A new Lagomorph from the Late Miocene of Chad (Central Africa).

Abstract

A new species of the genus Serengetilagus Dietricht 1941, here named S. tchadensis n. sp., is described from Toros Menalla deposits, Late Miocene of Djurab Erg (North Chad, central Africa). It shows primitive features, such as a simple archaeolagine-type p3, with only two main external folds, and upper cheek teeth strongly widened with wear. Its size and skeletal features resemble S. praecapensis Dietricht 1941 from the Middle Pliocene of Laetoli (Tanzania). They differ in several cranial and dental features (choanae width, zygoma, orbits, basicranial-basifacial angle, lack of hypoflexus in P2, short and asymmetric hypoflexus in P3-M2, lack of lingual folds in p3, etc). Individual variations in S. tchadensis n. sp. approach S. praecapensis, such as an incipient anteroflexid and a forward-curved hypoflexid in some p3. The genus Serengetilagus is here assigned to the subfamily Archaeolaginae Dice 1929 and related to Hypolagus Dice 1917, namely to H. gromovi Gureev 1964 from the Late Miocene of Southern Russia. Other related species are Serengetilagus orientieuropaeus Topachevsky 1987 and primitive species of the genus Trischizolagus Radulesco & Samson 1967, such as T. maritsae De Bruijn, Dawson & Mein 1970 and T. crusafonti (Janvier & Montenat 1971). Pliocene leporids from Spain, Ukraine, Russia, Afghanistan and Mongolia have been questionably attributed to Serengetilagus or Trischizolagus, which seem synonymous for some authors. Several features are here proposed to distinguish both genera: rounded versus rhombic-shaped p3, weak versus strong lingual anteroconid - anteroflexid, and forward versus backward hypoflexid bend. Serengetilagus could have a mixed fossorial-cursorial mode of life, as can be inferred by its ecomorphological traits (combining features of hare and rabbit) and taphonomical indications. This new African archaeolagine is contemporaneous of the widespread palaeolagine Alilepus Dice 1931, recorded in the Late Miocene of Kenya. The independence of these two lineages is favoured after revision of previous hypotheses on the phylogeny of the highly diverse Mio-Pliocene peri-Tethysian leporid species.