Smaller than a matchstick, the three newly discovered salamanders could become extinct within the next 50 years, researchers say.

From the remote mountains of Oaxaca in Mexico, scientists have described three new species of miniature salamanders that are smaller than a matchstick.

These tiny creatures belong to the elusive genus Thorius, members of which are the smallest four-legged animals on earth, scientists report in a new study published in PeerJ.

Thorius may also be the most endangered genus of amphibians in the world, and the newly discovered species are already on the verge of extinction, researchers warn.

“Salamanders of the highlands of Mexico are closer to extinction than any other on Earth,” study co-author David Wake of the University of California, Berkeley, said in a statement.

Thorius salamanders, also referred to as Mexican pigmy salamanders or minute salamanders, are found only in Mexico. Once abundant, these salamanders are now incredibly rare in the wild and living specimens are very hard to find. So Wake and his colleagues examined museum specimens collected more than 35 years ago.

Since most species of Thorius are difficult to distinguish based on appearance alone, partly because they are so small, the scientists analyzed the specimens’ DNA sequence as well as their external and internal anatomy. Their analysis revealed three new distinct species of Thorius among the specimens: the pine-dwelling minute salamander (Thorius pinicola), the long-tailed minute salamander (Thorius longicaudus) and the heroic minute salamander (Thorius tlaxiacus). Morphologically, the three species resemble one another in size, coloration and structure of the limbs and digits, the researchers write. But they show subtle differences in features like their overall adult body size and shape of their nostrils.

A long-tailed minute salamander (Thorius longicaudus) – one of the newly described species of minute salamander. Photo by Mario García-París.
A long-tailed minute salamander (Thorius longicaudus) – one of the newly described species of minute salamander. Photo by Mario García-París.

Nearly 30 species of Thorius are now recognized, and almost all the species are listed as endangered or critically endangered in the IUCN Red List, researchers say. The three new species, too, are likely on the brink of extinction, they add.

The researchers recommend listing all three species as critically endangered since their populations have declined by more than 80 percent at their few known localities over the last 30 to 40 years. While habitat loss seems to be the major driver of their disappearance, pollution, climate change and disease may also be contributing, scientists say. In fact, Thorius salamander populations have declined so drastically, they could become extinct within the next 50 years, they warn.

“We have known about the salamanders we have described for decades, at a time when they were exceedingly common, but only recently have we obtained evidence that they are indeed new species, though now critically endangered,” Wake said in the statement. “This is a common experience with other high-altitude species in Mexico, and a biological disaster is facing us.”


  • Parra-Olea G, Rovito SM, García-París M, Maisano JA, Wake DB, Hanken J (2016). Biology of tiny animals: three new species of minute salamanders (Plethodontidae: Thorius) from Oaxaca, Mexico. PeerJ 4:e2694