Thursday, 15 March 2012

The Salamanders Of Ancient China

The 157 million year old fossil of the salamander
Beiyanerpeton jianpingensis
Salamanders are some of the strangest amphibians on Earth. They are often mistaken for lizards on account of their shape. They have inspired the legend of the fire salamander, a creature which supposedly has the ability to survive in the heart of a raging fire. As they are very sensitive to environmental changes populations and species can easily decline and become extinct. Yet they remain a diverse class with many different species known throughout the world.

Their fossil record is quite sparse, however. Their soft bodies do not preserve well and they were often very close to the bottom layers of food chains. Palaeontologists have found the oldest remains of an extinct salamander species which sheds light on the origins of a subgroup of salamandroidea, which contains around 577 still living examples.

Six fossils were discovered in the late Jurassic rocks of the Tiaojishan Formation in the Liaoning province in China by a team led by Ke-Qin Qao, from Peking University in Beijing and Neil Shubin from the University of Chicago (a world expert on the evolution of amphibians). At just 15 to 20 centimetres in length, these creatures were small, but are easily recognisable as salamanders.

The shale was once volcanic ash from a nearby volcano which settled on the bed of an ancient lake. Named Beiyanerpeton jianpingensis, its name translates as 'the creeping animal from Beiyan.' What makes it important is its age. The fossils come from a sediment band which is 157 million years old. Beiyanerpeton was part of salamandroidea. This large group of salamanders is believed to share a common ancestor with cryptobranchoidea, a second group.

Research has given two different results for the point of divergence, either 140 million years ago or 183 million years ago. The first date is taken from the age of the previous oldest known salamandroid, which was discovered in Spain and the second from genetic analysis. These new fossils indicate the latter, revealing the origins of both salamandroidea and cryptobranchoidea.