More than one way of being a moa: differences in leg bone robustness map divergent evolutionary trajectories in Dinornithidae and Emeidae (Dinornithiformes).

The extinct moa of New Zealand included three families (Megalapterygidae; Dinornithidae; Emeidae) of flightless palaeognath bird, ranging in mass from 200 kg. They are perceived to have evolved extremely robust leg bones, yet current estimates of body mass have very wide confidence intervals. Without reliable estimators of mass, the extent to which dinornithid and emeid hindlimbs were more robust than modern species remains unclear. Using the convex hull volumetric-based method on CT-scanned skeletons, we estimate the mass of a female Dinornis robustus (Dinornithidae) at 196 kg (range 155-245 kg) and of a female Pachyornis australis (Emeidae) as 50 kg (range 33-68 kg). Finite element analysis of CT-scanned femora and tibiotarsi of two moa and six species of modern palaeognath showed that P. australis experienced the lowest values for stress under all loading conditions, confirming it to be highly robust. In contrast, stress values in the femur of D. robustus were similar to those of modern flightless birds, whereas the tibiotarsus experienced the highest level of stress of any palaeognath. We consider that these two families of Dinornithiformes diverged in their biomechanical responses to selection for robustness and mobility, and exaggerated hindlimb strength was not the only successful evolutionary pathway

Comparative hindlimb myology within the family Falconidae

A characteristical feature of a raptors’ hindlimb is their strengthen musculature that aids gripping prey with their sharp talons. To trace specific anatomical modifications it is necessary to study closely related species, with this aim, the myology of the hindlimb of the three subfamilies of Falconidae is explored. For this, a description of a Herpetotherinae member (Micrastur ruficollis) was made for the first time. The hindlimb muscle mass of Polyborinae, Falconinae and Herpetotherinae was compared according to their main function (flexion and extension) on their joints (femur, tibiotarsus, tarsometatarsus and digits). The pattern of Micrastur ruficollis resembles that of the Falconidae except for a few differences towards the development of certain muscles. As it is noteworthy the presence of the second belly of the musculus flexor cruris medialis (unique among birds), its identity will be discussed. Also, Micrastur ruficollis had the highest values of the hindlimb mass. Polyborinae and Falconinae had several differences between each other. The muscles mass of the hip and knee, both flexion and extension, were higher in the Polyborinae, this is in accordance to their more terrestrial habit. Instead, Falconinae had a higher mass in the m. flexor digitorum longus, m. flexor hallucis longus and m. tibialis cranialis, the most important muscles for gripping prey.Fil: Mosto, María Clelia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin