Monday, 9 January 2012

A New And Long Surviving Species Of Ichthyosaurid

The lush tropical seas of the Jurassic were inhabited by a vast range of organisms, from small cephalopods, such as ammonites, to larger creatures, such as plesiosaurs, giant vicious predators which cruised the oceans for hundreds of years, preying upon all others. One group of vertebrates which lie roughly in the middle of this scale were the ichthyosaurids. These creatures first evolved during the Triassic. They were strange forms similar in shape to seals; reaching their evolutionary prime in the Jurassic.

The fossils of Acamptonectes densus
The Jurassic specimens were perfectly adpated for life in the water. They had a very fish-like body and an elongated jaw, designed for a hydrodynamic lifestyle. Indeed the name Ichthyosaur means 'fish-lizard.' It was thought that they became extinct at the end of the Jurassic during a small extinction event. Now the discovery of a new species is making scientists re-think the history of the ichthyosaurids. In 2005, an ichthyosaur fossil was unearthed during roadworks in Northern Germany.

The remains were taken to State Natural History Museum in Braunschweig, where researchers dated to the fossil at 130 million years old. They gave it the name of Acamptonectes densus. The neck vertebrae were so tightly arranged that the species 'couldn't move its neck, so it must have shot through the water like a dart,' museum palaeontologist Ulrich Joger told the BBC. It was this feature that influenced the team's choice of scientific names. Acamptonectes densus translates as 'stiff swimmer.'

It is possible that its speed due to its inflexible form was the reason why it survived the Jurassic extinction event. While it would have been a fish-feeder, its speed would have made it a formidable opponent and swift enough to evade larger predators, such as Liopleurodon. 'It's a spectacular find,' he said. 'It raises new questions about the extinction theory.' Fresh Cretaceous ichthyosaur fossils will allow us greater insight into their evolutionary history and the extinction event.