Changes in Western European Rhinocerotidae related to climatic variations

The good record of Spanish Neogene Rhinocerotidae is used as the base of the study of their evolutionary patterns and their correlation with climatic changes. The sample has a temporal range from Lower Miocene to Lower Pliocene. From a taxonomical point of view, 15 species (and three indeterminate forms) of five main groups of Rhinocerotidae have been considered. General diversity and first and last records of the species have been signaled for each stage or biozone. Other features here analyzed are relative body size and weight and the gracility index. Rhinocerotid diversity in Spain varies through the Miocene, with a maximum of seven species in the Lower Aragonian falling down to one during the Middle Aragonian. Afterwards three or four species are present until the Upper Turolian and Alfambrian when a new minimal representation is reached. A general trend to size increase is established with an interesting change in the minimal values of each biozone at MN9. This change is supposed to represent the end of the small rhinos that were dominant before. Gracility indexes show a similar trend for all metapodials. There is a slight tendency towards robustness related to size increase, but some changes in gracility within the same sizes are also observed. Turnovers in rhinocerotid associations are here related to changes in environmental conditions. Small and gregarious species disappear in Upper Vallesian, and only large, solitary and more scarce forms remain later on.