An arachnid with a leg span of more than 13 inches has been discovered in the caves of the Southeast Asian nation of Laos.

Researcher Peter Jäger from the Senckenberg Research Institute in Frankfurt, Germany, found the creature (a type of harvestman) during a trip to Laos for a major TV production in April.

Harvestmen, referred to as daddy longlegs, are normally tiny and they are just one or two inches long. But Jager was surprised to find the gigantic male harvestman with a leg span of more than 13 inches.

"In between takes I collected spiders from the caves in the southern province of Khammouan. In one of the caves I discovered a harvestman that was absolutely huge," Jager said in a statement.

Harvestmen are often mistaken for spiders as both are types of arachnids. Both have eight legs, but have a different body. Harvestmen belong to an order of opiliones. So far, researchers have not been able to identify the species and haven't named it.

After consulting with other experts, Jager could only surmise that the harvestman probably belongs to the genus Gagrella in the Sclerosomatidae family.

"It's a shame we can't identify such an exceptional discovery correctly, i.e. its species," Jäger said.

"We haven't dealt with these and related genera from China and neighbouring South East Asia before. Specialists are also unavailable due to the fact that descriptive taxonomy is no longer the main focus of research funding," he added.

The newly found harvestman is in close contention for the world's largest harvestman. South American harvestman with one-foot-one-inch leg span (just over 34 centimeters) is the current record holder for the world's largest, said a report in the National Geographic.

This is not the first time such giant creatures have been found in Laotian caves. Researchers have earlier spotted huge arthropods of the same size as the harvestman in the region - the Laotian harvestman spider Heteropoda maxima with a leg span of up to 11 inches and the predatory centipede Thereuopoda longicornis with a total span of one foot, three inches.

It is still unclear what factors cause the creatures in the region to grow taller. What is certain is that the growth rate of these cave creatures has a limit - either due to lack of oxygen supply to the long appendages or the point beyond which they cannot move their long legs quickly to run or catch their prey, Jager said.

Jager and his team are planning to further study the Sclerosomatidae family in a detailed case study as the harvestmen have invaluable potential and can be found in virtually every habitat.