Cameroon scaly-tail

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Cameroon scaly-tail
Temporal range: Early Miocene to recent (genus) [1] 20–0  Ma
Aethurus glirinus.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Zenkerellidae
Genus: Zenkerella
Species:
Z. insignis
Binomial name
Zenkerella insignis
Matschie, 1898

The Cameroon scaly-tail (Zenkerella insignis), also referred to as the Cameroon anomalure, flightless anomalure or flightless scaly-tail, [3] is a rodent species endemic to West Central Africa. [3] [4] [5] The scientific literature has never (or possibly only obscurely) reported observations of live individuals. [3] [4] [6] The taxonomic classification of the species has been subject to recent revision.

Contents

Phylogeny

Previous common names for this species included flightless scaly-tail ‘squirrel’, but this is a misnomer as anomalures are very distantly related to the true squirrels of the rodent family Sciuridae and only superficially resemble them. [6] Z. insignis is the only extant species in the genus Zenkerella and family Zenkerellidae and is the only surviving species of a lineage that diverged from the other extant anomalures (genera Idiurus and Anomalurus ) ~49 million years ago (Ma). [6] Among mammals, very few species are the sole survivors of such ancient lineages, some other examples being the pen-tailed treeshrew and the monito del monte. [7]

Timescale and phylogenetic relationships of extant and extinct anomaluromorph rodents. Zenkerella phylogney.jpg
Timescale and phylogenetic relationships of extant and extinct anomaluromorph rodents.

Extinct fossil taxa which are putative close relatives of Z. insignis include: Zenkerella wintoni (~20 Ma, early Miocene, Kenya), [8] Prozenkerella saharaensis (~31 Ma, early Oligocene, Libya), [9] and possibly Oromys zenkerellinopsis (~33 Ma, earliest Oligocene, Morocco). [10]

In 2016, it was reported that three whole-body specimens of Z. insignis were recovered on Bioko Island, Equatorial Guinea. [6] At that time, it had been over 20 years since the scientific literature recorded new individuals. [5] [6] These specimens were used to sequence portions of the Z. insignis genome. Phylogenetic analysis using combined DNA and anatomical data place Zenkerella as the sister taxon of an Idiurus-Anomalurus clade. [6] This is contrary to a previous hypothesis that grouped Zenkerella with Idiurus within the family Anomaluridae. [6] [9] [11] The Z. insignis position in the rodent evolutionary tree supports a single origin of the anomalure gliding adaptation with no evolutionary reversals; [6] more complex evolutionary scenarios were previously envisioned. [9] The same analysis estimated an early Oligocene origin of anomalure gliding and an early Eocene divergence of the Z. insignis lineage. [6] These results were used to justify a taxonomic revision that erected the new rodent family Zenkerellidae in which Z. insignis is the only living species. [6]

Morphology

Photographs of a male museum specimen. Zenkerella photographs.jpg
Photographs of a male museum specimen.

The anomalures, including Z. insignis, are unique among rodents in having a set of scales on the ventral surface of the base of the tail. [6] These scales reportedly provide traction when climbing trees. [3] [4] Z. insignis is the only anomalure that lacks patagia (membranes that span between the forelimbs and hindlimbs). [3] [4] Anomalures that possess patagia are able to glide between trees. Thus, Z. insignis is unable to glide. The divergence of the Z. insignis lineage from other extant anomalures apparently occurred before the evolution of anomalure gliding. [6] Gliding is a relatively rare adaptation that has independently evolved in three lineages of extant placental mammals (anomalures, colugos, and flying squirrels). [12] Z. insignis has ashy-grey pelage and bushy black tail hair. [4] [6] Tufts of short, course, and spikey hairs are located on the lateral ankles. [4] [6] The hands and feet have four and five digits respectively. [4] [6] Pedal digit I (the first toe) is somewhat divergent. [6]

Z. insignis molars are distinct from other extant anomalures in having a continuous enamel crest that, in occlusal view, forms a full perimeter around the tooth and a single transverse crest divides the occlusal surface into two basins. [6] [9] [13] The fossilized molars of Z. wintoni and P. saharaensis also have these features and the lineage's tooth morphology is essentially unchanged since the early Oligocene. [6] [9] In mammals, dental morphology is an excellent indicator of the animal's diet; it therefore seems that the lineage has retained the same dietary niche for at least 31 million years. [6] Sole survivorship of an ancient lineage combined with the retention of morphology are characteristics which identify Z. insignis as a ‘living fossil’. [6] However, some biologists have questioned the usefulness of this popular term.

