Extinct Bat Fossils In Hawaii Seem Unique And 'New'

The Hawaiian Islands have just one "endemic" or native land mammal, the Hawaiian hoary bat, that is limited to one region throughout the brief geologic history of this archipelago.

Some fossils found here show that another different kind of bat co-existed with the hoary bat for thousands of years. However, it became extinct as soon as humans arrived here.

Called the Synemporion keana, this new bat's remains were discovered in a lava tube more than three decades ago.

"The Hawaiian Islands are a long way from anywhere, and as a result, they have a very unique fauna--its native animals apparently got there originally by flying or swimming," said Nancy Simmons, a paper co-author and curator-in-charge at the American Museum of Natural History's Department of Mammalogy. "Besides the animals that humans have introduced to the islands, like rats and pigs, the only mammals that we've known to be native to Hawaii are a monk seal, which is primarily aquatic, and the hoary bat. So finding that there actually was a different bat--a second native land mammal for the islands--living there for such a long period of time was quite a surprise."

Co-author Francis Howarth at the Bishop Museum in Honolulu discovered some bat skeletal residues in a lava tube in Maui in 1981. Howarth, Alan Ziegler and peers found more remains in four other islands.

"The initial specimens included skeletons embedded in crystals on the lava tube wall and thus were likely very old," said Howarth. "Ziegler eagerly guided me through the bat collection at the Bishop Museum to identify the bat and show me features to look for in order to find additional material for study."

The new extinct species seemed to be in the islands' fossil record more than 320,000 years ago. It survived till about 1,100 years ago, or maybe later.

This Synemporion keana, also called a vesper, or evening bat, possesses some ancient DNA that can give the scientists more information.

"This extinct bat really is something new, not just a slight variation on a theme of a known genus," said Simmons. "The new bat contains a mosaic of features from taxa seen on many different continents. At some point, their ancestors flew to Hawaii, but we can't tell if they came from North America, Asia, or the Pacific Islands - they really could have come from anywhere based on what we know now."

"It seems possible that the reduction of native forests and associated insects after human colonization of the islands contributed not just to the extinction of plants, birds, and invertebrates, but also to the extinction of this endemic bat," said Howarth.

The finding was published in the journal American Museum Novitates.