Prehistory to Be Squeezed From Suspected Sponge Fossil

From a pile of dirt excavated near his family’s gas station, Mike Potts lifted out a basketball-sized boulder, heaved it unsteadily over his head and smashed it against another rock.

There was no crystal inside, as he’d hoped. But embedded in one large limestone chunk was a glassy object, shaped a bit like a hand. Was it an ancient tree root? A bone from an animal that long ago roamed this land now gouged by the Finger Lakes? Or just an odd-shaped rock?

“I thought it might be a couple million years old,” said Potts, 34, a mechanic who scours nature as much for physical exercise as for any sense of intrigue. “To find out it’s 375 million years old is kind of a shock.”

Not only that: It is almost certainly a fossil, and no ordinary one. John Chiment, a paleontologist at Cornell University, suspects the black, grainy-textured stone was once the root of a branching glass sponge.

Such sponges, which are among the simplest forms of animal life, are found today miles down in the ocean, in very cold, dark waters. At that intense depth, the ocean floor is gelatin-like, and clams, shrimp and myriad microscopic creatures have few anchors other than sponges to hold onto.

The 5-inch-long find, with its unusual appendages and tiny fossils of ancient organisms attached, emerged in November from a cavity being dug for a 15-foot-deep gas tank. Potts was persuaded to pass it along to Cornell through a neighbor who works at the Ivy League school in nearby Ithaca.

It was no less an enigma in Chiment’s hands, but intriguing enough to unleash the kind of exhaustive detective hunt with unforeseen twists that is commonplace in the jigsaw-puzzle world of paleontology.

Chiment and graduate student Sande Burr finally found a promising match in Volume 21 of a 40-volume chronicle of the world’s first around-the-world oceanographic survey.

In the 1870s, while dredging the miles-deep waters off the Philippines, the crew of the British vessel HMS Challenger recovered the only known living specimen of a branching glass sponge. Chiment is hoping he’ll soon get to inspect it.

Distinct from squishy protein bath sponges or hard sponges made of calcium carbonate, glass sponges make their skeletons out of silica. Those equipped with branches the width of a finger appear to be extremely rare.

Some have been spotted lately using robotic submersibles. There may be plenty more in the murky depths. But there’s been no sight of them thus far in the fossil record of New York, one of the world’s best-explored strata.

Heralding Potts’ discovery via the Internet then produced a surprise: Folks around central New York sent in similar specimens they’d picked up over the years. Chiment now has amassed eight possible branching glass sponge fossils or “perhaps an unknown group of glass sponges.”

“I think what we’re onto is a locality that is preserving a different group of animals than most of the previously very well-known Devonian fossil localities around here,” he said.

During the Devonian Period some 410 million to 360 million years ago, eons before the advent of birds, dinosaurs and humans, an inland sea covered much of eastern North America.

Judging from the profusion of fossils gathered in New York since the 1810s, notably Devonian corals and non-branching glass sponges, the standard theory is that this sea was probably never more than 300 feet deep.

The existence of branching glass sponges would revive an old debate about whether the sea was much deeper in spots. However, paleontologists believe it’s more likely those sponges once flourished in sunlight-penetrating waters and then, for whatever reasons, retreated to the oceans.

“Maybe they were pushed out of their preferred habitat by something else, say, the corals,” Chiment mused. Or now that oceanographers are finding that the ocean abyss seems as rich in species as rain forests or coral reefs, “it may be the opposite. All of these questions are still open.”

Because minute marine fauna such as trilobites and brachiopods tended to accumulate on them, ancient sponges could turn out to be peerless storytellers of ocean evolution, Chiment said.

And since sponges seem to form part of the mysterious missing link between single-celled bacteria and multicelled animals, knowing them better might lend more immediate value--such as new disease-fighting drugs or clues to why some coral reefs are dying.

While paleontology continually raises tantalizing questions, many fossils end up in “problematica drawers--all those things we don’t understand yet because there’s little or nothing to compare them to,” Chiment said.

For now, Chiment and Burr are busy consulting glass sponge specialists, subjecting their specimens to an array of imaging tests and deciding whether to publish their findings. They’re also appealing to colleagues everywhere to dig through their problematica.

“More and better material could show up, and that would be very helpful,” said Warren Allmon, director of Ithaca’s Paleontological Research Institution, which boasts the world’s largest collection of Devonian glass sponges. “This is one of the best-explored places on Earth, and new things still keep coming up. Amateurs are out there collecting every weekend.”

Potts is a convert. He now spends a few hours a week “standing around like a chicken pecking at rocks” in the woods and fields near this village a few miles from Cayuga Lake. “It’s become a neat hobby,” he said.