Ae. Patak et J. Baldwin, PELVIC LIMB MUSCULATURE IN THE EMU DROMAIUS-NOVAEHOLLANDIAE (AVES, STRUTHIONIFORMES, DROMAIIDAE) - ADAPTATIONS TO HIGH-SPEED RUNNING, Journal of morphology, 238(1), 1998, pp. 23-37
Emus provide an excellent opportunity for studying sustained high-spee
d running by a bird. Their pelvic limb musculature is described in det
ail and morphological features characteristic of a cursorial lifestyle
are identified. Several anatomical features of the pelvic limb reflec
t the emus' ability for sustained running at high speeds: (1) emus hav
e a reduced number of toes and associated muscles, (2) emus are unique
among birds in having a M. gastrocnemius, the most powerful muscle in
the shank, that has four muscle bellies, not the usual three, and (3)
contribution to total body mass of the pelvic limb muscles of emus is
similar to that of the flight muscles of flying birds, whereas the pe
lvic limb muscles of flying birds constitute a much smaller proportion
of total body mass. Generally, the pelvic limb musculature of emus re
sembles that of other ratites with the notable exception of M. gastroc
nemius. The presence and arrangement of four muscle bellies may increa
se the effectiveness of M. gastrocnemius and other muscles during curs
orial locomotion by moving the limb in a cranio-caudal rather than a l
atero-medial plane. (C) 1998 Wiley-Liss, Inc.