Distribution and habitat

There are no (or possibly only obscure) entries in the scientific literature that document direct observations of living Z. insignis individuals. [3] [4] [6] Although the species was first described in 1898, trapping efforts have resulted in only 14 specimens deposited in world natural history museums. [5] [6] From these specimens, the geographic distribution of Z. insignis is recorded from south Cameroon, Equatorial Guinea (including Bioko Island), southwestern Central African Republic, and Republic of Congo. [3] [5] The species is not recorded from Gabon but probably occurs there. [3] [4] Based on collection localities, Z. insignis inhabits rainforest and semi-deciduous forests. [3] [5]

Ecology

Without direct scientific observation, lifestyle and diet are largely inferred from what is known of other anomalures [3] [4] and anecdotal information gathered by interviewing local people and subsistence trappers. [5] [6] The species is probably largely arboreal [3] [4] [5] but occasional captures in ground snares indicates it sometimes comes to the ground. [5] [6] Other anomalures are largely or exclusively nocturnal and sleep in tree-hollows during the day; [3] [4] these habits may also be true for Z. insignis. [6] The species is probably herbivorous. [3] [4]

Conservation

The IUCN previously assessed the species as Data Deficient, but in 2008 this was changed to the current listing of Least Concern as the species appears to have a relatively wide distribution with extensive suitable habitat, and occurs in several protected areas. [2] However, some conservation biologists state that “This rating belies the fact that threats such as habitat loss and degradation are intense and widespread in central Africa” and “Zenkerella may be under greater threat”. [7]

Related Research Articles

<span class="mw-page-title-main">Ratite</span> Polyphyletic group of birds

A ratite is any of a group of mostly flightless birds within the infraclass Palaeognathae. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal extant ratite.

<span class="mw-page-title-main">Anomalure</span> Family of rodents

The Anomaluridae are a family of rodents found in central Africa. They are known as anomalures or scaly-tailed squirrels. The six extant species are classified into two genera.

<span class="mw-page-title-main">Pedetidae</span> Family of rodents

The Pedetidae are a family of mammals from the rodent order. The two living species, the springhares, are distributed throughout much of southern Africa and also around Kenya, Tanzania, and Uganda. Fossils have been found as far north as Turkey. Together with the anomalures and zenkerella, Pedetidae forms the suborder Anomaluromorpha. The fossil genus Parapedetes is also related.

<span class="mw-page-title-main">Long-eared flying mouse</span> Species of rodent

The long-eared flying mouse or long-eared scaly-tailed flying squirrel, is a species of flying mouse from western and central Africa. It is not actually a squirrel, nor a mouse, though it is a rodent. Not much is known about them because they are very hard to keep alive in captivity.

<span class="mw-page-title-main">Flying mouse</span> Genus of rodents

The flying mice, also known as the pygmy scaly-tails, pygmy scaly-tailed flying squirrels, or pygmy anomalures are not true mice, not true squirrels, and are not capable of true flight. These unusual rodents are essentially miniaturized versions of anomalures and are part of the same sub-Saharan African radiation of gliding mammal.

<span class="mw-page-title-main">Flying and gliding animals</span> Animals that have evolved aerial locomotion

A number of animals are capable of aerial locomotion, either by powered flight or by gliding. This trait has appeared by evolution many times, without any single common ancestor. Flight has evolved at least four times in separate animals: insects, pterosaurs, birds, and bats. Gliding has evolved on many more occasions. Usually the development is to aid canopy animals in getting from tree to tree, although there are other possibilities. Gliding, in particular, has evolved among rainforest animals, especially in the rainforests in Asia where the trees are tall and widely spaced. Several species of aquatic animals, and a few amphibians and reptiles have also evolved this gliding flight ability, typically as a means of evading predators.

<span class="mw-page-title-main">Anomaluromorpha</span> Suborder of rodents

Anomaluromorpha is a clade that unites the anomalures, springhares, and zenkerella. It has alternately been designated as either a suborder or infraorder. Most recently, Carleton & Musser 2005 recognized it as one of five suborders of rodents.

<i>Anomalurus</i> Genus of rodents

Anomalurus is the largest genus in the rodent family Anomaluridae, with four species. It is the only genus in the subfamily Anomalurinae.

<span class="mw-page-title-main">Pel's flying squirrel</span> Species of rodent

Pel's flying squirrel or Pel's scaly-tailed squirrel is a species of rodent in the family Anomaluridae. It is found in Liberia, Ivory Coast, and Ghana, where it lives in lowland tropical rainforests. It is named after Hendrik Pel.

<span class="mw-page-title-main">Dwarf scaly-tailed squirrel</span> Species of rodent

The dwarf scaly-tailed squirrel is a species of rodent in the family Anomaluridae. It is found in Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea, Gabon and Uganda. The species is nocturnal and arboreal and lives in subtropical or tropical lowland rainforest. Membranes attached to its limbs and tail enable it to glide between trees. This squirrel is currently not considered to be threatened by habitat destruction; "much of the habitat within parts of the known range of this species is relatively intact, and the species is unlikely to be experiencing any significant declines."

<span class="mw-page-title-main">Pygmy scaly-tailed flying squirrel</span> Species of rodent

The pygmy scaly-tailed flying squirrel is a species of rodent in the family Anomaluridae. It is found in Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea, and Uganda. Its natural habitat is subtropical or tropical moist lowland forests.

