New Species of Frog With Weird Claw Thumb Discovered in Unexplored Part of Andes

Researchers have discovered a new species of tree frog on the slopes of a flat-topped mountain in a remote region of the Ecuadorean Andes, which is considered to be one of the richest areas for biodiversity in the world.

According to a study published in the journal ZooKeys, the amphibian has dark brown skin dotted with orange flecks and features a large and unusual claw-like structure protruding from the base of its thumb, known as a prepollex.

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At present, it's not clear what the purpose of this prepollex—which is essentially an undeveloped digit—could be. However, the team of researchers who discovered the frog—led by biologist Santiago Ron from Pontificia Universidad Católica del Ecuador—suggest it could be used to defend against predators, or wielded as a weapon to fight other individuals of the same species (for example, when males compete for mates).

The team first spotted the amphibian on a table-top mountain during a two-week expedition to the Cordillera del Cóndor in the Eastern Andes—a difficult-to-access area of which large tracts remain unexplored.

"To reach the table-top, we walked two days along a steep terrain," Alex Achig, one of the biologists, said in a statement. "Then, between sweat and exhaustion, we arrived [at the top] where we found a dwarf forest. The rivers had blackwater and the frogs were sitting along them, on branches of brown shrubs similar in color to the frogs' own. The frogs were difficult to find, because they blended with their background."

In total, the team examined six specimens—one adult female, three adult males and two juvenile females—conducting DNA tests and comparing them to similar species. They concluded that that the frog represented a previously undescribed species of the genus Hyloscirtus.

This genus contains 37 species of tree frog that reproduce along streams, with a range extending from Costa Rica to the Andes Mountains of Bolivia, Colombia, Ecuador, Peru and Venezuela.

The new member of the species has been named Hyloscirtus hillisi in honor of David Hillis, an American evolutionary biologist and expert in Andean amphibians and reptiles, who has discovered three other species in the same genus.

Even though H. hillisi is new to science, the researchers say that the species is at risk of extinction, not least because its range is limited to a small area that happens to be in the vicinity of a large Chinese mining operation. As a result, its habitat is under threat.

An image of the new frog species Hyloscirtus hillisi. Gustavo Pazmiño, BIOWEB Ecuador