Ancient discovery pushes back New Zealand bat history

Wednesday, 17 June 2015

Fossilised remains of a 16 million-year-old bat species which walked on four limbs and was three times larger than today's average bat, have been discovered in New Zealand.

Research published on Thursday described the new species, called Mystacina miocenalis, found through the fossilised remains in central Otago deposits.

University of New South Wales associate professor Suzanne Hand said the historic bat was related to New Zealand's endangered lesser short-tailed bat.

A closely-related species, the greater short-tailed bat, has not been seen since the 1960s and is thought to be extinct. Long-tailed bats are common throughout New Zealand but belong to a different group.

The New Zealand species are some of the only bats in the world that forage on the ground, using their folded wings as 'front limbs' for scrambling around.

Though Mystacina bats were suspected to have a long history in New Zealand, the oldest fossil known was from a cave in the South Island and dated to 17,500 years ago.

The new discovery pushed the date for the presence of the group back millions of years.

In many ways, the fossilised bat resembled its contemporary relative. Its teeth suggested a similar diet, comprised of nectar, pollen and fruit along with spiders and insects.

The ancient bat weighed in at 40 grams, making it about three times the size of present-day native bats. The lesser short-tailed bat weighs about 12-15g.

However, it was small compared to modern day fruit bats elsewhere in the world, which can weigh in around a kilogram.

Hand said the larger size gave some clear signs to the lifestyle of the extinct animal.

'The size of bats is physically constrained by the demands of flight and echolocation, as you need to be small, quick and accurate to chase insects in the dark,' she said.

'The unusually large size of this bat suggests it was doing less in-flight hunting and was taking heavier prey from the ground, and larger fruit than even its living cousin.' 

The bat species was dated to a period in the Miocene when New Zealand was bathed in sub-tropical conditions. A body of water, known as Lake Manuherikia, was formed in central Otago. It was at this site that the fossil was found.

Lake Manuherikia, at 5600 square-kilometres, was nine times the size of Lake Taupo.

The leftover sediment from the lake bottom has been a treasure trove for fossil hunters over the years. Discoveries from the site include New Zealand's oldest frogs, lizards and land birds as well as its only known crocodiles and terrestrial turtles.