A freshwater dolphin found only in China is now "likely to be extinct", a team of scientists has concluded.
The researchers failed to spot any Yangtze river dolphins, also known as baijis, during an extensive six-week survey of the mammals' habitat.
The team, writing in the Royal Society Biology Letters journals, blamed unregulated fishing as the main reason behind the dolphins' demise.
It would be the first extinction of a large vertebrate for over 50 years.
The World Conservation Union's Red List of Threaten Species currently classifies the creature as "critically endangered".
Sam Turvey of the Zoological Society of London (ZSL), one of the paper's co-authors, described the findings as a "shocking tragedy".
"The Yangtze river dolphin was a remarkable mammal that separated from all other species over 20 million years ago," Dr Turvey explained.
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