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The number of known species of geckos has just jumped upwards, with 15 new species being formally described this week.

“And if you count the four I’m looking at right now it’s 19,” says of La Sierra University in California. “When you called I was in the process of describing them.”

This is a big increase, as there are only around 1500 known species of these lizards, famed for the sticking power of their feet.

The 19 species all live in a small area of Myanmar just 90 by 50 kilometres in size. “That’s the really amazing thing about it,” says Grismer. “They all come from such a small area.”

It’s common to find lots of closely-related species of invertebrates like snails or insects in such a small area, but it is unprecedented for a backboned animal, say Grismer. “For lizards, it is remarkable.”

The reason is likely to do with the unusual landscape. In an otherwise-flat lowland area, great blocks of limestone rise up to 400 metres high. Their surfaces are highly corrugated and sculpted by erosion, and sometimes riddled with caves.

These limestone blocks, some just a kilometre across, are evolutionary islands where isolated geckos have evolved into separate species. The limestone-dwelling geckos tend to have longer legs and toes, and more slender bodies, than their lowland kin.

Grismer’s team was asked to explore the area in Myanmar by the charity , which is campaigning to preserve the unusual limestone habitat.

In their first trip in 2016, the team found the first 15 geckos, as well as new snakes and frogs. “It was fricking crazy, man,” says Grismer. “In 19 days we found 23 new species.”

In a later trip, they found the four geckos yet to be formally described.

While the newly found geckos are restricted to tiny areas, they are abundant there, maybe because they are safe from many of the predators on the surrounding plains.

“It’s like you’re the only one who occupies a 7-Eleven,” says Grismer. “It may not be a Wal-Mart, but it’s all yours.”

Some of the blocks are being mined for limestone, and there were explosions nearby as the team worked, says Grismer. But other blocks have caves regarded as sacred by Buddhists, and these are fiercely guarded by monks.

Most of the new species of gecko belong to a large genus collectively known as . But to Grismer’s surprise, the team also found three species of dwarf gecko, which are usually found only on cloudy mountaintops.

The formal descriptions will appear in.