December 2025 ESRFnews
15
PALAEONTOLOGY
the split between lizards and snakes. Together with
Breugnathair, the researchers propose that they now
form a newly defined family, Parviraptoridae (Nature
doi: 10.1038/s41586-025-09566-y). “Breugnathair
elgolensis is a remarkable addition to the fossil record,
helping to rewrite our understanding of the evolution
of snakes and lizards,” says co-author and curator Stig
Walsh at National Museums Scotland.
Although the phase-contrast X-ray tomography
available at the ESRF was already far better than
anything possible in the lab before the upgrade, the
brilliance and coherence of the new source has made it
even better Parallel improvements in computing and
optics have also enabled the routine use of hierarchical
imaging meaning that users can first perform a global
scan at voxel sizes of 25 m then zoom in to a particular
region of interest at voxel sizes of 08 μm The potential
size of specimens has gone up too with a new stage at
the EBS flagship BM18 beamline able to precisely rotate
and position samples up to 300 kg in mass The first
palaeontological studies based on BM18 imagery are just
emerging although not yet for Skye fossils see Ruffling
the feathers of reptile evolution above
As BM18 scientist Vincent Fernandez points out
however, Skye fossils are well-suited to the beamline
because their surrounding geology has often left them
dislocated and spread out throughout their host rock.
“You end up with large slabs with tiny specimens. You
need a lot of signal to get good data out of that.” He notes
that there are more and more palaeontologists interested
in using BM18 – partly because of the instrumentation
itself, and partly because of the 5–10 talks he and his
beamline colleague Kathleen Dollman do every year
to promote it. “We’ve made a strong user base even
stronger,” he says. “We get a lot of people contacting us,
saying theyve seen what other palaeontologists have
done at the ESRF saying they want to do it too
It is hard to say what is in store for ESRF palaeontology
though The chance nature of fossilhunting means that
researchers are never sure what questions will come up
never mind what the answers will be We have a wish
list of what we want to find but in the end its specimen
led enquiry says Panciroli Its a numbers game the
more we find the more likely well find the rare things
we suspect should be there like the juvenile and adult
Krusatodon We just have to keep looking
Jon Cartwright
RUFFLING THE FEATHERS OF REPTILE EVOLUTION
N A T U R E 6 4 3 1 2 9 7
Paleontological analyses take many years, but the f irst
results from BM18 – which opened to users three years
ago – are already being published. Stephan Spiekman
of the State Museum of Natural History in Stuttgart,
Germany, and colleagues recently used it to investigate
a tiny Middle Triassic fossil found in the 1930s in Alsace,
France. About the size of a book of matches, yet buried in
a large rock, the specimen had a long, mostly toothless
skull and a feathery dorsal appendage – looking rather
like an ancestor of modern birds. But the internal BM18
images were to show otherwise. “Without the ESRF we
could not have been able to do the reconstruction of the
skull,” says Spiekman. “The fossil is so small that it had
been incredibly dif f icult to scan.”
The synchrotron images showed that the creature
lacked key features of birds and their relatives, such as
openings in front of the eyes and in the jaw, and bony bars
behind the eyes. Meanwhile, a host of other techniques,
including electron and ultraviolet microscopy, showed
that the back appendage was not really feathers at all
but, something colourful, entirely solid and barbless.
This meant that specimen cannot have been a bird, but
a reptile – albeit one with a type of dorsal crest never
seen before. The researchers have named it Mirasaura
grauvogeli (Nature 643 1297).
Previously, fossil evidence for any feather-like
appendages had come mostly from the Jurassic at the
earliest, and only from bird relatives. “Mirasaura provides
the f irst direct evidence that such structures actually did
form early on in reptile evolution, in groups not closely
related to birds and extinct dinosaurs,” says Spiekman.
Clockwise from top left: The original fossil of Mirasaura, discovered in the
1930s in Alsace, France; Artist’s impression of the creature, displaying its
distinct solid dorsal crest; BM18 images of the skull, revealing features unlike
those of birds and their relatives.
N A T U R E 6 4 3 1 2 9 7 G A B R I E L U G U E T O