Abstract
The Somali Sengi or Somali Elephant-shrew (‘Elephantulus’ revoilii, Macroscelidea, Mammalia) has been considered a “lost species” and is primarily known from about 39 museum specimens, with no new vouchered occurrence records since the early 1970s. The scientific literature contains no data concerning living Somali Sengi individuals and the species’ current Data Deficient conservation status is attributable to an absence of modern information. Almost everything that has been published about the species is derived from anatomical examinations of historic specimens, gleaned from museum collection notes, or inferred from the known habits and ecology of other sengi taxa. Here we report new evidence that the Somali Sengi is currently extant. These data include voucher specimens, georeferenced occurrence localities, body measurements, habitat parameters, and DNA sequences. While the species is historically documented as endemic to Somalia, these new records are from the neighboring Republic of Djibouti and thus expand the Somali Sengi’s known range in the Horn of Africa. Furthermore, Djiboutian locality data near international borders suggests that the Somali Sengi is also a current inhabitant of both Somalia and Ethiopia. Criteria that inform conservation status assessments (e.g., suitable habitat contiguity and occurrence in wildlife protected areas) can be positively characterized in Djibouti and therefore bode well for the survival of the Somali Sengi species. New data also inform previously undocumented substrate and sheltering affiliations. DNA analyses indicate that the Somali Sengi is a descendant of the Macroscelidini lineage and therefore reveal that the species’ referral to the genus Elephantulus is incompatible with sengi phylogeny. This taxonomic issue is resolved by recognizing a new genus replacement and recombinant binomial that redesignates the Somali Sengi as Galegeeska revoilii(gen. nov., nov. comb.). An analysis of ancestral biogeography suggests that the Somali Sengi has inhabited the Horn of Africa for more than 5.4 million years—and the recognition of the species’ phylogenetic ancestry appends the already remarkable biogeographic story of the Macroscelidini tribe.
Galegeeska Heritage & Rayaleh 2020, new genus
Type species:Galegeeska revoilii (Hüet, 1881).
New binomial combination. The genus is currently monotypic.
Species Synonyms: Elephantulus revoilii, Elephantulus revoili,
Macroscelides revoilii
Holotype: The type specimen, MNHN ZM-MO-1881-11, is located at the National Museum of Natural History in Paris, France. See Data S5 for hypodigm voucher specimens.
Distribution: The documented geographic range includes Somalia and Djibouti. The species may also occur in other Horn of Africa countries.
Diagnosis and description: See Corbet & Hanks (1968), Hüet (1881), and elsewhere in this manuscript for full details. In brief, the Somali Sengi can be distinguished from all other macroscelidean species by a combination of traits including: the presence of a pale eye ring with a dark post-ocular mark, hair on the lower portion of the rhinarium, a tufted tail, and second upper incisors that are subequal in size to adjacent upper incisors.
Etymology: In the Somali language, the word geeska ([gey·skah], /'gāskä/) means corner or horn—as in Geeska Afrika (=Horn of Africa). This root is chosen to indicate that the species has a broader geographic range than was previously recognized. From the Ancient Greek, galê translates to weasel (Beekes, 2009) and has been widely used as a general descriptor for small mammal taxa (e.g., Galeopterus, Petrogale, Microgale). In Somali, gal (variants: gala, galay, gale) can refer to one who enters or inhabits. A direct translation of Galegeeska is “weasel of the horn”, but a Somali speaker’s interpretation could be “inhabitant of the horn”. The root gale is also chosen to honor Galen B. Rathbun (1944–2019), who devoted more than four decades of scientific inquiry to sengi biology and who hiked the Djiboutian hillsides in search of this species.
The genus-level taxonomic hierarchy for extant sengis is as follows:
Class: Mammalia Linnaeus, 1758
Supercohort: Afrotheria Stanhope et al., 1998
Order: Macroscelidea Butler, 1956
Family: Macroscelididae Bonaparte, 1838
Subfamily: Rhynchocyoninae Gill, 1872
Genus: Rhynchocyon Peters, 1847
Subfamily: Macroscelidinae Bonaparte, 1838
Tribe: Elephantulini Dumbacher, Carlen & Rathbun, 2016
Genus: Elephantulus Thomas & Schwann, 1906
Tribe: Macroscelidini Bonaparte, 1838
Genus: Macroscelides A. Smith, 1829
Genus:Petrodromus Peters, 1846
Genus: Petrosaltator Dumbacher, Carlen & Rathbun, 2016
Genus:Galegeeska Heritage & Rayaleh, 2020, new genus
Conclusion:
These new records confirm the Somali Sengi as an extant taxon and reveal a broader geographic distribution than was previously documented. Further, the species’ conservation status can now be reconsidered using modern evidence which we have discussed as positively informing assessment criteria. New data also characterizes habitat use (including substrate and sheltering affiliations)—a species attribute that has been hypothesized but never formally reported. DNA from voucher specimens have yielded a robust phylogenetic estimate that newly identifies the Somali Sengi as a descendant of the Macroscelidini lineage. The former taxonomic referral to the genus Elephantulus (and tribe Elephantulini) has been revised and the Somali Sengi species-group is now recognized as Galegeeska revoilii. Future fieldwork in the Horn of Africa should aim to further document extent of occurrence, to monitor population trends, and to study the behavioral ecology and life history of the species.
Steven Heritage, Houssein Rayaleh, Djama G. Awaleh and Galen B. Rathbun. 2020. New Records of A Lost Species and A Geographic Range Expansion for Sengis in the Horn of Africa.
PeerJ. 8:e9652. DOI:
10.7717/peerj.9652
