From a soul-sucking 'dementor' wasp named after a creature from the Harry Potter books to a half-metre long stick insect, scientists identified 139 new species in the Greater Mekong Region in 2014, according to a new report.
Many of the newly-described species are already under threat from new roads and dams and the region's rapacious demand for wildlife meat and luxury timber, the WWF said in its report.
Southeast Asia has a "treasure trove" of biodiversity with an average of three new species a week being discovered in the area between 1997 and 2014, the report said.
"We've only skimmed the surface of new discoveries in the Greater Mekong," said WWF expert Thomas Gray.
But unsustainable development and the illicit trade in wildlife is taking a terrible toll and it is possible that "many species have disappeared before they were even discovered," he said.
In Thailand, a new species of wasp (ampulex dementor) was named after the soul-sucking dementors from the Harry Potter books due to its grisly hunting skills. The wasp's venom effectively turns their prey into zombies before they are then eaten alive.
In the Harry Potter novels, dementors are a creature that consumes all positive feelings and happy memories from their victims.
In neighbouring Vietnam, a stick insect that measures 54 centimetres (21 inches) long was found less than one kilometre (0.6 miles) from a village in the north of the country.
Two new orchid species were discovered in Bangkok's famous Chatuchak Market -- being traded before they had been scientifically identified.
And a crocodile newt species found in Myanmar is already in demand in the international pet trade, with two of the newts being found in pet stores in Europe.
The list, dominated by plants, includes 23 reptiles, 16 amphibians, nine fish, and one mammal.
The Greater Mekong region consists of Thailand, Cambodia, Myanmar, Vietnam, Laos and the southwestern Chinese province of Yunnan.
The region forms part of one of the five most threatened biodiversity hotspots in the world, the WWF said.