TRAGELAPHINI BLYTH, 1863

Bibi, Faysal, 2011, Tragelaphus nakuae: evolutionary change, biochronology, and turnover in the African Plio-Pleistocene, Zoological Journal of the Linnean Society 162 (3), pp. 699-711 : 700-701

TRAGELAPHINI BLYTH, 1863

TRAGELAPHUS DE BLAINVILLE, 1816

Type species: Tragelaphus scriptus (Pallas, 1766) .

Revised diagnoses for relevant fossil tragelaphin species follow.

Tragelaphus moroitu is a small tragelaphin described from the latest Miocene and earliest Pliocene deposits of the Asa Koma and Kuseralee deposits of the Middle Awash ( Haile-Selassie, Vrba & Bibi, 2009). Tragelaphus moroitu is characterized by horn cores that spiral three-quarters of a whorl (270°), are only weakly inclined (angle of ~65–70°), with three well-pronounced keels (anterior, posterolateral, posteromedial), and a cross section that is very triangular and does not change significantly throughout the course of the horn core. The horn core bases possess weak to moderate anteroposterior compression [transverse diameter of the basal horn core (DT)/anteroposterior diameter ( DAP) range = 1.05– 1.37] and, in lateral view, the proximal portion of the horn core curves posteriorly. Although of smaller size, the horns of T. moroitu are very similar in overall form to those of the living nyala ( Tragelaphus angasii ) and sitatunga ( Tragelaphus spekii ). The horn core morphology of T. moroitu is taken to represent the primitive condition from which all other tragelaphin horn forms may have derived.

Tragelaphus kyaloae is a medium-sized tragelaphin best known from the Lokochot Member at Koobi Fora ( Harris, 1991) and Kanapoi ( Harris et al., 2003). Tragelaphus kyaloae is characterized by horns cores that spiral three-quarters of a whorl (270°), are weakly inclined (~70°), and with a weak anterior keel and a triangular to quadrangular basal cross-section (particularly in the holotype specimen KNM-WT 18673). The horn core cross-section changes from regular triangular with only weak compression and three strong keels distally to quadrangular with moderate to strong anteroposterior compression at the base (basal DT/DAP range = 1.10–1.45, holotype = 1.31). The horn cores display pronounced lateral divergence proximally, strong convergence in their distal parts, and posterior curvature in lateral view.

Tragelaphus saraitu is a medium-sized tragelaphin from 3.8–3.7 Myr old deposits from Woranso-Mille in the Afar ( Geraads, Melillo & Haile-Selassie, 2009). This species is characterized by horn cores that spiral three-quarters of a whorl (270°), are weakly inclined (~70°), with triangular basal cross-section; anterior keel and posterolateral keel more prominent in distal portions of the horn core and weakening towards the base, perhaps also accompanied by change to more regular cross-section with less compression distally; moderate basal anteroposterior compression present (range = 1.06–1.36, holotype = 1.27); horn cores more or less parallel in their distal tips .