Stepping into Oligocene. A reassessment of the early Oligocene mammal tracks from Saignon (SE France)

Abstract

ABSTRACT The Saignon ichnosite, located in the Apt syncline, yielded a high density of footprints with hundreds of mammal tracks preserved. It was discovered and first studied in the 1970s, and never re-examined since. Here we present a new analysis of the ichnosite with updates to ichnotaxonomy. The surface of the limestone bed bearing the prints was digitised by aerial photogrammetry (UAV). Best preserved tracks and trackways were digitised by short-range photogrammetric techniques. 3D data served as the basis for all measurements, including precise depth measurements. Of the hundreds of tracks present, this study focuses on the 20 best-preserved perissodactyl trackways. A review of the large perissodactyl morphotype is provided and Rhinoceripeda voconcense comb. nov. is defined. We also present possible evidence of social behaviour in early rhinocerotids. Based on fewer tracks a second smaller perissodactyl ichnotaxon, Lophiopus isp. is identified. Artiodactyl prints are attributed, when possible, to Bifidipes velox. The Saignon tracksite, dated as early Rupelian (MP21), is at an important faunal turnover, following the Grande Coupure. Its ichnofauna is characteristic of a post-Grande Coupure fauna with the presence of newcomer rhinocerotids that reached Europe from Asia and the persistence of endemic pre-Grande Coupure palaeotheriids.