Pelorovis
Pelorovis is an extinct genus of African wild cattle which existed during the Pleistocene epoch. Originally believed to be a giant member of Caprinae, related to modern sheep, it is now known to be a relative of cattle and buffalos. The best known and type species is Pelorovis oldowayensis, from the Early Pleistocene of Olduvai Gorge, Tanzania, though two others, P. turkanensis and P. howelli, are currently recognised. A fourth, P. praeafricanus, may exist, or it may represent the same species as P. oldowayensis. "Pelorovis" antiquus, from the Late Pleistocene-Holocene, and "P." kaisensis, have since been moved into Syncerus, the same genus as living African buffalo.
In many respects, Pelorovis resembles the modern cattle genus, Bos, and has been compared morphologically to aurochsen. It has been suggested that they represent the same genus, in which case Pelorovis would be a junior synonym of Bos, though this has been challenged. Assuming they are distinct genera, Pelorovis may be distinguished by having an elongated face and very long, half-moon-shaped horns. It was fairly sexually dimorphic, with males having longer and slightly straighter horns, though horn length and size also differed between species. Pelorovis species grew larger as they evolved: P. howelli had a hornspan of, while adult males of P. oldowayensis had a larger hornspan of around.
Pelorovis was likely a grazer. This was particularly true of P. oldowayensis, which had a broader snout than earlier P. turkanensis, suggesting a greater specialisation for grazing. Tooth wear patterns suggest that it occasionally fed on other plants, which may point towards seasonal dietary shifts.
Taxonomy
Early history
The holotype of Pelorovis, consisting of a skull and multiple horn cores and skull pieces, was found in Olduvai Gorge, in northern German East Africa, by geologist Hans Reck. The expedition in question was the first time the locality was explored by a palaeontologist. Initially, Reck believed that he had uncovered the remains of a large member of the subfamily Caprinae, which includes modern goats and sheep. Specifically, he believed that the fossils he had uncovered represented a close relative of the latter, though one that was quite geographically isolated. The fossils were kept in Berlin, and in 1928, Reck described a new genus and species, Pelorovis oldowayensis, to accommodate them. The binomial name chosen by Reck is compounded from the Greek πέλωρος in the sense of "monstrous" or "huge and terrible" and Latin ovis, meaning "sheep".In 1991, John Michael Harris described remains uncovered as part of the Koobi Fora research project in northern Kenya. Distinguishing it from Pelorovis oldowayensis based on its smaller and more upwardly curved horns, he named it P. turkanensis. In 2004, Denis Geraads, Véra Eisenmann and Germaine Petter further divided P. turkanensis into two subspecies: P. turkanensis brachyceras, and P. turkanensis turkanensis, the former distinguished from the latter by having horn cores with a thick base that quickly taper along their length.
In 2005, Djillali Hadjouis and Mohamed Sahnouni described a third Pelorovis species based on a partial skull recovered from the Aïn Hanech Formation of Algeria. The specimen preserved the upper part of the frontals and parietals, as well as both horn cores. The new taxon was named Pelorovis howelli, after palaeontologist Clark Howell. It differed from the other two species in having smaller horn cores that were set farther apart.
In 1979, Camille Arambourg named Bos bubaloides and B. praeafricanus, both from Aïn Hanech. In 1998, Denis Geraads & Fethi Amani re-examined the remains and tentatively reassigned them to Pelorovis. Thus, P. praeafricanus is occasionally regarded as a species of Pelorovis. However, the syntype of P. praeafricanus, a metacarpal, closely resembles that of P. oldowayensis, and it may represent the same taxon.
Possible synonymy with ''Bos''
A 2007 study by Bienvenido Martínez-Navarro and colleagues of the morphology of the fossil remains came to the conclusion that Pelorovis is probably not monophyletic. These authors reclassify the early forms of the genus, P. turkanensis and P. oldowayensis, in the genus Bos. In contrast, they find that the late Pleistocene form Pelorovis antiquus seems to be a close relative of the modern African buffalo. This approach essentially subsumes the genus as a synonym of Bos, because the type species is P. oldowayensis. A number of the authors of this study reiterated their classification of the taxa Pelorovis turkanensis and P. oldowayensis in the genus Bos in another paper published 2014. Alexandre Hassanin, in 2014, followed the interpretations of Martínez-Navarro et al., pointing to previous genetics work which show that the bovid lineages which produced the modern species within the genera Bos, Bubalus and Syncerus split from each other some eight to nine million years ago, indicating that either the fossil ancestors of these species have not yet been discovered, or that they already have been found, but are taxonomically misidentified. Hassanin further pointed out that Martínez-Navarro et al. were only looking for the ancestor of Bos primigenius in their studies of African fossil bovids, and that the Asian species of Bos may have been derived from other fossil species. Lastly, Hassanin notes that if Pelorovis is reduced into synonymy due to these studies, this also implies the other Pleistocene fossil genera Leptobos and Epileptobos are synonymous with Bos.A 2018 study by Tong et al. of the Chinese fossil representation of Bos primigenius uses morphology to dispute these conclusions regarding these taxa belonging to the genus Bos, as well as if they are the ancestral line from which Bos evolved, instead hewing to the traditional interpretation that the Indian Early Pleistocene fossil species Bos acutifrons is the primordial ancestor of Bos.