They discovered in Mexico six of the smallest frogs in the world, some smaller than a coin

Scientists have identified and described six new species of frogs, some smaller than the diameter of a coin, in an article recently published in the journal Herpetological Monographs.

Miniature amphibians were seen living in a variety of habitats in Mexico and have only been described because they bear a striking resemblance to other close relatives.

Dr. Jeff Streicher, chief curator of amphibians and reptiles at the Museum of Natural History in the United Kingdom, participated in the description of the species.

“As part of a chapter of my doctoral thesis, I was working on these little frogs in direct development from Mexico,” he said.

“My supervisor and I were interested in them because they are really abundant, while many frogs are quite difficult to find. Despite this, taxonomists have not studied the group much because they are very variable in size and coloration, so it felt like a special challenge,” the expert told local media.

In total, six new species were described, bringing the total number of Craugastor species in Mexico to 12.

These include C. bitonium, named for its two-tone color pattern, along with others so called by the local area.

“It's hard to pick a favorite, but C. cueyatl stands out because it's named after an Aztec word for frog,” Dr. Streicher said.

“It felt good to honor the rich and profound human history of the Valley of Mexico, as the Aztecs probably knew this species,” he added.

The scientist also declared himself “impressed” by C. candelariensis, which bears the name of the locality in which we find it, since males can be only 13 millimeters long.

“It's probably the smallest frog in Mexico, and I find it fascinating that a frog can be as small as it is an adult,” he explained.

One species, C. portilloensis, is even smaller at just over 11 millimeters long, but since the specimens are not fully developed, it is difficult to assess how much larger these frogs might be.

However, despite their tiny size, none of the new discoveries break the record for the smallest known amphibians.

For many years, the smallest frog in the world was thought to be the Brazilian golden frog (Brachycephalus didactylus), which is only 8.6 millimeters long and was discovered in the 1970s.

But in 2012, Paedophryne amanuensis was found in Papua New Guinea, with males averaging only 7.7 millimeters long.

Craugastor frogs from Mexico and Guatemala live in a variety of different forests, from mountain forests to tropical forests. They span a range of different sizes and colors, with many species living side by side.

This means that miniature frog species may have been mistaken for juveniles of larger relatives, the researchers said, so they set out to re-evaluate amphibians and find out how many species there are in reality.

Some are ranked at the lowest level of conservation interest, but others are in danger of extinction.

They face threats that include damage to their habitats and chytridiomycosis, a fungal disease that is decimating amphibian populations around the world.

PhD student Tom Jameson, lead author of the study, explained: “Even in the last decade, many of their populations seem to be declining.”

“Many of these small-bodied frogs are probably quite micro-endemic, so they don't have a great ability to disperse. As amphibians, they dry out quite easily, so if their habitats change due to land-use change or even natural events such as landslides, they may not be able to move away,” he added.

The researchers said that the six frogs should be classified as endangered, or listed as 'insufficient data', so that their conservation status can be better assessed in the future.

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