The mottled green creature was for years mistaken as belonging to a widespread variety of the leopard frog. But now scientists realize this is new.

"For a new species to go unrecognized in this area is amazing," UCLA biologist Brad Shaffer said Wednesday.

New York is surrounded by wetlands and other nature-filled areas. But this latest urban creature appears to have chosen one of the grittiest corners as the center of its habitat: Yankee Stadium in the Bronx.

In the journal Molecular Phylogenetics and Evolution, Shaffer and other scientists compared the frog's DNA to that of other leopard frog species in the region. That's when they understood they were looking at a leopard frog, but a different kind.

"Many amphibians are secretive and very hard to find, but these frogs are pretty obvious animals," said Shaffer.

"This shows that even in the largest city in the U.S., there are still new and important species waiting to be discovered."

Lead paper author Cathy Newman, now of Louisiana State University, was studying leopard frogs when her colleague Jeremy Feinberg at Rutgers University asked her to probe some "unusual frogs."

"There are northern and southern leopard frogs in that general area, so I was expecting to find one of those that for some reason had atypical behaviors or that were hybrids of both," Newman said.

"I was really surprised and excited once I started getting data back strongly suggesting it was a new species. It's fascinating in such a heavily urbanized area."

Feinberg said he'd been immediately curious.

This frog gave a repeated croak, not the "long snore" of other leopard frogs.

"When I first heard these frogs calling, it was so different, I knew something was very off," Feinberg said. (AFP)