New species of rat redefines rodents

The new species of rodent, Paucidentomys vermidax Image: Kevin Rowe Source: Museum Victoria

August 2012.Scientists have discovered an extreme species of rodent in Indonesia unlike any other on Earth; an almost toothless, worm-eating rat unable to gnaw or chew. The discovery of Paucidentomys vermidax illustrates how the process of evolution can lead to the loss of previously successful traits in species faced with new opportunities.

Only rodent with no molars
"There are more than 2,200 rodent species in the world and until this discovery all had molars in the back of their mouth and incisors at the front," said Dr. Kevin Rowe, Senior Curator of Mammals, Museum Victoria, and member of the team of scientists who discovered the new species.

The scientific name for the new species Paucidentomys vermidax reflects its dental and dietary adaptations, Paucidentomys meaning "few-toothed mouse" and vermidax meaning "devourer of worms".

Just one pair of incisors
"The specialised incisors of rodents give them the distinct ability to gnaw - a defining characteristic of rodents worldwide. In having lost all teeth except a pair of unusually shaped incisors that are incapable of gnawing, this new rat is unique among rodents," explained Mr Anang Achmadi, Curator of Mammals at Museum Zoologicum Bogoriense, and research colleague of Dr Rowe.

"This is an example of how species, when faced with a new ecological opportunity, in this case an abundance of earthworms, can evolve the loss of traits that were wildly successful in previous circumstances," said Dr. Rowe

Found on Sulawesi
The species was discovered in the rainforests of Sulawesi by a team consisting of researchers from Canada, Indonesia and Australia, including Dr Rowe.

"While we face a global crisis of biodiversity loss, this new species reminds us that we are still in an age of biodiversity discovery. Wild habitats where new species wait to be discovered are still out there," said Dr Rowe.

"In the mountains of Sulawesi, where we discovered Paucidentomys, healthy forests still nurture rare and remarkable species, however, they are isolated patches imperilled by expanding logging, mining, plantations and other human activities."

The research paper "Evolutionary novelty in a rat with no molars", which was announced in ‘Biology Letters' this month, is written by Jacob Esselstyn of McMaster University, Canada, Anang Achmadi of Museum Zoologicum Bogoriense, Indonesia and Kevin Rowe of Museum Victoria, Australia.