Fossil webs snagged dinosaurs

At Halloween our thoughts turn to spiders and all things scary but how about spiders and dinosaurs?

Martin Brasier of Oxford University's Department of Earth Sciences has shown that amber found by amateur dinosaur hunters contains threads of the world's oldest spider webs - webs that were spun 140 million years ago.

The Oxford team report their results in the latest issue of the Journal of the Geological Society.

Martin comments: ‘This amber is very rare. It comes from the very base of the Cretaceous, which makes it one of the oldest ambers anywhere to have inclusions in it.'

Their evidence shows that the webs these threads belong to would have graced lush prehistoric forests frequented by dinosaurs such as Iguanadon and Allosaurus.

The web-spinners in question were closely related to the modern day orb-web, or garden spider. ‘These spiders are distinctive and leave little sticky droplets along the spider web threads to trap prey,’ Martin explains.

‘We actually have the sticky droplets preserved within the amber. These turn out to be the earliest webs that have ever been incorporated in the fossil record to our knowledge.'

The cobwebs were preserved in tree sap, possibly emitted by trees in response to fire damage, which then fossilised into amber. To reconstruct the webs, the scientists focused through the amber at 40 different positions, tracing it through the layers and then splicing it together again using a computer technique called confocal microscopy.

As well as the amber, there are several other types of deposit at the site which are showing remarkable levels of preservation, including silica and phosphate minerals.

Martin adds: 'It’s part of a larger project which is yielding rich rewards. There’s still a lot more to find, and we have even more exciting things to report in the near future.'