A critical re-evaluation of the hindlimb myology of moa (Aves: Dinornithiformes)

Abstract

The extinct moa of New Zealand were an enigmatic group of flightless birds, some attaining gigantic size. To better understand the biomechanical consequences of their large size and unique anatomy on stance and locomotion, a critical re-evaluation of the evidence for muscular attachment in the hindlimb of moa was undertaken. Three focal taxa, Dinornis robustus, Emeus crassus and Pachyornis elephantopus, were studied in detail, although other moa species were also addressed. More than one thousand individual bones from a diverse array of localities across the South Island of New Zealand were examined, and interpretations were made within the context of extant palaeognath birds. The interpretations and reconstructions produced largely concur with those of previous workers in many respects. The reconstructed myology of these moa species is also quite comparable to that in extant palaeognaths, although some important differences are hypothesised to exist. The most significant of these is that it moa are posited to have had a very well-developed iliotrochantericus caudalis in comparison to extant palaeognaths. Digital computer reconstruction of this muscle in an adult female D. robustus supports this hypothesis. The great development of the iliotrochantericus caudalis in moa may be related to their large size, or reflect a different locomotor behaviour compared to extant palaeognath species. Finally, a number of myology-related features have been identified that may prove useful in the taxonomic identification of isolated or poorly preserved bones.