Researchers trying to piece together a 65 million-year-old turtle

Twenty-five-year-old Paul Ullmann pieces together65-million-year-old "Taphrosphys sulcatus" at Drexel University.
Twenty-five-year-old Paul Ullmann pieces together65-million-year-old "Taphrosphys sulcatus" at Drexel University. (AKIRA SUWA / Staff Photographer)
Posted: September 21, 2011

 Step one was to heave the 65 million-year-old fossil out of the ground - a job that taxed the muscles of seven sweaty men. Step two: Clear away several hundred pounds of surrounding plaster and wet, sandy muck.

Step three, currently under way in a Drexel University laboratory, is a task for finer motor skills: a prehistoric jigsaw puzzle.

The fossil is the shell of a big sea turtle called Taphrosphys sulcatus, which broke into hundreds of pieces during the eons that it lay buried in what is now near Sewell, Gloucester County.

Many of the fragments are smaller than a fingernail. There is no cardboard box with a helpful photo to show what the completed "puzzle" should look like.

And yet, little by little, the graceful curvature of an ancient reptile is emerging, as doctoral students Elena Schroeter, 27, and Paul Ullmann, 25, match up jagged edges and glue them together.

"It's a job for young eyes," said their supervisor, Kenneth Lacovara, an associate professor of biology at Drexel.

The finished product will be a nice display piece, perhaps at Drexel or its new affiliate, the Academy of Natural Sciences. It also may provide insight into various scientific questions, such as how turtles evolved and how they are related to other creatures.

The biggest question may be just what killed this animal and dozens of others whose fossils were buried nearby, in an age when much of New Jersey was underwater. The site, an old mine pit in the Sewell area, has yielded the remains of crocodiles, sharks, fish, clams, and snails over the years.

Hint: Like the turtle, all were found in a layer of sediment that dates to about 65 million years ago. Sound familiar? That's also when most dinosaurs met their demise.

Previously, some scientists have argued that the Gloucester County fossils were not the result of any one event but died in various places and happened to drift to the same resting spot.

But William B. Gallagher, an assistant professor of paleontology at Rider University who has been going to the site for decades, said that seemed unlikely. Like the turtle shell, many of the fossils are largely complete.

"This thing keeps producing these entire specimens, or near-entire specimens," Gallagher said of the site, where the Inversand Co. mines a mineral called glauconite. "This seems unlikely if you're talking about a random-chance process."

And the layer in which the fossils were found contains an elevated level of the element iridium, a sign of the meteor impact that is thought to have killed the dinosaurs. This year, Rutgers University scientists reported that the ratio of platinum to iridium in that sediment layer was an even stronger indication of ejecta - deposits - from a vaporized meteor.

Gallagher said the turtle and its compatriots were not wiped out in the initial blast, as they were somewhat protected underwater. But in the months and years after the meteor strike, there were radical changes in the ocean - starting with airborne debris that blocked the sun, killing plankton and causing a ripple effect up through the food chain.

"This is about as good as it gets," Gallagher said. "A mass murder with evidence of asteroid ejecta present."

All these eons after its death, the turtle is now the beneficiary of gentle handling.

Schroeter and Ullmann sift through the pieces, laying them out on a table and finally joining them with a specialized glue called Paleo Bond. If they make a mistake, they dab on some acetone to dissolve the glue, and they try again.

They consult each other on tricky pieces.

"This would go behind," Schroeter mused as the two put their heads together over one fragment.

"Something's crooked," Ullmann muttered.

Besides Paleo Bond, the tools of the fossil-assembly trade include an assortment of dental picks and an old Crest toothbrush.

The graduate students cannot say how many hours they have spent on the shell assembly. They tuck in an hour here and there to take a break from writing grants and papers.

"It's a repetitive, detail-oriented task you can lose yourself in," Schroeter said.

While many of the shell fragments are smaller than a dime, eventually the scientists intend to look for something even smaller - molecules of collagen and other prehistoric proteins that may be preserved inside the turtle bone.

A section of leg bone was handled with extra care when the fossil was excavated in June, picked up with gloved hands, and immediately wrapped up to avoid contamination from modern organisms.

Drexel's Lacovara hopes that an analysis of any proteins could help determine where turtles fit on the tree of life - a question that remains a matter of debate. Are they more closely related to dinosaurs or to other reptiles?

Sixty-five million years after it died, the turtle is ready to help piece together some puzzles.


Watch Drexel biologists assemble a 65-million-year-

old turtle shell at www.philly.com/ turtleshell


Contact staff writer Tom Avril

at 215-854-2430 or tavril@phillynews.com.

 

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