Reining in a galloping Triceratops.

Reining in a galloping Triceratops 

If the Triceratops model in your local museum stands with four straight legs planted firmly underneath its body, ask to have a word with the curator. A new analysis indicates these dinosaurs could not have walked with such a posture.

For two decades, paleontologists have hotly debated the limb position of ceratopsian dinosaurs, which include Triceratops. Early fossil collectors pictured these huge horned herbivores ambling with forelimbs sprawled lizard-like from the sdies of the body. Himdlimbs projected down underneath the body, like the legs of an elephant. But then Robert T. Bakker of the University of Colorado in Buoulder challenged that slowpoke image by showing ceratopsians in a stance with all legs descending directly under the body -- a posture that would have allowed the animals to gallop like rhinoceroses. Some museums have mounted ceratopsian dinosaurs in this position.

Now Rolf E. Johnson of the Milwaukee Public Museum and John H. Ostrom of Yale University think they have evidence that kicks the legs out from under the rhino-postured stance. WHile preparing to mount a recently discovered skeleton of Torosaurus -- a close relative of Triceratops -- the researchers tested the rhino-gaited and sprawling postures by constructing a flexible model using fiberglass casts of the shoulder and arm bones. This model shows that placing the Torosaurus forelimbs upright causes the elbow joint to point in an impossible postion. Johnson says that Torosaurs, Triceratops and probably all ceratopsian dinosaurs had sprawling lizard-like forelimbs after all, and therefore could not gallop. However, he adds, they could move quickly when necessary.

Other scientists contend the posture debate is not over.