New Zealand researchers have discovered the fossilised remains of a previously unknown species of bat that foraged on the ground and burrowed using its feet and wrists.
The find suggests New Zealand was home to walking bats 16 million years ago.
Although only thought to have weighed 40 grams, the ancient species was three times larger than its modern cousins.
The fossil was found near prehistoric Lake Manuherikia in Central Otago, which was once part of a subtropical rainforest.
The new species, Mystacina miocenalis, is related to another bat, Mystacina tuberculata, which still lives in New Zealand's old growth forests.
The new species was described in the journal PLOS ONE and the study's lead author, Associate Professor Suzanne Hand from the University of New South Wales, said the discovery showed that Mystacina bats had been present in New Zealand for upward of 16 million years.
New Zealand's only native terrestrial mammals are three species of bat, including two belonging to the Mystacina genus - one of which was last sighted in the 1960s.
They are known as burrowing bats because they forage on the ground under leaf-litter and snow, as well as in the air, scuttling on their wrists and backward-facing feet, while keeping their wings tightly furled.
These bats were believed to have an ancient history in New Zealand, but until now, the oldest fossil of a Mystacina bat in New Zealand was from a cave in South Island, dating to 17,500 years ago. This latest discovery forces a rethink of when these peculiar walking bats first crossed the ditch, arriving from what is present-day Australia.
"This helps us understand the capacity of bats to establish populations on islands and the climatic conditions required for this to happen," said Associate Professor Hand.
"Bats are important pollinators and seed dispersers that keep forests healthy. Understanding the connectivity between the bat faunas of different landmasses is important for evaluating biosecurity threats and conservation priorities for fragile island ecosystems."
Associate Professor Hand led the research along with Associate Professor Daphne Lee from the University of Otago, and Dr Trevor Worthy from Flinders University in South Australia.