[NATURE] "Cursoriality in bipedal archosaurs"

[Neil Taylor <Neil.Taylor@Informatix.co.uk>]

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"
-- Informatix Software International Ltd