X-rays reveal 'oldest reptile' fossil was actually an older lineage with gills

A study published September 30 in Nature found that the 345-million-year-old Westlothiana lizziae fossil from Scotland was not an early reptile but a stem tetrapod. Synchrotron X-ray micro-tomography revealed a primitive skull, internal gills and a fish-like mouth with thousands of tiny teeth.

• Fossil discovered in 1984 and named the earliest known reptile in 1990
• Scans showed internal gills and a primitive skull ruling out reptile ancestry
• Animal reclassified as a stem tetrapod, branching off before amphibians and reptiles split
• Five toes and claw-like tips evolved in more aquatic members of that older lineage