Ancient 'coal dragon' is now the oldest parareptile ever found

A unique fossil that is "literally a black piece of coal" found in the dump of a 19th-century coal mine is revealing new insights about life before the rise of dinosaurs. It has also unseated a fossil found by a P.E.I. boy as the oldest known species of an ancient group called the "parareptiles."

The new species, Carbonodraco lundi, was a small, lizard-like predator that scampered about in ancient swamps, snatching and stabbing insects and other prey with a sharp pair of fangs.

The animal, which was about 25 centimetres long from nose to tail, lived more than 306 million years ago during the Carboniferous Period in what is now Linton, Ohio, according to a new study by researchers at Carleton University in Ottawa published recently in the journal Royal Society Open Science.

The first part of its name, given by Emily McDaniel, an undergraduate student and co-author of the paper, means "coal dragon," because of the fossil's unique form and its prominent fangs.

Unlike most fossils, which are typically embedded in rocks like shale, limestone or sandstone, this one was "literally a black piece of coal," said Arjan Mann, a PhD candidate at Carleton University and lead author of the report. He said that type of fossil is "very unique."

It was found in the dump of a coal mine operated by the Ohio Diamond Coal Mine Co. by paleontologist Richard Lund of the Carnegie Museum, for whom the species is also named.

What Carbonodraco's world was like

The coal deposits at the mine, which opened in the 1800s, are the remains of a steamy, mangrove-like swamp that covered the region around 310 million to 306 million years ago, Mann said.

The swamp was fed by a river running through a forest of giant club mosses, and it was home to giant insects, crabs and shrimp, fish, salamander-like amphibians, mammal-like reptiles called synapsids, and many creatures that would have resembled blends of fish and amphibians or amphibians and reptiles.

Many of them were fossilized into an impure coal called cannel coal, which miners had to dig through and discard in order to reach the commercially valuable coal underneath.

Lund did regular collecting in the dump, picking up blocks of coal and splitting them open to look for fossils in the 1970s. Most of the time they were empty, Mann said.

But one of the first blocks Lund split open in 1972 contained a skull and the front part of an animal's body.

"It's a pretty rare find," Mann said.

Mann came upon the museum specimen while cataloguing reptiles found at a coal mine at Mazon Creek, Ill., which formed from the delta at the mouth of the river that flowed through Linton, Ohio, during the Carboniferous. One of them was identified as Cephalerpeton ventriarmatum — the same identification originally given to the fossil from Linton — so he decided to compare them. 

His comparison found that they weren't related at all. 

Cephalerpeton is a eureptile — related to all lizards, snakes and crocodile relatives alive today.

Now the oldest parareptile — but what were they?

The Linton fossil, now identified as Carbonodraco, was a parareptile — a diverse group that thrived during the Permian Period, after the Carboniferous but before the Age of Dinosaurs. 

There is some debate about whether modern turtles are parareptiles, but the group may also be completely extinct, Mann said.

Hillary Maddin, Mann's supervisor and a Carleton University paleontology professor, said the discovery adds to evidence that the creatures that lived during the Carboniferous were much more diverse and specialized than previously thought.

"I think you've got a pretty new, exciting picture of what was happening over 300 million years ago," said Maddin, a co-author of the study.

The new identification makes Carbonodraco the oldest known parareptile, unseating the previous record holder, Erpetonyx arsenaultorum. That species was found by a nine-year-old boy in P.E.I. in 1995 and named after him in 2015. It lived about 300 million years ago, making Carbonodraco at least six million years older. 

The first known reptile, which was also the first vertebrate fully adapted to land, lived about 315 million years ago, only five million to nine million years before Carbonodraco.

Over the course of this study, Mann actually worked with some of the researchers at the Royal Ontario Museum who described Erpetonyx and joked about it. "It's like, 'We got the older, older one,'" Mann said with a laugh.

He acknowledged that paleontologists are often competing for the oldest new discovery.

"They never last, I think. There's always going to be something older."