Hippopotamus gorgops

The species was described by German scientist Wilhelm Otto Dietrich in 1928.[2] It is closely related and possibly ancestral to the European species Hippopotamus antiquus.[3]

Hippopotamus gorgops is known from remains found across Northern and Eastern Africa, spanning from the Late Pliocene-Early Pleistocene boundary to the early Middle Pleistocene.[1] Remains assigned to H. gorgops alongside the species H. behemoth are known from the Ubeidiya locality in Israel, dating to approximately 1.6 million years ago, with some authors suggesting that H. behemoth is actually a synonym of H. gorgops, given their similar morphology.[4][5]

Life restoration showing the raised eye sockets

H. gorgops grew substantially larger than the living hippopotamus (H. amphibius),[6] with an estimated body mass of over 4,000 kilograms (8,800 lb).[7] In comparison to H. amphibius, the orbits and nasal openings are elevated higher above the rest of the skull, with the temporal fossa being shorter, resulting in the distance between the orbits and occiput being shorter. This likely meant a more forward attachment of the temporal muscles.[1] The nuchal and sagittal crests were also proportionally taller, and the palate was elongate.[8] In life H. gorgops would have likely greatly resembled H. amphibius.[1]

Isotopic analysis of specimens from the Lake Turkana Basin suggests a high consumption of C4 plants.[9] For specimens from Olduvai Gorge in Tanzania, dental microwear suggests a mixed feeding diet (including both browse and grass), while mesowear suggests a largely grazing diet.[10] The elevated orbits have led to suggestions of a more aquatic lifestyle than H. amphibius,[11] though its robust limbs indicate that it was probably capable of moving efficiently on land, like H. amphibius.[8]

Remains with cut or fracture marks from sites across Africa from the Early Pleistocene indicate that H. gorgops was butchered by archaic humans.[12][13][14] These include El-Kherba in Algeria, dating to around 1.8 million years ago (mya),[14] Kilombe caldera in Kenya, dating to around 1.76 mya,[13] and the Buia site in Eritrea dating to the late Early Pleistocene,[12] around 1 mya.[8] Often at these sites tools from the Oldowan industry are present.[13][14] At Kilombe and Buia, it is unclear whether the hippos were hunted or scavenged.[12][13] It is unlikely that healthy adult individuals were hunted, as with living hippopotamuses, they were likely dangerous.[1]

• Petronio, C. (1995): Note on the taxonomy of Pleistocene hippopotamuses. Ibex 3: 53–55. PDF fulltext