Paleontoriano

Scientists have long known that dinosaurs - the name meaning "terrible lizards" - weren't lizards at all.

And apparently, the prehistoric reptiles weren't always so terrible, either.

A Canadian-led study of a 190-million-year-old dinosaur nesting site in South Africa has shed new light on the patient, perhaps even nurturing parenting practices of an early species from the extinct clade of animals.

The findings are detailed this week in a paper co-authored by University of Toronto at Mississauga paleontologist Robert Reisz, Royal Ontario Museum curator David Evans and three colleagues from the U.S., Australia and South Africa.

The location is considered the oldest known dinosaur nesting site ever found, and includes at least 10 separate nests with up to 34 eggs in each clutch. Identifiable embryos are among the fossilized specimens.

The species utilizing the site was the six-metre-long Masso-spondylus, and females appear to have congregated in groups to lay their eggs and - at least temporarily - raise their young.

Footprint impressions left by juvenile dinosaurs have convinced the scientists that the hatchlings were staying at their birthplace long enough to have doubled in size before leaving the nesting area.

The discovery suggests at least "limited maternal care" may have been practised by the mother dinosaurs as the newborns gained weight and increased their chances of survival around the nest site.

Such signs of a "primitive form of parental care" and other evidence gleaned at the South African site underscore its significance "for understanding the evolutionary history of reproductive behaviours in dinosaurs," the researchers state in their paper, published in the journal Proceedings of the National Academy of Sciences.

"This research project, which has been ongoing since 2005, continues to produce groundbreaking results and excavations continue," said University of the Witwatersrand [South Africa] pale-ontological research director Bruce Rubidge, whose colleague Adam Yates was a co-author of the study.

"First it was the oldest dinosaur eggs and embryos, now it is the oldest evidence of dinosaur nesting behaviour."

Reisz, who has been involved in a host of high-profile dinosaur-related discoveries in recent years - including several others at the South African site - stated in a summary of the latest study that the weathered cliff where the 10 nests were discovered almost certainly will yield further finds.

"The eggs, embryos, and nests come from the rocks of a nearly vertical road cut only 25 metres long," he said. "Even so, we found 10 nests, suggesting that there are a lot more nests in the cliff, still covered by tons of rock."

Evans, curator of vertebrate paleontology at Toronto's Royal Ontario Museum, added "this amazing series of 190-million-year-old nests gives us the first detailed look at dinosaur reproduction early in their evolutionary history, and documents the antiquity of nesting strategies that are only known much later in the dinosaur record."