Bats can fly with terrific efficiency, but walking is an entirely different story.

A typical bat eats on the wing and sleeps high above the ground—a lifestyle that doesn’t require much contact with flat terrains—and natural selection has molded the vast majority of bats into magnificent flyers and sub-par walkers. Of the more than 1100 living species currently known, only two can physically handle long strolls across solid ground. One is the vampire bat, which uses its well-developed limbs to escape being trampled by the larger animals it's sucking blood from. The other is New Zealand’s lesser short-tailed bat (Mystacina tuberculata), which spends a full 30 percent of its time grounded and looking for foodfolding its wings up under a special, protective membrane to keep them from getting in the way. Paleontologists know that M. tuberculata's ancestors flew over from Australia, and, last week, they got a clue about when they might have arrived.

Scientists recently discovered a prehistoric short-tailed bat species, which they dubbed Mystacina miocenalis, that trekked through the land of the Kiwis between 19 and 16 million years ago. The animal had several of the same adaptations as M. tuberculata for roaming about on its hands and feet (like beefy limb bones). But M. miocenalis was huge: At 39.2 grams (0.086 lbs), it weighed three times more than M. tuberculata and most modern bats. Thanks to that impressive heft, the animal has been dubbed “Batman.”

“The unusually large size of this bat,” says Suzanne Hand, co-discoverer, team leader, and vertebrate paleontologist at the University of New South Wales in Australia, “suggests that it was doing less in-flight hunting and was taking prey heavier from the ground, and larger fruit than even its living cousin.” The study was published in a recent issue of PLOS One.