The Hindlimb Elements of the Maas (Aves, Dinornithidae): A Multivariate Assessment of Size and Shape

Abstract

A multivariate morphometric analysis of size and shape was performed on the hindlimb skeletal elements of the extinct New Zealand moas (Dinornithidae). Investigations were undertaken of size‐shape patterns within species and among moas as a group using principal components analysis; between species investigations used canonical analysis. In addition, standard allometric curve‐fitting of six femur, seven tibiotarsus, and nine tarsometatarsus variables against body size was performed.Size was the major discriminator along the first principal component for all three bones in the intraspecific and whole‐group analyses. Shape was the important discriminator along the second component: in the whole‐group analysis of all three bones, separation was based on relative robustness of the shaft, whereas in the intraspecific analyses shaft robustness was only expressed in the analysis of the femur, there being little correspondence in the results between the intraspeci fic and whole‐group analyses of the tibiotarsus and tarsometatarsus. Size was the major discriminator along the first canonical axis for the between‐group investigations of the femur and tibiotarsus, but in the analysis of the tarsometatarsus shape influences were equally as important as those of size. The second canonical axis separated groups on the basis of shape differences in all three hindlimb elements.The genus Dinornis, which contains the largest species of moas, has evolved sizeshape patterns very different from those of other moas. The species of Dinornis did not follow size‐dependent allometric trends and evolved proportionately thinner legs than might be expected for their body size. All other moas exhibit allometric increase in all hindlimb variables except bone lengths. Dinornis may have evolved a cursorial mode of locomotion as an adaptation for certain intraspecific behavioral interactions.