A famous specimen, a new identity
For almost 30 years, a small fossil found in Scotland has been described as one of the earliest known reptiles. A study published on 30 September in the journal Nature says that label was wrong.
The specimen, nicknamed Lizzie, is about 345 million years old. Researchers at the American Museum of Natural History, the University of Oxford and the European Synchrotron Radiation Facility in Grenoble rebuilt its insides in three dimensions using synchrotron X-ray computed micro-tomography, a method that maps structures still buried in rock.
Gills, and thousands of teeth
The scans found internal gills and a fish-like mouth lined with thousands of tiny teeth. Those features place the animal in a much older lineage, a derived stem tetrapod, rather than among the first amniotes, the group that today includes reptiles, birds and mammals.
That matters because the fossil had been used as evidence for when vertebrates completed the move onto land. If the animal lived in water, or moved between water and land, that timeline has to be read differently.
Why the scans matter
The fossil is small and embedded in hard rock, so earlier work relied on what could be seen at the surface. X-ray imaging let the team see bones, jaw structures and gill arches that had been invisible.
The paper, led by Ben Igielman, includes co-authors from Cambridge, the Natural History Museum in London and the University Museum of Zoology Cambridge. Its title describes the animal as a derived stem tetrapod whose anatomy reveals how terrestrial body plans evolved.
The result is a reminder that well-known fossils can carry outdated labels for decades. As scanning tools improve, other museum specimens once treated as settled evidence may need a second look.
How the imaging works
The synchrotron method rotates a sample through a bright X-ray beam and builds a digital model slice by slice, so the original fossil is never cut or damaged. It has become a standard tool for palaeontologists working on specimens locked inside hard stone.