SUMMARY:The morphology and morphometry of the cranial bones of Chaetophractus villosus were studied. The skull components are morphologically similar between adults of both sexes, and follow the generalized pattern for most of described dasypodids. The morphometric analysis, however, demonstrated that the bones lying in the rostrocaudal plane are mostly longest in females, determining higher values of the total, basal and condilobasal lengths of the skull, which are the main variables that contribute to a sexual dimorphism in this species.
SQUARCIA, S. M.; SIDORKEWICJ, N. S. & CASANAVE, E. B. The hypertrophy of the tympanic bulla in three species of dasypodids (Mammalia, Xenarthra) from Argentina. Int. J. Morphol., 25(3):597-602, 2007. SUMMARY:The morphology and relative size of the tympanic bulla of three species of dasypodids from Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy, were studied. The bulla was observed to be morphologically similar and evidently hypertrophied in the three species. The degree of hypertrophy was higher in C. vellerosus and C. villosus than in Z. pichiy. By means of ANCOVA it was clear that, although C. villosus has a bigger skull than C. vellerosus, the relative size of their tympanic cavity was similar in both species. On the other hand, the skull of C. vellerosus and Z. pichiy are of similar size but the bulla was relatively shorter in the later. KEY WORDS: Chaetophractus villosus; Chaetophractus vellerosus; Zaedyus pichiy;Middle ear; Tympanic bulla. SQUARCIA, S. M.; SIDORKEWICJ, N. S. & CASANAVE, E. B. La hipertrofia de la bula timpánica en tres especies de dasipódidos (Mammalia, Xenarthra) de Argentina. Int. J. Morphol., 25(3):597-602, 2007.RESUMEN: Fueron estudiados la morfología y el tamaño relativo de la bula timpánica, en tres especies de dasipódidos de la Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy. Se observaron una morfología similar y una hipertrofia evidente en la bula en las tres especies. El grado de hipertrofia fue mayor en C. vellerosus y C. villosus que en Z. pichiy. Mediante ANCOVA se demostró que, aunque el cráneo de C. villosus es mayor que el de C. vellerosus, el tamaño relativo de la bula fue similar en ambas especies. Por otra parte, la bula de Z. pichiy es relativamente más pequeña que la de C. vellerosus, a pesar que sus cráneos son de tamaño similar.
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.
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