Friday, 16 September 2011

Dinosaur Feathers Preserved In Amber

One of the truly incredible fossil feathers preserved in amber
Amber has provided many spectacular fossils over the years. Surprising things such as insects, plants, spider webs, sea shells and even lizards have been discovered within the hardened tree resin. The fossils lose all their water and because of the oxygen-less environment, they end up perfectly preserved. However scientists in Canada have unearthed amber fossils containing perfectly preserved dinosaur feathers that yield the most complete story of feather evolution ever.

The eleven amber fragments show a progression from hair like filaments to double branched feathers. Some are incredibly primitive, while others are at the other end of the spectrum and are more similar to modern feathers. 'We're finding two ends of the evolutionary development that have been proposed for feathers trapped in the same amber deposit,' said Ryan McKellar of the University of Alberta, the lead author of the report. Unusually, the amber fossils date to 80 million years old. Most amber is much younger at around 40 to 50 million years old.

'We've got feathers that look to be little filamentous hair-like feathers, we've got the same filaments bound together in clumps, and then we've got a series that are for all intents and purposes identical to modern feathers,' Mr McKellar told BBC News. The team's find confirms that the filaments progressed to tufts of filaments from a single origin, called barbs. In later development, some of these barbs can coalesce into a central branch called a rachis. As the structure develops further, further branches of filaments form from the rachis.
The feather of the modern, water dwelling bird, the grebe
is similar to some of the more advanced feathers

'We're catching some that look to be dinosaur feathers and another set that are pretty much dead ringers for modern birds.' It was incredibly lucky that the full range was preserved next to each other. By the late Cretaceous, feathers had nearly finished evolving and therefore such a fossil find is truly amazing. The most primitive feathers were more like filamentous hairs which hints at their origins while the most advanced are similar to the downy feathers of water birds. This fits in within the evolution of Cretaceous birds. Hesperonis was an advanced avian and led an aquatic lifestyle.

The scientists conducted further tests to try and find out more about the feathers themselves. While some displayed vestigial colour traces, others needed deeper analysis. Colours are determined by cellular structures called melanosomes. These degrade easily and therefore colours are lost. Dr Roy Wogelius from the University of Manchester has shown a method using high-energy rays of light from a synchrotron that can spot tiny amounts of metal atoms left behind by eumelanin, one of the types of melanin responsible for a range of black and brown colours.

'But, with the technological advances we are optimistic that we will be able to find chemical details beyond simply dark and light patterning. A perfect understanding of colour is unlikely except in perhaps exceptional cases,' Dr Wogelius said in an online chat about the work in JulyIn fact, a picture is emerging that many dinosaurs were not the dull-coloured, reptilian-skinned creatures that they were once thought to be.

'We're getting more and more evidence... that these animals were also brightly coloured, just like birds are today. If you were to transport yourself back 80 million years to western North America and walk around the forest... so many of the animals would have been feathered,' said Dr Mark Norell, chairman of the palaeontology division of the American Natural History Museum.