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The world has one more sloth species in it than previously thought. Maned sloths live in a small belt of forest in Brazil and an analysis now suggests those in the south are a different species from those found farther north.

Three-toed sloths were conventionally thought to be divided into four species. One 鈥� the maned sloth (Bradypus torquatus) 鈥� sports a thatch of coarse, brown hair, making the head resemble a husked coconut.

But there were hints that not all maned sloths were alike, says at the Federal University of Minas Gerais in Brazil. The sloths occupy a strip of forest along Brazil鈥檚 Atlantic coastline, and in 1850, zoologist John Edward Gray described a unique sloth species in the southern coast based on a strange skull. Though later scientists considered this to simply be B. torquatus, recent research also showed a strong genetic break between northern and southern populations.

Investigating further, Casali and his colleagues compared existing genetic data on 24 maned sloths and the physical features of 55 more.

Sloths from the southern states of Esp铆rito Santo and Rio de Janeiro had flatter skulls, broader cheekbones and rounder jawbones than sloths from the northern state of Bahia. Comparisons of their genes confirmed a deep evolutionary split.

The researchers say that the southern maned sloth is a fifth species of three-toed sloth, separated from B. torquatus in the north by more than 4 million years of evolution. They have given the sloth Gray鈥檚 old name for it: Bradypus听肠谤颈苍颈迟耻蝉.

The findings 鈥渃hallenge our view of sloths as a well-known group in terms of diversity,鈥� says at the Chinese Academy of Sciences in Beijing.

at the University of Tennessee says that, given the size and landscape complexity of South America, there are 鈥渁lmost certainly鈥� other sloth species yet to be recognised by science.

Thanks to a long history of deforestation, the sloths鈥� Atlantic Forest home is an acutely imperilled ecosystem. So, the findings鈥� implications for the conservation of maned sloths 鈥� already considered vulnerable to extinction by the International Union for Conservation of Nature 鈥� are substantial, says at the State University of Santa Cruz in Brazil, part of the team.

鈥淭he conservation status will change abruptly,鈥� she says. Both maned sloth species now have ranges roughly 400 square kilometres in size, she says and 鈥渂oth would be considered endangered鈥�.