Student scientists name 309-million-year-old amphibian after moms

By Stephen Beech

A newly identified frog-like creature that lived before the dinosaurs has been named by the student scientists that discovered it — after their moms.

Allison Sefcovic and Payton Kohlberg described the early amphibian that lived in what is now the United States over 300 million years ago, and then named it in honor of their mothers — who both happen to be called Jean.

Jeanerpeton mazonensis — meaning "Jean's crawler from Mazon Creek" — is an early ancestor of today's amphibians.

It looked a salamander — but was squat and chubby like a frog, according to the study published in the Journal of Vertebrate Paleontology.

J. mazonensis lived 309 million years ago, long before the dinosaurs, in the area around present-day Chicago in the United States that was a swampy river delta swarmed with early land-dwellers, giant insects and strange swimming animals.

What was once a hotbed for new forms of life to flourish and evolve, became one of today's richest Carboniferous period fossil deposits

Because the Mazon Creek area was a river delta during the Carboniferous period, the researchers explained that sediment was quickly deposited on dead animals and plants — a "perfect recipe" for fossilization.

Today, Mazon Creek is home to one of the world's best fossil sites, with fossils that preserve records of soft tissues and fine details that are normally lost.

Study co-lead author Sefcovic, an intern at the Field Museum in Chicago, said: "What's really cool about Mazon Creek is that it preserves all of these unusual details — things like toe pads and body outlines.

"In the fossil of Jeanerpeton, we can see some of the scales on its back and tiny 'belly ribs' called gastralia.

"You can even see the eye impressions. It's so cool to see."

She says the findings point to a 309-million-year-old origin of classic traits we see in today's frogs and salamanders.

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The fossil specimen was found several years ago by an amateur collector and donated to the Field Museum.

At a glance, the fossil was classified as another species with a well-established presence in the region, Amphibamus grandiceps.

Sometimes, poorly understood specimens are lumped together into what scientists call a "waste bin taxon" — which serves as a metaphorical dumping ground for specimens that seem related but haven't been well studied yet.

Study co-author Cam So, a postdoctoral researcher at the Field Museum, said: "What we're finding from the Field Museum's collection are a bunch of things that historically were grouped together into this waste bin taxon known as Amphibamus grandiceps.

"Jeanerpeton is one of those species.

"And now, we've found enough evidence to support it being an anatomically distinct animal.

"With this publication, we officially pull Jeanerpeton out of this waste bin taxon."

Payton and Allison were part of last year's group of Women in Science Interns at the Field Museum.

They, along with So, are all part of the lab group of Arjan Mann, the Field's assistant curator of fossil fishes and early tetrapods.

Kohlberg said: "Before working in the Mann Lab, I didn't know much about paleontology.

"My experience at the Field and in the Women in Science program has made me more confident in my abilities to try something new.."

She added: "It is scary to take on a project when you feel like you don't know as much as you should.

"But I learned with my practical experience that it is possible to overcome that fear with hard work."

So says the description of J. mazonensis opens a door for researchers as they continue to chronicle the biodiversity that lived in Mazon Creek millions of years ago.