Wednesday, 25 January 2012

Tiny Footprints And The Oldest Dinosaur Eggs On Earth

One of the 190 million year old, embryonic fossils of Massospondylus
 from South Africa's  Golden Gate Highlands National Park
Dinosaur eggs are some of the most enigmatic fossils on Earth. They have become part of our culture, embedded within the fabric of science fiction, and films such as Jurassic Park. Yet their true value extends far beyond their place in the media. Even poorly preserved eggs can reveal a lot about the organism which it came from and the environment which it was laid in. They can indicate how intelligent the parent was, whether they were herbivorous or carnivorous and even how they migrated.

Exceptionally well preserved eggs containing embryos give us insight into growth rates and how dinosaurs raised their young and, in the case of herbivorous dinosaurs, existed as a herd. The oldest known eggs were around 90 million years old and came from Asia. Now a nesting site has been found which is 100 million years older. This is a truly remarkable find as it is thought that dinosaur eggs with calcite-based shells evolved around 100 million years ago, meaning that they are preserved far more often.

The nesting site in question was 190 million years old and was discovered in a 25 metre stretch of exposed bedrock at South Africa's Golden Gate Highlands National Park. The site was composed of 10 nests each containing up to 34 close-knit clusters of eggs. They belonged to an Early Jurassic, herbivorous dinosaur called Massospondylus carinatus. This creature was small in comparison to other Jurassic reptiles, at 4 to 6 metres in length.

Dessication cracks and ripple marks in the surrounding rock showed that the area was once an intertidal zone. The eggs contained well preserved embryos and tiny tracks around the nests showed that the young were quadrupeds for a few years before moving onto two legs as they matured. David Evans, Associate Curator, Vertebrate Palaeontology at the Royal Ontario Museum reports the find as important, as there is very little information about dinosaur reproductive biology, particularly for early dinosaurs.

'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.' Unfortunately the site is subject to violent changes in weather and the nests, and unless collected for preservation, will be eroded over the subsequent decades. The area's status as a national park suggests the latter.