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Though dinosaurs have been extinct for nearly 80 million years, it is still possible to learn about their behavior by studying their fossils, according to one of the world's most famous dinosaur hunters.

Also, some of the current discoveries about dinosaur behavior may shatter most people's illusions about the extinct animals, said Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont.Horner, speaking at BYU's Monte L. Bean Life Science Museum, said many ideas about dinosaurs - including the theories that they were coldblooded and very similar to modern reptiles - may prove to be groundless after recent discoveries in the Rocky Mountains.

"People have made their decisions as to what they think dinosaurs should have acted like, based on the idea that they should be classified similarly to reptiles, and that may not be correct," Horner said.

"There are ways of looking at such animals - animals that have been dead for a long time - and discovering much about their natures. We can examine what the animal probably looked like and find out much from that."

For example, one of the largest carnivorous dinosaurs - the Tyrannosaurus Rex - has been made out to be one of the world's largest predators, but that may not be necessarily so, Horner said.

Tyrannosaurus Rex was probably not swift enough to catch many other dinosaurs (because it had to keep its tail erect behind it) and its nearly useless front limbs would have proved ineffective in holding large animals, Horner said.

In fact, the Tyrannosaurus, "which had a mouthful of steak knives," may have been the world's largest scavenger, he said.

One of the world's most exciting set of discoveries about dinosaur behavior was spawned by excavations in a site called Egg Mountain, located near Glacier National Park in Montana, Horner said.

That site, which scientists believe was at one time a small island, has yielded large concentrations of dinosaur egg deposits, hence the name, he said.

"There are more dinosaur eggs at this site than there are anywhere else in the world, and these have prompted some new theories about dinosaurs' maternal instincts."

Eggs belonging to the relatively small herbivore Hypsilophodont (which grew up to 8 feet) and the similarly sized carnivore Troodont have been found at that site and have yielded many surprises about mothering instincts, he said.

While the Hypsilophodont eggs suggest nesting similar to modern reptiles, the fact that many nests were found very close to one another suggests the animals nested in colonies, a birdlike behavior, he said.

Also, both egg-laying patterns (Hypsilophodont laid eggs in a vertical, circular pattern and Troodonts laid eggs in horizontal, straight-line patterns) suggest that the mothers laid eggs very carefully, Horner said.

In addition, studying cross-sections of baby and adult dinosaur skeletons found at the site has revealed that those dinosaur bones have mass vascularization (blood vessels located within bones) that allowed for quick growth of the baby animals, something much closer to the growth patterns of large birds like ostriches than to reptiles, he said.

When combined with discoveries about shapes and structures of dinosaur eggs, as well as herding and nesting behaviors, the vascular pattern suggests that dinosaurs may have been very similar to birds, he said.

"Now I'm not saying they were birds, but dinosaurs were very, very special kinds of animals."