A Late Pleistocene third molar of Hylochoerus (Suidae, Mammalia) from Rusinga Island, Kenya: paleoenvironmental implications and a note on the hypsodonty of African forest hogs

African forest hogs (genus Hylochoerus) are extant Afro-tropical suids that inhabit a variety of forest environments and thick bushlands and are predominantly herbivores. Hylochoerus likely evolved from a Pleistocene Kolpochoerus majus-like ancestor, but its recent evolutionary history is virtually unknown. Here, we describe a partial right lower third molar from the Late Pleistocene Wasiriya Beds of Rusinga Island (similar to 50-36 ka). The crowns are mesiodistally compressed in a bunolophodont fashion and arranged in columnar pillars that resemble those of extant Hylochoerus. We provide accurate data derived from computed tomography on the hypsodonty index (HI) of extant Hylochoerus and show that the Rusinga third molar crown was as tall as those of its modern counterpart (HI = 1.8-2.0). Stable carbon isotope analyses suggest that the diet of the Rusinga specimen (delta C-13 = -17.0 parts per thousand) was also like that of extant forest hogs (delta C-13 average = -17.6 parts per thousand). This extremely negative value contrasts strikingly with those of other fossil large herbivores at Rusinga (delta C-13 average = -0.7 parts per thousand.). Among the potential explanations for this anomaly, the most likely is that the Late Pleistocene paleoenvironments were more heterogeneous than previously considered and may have included closed-canopy woodland in the highlands of Rusinga.