Scientista say prehistoric creature named after Kermit the Frog offers clues on amphibian evolution
There were definitely no muppets 270 million years ago, but there was a Kermit — or at least an ancestor of modern amphibians, according to scientists who uncovered its fossilised skull.
In a zoological paper published on Thursday, the team of researchers described the fossil as "a new species of proto-amphibian", which they named Kermitops gratus because it bears a likeness to the iconic puppet, Kermit the Frog.
"We thought that the eyelid bones gave the fossil a bug-eyed look," said Calvin So, a George Washington University palaeontology doctoral student and the lead author of the study.
"Combined with a lopsided smile produced by slight crushing during the preservation of the fossil, we really thought it looked like Kermit the Frog."
The researchers said Kermitops lived during the prehistoric Permian Period in what is now Texas and belongs to a lineage that is believed to have given rise to frogs, salamanders and their other kin.
Analysis of the 3-centimetre skull revealed a "mishmash of traits", which are different from features seen in the skulls of older tetrapods, the four-legged ancestors of modern amphibians.
Kermitops had a rounded snout similar to frogs. Preserved in its large eye sockets were palpebral bones — or eyelid bones — a feature absent in today's amphibians.
While only the skull was discovered, researchers think Kermitops had a stoutly built salamander-like body roughly 15 to 18cm-long, though salamanders would not evolve for another 100 million years.
"The length of the skull in front of the eyes is longer than the length of the skull behind the eyes, which differs from the other fossil amphibians living at the same time," So said.
"We think this might have allowed Kermitops to snap its jaws closed faster, enabling capture of fast insect prey."
An evolutionary puzzle
The researchers said the early fossil record of amphibians and their ancestors is spotty, making it difficult to understand how they originated.
"Adding relatives like Kermitops into the fold is essential for fleshing out the early branches of the amphibian family tree," they said.
So said, in particular, "Kermitops helps us understand ... there isn't a clear trend of step-by-step becoming more like the modern amphibian".
The fossil they identified was actually collected four decades ago in 1984 near Lake Kemp in Texas.
It was kept in the expansive collection of the Smithsonian National Museum of Natural History in Washington, but it was not thoroughly studied until recently.
"Kermitops, with its unique anatomy, really exemplifies the importance of continuing to add new fossil data to understanding this evolutionary problem," said the study's co-author Arjan Mann.
He said Kermitops belonged to a group called temnospondyls that arose a few tens of millions of years after the first land vertebrates evolved from fish ancestors.
The biggest temnospondyls superficially resembled crocodiles, including two that were each around 6 meters in length, Prionosuchus and Mastodonsaurus.
In the grand scheme of the Earth's history, Kermitops existed about 40 million years before the first dinosaurs.
Meanwhile, Kermitops' namesake was created by the late American puppeteer Jim Henson in 1955.
Kermit the Frog was the host of The Muppet Show and has appeared in various sketches on Sesame Street.
