Biologists discover ‘extraordinary’ frog with a truly strange appendage

3 Jan 2019

Image: © Kseniya Ragozina/

Researchers in Ecuador have been left baffled by the discovery of a new species of treefrog that has a strange claw-like structure on its thumb.

In one of the least explored regions of the eastern Andes mountain range in Ecuador, a frog unlike any other found to date has been seen roaming the thick rainforest.

During a two-week expedition to the region known as Cordillera del Cóndor, a team of researchers from the Catholic University of Ecuador was shocked to see that this frog has an extraordinary, enlarged claw-like structure located at the base of its thumb.

While findings on the frog have been published to the journal ZooKeys, the team has not been able to determine what the appendage is used for. However, it is thought that it could be used either as a means of defence against predators, or as a weapon when fighting with competing males.

After conducting analyses of genetic and morphologic data on the frog, the researchers said it represents a previously unknown species.

Close-up of the treefrog's foot with a strange, claw-like appendage.

Unlike other frogs, the new species has a claw at the base of the thumb. The function of this unusual structure is still unknown. Image: Gustavo Pazmiño/Bioweb Ecuador

“To reach the tabletop, we walked two days along a steep terrain. Then, between sweat and exhaustion, we arrived to the tabletop where we found a dwarf forest,” said one of the field biologists, Alex Achig. “The rivers had blackwater and the frogs were sitting along them, on branches of brown shrubs similar in colour to the frogs’ own. The frogs were difficult to find, because they blended with their background.”

The new frog species has been named Hyloscirtus hillisi, in honour of Dr David Hillis, a member of the National Academy of Sciences in the US who discovered three closely related frog species in the same genus in the 1980s, while conducting a series of field trips to the Andes of southern Ecuador.

Even though the species has just been discovered, the researchers said it is already at risk of extinction, with its very small distribution range located near a large-scale mining operation.

Colm Gorey was a senior journalist with Silicon Republic