Once Known Only from Fossils, Now Found Alive: The Pygmy Long-fingered Possum (Dactylonax kambuayai)

On the Vogelkop Peninsula of western New Guinea, also known as the Bird's Head or Doberai Peninsula, a tiny marsupial called the Pygmy Long-fingered Possum (Dactylonax kambuayai) has returned from what once seemed like extinction. It is the smallest known member of the striped possum subfamily Dactylopsilinae. Its first scientific record came not from a living animal, but from a series of jaw and tooth fossils recovered from Kria Cave on the Ayamaru Plateau of the Vogelkop Peninsula. These remains, dated to about 7,500 to 6,000 years ago, were described as belonging to a diminutive striped possum. Because no living individuals were known for many years, later reference works listed the species as extinct. Yet in a region as incompletely surveyed as New Guinea, such a conclusion always carried uncertainty.

The story changed when researchers examined fluid-preserved specimens in the collection of the University of Papua New Guinea. There they found two specimens that had previously been misidentified as the Western Long-fingered Possum (Dactylonax palpator): an adult female and an associated pouch young. Re-examination showed that the skull, teeth, and external morphology matched the Pygmy Long-fingered Possum. These specimens became crucial evidence that the species had survived into modern times, and they were later transferred to the Australian Museum for long-term preservation.

Vogelkop Peninsula, Indonesia（Image source：Flannery TF et al. (2026)， CC BY 4.0 ）

A photograph of the Pygmy Long-fingered Possum（Image source：Flannery TF et al. (2026)， CC BY 4.0 ）

After 2023, researchers and field observers obtained additional photographic records of living individuals. These records came from the area around Klalik Village in Sorong Regency on the Vogelkop Peninsula, about 65 km northwest of Kria Cave, where the original fossil material had been found. The surrounding lowland forest still retains features of primary forest, though there is also some evidence of local tree felling. During one night-time observation, a villager brought a live Dactylonax to a mammal-watching group. Before releasing the animal onto a tree trunk, the observers documented it with photographs and video. Together, the modern museum specimens and field images matched the fossil material taxonomically, turning the Pygmy Long-fingered Possum from a fossil species into a living one.

In paleontology, a lineage that disappears from the fossil record for a long interval and then reappears is called a Lazarus taxon. The idea can also be extended to living species that were first known only from fossils and later found alive. Australia and New Guinea have produced several such examples, including the Mountain Pygmy Possum (Burramys parvus), the Northern Hairy-nosed Wombat (Lasiorhinus krefftii), Bulmer's Fruit Bat (Aproteles bulmerae), and the recently rediscovered Vogelkop marsupial Tous ayamaruensis.

The known adult female Pygmy Long-fingered Possum had a head-body length of about 17.6 cm and a tail length of about 18 cm, giving a total length of roughly 35.6 cm. It weighed about 216 g, and its tail was almost equal to the head and body in length. Its ears are relatively large, reaching about 3 cm. In appearance, it bears the dorsal striping typical of dactylopsilines, but its overall colouration is more subdued. The limbs are covered with darker fur, and the tail is mostly black, with white fur mainly at the base and tip. One of its most distinctive features is a band of white fur extending from the upper lip to the lower margin of the eye.

The fourth digit of the hand is strongly elongated, a defining feature of the genus Dactylonax. This finger appears to function as a specialized feeding tool. The researchers suggest that, much like the aye-aye, these long-fingered possums may use the elongated digit to extract wood-boring insect larvae from timber. In the small-bodied D. kambuayai, the fourth digit is nearly as long as in its larger relatives, making it proportionally even more striking. Its length may be related to the depth or diameter of the tunnels made in wood by its invertebrate prey, or perhaps to the body length of the prey itself.

The fourth digit is exceptionally long in the genus Dactylonax: (a) Pygmy Long-fingered Possum (Dactylonax kambuayai, specimen AM M.56796); (b) Western Long-fingered Possum (Dactylonax palpator, specimen AM M.29254); (c) Eastern Long-fingered Possum (Dactylonax ernstmayri, specimen AM M.27312)（Image source：Flannery TF et al. (2026)， CC BY 4.0 ）

The genus Dactylonax was once often merged into Dactylopsila, but the authors argue that the two are distinct enough to be treated as separate genera. Species of Dactylonax have a short, broad skull, enlarged incisors, a highly elongated fourth digit, and a relatively short tail. These traits point to a more terrestrial lifestyle and a specialized diet of wood-boring insect larvae. By contrast, species of Dactylopsila have much longer tails and are more strongly arboreal. Molecular evidence also suggests that the two lineages diverged about 10 million years ago, a depth of separation comparable to that between many well-recognized marsupial sister genera.

Under the revised classification, Dactylonax includes three living species: the Pygmy Long-fingered Possum (D. kambuayai), the Western Long-fingered Possum (D. palpator), and the Eastern Long-fingered Possum (D. ernstmayri). The Western Long-fingered Possum had often been treated as a widespread montane form across New Guinea, but this study restricts it to the Arfak Mountains of the Vogelkop Peninsula. The Eastern Long-fingered Possum, formerly treated as a subspecies or population of D. palpator, is recognized as a distinct species distributed along the New Guinean Central Cordillera and the Huon Peninsula, generally at elevations above 800 m.

The authors propose an evolutionary scenario in which a lowland ancestor resembling D. kambuayai colonized montane habitats on the Vogelkop Peninsula and gave rise to the larger-bodied D. palpator. This montane lineage may then have dispersed eastward into the Central Cordillera, eventually giving rise to the more specialized montane species D. ernstmayri. The pattern is intriguing because the montane lineage apparently spread eastward, whereas the lowland form did not, suggesting that some unusual elevational or zoogeographic filter may have shaped the history of the genus.

Field observations suggest that the Pygmy Long-fingered Possum often moves close to the ground and is reluctant to climb high. It has been seen jumping from the base of one tree to another, in a manner compared to African galagos. This behaviour may also make it easier for local hunters to catch: by switching off their torch, creeping closer, and then pouncing.

The lowland forests of western New Guinea remain deeply underexplored. When an animal once thought to have vanished for six or seven thousand years is found alive, the discovery brings more than surprise. It is also a reminder of urgency. Before these forests are further transformed by human activity, how many species are still hidden in the memories of local hunters and among the shadows of trees at night, waiting for science to recognize their names and their place in the living world?

An illustration of the Pygmy Long-fingered Possum based on fluid-preserved specimens from the University of Papua New Guinea, identified in 1999（Image source：Flannery TF et al. (2026)， CC BY 4.0 ）

Author: Shui-Ye You

Reference:

Flannery TF et al. (2026). Found alive after 6,000 years: modern records of an 'extinct' Papuan marsupial, Dactylonax kambuayai (Marsupialia: Petauridae), with a revision of the systematics and zoogeography of the genus Dactylonax. Records of the Australian Museum.