Fish fossil sheds light on 'Euramerica' phase

Ted Daeschler of the Academy of Natural Sciences said discovering the fish fossil was "like finding a Rosetta stone."
Ted Daeschler of the Academy of Natural Sciences said discovering the fish fossil was "like finding a Rosetta stone." (MICHAEL S. WIRTZ / Staff Photographer)
Posted: September 12, 2011

It was a lumbering, wide-headed creature with tiny, close-set eyes, and it likely had to wait on a stream bottom for its prey to swim within reach. But when that happened, watch out! One powerful chomp, with fangs up to one-and-a-half inches long. . .

Rest assured that this scenario comes from the distant past - 375 million years ago, more or less - but a team of scientists from Philadelphia, Harvard, and Chicago breathed new life into it late last week.

They announced the discovery of this six-foot-long prehistoric predator found in a harsh rockscape 700 miles north of the Arctic Circle. Dubbed Laccognathus embryi, it was among various kinds of fish that had developed bony, muscular "lobed" fins - the precursors of limbs.

The team included paleontologists Jason P. Downs and Ted Daeschler from the Academy of Natural Sciences in Philadelphia, along with Harvard's Farish A. Jenkins Jr. and the University of Chicago's Neil Shubin, who have been studying these kinds of creatures for years.

Daeschler, Jenkins, and Shubin are best known for their 2006 discovery of another ancient fish, Tiktaalik roseae, which had a very unfishlike neck and limb-like fins that may have allowed it to creep onto land for brief periods.

Laccognathus, the "new" fish, is a more primitive beast, though it lived at the same time. It is a distant cousin of humans, not a direct ancestor. Yet already it is helping to provide a richer picture of a time when Europe and North America were fused together.

Previously, close cousins of this fish had been found in Latvia and Russia, so the new find provides further confirmation that there was once a "Euramerican" landmass, said Richard Cloutier, a biology professor at the University of Quebec at Rimouski.

"Ted and his team have been doing a fantastic job," said Cloutier, who was not involved with the research.

Over the course of five field trips from 2000 to 2008, the authors of the new paper, published online in   the Journal of Vertebrate Paleontology, found parts of at least 22 Laccognathus specimens.

The fossils have a burnt reddish color, not unlike the red brick of the building where they are housed, the Academy of Natural Sciences on Logan Square. The best specimen is a nearly complete skull, found in 2004, which enabled the team to see how many of their previously discovered fragments fit together.

"It's kind of like finding a Rosetta stone," Daeschler said. "That becomes the proof that all these things belong to one species."

Though Laccognathus is not an ancestor of humans, it is more closely related to us than to modern "ray-finned" fish, said Daeschler and Downs, who is also a visiting professor of biology at Swarthmore College.

During a tour of his lab, Daeschler held up various fossilized fish bones to his body, showing how shoulder, jaw, and other body parts corresponded to their human equivalents.

Yet the Laccognathus jaw has one curious feature that humans lack - small "pits" or openings that apparently allowed the creature to sense water pressure or vibration. (Laccognathus means "pitted jaw," whereas the second part of the name, embryi, comes from the surname of a Canadian geologist.)

"It's like an ear, almost," Daeschler said of the jaw openings. "The pressure goes into the tube and stimulates some nerves back in there."

Downs, who was the first author of the paper, got an early start in paleontology.

A dinosaur buff as a child, he started volunteering at the academy as a high school sophomore in 1993, when he helped answer museumgoers' questions at an exhibit about the science of Jurassic Park.

He started working behind the scenes the next summer and met Daeschler, serving as an unpaid intern.

"I've sort of been hanging around the lab in one capacity or another ever since," Downs, 33, said.

Plenty of work remains to keep him and his colleagues busy. The site that yielded Laccognathus and Tiktaalik, for example - on Ellesmere Island in Canada's Nunavut province - was home to as many as six other species that remain to be analyzed. All were apparently deposited in one spot by a flood, providing a valuable snapshot of a moment in prehistory.

"They may have just all gotten buried quickly in a load of muddy sediment," Daeschler said.

It is a bleak, unforgiving environment in which to conduct science, so remote that the only way in is by helicopter. The sun never sets, the wind is cold and biting, and the tracks of polar bears are a reminder to stay watchful.

Daeschler has yet to see a polar bear. Fish with powerful jaws, on the other hand. . .


To view a video on Ted Daeschler and the lobe-finned fish, go to www.philly.com/fishfossil


To view a video on Ted Daeschler and the lobe-finned fish, go to www.philly.com/fishfossil


Contact staff writer Tom Avril at 215-854-2430 or tavril@phillynews.com.

 

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