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[NATURE] "Cursoriality in bipedal archosaurs"
from this weeks Nature
17 August 2000
Nature 406, 716 - 718 (2000) © Macmillan Publishers Ltd.
Cursoriality in bipedal archosaurs
TERRY D. JONES, JAMES O. FARLOW, JOHN A. RUBEN, DONALD M. HENDERSON &
WILLEM J. HILLENIUS
Modern birds have markedly foreshortened tails and their body mass is
centred anteriorly, near the wings. To provide stability during powered
flight, the avian centre of mass is far from the pelvis, which poses
potential balance problems for cursorial birds. To compensate, avians
adapted to running maintain the femur subhorizontally, with its distal end
situated anteriorly, close to the animal's centre of mass; stride
generation stems largely from parasagittal rotation of the lower leg about
the knee joint. In contrast, bipedal dinosaurs had a centre of mass near
the hip joint and rotated the entire hindlimb during stride generation.
Here we show that these contrasting styles of cursoriality are tightly
linked to longer relative total hindlimb length in cursorial birds than in
bipedal dinosaurs. Surprisingly, Caudipteryx , described as a theropod
dinosaur, possessed an anterior centre of mass and hindlimb proportions
resembling those of cursorial birds. Accordingly, Caudipteryx probably used
a running mechanism more similar to that of modern cursorial birds than to
that of all other bipedal dinosaurs. These observations provide valuable
clues about cursoriality in Caudipteryx , but may also have implications
for interpreting the locomotory status of its ancestors.
-- Neil Taylor "Creo Imaginem Mente"
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