The largest land mammal ever imagined



The Oligocene giant rhinocerotoid Indricotherium transouralicum (= Baluchitherium grangeri), ‘the largest mammal that ever lived,’ was smaller than is generally believed. Over 90 estimates based on head-and-body length, skull size, molar length and proximal limb bone diameters agree well on a mean mass estimate of about 11 tonnes (t) rather than the 20–30 t given by most texts. A maximum mass estimate between 15 and 20 t seems probable. Marked sexual dimorphism is possible but the material is insufficient to assess the problem properly. The single source of the inflated, widely cited mass estimates seems to be the famous Granger-Gregory-Ziska reconstruction from 1935–36, which was itself inflated by arbitrary, isometric scaling up of individual elements ‘to a hypothetical maximum size’. Paraceralherium bugtiense and P. prohorovi seem to have been somewhat smaller than I. transouralicum. The largest indricotheres were similar in size to the largest fossil proboscideans, and extend the known size range of terrestrial mammals marginally if at all.