Mall-sprawl site yields a treasure from eons past

Tufts geology senior Richard J. Knecht with his North Attleborough fossil discoveries, including the 310 million-year-old footprints of what is believed to be a primitive flying insect. (JODI HILTON FOR TUFTS UNIVERSITY)

When it comes to jaw-dropping fossil discoveries, distant places where T. Rex and other prehistoric beasts once roamed come more quickly to mind than southeastern Massachusetts. But yesterday, Tufts University announced the discovery of what may well be the world's oldest fossil imprint of a whole flying insect - found by researchers behind a strip mall in North Attleborough.

Tufts geology senior Richard J. Knecht, working with paleontologist Jacob Benner, uncovered an exquisitely etched impression made some 310 million years earlier by a primitive insect - probably an early form of the common mayfly. The insect lighted on a damp outcropping in what was then a steamy Carboniferous Period flood plain - and in that fleeting moment left a 3-inch-long outline that was captured for eternity in mud that hardened into rock. That was the same rock discovered by the Tufts team.

Discovery of the fossils, dated by comparing the sandstone strata that contained them to rock layers above and below, could lead scientists to greater understanding of how primitive insects functioned and evolved.

Almost everything about the find is offbeat, from the path that led to the prosaic site to the fact that Knecht, a 30-year-old native of Chatham, is a student in the university's adult education program, not a seasoned field paleontologist.

Although the discovery was just announced, it's been generating a quiet buzz in paleontological circles since the researchers presented their "trace fossil" at a scientific conference in Poland last month. The find is called a trace fossil because it represents the behavior of the animal, not an actual body or bone.

"This is a record of body movement, of action, a snapshot of this insect going about its life," Knecht said. "The detail is fantastic. You can see where it wiggled its legs, you can tell exactly how it positioned its body."

Said Michael S. Engel, a prominent paleoentomologist at the University of Kansas: "This is like a short home movie of an insect's ordinary flutter - only this moment happened more than 300 million years ago. It's exciting, it's valuable, and it's really very beautiful."

The genesis of the discovery is as improbable as the actual find.

While poring over dusty papers as part of his studies into sedimentary rocks, Knecht chanced upon a 1929 master's thesis (written by a Brown University student) that mentioned tiny footprints - believed amphibious - of some sort observed in a rock outcropping near the Rhode Island border.

The researchers set out to find the spot. The 1929 paper described where the fossil-rich outcroppings could be found, but some of the formations had vanished under earth-moving equipment and housing tracts. It also gave as reference points old restaurants and saloons, which were long gone. The researchers then used geological maps, old and new, to find any rock formation similar to the ones noted in the thesis. That led them to a spot on private land near a North Attleborough shopping strip. There, they picked through the shale and sandstone with chisels and hammers.

Their efforts yielded a bonanza of fossilized tracks left by amphibians and precursor reptile species, as well as insects, that inhabited the region tens of millions of years before the emergence of dinosaurs.

Roughly 1,000 specimens were found at the site; the exact location is being kept secret for fear of fossil thieves.

Although the fossilized imprint is believed to be the oldest winged insect trace fossil ever identified, there is, ironically, no clear imprint of wings. Yet all of the evidence suggests that it landed at the site and then left by air.

"There are no walking prints leading to the body impression," Knecht said. "This creature came from above."

"What's been captured is a moment in time, an instant when a flying insect landed with just the perfect amount of pressure, in mud possessing just the perfect amount of moisture, to capture the imprint - and leave this story behind," Benner said.

Engel believes the insect that left its ancient mark in North Attleborough was probably an early ancestor of today's mayfly. "It landed in a very squat position, legs sprawled and belly pressed down," Engel said. "The imprint strongly suggests mayfly."

Engel hypothesized the insect might have landed for a sip of water or to lap up nutrients. "It seems to have landed of its own accord. This doesn't look like the crash landing of a stricken animal," he said.

Asked about the incongruity of a significant paleontological find being made in the well-explored semi-urban sprawl of southeastern Massachusetts, Engel said: "This just goes to show that great science can happen anywhere."

Colin Nickerson can be reached at nickerson.colin@gmail.com