An unusual looking penis has lead to the recent discovery of a new monkey species, according to scientists.

The white-cheeked macaque was found in the remote highland forests of southeast Tibet after researchers set up camera traps. It was identified by its distinctive rounded penis, which is different than the arrow shaped genitalia found on other species in the area - although, scientists named (Macaca leucogenys) it for the pale whiskers on its chin and the side of its face, rather than its penis shape.

Videos have also revealed that the animal has a distinctive alarm calls compared to other macaques in Tibet.

For years, this monkey had been a victim of mistaken identity, confused for another species. And due to its remote location, in Medog County of Tibet, its true identity has remained a mystery.

"This species has long been identified as Assamese macaque (Macaca assamensis) because no clear photos or good specimens are available," corresponding author Dr. Peng-Fei Fan from Dali University in the province of Yunnan, China, told the Daily Mail. 

"Using camera traps, we were just so lucky to capture some good photos of the white-cheeked macaque, which clearly showed characteristics of it and allowed us to claim it as a new species," he told BBC News.

To better understand the species, researchers set up camera traps in the area's remote tropical and evergreen mountain forests. They captured 685 photos of macaques, which revealed some monkeys that had different features.

The animals had relatively short hairless tails, almost white hairs around their face, and long, thick hairs on their neck. But their most defining feature was their genitalia.

Most macaques from that area have arrow shaped penises, however, M. leucogenys had far more rounded penis and a dark hairy scrotum.

Although other scientists might have noticed differences between the Assamese macaque and the white-cheeked macaque, until now there has not been solid evidence for its existence.

"This discovery was a big surprise for all of us," Fan told BBC.

The new macaque species is described in more detail in the American Journal of Primatology.

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