Researchers have now found that a species of mouse lemurs is actually two distinct species. The new study brings the number of identified tea-cup sized lemur's species to 20.

Researchers had to use DNA sequencing to identify the two mouse lemur species, as they look pretty similar. These mouse lemurs have gray-brown fur and weigh about 2.5 to 3 ounces.

"You can't really tell them apart just looking at them through binoculars in the rainforest," said Peter Kappeler of the German Primate Center in Goettingen, and senior author of the study. Kappeler earned his PhD from Duke University in 1992. The mouse lemurs are native to Madagascar in Africa.

One of the mouse lemur species has been named Anosy mouse lemur or Microcebus tanosi, and the other has been named as Marohita mouse lemur or Microcebus marohita. In Malagasy, the word "marohita" means "many views". Anosy mouse lemurs are quite similar to the gray mouse lemurs, but according to the available genetic data, both species don't interbreed.

Mouse lemurs also develop a neurological condition similar to Alzheimer's disease. Researchers say that their brains could serve as models to study the development of the condition in humans.

"But before we can say whether a particular genetic variant in mouse lemurs is associated with Alzheimer's, we need to know whether that variant is specific to all mouse lemurs or just select species," said Anne Yoder, Lemur Center Director.

The mouse lemurs species described in the current study were first caught by Rodin Rasoloarison of the University of Antananarivo in Madagascar between 2003 and 2007. Rasoloarison weighed the primates and took samples for genetic analysis.

Although genetic analysis of the species was conducted and published by 2010, it is only now that the researchers have described the species in detail.

The study is published in the International Journal of Primatology.

Mouse lemurs threatened by human activity

Mouse lemurs have lived in Madagascar for millions of years (about 7 to 10 million years); however, the arrival of humans in the region has destroyed their habitat. Only about 10 percent land in Madagascar has a forest-cover.

"This species is a prime example of the current state of many other lemur species," Kappeler said in a news release.

Recently, another team of researchers sequenced the entire genomes of three endangered populations of aye-ayes - a type of lemur. Researchers hope the study will help conserve the animals.