Researchers have discovered a new species within the marsupial genus Marmosa from a single specimen found on the eastern slopes of the Andes in the San Martin region of Peru.

Marmosa is a relatively small genus of neotropical mammals belonging to the family Didelphidae.

It represents one of three genera commonly referred to as mouse opossums, with the others being Tamarins and Tracuatine.

Marmosa Professor Sylvia Pavan from California Polytechnic University and her team stated:

“In addition to the naming of this species Marmosa, phylogenetic analysis has recently identified two potential new species from northern Peru. One has been classified under the subgenus Stegomarmosa, while the other is situated among the species of the subgenus Mikureus.

The new Marmosa species was found at altitudes where no other species of this genus had previously been recorded.

Designated as Marmosa Chachapoya, these animals exhibit reddish-brown fur and distinct mask-like facial markings.

They have a combined body and tail length of up to 25 cm (10 inches), with the body measuring approximately 10 cm (4 inches).

Researchers note that Marmosa Chachapoya is closely related to two species in the subgenus Stegomarmosa: Marmosa Repida and Marmosa Undersoni.

“I quickly realized this was an extraordinary find,” said Professor Pavan.

“Currently, we know very little about this species, as only a single specimen has been collected.”

To verify its classification as a new species, scientists analyzed its DNA and physical characteristics, concentrating on notable features such as the elongated nose and slender body.

“Marmosa Chachapoya is not the only new species discovered during our expedition,” Professor Pavan remarked.

“We have collected several other specimens, including new semi-aquatic rodents that have yet to be officially described.”

“These discoveries are crucial for biodiversity and conservation efforts, underscoring the ongoing mysteries of biodiversity in this region.”

“The results suggest that there are additional undiscovered species, many of which may be at risk without proper protection.”

“It emphasizes the significant role of scientific exploration and conservation in areas like the Rio Abysseo.”

The team’s paper was published in the journal Novitate at the American Museum on June 19, 2025.

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Sylvia E. Pavan et al. 2025. New species of Marmosa (Mammals, Didelphimorphia, Didelphidae) from Peru’s Parque Nacional del Rio Abysseo. Novitate at the American Museum 4037