Tachyoryctes makooka (Tachyoryctini, Spalacidae, Rodentia) and its bearing on the phylogeny of the Tachyoryctini

摘要

The Rhizomyinae is a subfamily of myomorph rodents within the family Spalacidae. It is subdivided into two tribes: the Asian Rhizomyini and the Tachyoryctini. Even though the origin of the Tachyoryctini is to be found in Asia, they are nowadays restricted to Africa. African Tachyoryctini are known from the Late Miocene and include a single genus with five species: the recently discovered Tachyoryctes makooka, which is described in detail in this work, T. pliocaenicus, T. konjiti and the two extant T. splendens and T. macrocephalus. Their closest Asian counterparts are the Late Miocene Protachyoryctes and Eicooryctes. A cladistic analysis involving all the above-mentioned taxa was carried out. Protachyoryctes tatroti turned out to be the most basal species of the ingroup followed by the Ethiopian T. makooka. Both taxa show some primitive traits like the protosinus on the first upper molars, short but distinct mesolophids on the lower molars and the presence of the mure on the cheek teeth. T. pliocaenicus and the most derived Tachyoryctini share the synapomorphic reduction or loss of these characters. The increase in hypsodonty evidenced in this lineage is correlated with the transition from a humid to a drier climate that started at the beginning of the Pliocene.