Robustostrongylus aferensis gen. nov. et sp. nov. (Nematoda: Trichostrongyloidea) in kob (Kobus kob) and hartebeest (Alcelaphus buselaphus jacksoni) (Artiodactyla) from sub-Saharan Africa, with further ruminations on the Ostertagiinae.

Abomasal nematodes (Ostertagiinae: Trichostrongyloidea), representing a previously unrecognized genus and species, were discovered in kob (Kobus kob) and kongoni (hartebeest) (Alcelaphus buselaphus jacksoni) from Uganda during surveys of ungulate parasites in the 1960s. Robustostrongylus aferensis gen. nov. et sp. nov. is characterized by a ventriculus-like, bilobed valve at the junction of the esophagus and intestine, a synlophe with unusually robust ridges, cervical papillae and excretory pore situated posterior to the mid-length of the esophagus, a unique body form and large diameter in males and females, a relatively anterior position for the vulva, and strongly convoluted and spiraled ovarian tracks in females. Bursal structure is 2-1-2, with subequal Rays 2/3, strongly reduced and robust Rays 8, and relatively narrow Rays 9/10 contained within a reduced, laterally inflated dorsal lobe. Spicules are filamentous and tripartite; the gubernaculum is cryptic, alate, and heart-shaped in the anterior. Robustostrongylus aferensis, with narrow filamentous spicules that trifurcate distally near 80%, paired arcuate "0" papillae that terminate in bulbous expansions, and a reduced dorsal lobe and ray most closely resembles species of Longistrongylus. A suite of unique characters, consistent in males and females, however, unequivocally distinguishes specimens of R. aferensis from all ostertagiines with either a 2-1-2 or 2-2-1 bursal pattern. Among 15 genera of the Ostertagiinae in the global fauna, 5 are entirely limited in distribution to Africa, including Africanastrongylus, Hamulonema, Longistrongylus, Pseudomarshallagia, and Robustostrongylus gen. nov.; species among 5 additional genera, including Cervicaprastrongylus, Hyostrongylus, Marshallagia, Ostertagia, and Teladorsagia, also occur in Africa, but they are represented as mosaics, with diversity centered in Eurasia or the Holarctic.