Zenkerella insignis: Scientists Analyze DNA of Enigmatic African Rodent

For the first time, scientists have sequenced and analyzed the nuclear and mitochondrial DNA of the Cameroon scaly-tail (Zenkerella insignis), one of Africa’s most elusive mammals.

The Cameroon scaly-tail (Zenkerella insignis) by Joseph Smit, Proceedings of the Zoological Society of London 1898.

Also known as the flightless scaly-tailed squirrel, the Cameroon scaly-tail is the only species in the genus Zenkerella.

This species was first described in 1898 by German zoologist Paul Matschie.

It lives in the tropical moist forests and the semi-deciduous forests of southern Cameroon, Equatorial Guinea, Congo, and Central African Republic.

According to scientists, the Cameroon scaly-tail is a small rodent, measuring around 7-9 inches (18-23 cm) in body and head length and weighing only 0.4 to 0.5 pounds (180-220 grams).

The species has a dense, soft, slate grey fur, with ochre tints on the forearms, lower shins, and cheeks.

It has a lighter underside, and a darker tail that measures 5.9 to 6.7 inches (15-17 cm) in length.

The ankles of the rodent also have a tuft of darker ‘spoon-hairs’, which cover a glandular area. The function of this glandular area is still not known.

The species is primarily nocturnal, and it is considered likely to be solitary, with little information available on its habitats or ecology.

The Cameroon scaly-tail is considered one of the least studied mammals in the world. It has never been observed alive by scientists.

Notably, only 11 specimens of this species are curated in museums around the world. Three whole-body specimens recently found on Bioko Island in Equatorial Guinea bring the count to 14.

“Zenkerella could be seen as the ultimate Pokémon that scientists have still not been able to find or catch alive,” said study senior author Prof. Erik Seiffert, a researcher in the Keck School of Medicine at the University of Southern California, Los Angeles.

“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.”

Using the three specimens from Bioko Island, Prof. Seiffert and his colleagues from Equatorial Guinea, Egypt, the United States and the UK sampled DNA of the Cameroon scaly-tail for the first time.

The study, published this week in the journal PeerJ, details how the team analyzed Cameroon scaly-tail’s genes using cells from cheek swabs.

Then they compared animal’s DNA with a large sample of other rodents in an online database called GenBank, which includes all rodent suborders and families.

Based on DNA results, the scientists determined that, contrary to expectation, the Cameroon scaly-tail is a very distant cousin of Anomalurus and Idiurus, scaly-tailed squirrels with webbing between their legs and elbows that allows them to glide from tree to tree.

“Thus, Zenkerella, who cannot glide, should be placed in the newly named Zenkerellidae family,” they said.

“All three cousins are part of the Anomaluroidea superfamily, partially because they all have a set of scales on the bottom of their tails that reportedly provide support and traction for tree climbing.”

The study adds to a growing body of evidence: extreme anatomical adaptations that evolved and enabled some mammals to perform tasks such as gliding, flying or swimming are unlikely to be lost or reversed over the course of evolution.

“Of the about 5,400 mammal species alive today, only Zenkerella insignis and five others are the ‘sole surviving members of ancient lineages’ dating all the way back to the early part of the Eocene epoch, 49 million years ago or more,” Prof. Seiffert said.

“Within this select group, only Zenkerella, the monito del monte (Dromiciops gliroides) and the pen-tailed tree shrew (Ptilocercus lowii) have been given the medal ‘living fossil.’

“They closely resemble what is observed in their species’ fossil record. In other words, although they have evolved over time, the changes were minimal.”

“It’s an amazing story of survival,” he added. “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.”