<span class="mw-page-title-main">Lord Derby's scaly-tailed squirrel</span> Species of rodent

Lord Derby's scaly-tailed squirrel is an anomalurid rodent native to Africa. It was named after Edward Smith-Stanley, 13th Earl of Derby.

<i>Zenkerella</i> (rodent) Genus of rodent

Zenkerella is a genus of rodent, the only member of the family Zenkerellidae. It was formerly classified in Anomaluridae until phylogenetic studies made its distinctiveness clear. While the Anomalurus of the family Anomaluridae has gliding membranes between its forelimb and hindlimb, the Zenkerella has no such adaptation. It is estimated from fossil records that this divergence might have occurred in the middle of the Eocene.

Z. insignis may refer to:

Zenkerella wintoni is in extinct species of rodent from the family Zenkerellidae. It is known from a single mandible from Songhor, Kenya dated to the Early Miocene.

References

  1. ↑ "Mindat.org". www.mindat.org. Retrieved 2021-06-13.
  2. 1 2 Hutterer, R.; Decher, J. (2017). "Zenkerella insignis". IUCN Red List of Threatened Species . 2017: e.T23204A22183548. doi: 10.2305/IUCN.UK.2017-2.RLTS.T23204A22183548.en . Retrieved 15 November 2021.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 Kingdon, J (2013). "Family Anomaluridae: Anomalures". In Happold DCD (ed.). Mammals of Africa. Volume III: rodents, hares and rabbits. London: Bloomsbury Publishing. pp. 602–617.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 Nowak, RM (1999). Walker's Mammals of the World . Baltimore: Johns Hopkins University Press. pp. 1617–1620.
  5. 1 2 3 4 5 6 7 8 Pérez del Val, J.; Juste, J.; Castroviejo, J. (1995). "A review of Zenkerekka insignis, Matschie, 1898 (Rodentia, Anomaluridae) first records in Bioko island (Equatorial Guinea)". Mammalia. 59 (3): 441–443. doi:10.1515/mamm.1995.59.3.437. hdl: 10261/49354 .
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Heritage, S.; Fernández, D.; Sallam, H. M.; Cronin, D. T.; Echube, J. M. E.; Seiffert, E. R. (2016). "Ancient phylogenetic divergence of the enigmatic African rodent Zenkerella and the origin of anomalurid gliding". PeerJ. 4: e2320. doi: 10.7717/peerj.2320 . PMC   4991859 . PMID   27602286.
  7. 1 2 Vuong, Z (2016). "On the prowl for an elusive rodent called 'the ultimate Pokémon'". USC News. Retrieved 25 August 2016.
  8. ↑ Lavocat, R (1973). Les rongeurs du Miocène d'Afrique Orientale, Miocène inférieur. Memoires et Travaux de l'Institut de Montpellier de l'Ecole Pratique des Hautes Etudes 1:1-284.
  9. 1 2 3 4 5 Coster, P.; Beard, C.; Salem, M. J.; Chaimanee, Y.; Jaeger, J. J. (2015). "New fossils from the Paleogene of central Libya illuminate the evolutionary history of endemic African anomaluroid rodents". Frontiers in Earth Science. 3: 56. Bibcode:2015FrEaS...3...56C. doi: 10.3389/feart.2015.00056 . hdl: 1808/22093 .
  10. ↑ Marivaux, L.; Adnet, S.; Benammi, M.; Tabuce, R.; Benammi, M. (2016). "Anomaluroid rodents from the earliest Oligocene of Dakhla, Morocco, reveal the long-lived and morphologically conservative pattern of the Anomaluridae and Nonanomaluridae during the Tertiary in Africa". Journal of Systematic Palaeontology. 15 (7): 1–31. doi:10.1080/14772019.2016.1206977. S2CID   88750294.
  11. ↑ Dieterlen F (2005). "Family Anomaluridae". In Wilson DE, Reeder DM (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (Third ed.). Baltimore: Johns Hopkins University Press. pp. 1532–1534.
  12. ↑ Jackson, SM; Thorington, R (2012). "Gliding Mammals: Taxonomy of Living and Extinct Species". Smithsonian Contributions to Zoology. 638 (638): 1–117. doi:10.5479/si.00810282.638.1. hdl:10088/18186.
  13. ↑ Marivaux, L.; Adaci, M.; Bensalah, M.; Rodrigues, H. G.; Hautier, L.; Mahboubi, M. H.; Mebrouk, F.; Tabuce, R.; Vianey-Liaud, M. (2011). "Zegdoumyidae (Rodentia, Mammalia), stem anomaluroid rodents from the early to middle Eocene of Algeria (Gour Lazib, Western Sahara): new dental evidence". Journal of Systematic Palaeontology. 9 (4): 563–588. doi:10.1080/14772019.2011.562555. S2CID   55989532.
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