The hippo's tale: How the anatomy and physiology of Late Neogene Hexaprotodon shed light on Late Neogene environmental change

Modern hippopotamuses are strongly dependent on permanent water because of the structure and properties of their skin, and because they forage on vegetation located close to watercourses. In the fossil record of Asia, the disappearance of hippopotamids (best represented by Hexaprotodon sivalensis ) during the late Neogene and Pleistocene was due to a dramatic increase in seasonal patterns of rainfall and river flow, which would have resulted in many river systems being dry for months of the year. The lack of permanent water resulted in the disappearance of He. sivalensis from Asia. Heightened seasonality of rainfall resulted from an intensification of the winter and summer monsoons during the period between 3.6 and 2.6 Ma. Because of the exquisite sensitivity of hippopotamuses to the availability of permanent water, well-established dates for the last appearance of He. sivalensis in Asian fossil sequences can be used as direct indicators of the onset of highly seasonal patterns of rainfall and river flow.