SA fossil find stuns world
2005-07-28 22:17
Washington - Scientists have uncovered the oldest dinosaur embryos found until now, dating to the beginning of the Jurassic age 190 million years ago.
The dinosaur eggs were discovered in South Africa in 1978 during road works in the Golden Gate Highlands National Park.
However, the find had not come under study until three years ago, when Robert R Reisz of the University of Toronto and his team began to analyse them.
The find, which has taken years to decipher, is helping them understand the development of a long-necked, plant-eating giant called Massospondylus carinatus.
'Cool' and 'beautiful'
The discovery is producing three important results, said Reisz.
The first, he said, was the "Gee whiz, Guinness world record that we have found the oldest dinosaur embryo".
"That's cool and they are
beautiful."
The second was the hard science, Reisz said.
Scientists are now able to look at the growth pattern of the animal from embryo to adult because they now had skeletons from various stages of its life and could compare changes as the animal grew.
The third area, he said, was mostly speculative.
Some of the embryos were clearly ready to hatch, he said, but they had no teeth, "and that suggests to us that some form of parental care was required... not just protecting, but active feeding".
The report by Reisz and others at the University of Toronto, the University of the Witwatersrand and the Smithsonian Institution's National Museum of Natural History is published in Friday's issue of the journal, Science.
James Clark of George Washington University in Washington, who was not part of the research group, concurred that these were the oldest dinosaur embryos yet found.
Rare
"The importance of the discovery is that they are from a primitive member of the sauropodomorphs, a large group that included the largest land animals that ever lived.
Sauropodomorph embryos were rare, and the only previously known embryos of this group, from Argentina, were from a much-later and more-specialised form," said Clark.
The find enables researchers to study the animal's growth and development because they now can compare skeletons at different ages.
"Surprisingly, the proportions of the limbs, neck and head suggest that as a baby and young animal this species walked on four legs, but as an adult it was able to walk on two legs some of the time.
This kind of change in posture hadn't been documented in any other dinosaur," Clark noted.
Hatchlings were different from adults
Indeed, Reisz and colleagues reported that the Massospondylus
hatchling was born four-legged with a relatively short tail, a
horizontally held neck, long forelimbs and a huge head.
As the animal matured, the neck grew faster than the rest of the body, but the forelimbs and head grew more slowly.
The end result was a two-legged animal that looked very different from the four-legged embryo.
Reisz suggested the change from four- to two-legged could be a
matter of balance related to the development of the animal's neck.
An adult Massospondylus could grow more than 4.6m long.
On the net:
www.sciencemag.org
www.erin.utoronto.ca
www.wits.ac.za
www.mnh.si.edu
- AP