The hind limb musculature of the brown kiwi, Apteryx australis mantelli

Abstract

The most complete account of the hind leg muscles of the kiwi was published a century ago by Sir Richard Owen, in his seventy-fifth year. This extensively-cited work has several omissions and errors, and while certain of these were corrected by subsequent authors, sufficient uncertainty remains to warrant a reinvestigation. In the present study a detailed description of the hind leg musculature is given, based upon dissections of two frozen specimens. An indication of the possible function of each muscle is given by assessing its size, action, and fiber-arrangement, together with tentative data on the relative abundance of twitch and tonus fibers. The correlation between surface features of bones and muscle attachments is investigated with a view to interpreting palaeontological material. Although the limb and pelvic bones are marked by numerous features which suggest muscle attachments, relatively few can be positively identified with specific muscles. Only 23% of the muscle origins and insertions can be identified, and, with three possible exceptions, no indication of relative size is given by the scars. The possibility of being able to reconstruct the musculature of the kiwi from its skeletal anatomy, much less that of its extinct relatives, is remote.

The effect of endurance exercise on the morphology of muscle attachment sites

“…Moreover, the lack of correlation between muscle size and either attachment site size or complexity in the sedentary control animals in this study further indicates that these skeletal features do not accurately reflect the size of the attaching musculature. These results are consistent with previous studies that have reported discrepancies between muscle size and attachment site morphology in some birds and reptiles (McGowan, 1979(McGowan, , 1986Nicholls and Russell, 1985) and other mammals (Bryant and Seymour, 1990;Davis, 1964a). The results of this experiment therefore do not substantiate the long-held assumption that attachment site morphology reflects in vivo activity and muscle size.…”

“…There are a number of studies that indicate that the visible features on bony surfaces do not fully or reliably reflect the actual extent of muscle attachment, and that the degree to which muscle scars reflect soft tissue attachment appears to vary between vertebrate lineages (Bryant and Seymour, 1990;Davis, 1964a;McGowan, 1979McGowan, , 1986. Additionally, the asymmetry or relative robusticity of an individual's skeleton may skew an observer's assessment of the degree to which the sites are developed (Robb, 1998;Weiss, 2002).…”

Quantitative microanatomy of jaw muscle attachment in extant diapsids

“…); four others have exceedingly subtle correlates even in older, well-ossified individuals, and the remaining two leave no grossly visible bony remnant. Trends in preservation appear when these correlates are examined together with a further sample of 117 tendinous and aponeurotic attachments reported from the forelimb of the New Zealand rail Gallirallus australis and the fore-and hindlimb of the kiwi, Apteryx australis, by McGowan (1979McGowan ( , 1982McGowan ( , 1986. As might be expected, more robust tendons seem more likely to produce recognizable scars, but visible scars are nevertheless only present in 38% of these attachments.…”

Pelvic and hindlimb musculature of Tyrannosaurus rex (Dinosauria: Theropoda)

“…Caution is warranted when attempting to reconstruct the musculature of any extinct animal (McGowan, 1979(McGowan, , 1982Bryant and Seymour, 1990), particularly a member of a group (such as nonavian dinosaurs) that may have differed significantly from its extant relatives in locomotor habit (Gatesy, 1990(Gatesy, , 1995Carrano, 1998a;Hutchinson and Gatesy, 2000). Parsimony requires a conservative reconstruction of the primary pelvic and hindlimb musculature in dinosaurs-i.e., one that requires a minimum number of inferred differences from extant forms (Rowe, 1986).…”

“…Nonetheless, it is exceedingly difficult to quantify muscle size precisely from osteological data alone (McGowan, 1979(McGowan, , 1982Bryant and Seymour, 1990), and other unpreserved features-such as fiber length, pennation (and hence physiological cross-sectional area), force output, histochemistry, and activation pattern-are even more remotely accessible. Because the cross-sectional area of a muscle often differs in size from the area of muscle scarring (Bryant and Seymour, 1990;Hutchinson, 2001a), we assume that a scarred area allows only a general estimate of that muscle's size.…”