In 2015, a plantation worker in Indonesian Papua photographed an unfamiliar tree-dwelling marsupial. That single image has become one of biology's rarest finds: evidence of an entirely new genus of living mammal, thought extinct since the Ice Age.
Scientists have named the animal Tous, confirmed it is distinct enough to require an entirely new genus. The Ring-tailed Glider, as Tous ayamaruensis is formally known, represents the first new genus of New Guinean marsupial described since 1937. To grasp how uncommon this is, consider the baseline: there are only about 1,300 genera of living mammals worldwide, and discovering a totally new genus of mammal happens only a few times a year.
The animal itself is modest in appearance. The ring-tailed glider is a gliding possum that lives in hollows in large trees and can glide from tree to tree using a large flap of skin on each side of its body that serves as a gliding membrane. Smaller than its Australian cousins, with unfurred ears and a strongly prehensile tail, the Ring-tailed Glider forms lifelong pair bonds and only raises one young annually. Yet its significance runs deep.
Scientists had presumed the lineage had gone extinct around 6,000 years ago, but the photograph provided evidence this was not the case, appearing to be a "Lazarus species": one that had vanished from the fossil record, only to reappear alive. The plantation worker who caught the animal was part of a citizen science-based biodiversity monitoring project which asked plantation workers to photograph or record the sounds of wildlife they encountered during their work.
Confirming the discovery required painstaking detective work. Scientists examining the photographs realised the animal closely resembled a possum known only from a handful of fossil bones initially named Petauroides ayamaruensis, discovered decades earlier in archaeological sites in West Papua and Papua New Guinea, bones from a small member of a group of Australian gliding possums called hemibelidines, or ringtail possums, a lineage thought to exist only in eastern Australia until recently.
The breakthrough came through knowledge held by the landscape itself. Scientists drew on knowledge shared by local Indigenous landowners who have always known about this animal, with elders identifying the animal in photographs as "Tous wansai", distinguishing it from other similar arboreal marsupials. Some of the Indigenous communities of the region regard the glider as sacred and an animal to be avoided and protected, which may have contributed to it remaining unknown to science until now.
The discovery carries a sobering edge. The typical lowland forest habitat where the new species is found is under increasing pressure from agricultural expansion, with scientists still not knowing its full range but all evidence suggesting it is restricted to a small region of New Guinea where lowland forests are under pressure from logging and agricultural expansion, with logging debris and planted oil palm visible even in the photographs. Like greater gliders, the species faces threats from logging.
The story illustrates a complex reality about conservation in the 21st century. Yes, vast tracts of Earth remain biologically unknown. But finding that biodiversity is not the final step; protecting it is harder still, especially when discovery itself can attract unwanted attention. In an era of social media-driven wildlife trade, that appeal can be dangerous, with newly discovered species sometimes pushed toward exploitation almost as soon as they are announced, including the example of the Javan rhinoceros, with only 22 years between its rediscovery in Vietnam in 1988 and its confirmed extinction because of poaching in 2010. For Tous, the work of protection has already begun, but it will require sustained commitment from both scientists and the Indigenous communities who have safeguarded this animal for millennia.