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

African forest hogs (genus <i>Hylochoerus</i>) are extant Afro-tropical suids that inhabit a variety of forest environments and thick bushlands and are predominantly herbivores. <i>Hylochoerus</i> likely evolved from a Pleistocene <i>Kolpochoerus majus</i>-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 (~50-36 ka). The crowns are mesiodistally compressed in a bunolophodont fashion and arranged in columnar pillars that resemble those of extant <i>Hylochoerus</i>. We provide accurate data derived from computed tomography on the hypsodonty index (HI) of extant <i>Hylochoerus</i> 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 (δ¹³C = −17.0 ‰) was also like that of extant forest hogs (δ¹³C average = −17.6 ‰). This extremely negative value contrasts strikingly with those of other fossil large herbivores at Rusinga (δ¹³C average = −0.7 ‰.). 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.