New 270-million-year-old amphibian species could help explain evolution of frogs

Scientists have discovered a new ancient amphibian species that could bridge the gap in understanding how modern-day frogs and salamanders developed.

The fossilized skull of the 270-million-year-old amphibian ancestor was first unearthed in 1984 in a rock formation in Texas. However, it spent decades sitting in a collection at the Smithsonian Institution's National Museum of Natural History waiting to be studied.

In 2021, a group at the Smithsonian finally began examining the fossil to determine what prehistoric creature the fossil belonged to. The findings were published Thursday in the Zoological Journal of the Linnean Society.

Paleontologists have playfully named the new species Kermitops gratus in honor of the Kermit the Frog, created by Jim Henson.

Calvin So, a doctoral student at the George Washington University and the paper's lead author, said naming the creature after the beloved character is also an opportunity to get the public excited about the discovery.

"Using the name Kermit has significant implications for how we can bridge the science that is done by paleontologists in museums to the general public," he said in a release. "Because this animal is a distant relative of today's amphibians, and Kermit is a modern-day amphibian icon, it was the perfect name for it."

Researchers said they discovered the fossil was a type of temnospondyl, a primitive amphibian that lived more than 200 million years ago mainly during the the Carboniferous, Permian and Triassic periods.

The one-inch-long fossil has many unique characteristics that scientists realized made it different from previously discovered species. It has large, oval-shaped eye sockets and a skull with a short region behind the eyes but an elongated, curbed snout.

This head shape suggests the animal ate grubs -- which are the larval form of certain beetle species -- and other small insects, similar to frogs and salamanders.

There are some differences between Kermitops and present-day amphibians. The team discovered the skull has palpebral bones, or eyelid bones. Meanwhile, amphibians have moveable eyelids and have a third eyelid called a nictitating membrane that provides lubrication and protection.

Additionally, researchers found evidence of teeth, though not in the same place as modern-day frogs, most of which have small teeth on the upper jaws and roof of their mouths.

The Smithsonian team said that the history of amphibians and their ancestors documented through fossils is "fragmentary" due to their small and delicate bones, which has made it a challenge to study the evolution to their modern-day counterparts. The discovery of Kermitops, however, could help answer some questions about the evolutionary path.

"Kermitops offers us clues to bridge this huge fossil gap and start to see how frogs and salamanders developed these really specialized traits," So said.