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The wing musculature of the Brown kiwi Apteryx australis mantelli and its bearing on ratite affinities
Author(s) -
McGowan C.
Publication year - 1982
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/jzo.1982.197.2.173
Subject(s) - biology , wing , anatomy , kiwi , humerus , quadrupedalism , zoology , ecology , engineering , aerospace engineering
Most previous accounts of the wing muscles of the kiwi have only dealt with the proximal muscles. The few accounts that have treated the distal muscles are incomplete in other respects and sufficient uncertainty exists to warrant the present study. The wing musculature of the kiwi is closely similar to that of other ratites but markedly dissimilar to that of the carinates. In this regard the wing muscles differ from those of the leg. Ratites have far fewer wing muscles than carinates. Significantly, they lack propatagial muscles (and almost certainly propatagia), and neither the M. pectoralis nor the M. supracoracoideus is well developed; in carinates these two flight muscles comprise the bulk of the wing musculature. Furthermore, the insertion tendon of the M. supracoracoideus does not loop through a triosseal canal to effect wing elevation as it does in the carinates. In all of these regards the ratite condition is closer to that of reptiles than of carinates. This raises the question of whether ratites should be regarded as primitive birds, rather than as advanced birds that evolved from carinates. The present skeleto‐muscular data, taken with other evidence, suggests that ratites are primitive birds that evolved from a primitive, volant ancestor. The elements of the pectoral skeleton show a greater degree of individual variation than those of the pelvic skeleton. Aside from its extreme curvature the humerus is the most rudimentary element and few of its features can be compared with those of the carinate humerus. Few of the wing muscles have attachments that can be identified with specific osteological features. Myological data for the kiwi are therefore virtually irretrievable from osteological material, as noted previously for the pelvic muscles. While this might be peculiar to the kiwi (which seems unlikely) the fact should serve as a cautionary note to palaeontologists attempting to reconstruct the muscles of extinct animals.