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Quantifying intraspecific shape variation in the Kangaroo Humerus using geometric morphometrics

Miglori, Nicole (2015) Quantifying intraspecific shape variation in the Kangaroo Humerus using geometric morphometrics. Honours thesis, Murdoch University.

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Kangaroos exhibit one of the largest variations in body size for any vertebrate, with males being 1.5 times larger in body mass compared to females. Therefore it is assumed that sexual selection plays a major role in the behavioural and physical characteristics of kangaroos. Male and female kangaroos demonstrate marked differences in musculature of the forelimb. I investigated if the humerus (the upper bone of the forearm) of the western grey kangaroo (Marcopus)fuliginosus) displays sexual dimorphic characteristics, and if these characteristics are correlated with muscle mass. 28 landmarks were digitised in 72 male and 23 female humeri and analysed using geometric morphometric approaches. Muscles were collected from fine dissection and residual muscle masses were calculated for analyses of each sex. Males and females were sexually dimorphic in shape, with the most obvious change at the deltoid crest where the crest was significantly increased in size and the shaft was in a bent orientation. This study suggests that a humerus from a western grey kangaroo can be classified by correct sex 92% of the time. There was a significant relationship between muscle mass and bone shape that indicate that muscles affect the morphology of the humerus. Male humeri are robust and slightly bent, conversely female obtain a more gracile form. Geometrics morphometrics is an advantageous technique that allows the morphology of shape to be investigated; by including fine muscle dissection we have determined how shape and muscles influence one another. The methods in this study can be applied to multiple studies that wish to investigate the morphology of shape and the influence of muscles.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Warburton, Natalie, Fleming, Trish and Bateman, Bill
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