Evolution of dietary preferences of the Lophiodontidae (Mammalia, Perissodactyla) from Southern France

During the Eocene, the Lophiodontidae experienced an increase in body mass and a tendency towards the molarisation of the premolars, two phenomena often related with dietary changes. Although being amongst the largest herbivores of the European landmass at that time, the ecology of this successful perissodactyl family has rarely been investigated. This work is the first to take interest in the temporal evolution of dietary preferences of lophiodontids using enamel microstructure, dental mesowear and microwear (DMTA), in relation to body mass. We studied the Lophiodontidae (188 specimens) from seven Southern France localities dated from the early Ypresian (Mammal Palaeogene levels ]MP7–8 + 9[ interval, Palette), middle Ypresian (∼MP8 + 9, La Borie, Sainte-Eulalie), late Ypresian (∼MP10 Naples 2; ]MP10–11[interval, Aumelas), Lutetian (?MP11–12, Saint-Martin-de-Londres) and late Bartonian (MP16, Robiac; Last Appearance Datum of the family). Regarding enamel microstructure only Lophiaspis maurettei from Palette can be discriminated by its Schmelzmuster, with a large proportion of inner radial enamel, low decussation and straight Hunter-Schreger bands. The mesowear of the three oldest and smallest lophiodontids (85–350 kg) suggests similar browsing preferences, while the DMTA and microstructure exclude the consumption of abrasive and hard items. All proxies indicate tough foliage browsing, contrasting with the traditional view of all stem perissodactyls being frugivorous. Our results suggest that the younger and giant-sized Lophiodon lautricense (∼ 2300 kg) consumed more abrasive and harder items. Relative reduction of enamel thickness and increase in molarisation appears as a tentative dietary adaptation prior to the family extinction in relation with the MECO event.