While tending to their garden this fall, homeowners in upstate New York spotted what appeared to be two giant teeth protruding from the soil, partially concealed by plant fronds. A bit more digging revealed two more massive chompers just below the earth's surface, convincing the couple they'd chanced upon something significant. So, they called in the experts.

In October, a team from New York State Museum and SUNY Orange came to excavate the site and confirmed the pair's hunch. There, in their backyard about 70 miles northwest of New York City, the homeowners had uncovered a full mastodon jaw, remarkably well preserved. The researchers also found a toe bone and rib fragments belonging to the prehistoric animal, an extinct relative of modern elephants that predates another of its cousins, the wooly mammoth.

That a mastodon jaw popped up at a residence near the hamlet of Scotchtown doesn't surprise Ross MacPhee, senior curator in residence of mammalogy and vertebrate zoology at the American Museum of Natural History in New York. More than 150 mastodon fossils have been found across New York State, about a third in Orange County, Scotchtown's home, though it's been 11 years since the last complete jaw surfaced.

"This is not an insignificant find, despite the fact that it is one of many," MacPhee, who was not part of the team that found the jaw, said in an interview. Every specimen of a long vanished species, he said, helps fill in the picture of its history and habitat. "It's all fossil by fossil and site by site," he said. "This is a very aggregational kind of discipline."

American mastodon (Mammut americanum) fossils have been found throughout North and Central America, revealing that the massive creatures stood nearly 10 feet tall at their highest point with tusks that curved upward. Their teeth have high, pointed crowns that functioned well for chewing on leaves and twigs.

What most excites MacPhee about finds like the latest in New York is their potential to shed light on the mysterious disappearance of mammoths, mastodons, giant beavers and dozens of other species in a "geological blink" around 11,000 to 12,000 years ago.

"It's a weird thing to think that they all died out at once," the paleontologist said. "They just all disappeared." Theories explaining the mass extinction range from climate change and overhunting by humans to inbreeding, infectious diseases and cosmic events. "Something very complicated ecologically was going on and we really have tried to come to grips with this for well over a century," MacPhee said.

The scientists studying the Scotchtown mastodon say the remains belonged to an adult animal. They plan to conduct further analyses using methods like carbon dating to determine how old the mastodon was when it died and determine more about its diet and habitat.

"While the jaw is the star of the show, the additional toe and rib fragments offer valuable context and the potential for additional research," Cory Harris, chair of SUNY Orange's behavioral sciences department, said in a statement. "We are also hoping to further explore the immediate area to see if there are any additional bones that were preserved."

Mastodon bones have turned up in New York's Orange County since the beginning of the 19th century, when early farmers plowing soil -- once at the bottom of large lakes produced by melting glaciers -- began digging up bones. The fossil record, MacPhee said, shows that mastodons favored roaming near water, drawn by the abundance of plant species they liked to dine on.

"Fossils are resources that provide remarkable snapshots of the past, allowing us to not only reconstruct ancient ecosystems but also provide us with better context and understanding of the current world around us," Robert Feranec, director of research and collections and curator of Ice Age animals at the New York State Museum, said in a statement.

The couple whose garden yielded the fascinating fossils prefers to remain anonymous out of concern publicity will draw unwanted crowds. Through the New York State Museum, however, they said they're thrilled their property can play a role in scientific inquiry.