Miocene Mammalian footprints in coprolites from Lisbon, Portugal

Abstract

For the first time, at least for the Lisbon Miocene series, uncommon ichnologic evidence has been recognized, i.e. mammalian footprints in coprolites. Three coprolites were recorded in three successive stratigraphic units, IVb and Va2 from the Lower Miocene to Vb from the early Middle Miocene. The largest, tridactyl footprint can be ascribed to a right foot of a rhinoceros. Size excludes all the rhinocerotids known from the Vb unit except Hispanotherium matritensis. A smaller coprolite (Va2 unit) shows a tridactyl, left foot impression of a perissodactyl. It is clearly too small for a rhinoceros, even for a young one. It seems to have been made by an Anchitherium Equid. The pes had a plantar pad as still found in the Mesohippus–Anchitherium lineage but not in more advanced Equids. Both tridactyl imprints may have been produced by the coprolite-makers. A large coprolite (IVb unit) that may have been produced by Brachyodus onoideus shows a few didactyl imprints. An artiodactyl trampled the dung with hoofs sliding on its surface and producing two incomplete imprints. It also trampled the dung in a more stable position, producing the best imprint, whose structure indicates it was produced by the left manus. The lack of lateral toe marks excludes suids (and Brachyodus, also because its size is too much small). It is from a small-sized ruminant, most probably a cervid, genus Procervulus. In all cases, defecation occurred on dry land, albeit in eventually or seasonally flooded areas near a river.