Tuesday, 27 March 2012

New Insight Into Ancient Pterosaur Bones

Recently, I reported on a specimen of Velociraptor which had the wing bone of a pterosaur in its stomach cavity. The nature of the meal provided the first direct evidence that dinosaurs ate carrion, as the two metre Velociraptor would never have been able to take down the seven metre giant. The discovery adds to the debate as to whether large dinosaurs, such as Tyrannosaurus, were scavengers as well as hunters.

New research shows that pterosaurs themselves may have been scavengers. In late 1904, the skull of a bizarre species of flying reptile was recovered from the Isle of Wight. It was dated to around 125 million years old, named Istiodactylus latidens and then stored away in the vaults of the London Natural History Museum in 1911. Its description noted that it had an unusual shape and bone dimensions, but it was given no attention until early this year.

Dr Mark Witton, a palaeontologist at the University of Portsmouth, and an expert on pterosaurs, realised that the specimen was far more important than previously thought. Only the brain case and the tips of the jaws with a few teeth were present. Researchers at the museum when the specimen was found estimated the proportions of the missing middle section and concluded that the complete cranium would have been long, slender and low, topping half a metre in length.

In analysing the skull, Dr Witton found that the middle section was actually far shorter, giving it a total length of around 40 centimetres and a shape which was tall and wide. He then took into consideration the shape of its teeth. These were semicircular, razor sharp and interlocking, suggesting that it had been a carrion feeder. Most pterosaurs lived on the coast, feeding on fish.

They had long jaws lined with barbed teeth, designed to hold onto slippery, struggling water dwellers. Other pterosaurs had very short thick skulls with flat teeth, designed for crushing crustacean shells. This creature has cookie cutter shaped teeth, which would have been useless for grabbing onto fish, as well as disproportionally powerful neck muscles. The only possible food source it could have eaten was carrion, by slicing into the flesh with its edged teeth and pulling strips off using its neck muscles.

The robust nature of the front and end portions of the skull backs this up. 'Modern scavenging birds have similar skull constructions, possessing both strong and weak skull components. Feeding on dead flesh allows them almost complete control over how they feed, so they can afford to have some weaker regions along their jaws without the worry of breaking them when biting into carcasses,' said Dr Witton.