by The world’s first worm dating back 220 million years has been unearthed in Arizona.
It is a “missing link” in evolution that sheds new light on the origins of amphibians.
Called Funcusvermis gilmorei, it lived at the beginning of the dinosaur era.
The primitive creeper was identified by its tiny jaws and teeth, which remarkably survived fossilization.
It belongs to a group called caecilians, which also includes frogs and salamanders.
Ben Kligman, a doctoral student at Virginia Tech who led the excavations at Petrified Forest National Park, said: “The discovery of the oldest Caecilian fossils highlights the crucial nature of the new fossil evidence.
“Many of the biggest loose ends in paleontology and evolution cannot be resolved without fossils like this one.”
Mr Kligman, who had previously discovered a 220-million-year-old species of cynodont or stem mammal that was the precursor to modern mammals, added: ‘Fossil caecilians are extraordinarily rare and are found accidentally when paleontologists look for fossils for other animals. Most common.
“Our discovery of one was totally unexpected and transformed the trajectory of my scientific interests.”
He had previously discovered a species of cynodont or mammalian stem – a precursor to modern mammals – from the same period.
Funcusvermis has been found in a layer known as the Chinle Formation. The rocks at the time were positioned near the equator, in the center of the supercontinent Pangea.
The region was as warm as today, but much wetter.
Mr Kligman said: ‘Seeing the first jaw under a microscope, with its distinctive double row of teeth, sent shivers down my spine.
“We immediately knew it was a caecilian – the oldest caecilian fossil ever found – and a once-in-a-lifetime find.”
It fills an 87-million-year gap in the fossil record that hid the early evolutionary history of caecilians.
Scientists have debated caecilian relationships with their amphibian relatives for decades.
Mr Kligman said: ‘Funcusvermis extends the moist equatorial pattern of occurrence seen in all known living and fossil caecilians.
“It suggests that the biogeographic history of caecilians has been driven by restriction to these ecological environments.
“It was probably due to physiological constraints related to moisture and constrained by the drift of continental plates in and out of the wetland-equatorial after the fragmentation of Pangea.”
Modern caecilians are limbless amphibians with cylindrical bodies.
A compact bullet-shaped skull helps them dig through leaf litter or soil for prey items such as worms and insects.
Now they are found only in South and Central America, Africa and South Asia.
An underground existence has made it difficult for scientists to study them.
Mr. Kligman joked: “I’m like a puppet with no eyes, with the body of a worm.”
Funcusvermis also shares skeletal features with early frogs and salamanders.
It adds to evidence of a common ancestor. Funcusvermis also resembles dysorophoid temnospondyls, an ancient group of amphibians.
Kligman said, “Unlike living caecilians, Funcusvermis lacks many adaptations associated with burrowing underground, indicating a slower acquisition of characteristics associated with a subterranean lifestyle in the early stages of caecilian evolution.”
Many of the biggest loose ends in paleontology and evolution cannot be resolved without fossils like this one
Funcusvermis takes its name from “Funky Worm” from the album Pleasure by the 1970s American band Ohio Players.
The song was often played during fossil excavations at Thunderstorm Ridge.
“Funcus” comes from the English word Funky for the upbeat, rhythmic form of dance music, while “vermis” is Latin for worm.
Chief paleontologist Adam Marsh said, “Like the song of the same name goes, it’s the funniest worm alive.”
The lower jaws of at least 70 Funcusvermis individuals have since been recovered since last summer, making the area the most abundant bone bed of fossil caecilian production ever discovered.
Only a handful of disarticulated bones were found including upper and lower jaws, one vertebra and part of a hind limb.
Without full skeletons, the body length of Funcusvermis cannot be accurately determined.
But inferences from isolated evidence such as the lower jaw less than a quarter of an inch long indicate that Funcusvermis was a very small animal.
Kligman said, “Since its discovery in 2017, the Thunderstorm Ridge site has yielded a diverse assemblage of more than 60 animals ranging from freshwater sharks to dinosaurs.
“Many other new species discovered at this site have recently been described.”
Many more new species from this site are currently under study and will be published in the coming years.”
Funcusvermis is featured in the journal Nature.
