Scientists have discovered a new species of giant salamander, which they suspect is the world's biggest amphibian.
The new species was identified by researchers from the Zoological Society of London (ZSL) and London's Natural History Museum, using DNA from museum specimens collected in the early 20th century.
The 17 historical museum specimens and tissue samples were all previously thought to be from a single species of wild Chinese giant salamander, known as Andrias davidianus.
However, the new analysis identified three distinct genetic lineages in salamanders from different river systems and mountain ranges across China.
These lineages are sufficiently genetically different that they represent separate species: Andrias davidianus , Andrias sligoi , and a third species which has yet to be named.
The largest of the three, Andrias sligoi, can reportedly grow up to two metres in length, making it the largest of the 8,000 or so amphibian species alive today.
"Our analysis reveals that Chinese giant salamander species diverged between 3.1 and 2.4 million years ago," said Professor Samuel Turvey of ZSL's Institute of Zoology.
"These dates correspond to a period of mountain formation in China as the Tibetan Plateau rose rapidly, which could have isolated giant salamander populations and led to the evolution of distinct species in different landscapes."
Chinese giant salamanders, now classified as "Critically Endangered", were once widespread throughout central, southern and eastern China.
However, the decline in numbers has been catastrophic, mainly due to recent over-exploitation for food.
"Salamanders are currently moved widely around China, for conservation translocation and to stock farms that cater for China’s luxury food market," said Professor Turvey.
"We hope that this new understanding of their species diversity has arrived in time to support their successful conservation, but urgent measures are required to protect any viable giant salamander populations that might remain."
Melissa Marr, PHD researcher at the Natural History Museum London, added that "urgent interventions" are required to save Chinese giant salamanders in the wild.
"Our results indicate that tailored conservation measures should be put in place that preserve the genetic integrity of each distinct species," she said.
There are currently four giant salamanders at London Zoo, which were seized by Border Force after an attempt to illegally import them.
One of the salamanders, named Professor Lew, is on display in the Zoo's Reptile House, while the three others are being cared for behind the scenes.
Keepers will eventually introduce another animal to Professor Lew as a mate and the remaining two may then move to a different zoo, as the adults are highly territorial and need to be housed in separate enclosures.