Scientists have used X-ray computed tomography to produce 3D images of a 49 million-year-old spider trapped inside an opaque piece of fossilised amber resin.
Manchester University researchers, working with colleagues in Germany, showed that the amber fossil — housed in the Berlin Natural History Museum — is a member of a living genus of the Huntsman spiders (Sparassidae).
As well as documenting the spider, the scientists showed that specimens in historical pieces of amber can yield important data when studied by computed tomography.
‘More than 1,000 species of fossil spider have been described, many of them from amber,’ said Dr David Penney, from Manchester’s Faculty of Life Sciences. ‘The best-known source is Baltic amber, which is about 49 million years old and that has been actively studied for more than 150 years.
‘Indeed, some of the first fossil spiders to be described back in 1854 were from the historically significant collection of Georg Karl Berendt, which is held in the Berlin Natural History museum. A problem here is that these old, historical amber pieces have reacted with oxygen over time and are now often dark or cracked, making it hard to see the animal specimens inside.’
According to Manchester University, Berendt’s amber specimens were supposed to include the oldest example of a so-called Huntsman spider but this seemed counterintuitive as huntsman spiders are strong, quick animals that would be unlikely to be trapped in tree resin.
To test this, an international team of experts in the fields of fossils and living spiders, and in modern techniques of computer analysis decided to re-study Georg Berendt’s original specimen to determine what it was.
‘The results were surprising,’ said Dr Penney. ‘Computed tomography produced 3D images and movies of astounding quality, which allowed us to compare the finest details of the amber fossil with similar-looking living spiders.
‘We were able to show that the fossil is unquestionably a Huntsman spider and belongs to a genus called Eusparassus, which lives in the tropics and also arid regions of southern Europe today, but evidently lived in central Europe 50 million years ago.’
Manchester’s Prof Philip Withers added: ‘Normally such fossils are really hard to detect because the contrast against the amber is low but with phase contrast imaging the spiders really jump out at you in 3D.
‘Usually you have to go to a synchrotron X-ray facility to get good phase contrast, but we can get excellent phase contrast in the lab. This is really exciting because it opens up the embedded fossil archive not just in ambers.’
The scientists’ findings are detailed in a report entitled ‘Computed tomography recovers data from historical amber: an example from huntsman spiders’, which is published in Naturwissenschaften.