Nesiotites


Nesiotites is an extinct genus of large red-toothed shrews belonging to the tribe Nectogalini that inhabited the Balearic Islands from the latest Miocene/Early Pliocene up until the arrival of humans on the islands during the late Holocene. It was present on Mallorca and Menorca. It represented one of only 3 native land mammals to the islands at the time of human arrival, alongside the dwarf goat-antelope Myotragus and the giant dormouse Hypnomys. The genus is closely related to the also recently extinct Corsican-Sardinian shrews belonging to the genus Asoriculus, with their closest living relatives being the Himalayan shrews of the genus ''Soriculus.''

Taxonomy

Nesiotites was originally described by Dorothea Bate in 1945, with the type species being Nesiotites hidalgo. Originally, two species from the islands of Corsica and Sardinia were included in the genus, but these are now rejected from the genus, and Nesiotites is now generally used exclusively for the Balearic species, as otherwise the genus would likely be polyphyletic.
The genus includes the chronospecies N. rafelinensis N. ponsi, N. meloussae/''N. aff. ponsi and N. hidalgo. These are largely distinguished by differences in body size, and to a lesser extent differences in the shape of the teeth, though whether dental characters are distinguishing traits between different Nesiotites species has been questioned.
Based on a mitochondrial genome from Nesiotites hidalgo, their closest living relative is the terrestrial Soriculus shrews native to the Himalayas and surrounding areas, and related to other terrestrial nectogaline shrews known from Asia, rather than to the nectogaline water shrews. A molecular clock analysis suggests that Himalayan shrews and Balearic shrews genetically diverged approximately 6.44 million years ago. Based on morphological data, it is thought that Nesiotites is closely related and likely descended from the extinct genus Asoriculus, known from the Late Miocene-Holocene of Europe and North Africa, which now includes the Corsican and Sardinian species formerly included in Nesiotites.
Position of Nesiotites'' within Nectogalini based on DNA and morphological characters after Bover et al :

Description

Members of Nesiotites exhibited a large body size compared to their likely mainland ancestor, Asoriculus gibberodon, as well to most other members of Nectogalini, an example of island gigantism. The species of the genus showed an increase in body size over time, with the estimated weight of N. ponsi being while the last species, N. hildalgo being estimated at, being exceeded in size amongst Nectogalini only by Asiatic water shrews. Most of the skull is unknown as is typical of fossil shrews, due to the thinness of many of the skull bones. The number of upper antemolars varies between three and four. The morphology of the teeth is somewhat variable.

Evolutionary history

Nesiotites originally colonised Mallorca during the Messinian stage of the Late Miocene, when during the Messinian salinity crisis the Mediterranean sea evaporated allowing animals from the Iberian Peninsula to disperse to the Balearics. Later becoming isolated on the island when the Mediterranean refilled as result of the Zanclean Flood around 5.3 million years ago, at the beginning of the Pliocene. Nesiotites later spread to Menorca during the Pliocene-Pleistocene transition, when episodes of low sea level connected the two islands. During most of its existence, it represented only one of three terrestrial mammal lineages native to the Balearic islands, alongside the giant dormouse Hypnomys and the dwarf goat-antelope Myotragus. The last Nesiotites chronospecies, N. hidalgo, probably became extinct shortly after human settlement of the Balearics, which occurred sometime prior to 2282 BC, with the youngest radiocarbon date for the species dating to approximately 3027 BC.