‘Long’-legged cave creature found in sinkhole in Argentina. It’s a new species
At the bottom of a sinkhole in a hard-to-reach cave of western Argentina, a pale yellow creature with “long” legs climbed across a pile of bat guano. Something about it caught the attention of visiting scientists — and for good reason.
It turned out to be a new species.
A team of researchers visited Rolo Vergara Cave in 2023 to survey subterranean life, Juan Romero-Rincon and Rodrigo Lopes Ferreira wrote in a study published Sept. 3 in the peer-reviewed journal Arthropoda.
Rolo Vergara Cave has “a single entrance located at the base of a sinkhole,” researchers said. The entrance leads to “a descending passage, partially obstructed by collapsed blocks,” and connects to a roughly 600-foot-long central passageway with “side galleries.”
During their visit, researchers noticed dozens of millipedes on the cave floor, the study said. Intrigued, they collected some of the animals, took a closer look and quickly realized they’d discovered a new species: Pleonaraius spelaeus, or the Pleonaraius cave millipede.
Pleonaraius cave millipedes can reach about an inch long, the study said. They have 20 body segments, “long” legs and “long” antennae.
A photo shows the pale yellow coloring of the new species. A crystal white line runs down its back and its antennae are slightly pinkish.
Pleonaraius cave millipedes were primarily found “on small accumulations of bat guano,” the study said. “Dozens of individuals, particularly immatures, were recorded during a single visit by one of the authors, suggesting the presence of a potentially large and well-established population.”
The new species is “the first strictly cave-dwelling millipede species recorded in Argentina,” researchers said. It shows several physical adaptations for its environment, including “depigmentation and a thin cuticle,” or exoskeleton, and likely an “elongation” of its appendages.
Researchers said they named the new species after the Latin word for “cave” because of its habitat.
So far, Pleonaraius cave millipedes have only been found at Rolo Vergara Cave in Neuquén Province of western Argentina, bordering Chile, and a roughly 780-mile drive southwest from Buenos Aires.
The new species was identified by its body shape, coloring, appendages, genitalia and other subtle physical features, the study said. Researchers did not provide a DNA analysis of the new species.
This story was originally published September 11, 2025 at 9:54 AM with the headline "‘Long’-legged cave creature found in sinkhole in Argentina. It’s a new species."
