Sorry, Barney fans. A new report suggests the notion of some dinosaurs being caring, nurturing parents to helpless youngsters may be stretching the facts. It turns out the kids were a precocious bunch.
Writing in the latest issue of the journal Science, paleobiologists Nicholas Geist and Terry Jones of Oregon State University say their analysis of infant dinosaur fossils leads them to believe the animals were up and running early in life, rather than nestbound.They contend the dinos were much the same as modern reptile species, perhaps attentive to their young before they hatch, but likely to be standoffish later.
"Current evidence suggests that the nesting behavior was likely similar to that of modern crocodilians," Geist and Jones conclude.
This interpretation is bound to stir up the world's elite group of dinosaur researchers, which has always been divided over whether the beasts that ruled Earth for nearly 100 million years were warm or cold-blooded, slow-moving or fast, more bird-like or reptilian in behavior.
Veteran fossil finder Jack Horner of Montana State University - who served as director Steven Speilberg's technical adviser on Tyrannosaurus Rex in "Jurassic Park" - started the new thinking about dinosaur parenting just in the last decade.
First he found evidence that at least one species nested together in carefully patterned rookeries year after year. Then, he found nests of another species of a family of dinos called Hadrsaurs, filled with crushed eggshells, suggesting youngsters bumping around a nest after they hatched.
Fossils of infants in and around the nests showed knees and hips too weak to carry the animals, perhaps for weeks after they were born, indicating at least one parent must have fed and watched over the brood. Horner named the species Maiasaura, Latin for "good mother lizard."
The clincher seemed to come a few years later, with the discovery of the fossilized Oviraptor, found brooding a nest of eggs.
Horner's main anatomical argument lies in the amount of cartilage that had developed at birth in the baby Maiasaura's leg joints, and more recently in evidence that the animal's bones were slow to grow after they hatched.
But Geist and Jones looked at the same fossils in a different light, noting that the pelvises of the Maiasaura as well as four other types of infant dinosaurs were well-ossified at birth, indicating an ability to walk and run almost immediately.
They compared the fossilized bones to skeletons of distant cousins alive today - ostriches, crocodiles, ducks and quail - that are known to hatch precocious babies. All had a well-ossified pelvis.
By contrast, birds like the dove, starling and finch that stick to the nest for a longer period all have a poorly ossified pelvis.
Geist and Jones note that "nest-attending and brooding behavior is widely distributed among extant crocodilians, lizards, snakes and amphibians," not to mention some mammals.
Horner counters that the anatomical similarities to birds outweigh any particular characteristic that some dinosaurs had in common with reptiles as well.
Despite the seeming contradictions, the message to a growing number of dinosaur experts is that the animals were an extremely diverse group that may have evolved and discarded any number of traits over millions of years on a changing planet.