Zenkerella insignis
A male specimen of Zenkerella insignis which was found near the village of Ureca on Bioko, an island off the west coast of Africa. Steven Heritage

Researchers are on a mission to find an elusive animal that has been described as "the ultimate Pokémon" due to the fact that it has never been seen alive by scientists.

The creature - a rodent called Zenkerella insignis, native to central Africa - is among the least studied of all living mammals, according to Erik Seiffert, a senior author of a study into the animal's DNA and a professor of cell and neurobiology at the Keck School of Medicine at the University of Southern California.

To give an idea of how difficult studying Zenkerella is, just 11 specimens are currently held by museums around the world, although biologists have recently gained access to three dead rodents which were unintentionally caught in ground traps placed by hunters on Bioko Island, just off the Cameroonian coast.

"Zenkerella could be seen as the ultimate Pokémon that scientists have still not been able to find or catch alive," Seiffert said. "After all, it probably only shows up in the middle of the night, deep in the jungles of central Africa, and might spend most of its time way up in tall trees where it would be particularly hard to see."

The finding of the three specimens enabled scientists to examine samples of Zenkerella's DNA for the first time, which they then compared with a large sample of other rodents in an online database called GenBank.

Contrary to expectation, the findings, which were published in the journal PeerJ, suggest that Zenkerella is a very distant cousin of two scaly-tailed squirrels which have webbing between their legs and elbows, giving them the ability to glide between trees.

Zenkerella cannot glide, so based on the study, it will be placed in the newly named Zenkerellidae family, part of the Anomaluridae superfamily of rodents, which is comprised of scaly-tailed squirrels all native to central Africa.

The research is the latest in a growing body of scientific work which suggests that extreme anatomical adaptations that evolved over time – enabling some mammals to glide, fly or swim – are unlikely to be lost or reversed over the course of evolution.

Adding to the allure of the mysterious rodent, out of the 5,400 mammal species known to be in existence today, only Zenkerella and five others are the "sole surviving members of ancient lineages" which date back roughly 49 million years, Seiffert said.

Among these five species, Zenkerella, the pen-tailed shrew (Ptilocercus lowii) and the monito del monte (Dromiciops gliroides) have been labelled as "living fossils" – meaning that they have evolved very little over time and thus closely resemble ancient specimens observed in their species' fossil record.

"It's an amazing story of survival," Seiffert said. "In strong contrast to Zenkerella, all of these five other 'sole survivor' mammal species have been fairly well studied by scientists. We are only just starting to work on basic descriptions of Zenkerella's anatomy. It's fun to think that there might be other elusive mammalian species out there, deep in the rainforests of central Africa that will be new to science."

Locals on Bioko Island where the three specimens were found say the rodent is active at night, however, scientists know next to nothing about its behaviours, something which future studies will focus on.

Despite the fact that the International Union for Conservation of Nature has categorized the species as "least concern" some experts are worried that it could face threats from habitat loss and degradation, which are widespread problems in the region.

Drew Cronin, a co-author of the study and researcher with the Bioko Biodiversity Protection Program at Drexel University said: "Zenkerella may be under greater threat. The more information and visibility for the species that we can generate, the more likely we are to facilitate the research and conservation attention a unique species like Zenkerella requires."