COMMENT
In the late winter of 1976, the world-famous fossil collector James Kitching was conducting a survey near South Africa’s border with Lesotho. To his surprise he found a tiny clutch of six fossilised eggs along the side of the road at a place known as Rooidraai.
It took five years for palaentologists to remove enough rock from the eggs for them to be preliminarily identified as the first dinosaur embryos from South Africa and the oldest dinosaur embryos in the world.
Research on dinosaurs has blossomed in the years since Kitching’s find, and a great deal more is now known about the baby dinosaurs in the eggs. But the secrets of the embryonic dinosaurs, whose parents roamed South Africa 200-million years ago, are only now being fully uncovered.
This month, the eggs were flown to Grenoble, at the foot of the French Alps, where they have been examined under a powerful CT scan at the European Synchrotron Facility.
With advances in modern imaging methods we are now able to digitally remove rock matrix while making 3D models of the bones inside.
Diane Scott, one of the world’s greatest fossil preparators, painstakingly removed as much rock as possible from the clutch of eggs to expose the embryos for study, and a collaborative international team led by palaeontologist Dr Mike Raath, in partnership with researchers from the University of Toronto and the Smithsonian institution, has been able to study the embryos in much greater detail.
A second group went back to Rooidraai and excavated the site where Kitching discovered the eggs.
Striking results
The results of the new studies were striking. The findings of the additional preparation, published in 2005, revealed two nearly complete embryonic skeletons of the dinosaur Massospondylus, a 5m-long herbivore that roamed South Africa in the Early Jurassic Period.
Unlike adult Massospondylus, which had a small head and walked on two legs, the embryos had big heads and when they hatched would have walked on all fours.
The second team also unearthed remarkable new findings.
The excavations, published in 2012, found 10 additional egg clutches, some with as many as 34 eggs, scattered across the low cliff-face at Rooidraai. This was clear evidence that Massospondylus were returning year after year to nest in the Eastern Free State.
So what remains to learn about the Massospondylus embryos after nearly 40 years of study? Although Scott’s masterful preparation exposed many anatomical features of the tiny skeletons inside the eggs, there was a limit to even her abilities and many features remain buried beneath rock.
Learning more from the finds has been difficult: the embryos are extremely small. The femur or thigh bone is only 1.4mm in diameter. And understanding the anatomy of the bones is difficult because they have remained forever affixed to the stone.
Figuring out the details of how baby Massospondylus grew requires peering inside the bones themselves, but doing this with histological techniques, which analyse tissue on a microscopic level, would require destroying the specimens.
Egg scan
CT scanning is a viable alternative, but the resolution needed to study the embryos is so high that only a few facilities in the world are capable of performing the study.
In late 2014, a team of us put together a winning proposal to scan the eggs at the European Synchrotron Radiation Facility in Grenoble. At the facility, a huge ring of electrons (almost a kilometre in circumference) travelling at .99% of the speed of light continuously generates beams of high-energy X-rays. These beams can be harnessed with great precision to peer through rocks and image the fossils inside.
A few weeks ago we travelled to Grenoble to start the first stages of data collection. Carefully packing the original clutch of six eggs in a custom-made cushioned travel box, we negotiated curious customs officers and surprisingly indifferent airline officials to spend seven days of round-the-clock work obtaining thousands of individual x-ray scans.
Processing this vast amount of data (more than a terabyte) will take months of work at the University of the Witwatersrand’s state-of-the-art Virtual Palaeontology Lab in Johannesburg. But our preliminary results show great promise.
Laid 200-million years ago, studied for more than 40 years across several continents, Kitching’s famous discoveries are still yielding scientific dividends. – TheConversation.com
Jonah Choiniere is the senior researcher in dinosaur palaentology at University of the Witwatersrand.