Mammals, despite their iconic status in biodiversity, are not as numerous as other animal groups. Approximately 6,800 mammal species exist, compared to around 8,800 amphibians, 11,000 birds, and 12,500 reptiles. Yet, when people think of biodiversity, charismatic mammals such as pandas, orangutans, elephants, or tigers often come to mind. This visibility brings scrutiny, making mammals some of the most studied and threatened organisms on Earth. Over a quarter of mammal species are listed as vulnerable, endangered, or critically endangered on conservation inventories.
Given the extensive research on mammals, the discovery of a new mammal species is rare. The olinguito (Bassaricyon neblina) made headlines as the first new carnivorous mammal identified in the Americas in 35 years. Similarly, in 2017, the identification of the Tapanuli Orangutan (Pongo tapanuliensis) as a distinct species brought the total number of great ape species to seven, marking the first new great ape species in nearly a century.
Unveiling a New Genus
While discovering a new species is noteworthy, identifying an entirely new genus is an extraordinary event. A genus encompasses multiple species and sits one level above species in the Linnaean classification system. For instance, in Homo sapiens, Homo is the genus. There are only about 1,300 genera of living mammals worldwide, and the discovery of a new genus is a rare occurrence.
Recent examples include Nagasorex, a shrew from Nagaland, India in 2025; Paucidentomys, a rodent from Sulawesi in 2012; and Laonastes, a rock rat from Laos in 2005. Now, the scientific community celebrates the identification of a new genus of a small gliding possum in Indonesian Papua.
Finding a Lazarus Species
The journey to this discovery began with a single photograph in 2015. A plantation worker in Indonesian Papua captured images of an unfamiliar marsupial as part of a citizen science biodiversity monitoring project. The creature, with its large eyes, brown fur, and unfurred ears, resembled an Australian greater glider but had distinct features, including a gliding membrane and a prehensile tail.
Upon examining the photographs, researchers realized the animal closely resembled a possum known only from fossil bones, initially named Petauroides ayamaruensis. These fossils were found in archaeological sites in West Papua and Papua New Guinea, and belonged to a group of Australian gliding possums called hemibelidines. Scientists believed this lineage went extinct around 6,000 years ago, but the photograph suggested otherwise.
“The photo was evidence this was not the case. What we were looking at appeared to be a ‘Lazarus species’: one that had vanished from the fossil record, only to reappear alive.”
Other famous examples of “Lazarus species” include the Coelacanth, a fish thought extinct for 66 million years until rediscovered off the South African coast in 1938.
Meet the New Genus, Tous
To confirm their suspicions, scientists analyzed the photographs and compared them with fossil teeth from Papua and new partially fossilized material from Papua New Guinea. The analysis suggested these all referred to the same animal. Local Indigenous landowners, who have always known of this animal, confirmed its existence and distinctiveness, leading to the naming of a new genus: Tous.
“Tous” is a local term for this forest species, recognized as distinct from smaller gliders. Interviews with traditional landowners revealed the animal, identified as “Tous wansai,” is sacred to some tribal groups. Establishing a new genus signifies identifying a lineage evolutionarily separate for millions of years.
The evidence suggests Tous belongs to an ancient branch of the possum family, once spanning Australia to New Guinea, now surviving in a small, vulnerable part of the Papuan forests. Traditional knowledge indicates Tous roots in tree hollows in tall rainforest trees and, like Australia’s greater glider, is vulnerable to logging.
Protecting the New Species
The vulnerability of Tous is a significant concern. When formally describing the genus, researchers withheld the precise location of the original photograph to protect the species from wildlife traffickers. With its appealing features, Tous is at risk in an era of social media-driven wildlife trade. Newly discovered species often face exploitation soon after being announced, as seen with the Javan rhinoceros, which went extinct due to poaching just 22 years after its rediscovery in Vietnam.
Protecting Tous will be challenging. Its range is likely restricted to a small region of New Guinea, where lowland forests face threats from logging and agricultural expansion. The photos reveal logging debris and planted oil palm in the background. Local knowledge suggests Tous forms monogamous pairs and produces a single offspring annually, making it particularly vulnerable to habitat loss and hunting.
The discovery of Tous was made possible by combining fossil evidence, photographs, and the knowledge of local communities who have known this animal for generations. Conservation efforts must build on this knowledge, ensuring communities benefit from preserving wildlife rather than exploiting it.
If successful, Tous may have both a past and a future.
This article is republished from The Conversation. It was written by Erik Meijaard, University of Kent; Kristofer M. Helgen, University of Technology Sydney, and Tim Flannery, Australian Museum.
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Kristofer M. Helgen is affiliated with the Bernice Pauahi Bishop Museum, Honolulu, Hawaii. Erik Meijaard and Tim Flannery do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
