A Dutch scientist working in Brazil, Marc Van Roosmalen, has discovered two previously unknown species of monkey in the Amazon jungle.

The monkeys, from the Callicebus family, are the size of small cats and live on fruit and leaves.

It's not that I'm so special... the fact is that since the 1800s nobody did any work like I'm doing in the last five years

Marc Van Roosmalen

They live in a remote part of the central Amazon region which is still being explored.

Brazil is home to almost a third of the world's 300 monkey species - although many are in danger of extinction.

In the last decade, 13 new species have been found there.

Royal connection

The discovery of the monkeys, Callicebus bernhardi and Callicebus stephennashi, were announced by Conservation International.

"This once again demonstrates how little we know about biodiversity, these are the 37th and 38th new primate species described since 1990," said Conservation International's President Russell Mittermeier.

Mr Van Roosmalen, who made the discoveries, works at Brazil's National Institute for Amazon Research in Manaus, 2,900 kilometres (1,800 miles) north-west of Rio de Janeiro.

He found the bernhardi monkey between the east bank of Madeira river and the lower reaches of the Aripuana river.

He named it after the Netherlands' Prince Bernhard, a noted naturalist.

He said he discovered the monkey by accident when he was travelling in the region searching for another new species, the dwarf marmoset.

Past success

The bernhardi monkey has dark orange sideburns, chest and inner sides of its limbs. It has a reddish-brown back, and a white-tipped black tail.

The monkey's head and body measure about 37.5 centimetres (15 inches), with the tail adding another 55 cm. An average individual weighs about 950 grams (33.25 ounces).

Mr Van Roosmalen found the second monkey, the stephennashi, last year near the Purus river.

Brazil is home to a third of the world's monkey species

It is a silver monkey with a black forehead and red sideburns and chest and inner sides of its limbs.

Its head and body measures about 27.5 cm, with the tail adding some 42 cm. An average individual weighs 690 grams.

In the past Mr Van Roosmalen has discovered three other species of monkey, but he is keen to play down his success.

"It's not that I'm so special. The fact is that since the 1800s nobody did any work like I'm doing in the last five years," Mr Van Roosmalen told the Associated Press.

Mr Van Roosmalen says he is lucky to work in a region of the Amazon where the numerous rivers had created a natural barrier that allowed several species to evolve in isolation, creating great diversity.