The world’s first worm dating back 220 million years has been unearthed in Arizona.
It’s a ‘missing link’ in evolution that sheds fresh light on the origins of amphibians.
Named Funcusvermis gilmorei, it lived at the beginning of the age of the dinosaurs.
The primitive creepy-crawly was identified from its tiny jaws and teeth – which remarkably survived fossilisation.
It belongs to a group called caecilians, which also include frogs and salamanders.
Ben Kligman, a doctoral student at Virginia Tech who led the dig at Petrified Forest National Park, said: “The discovery of the oldest caecilian fossils highlights the crucial nature of new fossil evidence.
“Many of the biggest outstanding questions in palaeontology and evolution cannot be resolved without fossils like this.”
Mr Kligman, who previously discovered a 220-million-year-old species of cynodont or stem-mammal, a precursor of modern-day mammals added: “Fossil caecilians are extraordinarily rare and they are found accidentally when palaeontologists are searching for the fossils of other more common animals.
“Our discovery of one was totally unexpected and it transformed the trajectory of my scientific interests.”
He previously discovered a species of cynodont or stem-mammal – a precursor of modern-day mammals – from the same period.
Funcusvermis was found in a layer known as the Chinle Formation. The rocks were positioned near the equator at the time – in the centre of the supercontinent Pangaea.
The region was just as hot as today – but much more humid.
Mr Kligman said: “Seeing the first jaw under the microscope – with its distinctive double row of teeth – sent chills down my back.
“We immediately knew it was a caecilian – the oldest caecilian fossil ever found – and a once-in-a-lifetime discovery.”
It fills an 87 million-year gap in the fossil record – which hid the early evolutionary history of caecilians.
Many of the biggest outstanding questions in palaeontology and evolution cannot be resolved without fossils like this
Scientists have debated over the relationships of caecilians to their amphibian relatives for decades.
Mr Kligman said: “Funcusvermis extends the humid equatorial pattern of occurrence seen in all known fossil and living caecilians.
“It suggests the biogeographic history of caecilians has been guided by restriction to these ecological settings.
“It was likely due to physiological constraints linked to humidity and constrained by the drift of continental plates into and out of the humid-equatorial zone after the fragmentation of Pangaea.”
