London: Scientists have discovered a unique new species of fish where the males have their reproductive organs located on their head.
The fish 'Phallostethus cuulong' is just 2 centimetres long, and is part of little known group where the males have their reproductive organs on their chin.
The newly discovered specimen from Vietnam's Mekong Delta, is only the 22nd known priapiumfish, which are named after the ancient Greek fertility deity, Priapus.
They all belong to a family called 'Phallostethidae' and live in south-east Asia, the 'Daily Mail' reported.
Researchers said that they are baffled as to why the fish have their sexual organs on their chin, and their anus in the throat.
"We don't know why priapiumfish evolved their peculiar arrangement," Lynne Parenti of the Smithsonian Institution in Washington, DC, said.
"The fish's anus is on its priapium, slightly forward from the genital opening. Its guts perform a U-turn to reach it. There's not much going on at the back of these fish," Parenti said.
The new species was first discovered in July 2009 by Koichi Shibukawa of the Nagao Natural Environment Foundation in Tokyo, Japan.
He saw one swimming alone in a canal near the Mekong River in Vietnam, and managed to catch it in a net.
Working with colleagues at Can Tho University in Vietnam, he realised it was a new species, the report said.