General Chat

BEHIND the war of words over the significance of Ida, the 47-million-year-old primate fossil unveiled last week, a quiet revolution in palaeontolgy is unfolding. Thanks to a souped-up version of a technique better known for its use in medical diagnostics, we are gaining unprecedented insights into the way prehistoric creatures lived, breathed and grew.

The technique is X-ray computed tomography (CT). Though X-rays have been used to look into fossils since this type of radiation was discovered in 1895, the flat images it produced changed little over the following century. As recently as 2004, a review in The British Journal of Radiology (vol 77, p 420) saw little merit in X-ray images of fossils beyond acting as a guide to palaeontologists chipping away the rock encasing them.

CT changes all that. It takes X-rays of an object from many directions, then crunches the resulting data to create a 3D image. Researchers can rotate this "virtual fossil" to inspect it from any angle, zoom in to view details, or fly straight through it to admire what's hidden inside. "It's revolutionising the way we see fossils," says Jørn Hurum of the Natural History Museum in Oslo, Norway, one of the team who studied Ida.

This requires much more energetic X-rays than normal radiography and it is only recently that CT scanners capable of both penetrating dense fossils and imaging them at high resolution have become available. "A few years ago, if someone showed a 3D CT model at a conference, you'd get gasps from the audience," says Paul Barrett, a palaeontologist at the Natural History Museum (NHM) in London. "Now it's one of the first things that people think of."

The technology has vastly increased the range of samples that can be studied and the information gleaned from them. Many fossils are just too intricate or delicate to be separated physically from the surrounding rock. Even Ida's beautifully prepared skeleton could not reveal crucial information about her growth and development. For this, the researchers needed to study individual teeth, which would have required destroying the skull

Many fossils are too intricate or delicate to be separated physically from the surrounding rock. Instead, the team used CT to generate virtual reconstructions of the teeth. Their next step will be to do the same for Ida's foot and ankle bones, especially the talus bone. This will be key to relating Ida to other species, because in many primate specimens the talus is the only bone to survive.

In other situations, CT may be the only way to tell that a fossil is there at all. Paul Tafforeau, a palaeontologist at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, has used high-energy X-rays produced by the synchrotron to peer inside hundreds of pieces of opaque amber from a site in south-west France. "We found 356 inclusions in just four days," he says.

The 100-million-year-old creatures he found range from snails to damselflies, and Tafforeau's 3D images reveal unprecedented detail, down to submicrometre resolution. Many are new species, including two cockroaches and a wasp (Geodiversitas, vol 31, p 7, p 73 and p 137).

The fossils are invisible to anyone without a particle accelerator. So Tafforeau has used the scans to make magnified plastic models of the reconstructed creatures, and last week made them available on an online database.

Perhaps the most revolutionary application of CT is the insight it can give into fossils' internal structures. "For the first time, we can see inside things without breaking them," says Hurum. And that allows palaeontologists to move beyond surface anatomy to probe how ancient creatures ticked. "You can start to look at questions relating to the biology of extinct species," says Barrett. Over the last three years or so, CT has been used to reveal structures as diverse as the cleavage patterns inside billion-year-old worm embryos (Nature, vol 442, p 680), the optic lobes of a fossilised fish brain (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0807047106) and the spacing of vertebrae inside a 4-tonne mummified dinosaur.

Fascinating Len

I love your posts and do read them even if I don't have an answer :-)

Er ... ditto. Just read the whole thing!

Scuse me, I'm shoving my nose in again,this is very interesting, but the cynic in me wonders whether the money would be better spent on medical research for the living ????

Interesting reading.
Brian(i)

I am taking a fossil to have a CT scan tomorrow. My OH who is 79 is having another brain scan to see if there are any cells left. Be interesting to know how much difference from the scan he had almost 3 years ago. I would imagine there would be a big difference as his memory and behaviour or so very different now :((( He has Alzheimers.

Huia.

My mum had her latest scan yesterday (to check progress of lymphoma after several chemo treatments) -- I'll work the fossil scan into the conversation, Huia ... ;)