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T was in 2016 that one of Elsa Panciroli’s team

spotted the fossil on the southern shore of Skye.

Only just protruding from a barnacle-covered

rock, it looked more like a smear of ash. But on this

west Scottish island, which is home to more remains of

Middle Jurassic vertebrates than anywhere else known

on Earth, appearances can be deceiving.

The team cut out the fossil and took it back to their

mainland lab at National Museums Scotland. From

there they sent it to the University of Oxford, where they

removed as much of the surrounding rock as possible so

that they could scan it with an X-ray micro computed-

tomography (CT) machine. Emerging from the images

was what looked like almost an entire juvenile skull of

an early mammalian ancestor – similar, albeit smaller,

to that of another fossil found over 40 years earlier. But

the lab-CT images of that older fossil had been murky

and hard to make out. “That’s the trouble with lab CT,”

says Panciroli. “I once took that older fossil to Nikon

headquarters, but even their CT system couldn’t see

more than a ghost in the rock.”

Curious, Panciroli’s team took the older fossil to the

ESRF’s ID19 beamline to perform several scans. Even

though the fossil was buried inside a stone the size of

a breeze block, the ESRF’s X-rays were well able to

penetrate and deliver clear, high resolution and very

high contrast images. And what they revealed was

unprecedented: a fossil of exactly the same species as the

one just discovered – but an adult rather than a juvenile,

and almost entirely intact. “The difference between the

lab and synchrotron images was night and day,” says

Panciroli.

Synchrotron palaeontology based on phase-

contrast CT was pioneered at the ESRF at the turn

of the millennium and has since enjoyed a quarter

of a century of rising interest and impact From the

childhood growth of our earliest human ancestors to

the domination of reptiles after Earths greatest mass

extinction to the crawling of the first vertebrates from

water onto land ESRF studies have helped to rewrite

key chapters of evolutionary history In the past five

years alone there have been 29 highimpact papers in

journals with an impact factor greater than 10 9 of

which have appeared in the journals Science and Nature

Moreover the first analyses are emerging from the EBS

upgrade thanks to which scientists have been able to

PALAEONTOLOGY

I S T O C K M O R I T Z W I C K L E I N

The Skye’s the limit

Under the ESRF lens, fossils from a small west Scottish island

are elevating our understanding of early mammals and reptiles.