New species of opossum discovered by Cal Poly Humboldt professor

By Mike Green,

Published October 7, 2025 at 11:15 AM PDT

Close up of new opossum species showing mouse-like face, round leathery ears, pointed pinkish nose, long whiskers, reddish fir with black rings around the eyes. — Some of the mammals from RANP present remarkable morphological features, such as this new species of Marmosa (Stegomarmosa) that has a bright reddish fur and a super long and delicate rostrum which promptly distinguishes it from its closest relatives.

Dr. Silvia Pavan was on a search for a squirrel that was missing from the genealogy tree when she and her team stumbled upon a new species of opossum in Abiseo River National Park on the eastern slopes of the Peruvian Andes, at the edge of the Amazon Basin. They found the squirrel they were looking for and more. Dr. Pavan joins the Exchange to discuss her adventure and what the discovery means.

View of Rio Abiseo National Park: in the background mountain peaks covered in dense foliage in the mist. Left foreground, a wood carving of a human figure hanging from masonry or rack wall at an archaeological site. — View from Archeological site - Los Pinchudos, in Rio Abiseo National Park.

Extremely remote and difficult to access, the 3000 square kilometer UNESCO World Heritage site contains significant archaeological sites revealing the presence of pre-Incan Chachapoya civilization, as well as signs of pre-Chachapoya occupation.

*The Marmosa chachapoya’s is a small mammal with a delicate body about 4 inches in length and a long tail.*

It is also home to a wide variety of of known and unknown fauna, including the the recently discovered unknown marsupial, dubbed the Marmosa chachapoya. Measuring just four inches long (approx. ten inches including the tail), this small member of the opossum family has reddish fur, a mouse-like face with a a long pointed nose and distinctive, black, goggle-like rings around the eyes.