|The 170 million year skeletal remains of Eoabelisaurus mefi|
A team of 25 palaeontologists, from the Edigio Feruglio Museum of Paleontology and led by Dr Diego Pol, excavating in 170 million year old rocks at Condor Hill in the Patagonian province of Chubut, some 1800 kilometres south of Buenos Aires, have uncovered the remains of the oldest abelisaurid yet.
The skeleton was actually discovered on a dig in 2006, but the team was forced to abandon excavations due to the onset of winter. While Patagonia is a desert region, its winters are harsh and long. On their return they found the remains were relatively complete with vertebral column, partial rib cage, hind and forelimbs. Yet most of the skull, and parts of the tail and neck, were missing.
|One of the bones inside its plaster transportation jacket. |
The image shows off the sheer scale of the bones
It was obviously an abelisaurid, but it had a number of bizarre features. It was six metres in length, quite small for the group it came from, and its arms were tiny. The size difference between the forelimbs and the body was even more extreme than that seen in Tyrannosaurus. These facts, combined with its age led the team to conclude that this creature, named Eoabelisaurus mefi which translates as 'dawn' abelisaurid, was the first of its kind or very close to the base of the group's evolutionary tree.
This group of dinosaurs were all top predators. Therefore the lack of arm size was most likely an adaptation to increase jaw size and power in a fashion similar to the later tyrannosaurids. Pangaea was a desert at its heart and the later continents of Gondwana and Laurentia were separated by an ocean. The north and the south of the planet could be traversed only by the hardiest and most well adapted of creatures.
The jaws of Eoabelisaurus would have allowed it to feed on almost anything, enabling it to survive in the red wastes of the Mesozoic continents. This simple adaptation, combined with another 40 million years of evolution, facilitated the rise of the abelisaurids. Even so,the group are only known in the southern hemisphere, showing that not even the forces of evolution could overcome the forces of nature.
As a result, some truly unique ecosystems evolved in the south. This has happened a number of times, but this was on the largest possible scale. The record breaking dinosaurs in terms of physical size and weight have been found in rocks in Argentina and Chile. Yet Eoabelisaurus is just one small part of the complex network of prehistoric life. It will be many years before we understand Mesozoic South America in full.