Sunday, 2 September 2012

On The Origins Of Pangolins

Pangolins are the most bizarre mammals, and some of the most prehistoric-looking creatures on the planet. They are covered in large scales, with some species coming in at over a metre. Such a distinctive morphology should mean that reconstructing their evolutionary history should be an easy task. Genetic trees would be easy to trace. Indeed, some headway with their genetic heritage has been made.

A comparison between a modern pangolin (top) and Ernanodon antelios
It is the actual physical evidence, however, which has proved elusive. Yet a discovery from China could close the gap in the fossil record. In the 1970s, a mysterious skeleton was recovered from early Palaeogene rocks in China. For over 30 years it remained in storage until researchers from the Russian Academy of Sciences rediscovered it. At first, it was heralded as a fake on account of its warped nature.

Preliminary analysis of the fossil soon debunked this theory. Yet its true nature and value would not become apparent until the study was complete. Luckily the skeleton was incredibly well preserved and complete, a rare occurrence for Palaeogene Asia. In the end, the researchers were able to conclude that this 57 million year old, dog-sized mammal was the one of the earliest pangolins to walk the Earth.

Various elements of the skeleton
All modern day members of the group feed on insects and so have very long tongues, enabling them to delve down deep inside ant hills and beehives to reach prey.

Pangolins had large claws and strong forelimbs which would have enabled it to dig into and rip apart the nests of its quarry. Its small, weak teeth also suggested that it was used to feeding on soft food. 'It's the real deal,' said Peter Kondrashov from the Kirksville College of Osteopathic Medicine, Missouri.

A study of other fossils from the region showed that the ancient pangolin, now named Ernanodon antelios, lived in a world of dense forest and open plains. Some pangolins hang from trees by their strong, armored tails, others live in environments with steep, rocky climbs, but this creature almost certainly dwelt in flatter, more gentle biomes.

'It was definitely a terrestrial mammal. It doesn't have any adaptations for climbing trees,' Kondrashov said. 'It was just designed to walk on fairly flat surfaces. This is the time when all the main groups of mammals were established on the planet. This history is really well-deciphered in North America, and there's very little known about Asia,' he went on to say. 'This helps us to understand how these early steps in the evolution of major groups of mammals occurred in Asia.' Palaeogene Asia is still poorly understood, but in time information will become clearer. Pangolins are a small particle of this.