Mura's saddleback tamarin, which was first spotted in a remote area of the Amazon, is shown in this artist's rendering. (Stephen Nash)

Researchers have discovered a new type of long-tailed monkey in the remote reaches of Brazil's Amazon rainforest.

The new monkey, which was first spotted in 2007 in the northwestern state of Amazonas, is related to the saddleback tamarin, a species known for distinctive markings on its back.

The Wildlife Conservation Society researchers have named the subspecies Mura's saddleback tamarin (Saguinus fuscicollis mura) after the Mura Indians who inhabit the area.

The researchers published their findings in the June online edition of the International Journal of Primatology.

The small monkey is mostly grey and brown. It has distinctive mottling on its back, and weighs around 213 grams.

It is 240 millimetres tall and has a tail that measures 320 millimetres.

"This newly described monkey shows that even today there are still major wildlife discoveries to be made," said the study's lead author, Fabio Rohe, of the New York-based Wildlife Conservation Society.

"This discovery should serve as a wake-up call that there is still so much to learn from the world's wild places, yet humans continue to threaten these areas with destruction," he said in a Tuesday statement.

The study authors caution that the monkey's habitat is threatened by a number of development projects. They say they are particularly concerned by the prospect of widespread deforestation they fear will accompany the planned paving of a major highway through the Amazon.