Factual fiction: An artist’s interpretation of the Grallator, which stood about two metres high and grew to a length of about three metres. It is likely that this animal made the trackway found at Storm Shelter in the Eastern Cape
Around 200-million years ago, a tiny creature, resembling something like a miniature Tyrannosaurus rex, took five quick steps in the mud, in a tiny nook of the Eastern Cape called Storm Shelter. In the grander scheme of things — mass extinctions, meteors, ice ages, genocides and plagues, this early Jurassic dash is barely a blip on the radar. But now, millions of years later, this animal’s short trip is making waves.
That’s because, for years, scientists have been trying to understand how this group of animals, called theropods, became the most dominant carnivores on Earth. Scientists think that changes in their body sizes were key to this development. To answer the question, scientists need huge amounts of skeletal and fossil data. And that is why the tiny dinosaur from the Eastern Cape is so important.
It forms part of an existing record of animals like this from the Karoo Basin. Collectively, these fossils could reveal how animals like the Tyrannosaurus Rex came to dominate the earth. The minute size of the Storm Shelter footprints suggests that there was an even smaller theropod travelling the plains of the Karoo Basin than those already discovered. Could it be a smaller version of an existing species? It is too early to say. Alone, it is not enough to show how theropods’ bodies changed over time. But it is a very important part of the evolutionary puzzle.
New research, conducted by Professor Emese Bordy from the University of Cape Town’s school of geological sciences and published in the South African Journal of Science, shows just how important these tracks turned out to be.
These are the smallest, and most elongated, theropod fossils yet discovered. They are also the smallest dinosaur tracks ever to be discovered in the region, also known in archaeological terms as the Clarens Formation. It’s thought that the animal ran at about 12.5km per hour.
Scientists don’t yet know for sure which animal made the tracks. But a likely candidate is the Megapnosaurus rhodesiensis.
The tracks were originally spotted by a local resident, Adele Moore, a stone’s throw from the small town of Maclear, Eastern Cape, in the foothills of the Drakensberg. They have been the subject of intense research ever since.
The small animal’s feet were just 7.5cm long and 3.6cm wide. There’s evidence that the animal might have had claws, and that it once had a hindfoot, in a previous evolutionary iteration.
Theropods were considered the main terrestrial carnivores during the Jurassic and Cretaceous periods. Theropods were bipedal, with three toes on each foot.
“Their smaller bodied varieties, like the Storm Shelter tracks, most probably took on the dual role of predator and prey, and thus had good reason to leave behind tracks indicative of a running gait,” wrote Bordy.
The Karoo Basin is the perfect place to investigate the question of where they came from. It is a gold mine of fossils.
This central South African area was once covered by ice. As the ice retreated, some 250-million years ago, the area became a swampland, in which all manner of primitive reptiles roamed. Gradually, these gave rise to the first mammals. That process was cut short by volcanic activities, which killed off the dinosaurs evolving there, but left behind a treasure trove of fossils.
The area is so well-preserved that at least three types of dinosaurs have been found there. Some of these are even thought to have walked on the lava before they died.
Scientists might never know where the Storm Shelter animal was going when it made those five crucial steps. But the mere confirmation of its existence will echo throughout the world’s fossil record. This creature’s short run could help scientists to piece together the history of some of the most vicious creatures in Earth’s history.