorfismo sexual dos adultos de Chaetophractus villosus (Desmarest, 1804) do norte da Patagônia Argentina. Oito parâmetros mandibulares foram medidos em 37 machos e 34 fêmeas. Análises morfométricas univariada e multivariada foram aplicadas à série de dados. Os resultados mostraram que C. villosus apresenta dimorfismo sexual, com todos os valores absolutos mais elevados nas fêmeas. O comprimento total da mandíbula foi a variável mais importante para discriminar os sexos, seguidos pela altura no nível dos últimos dentes e pelo comprimento do corpo da mandíbula. As porcentagens de discriminação dos sexos foram elevadas, quando uma amostra nova (17 machos, 13 fêmeas) foi testada. As fêmeas têm as mandíbulas maiores que os machos, independentemente de seu tamanho cranial maior. Mostraram também um grau mais elevado de correlação entre variáveis, sugerindo uma forma mais estável para a mandíbula que nos machos.Palavras-chave: Xenarthra, diferenças do sexo, mandíbula, morfometria, análise discriminante.

Rostrofacial Indices of the Nigerian Local Dog: Implications in Veterinary Oral and Maxillo-facial Anaesthesiology of the Dolichocephalic Canine Breed

“…This is in consonance with what was previously observed in the swine (Olopade & Okandeji) and armadillos (Squarcia et al, 2009). …”

Morphological characterization and sex-related differences of the mandible of the armadillos Chaetophractus vellerosus and Zaedyus pichiy (Xenarthra, Dasypodidae), with consideration of dietary aspects

“…In C. vellerosus, both the univariate and multivariate analysis indicated a size-based differentiation of sexes, with females larger than males. Similar results were found by Squarcia et al (2009) for another Chaetophractus species, C. villosus. By contrast, the differences between genders of Z. pichiy did not involve an absolute size factor, but males characterized by taller mandibles and females by longer ones.…”

“…Wible & Gaudin (2004) performed an exhaustive morphological characterization of the mandible of E. sexcinctus as part of a bone-by-bone description of the skull, and they made comparisons with other xenarthrans and nonxenarthrans taxa in order to place the cranial osteology of this species in a phylogenetic context. Squarcia et al (2006) performed a morphological description of the mandible of Chaetophractus villosus; subsequent work demonstrated the existence of sexual dimorphism in the mandible of this species, being females the larger sex (Squarcia et al, 2009).…”

Accuracy of mandibular measurements of sexual dimorphism using stabilizer equipment

“…Additionally, a less subjective argumentation highlights the reliability of the data. 9,10,11,12,13 However, the quantification of the structures used in the metric method is not yet well understood.…”