First insights into the life history of the early Miocene deer Procervulus ginsburgi from Spain.

The small-sized cervid Procervulus is considered as the most basal member of the Cervidae and one of the earliest ruminants bearing antler-like appendages. The Iberian Miocene record of this stem-cervid is extensively documented and largely overlaps with the Miocene Climatic Optimum (MCO), a transient period of global warming of particular interest when comparing present and near future conditions. Despite receiving a substantial amount of attention, histological studies on Procervulus are very scarce and only limited to postcranial remains of Procervulus praelucidus from Germany (MN3). Here we focus for the first time on the dental histology of Procervulus ginsburgi from the Early Miocene Iberian site of Artesilla (MN4, 16.49 Ma), and examine its daily enamel secretion rate (DSR), enamel extension rate (EER) and crown formation time (CFT). Results reveal a brief CTF and high DSR and EER for P. ginsburgi and suggest a fast development at least early in its ontogeny. In addition, the pronounced growth rate of P. ginsburgi emerges as higher than that of the roe deer C. capreolus-documented as an r-strategist and here examined as a possible extant analog. Overall, our findings point toward a fast life history strategy for P. ginsburgi, which unexpectedly contrasts with that of the 2 million-year-older P. praelucidus from Wintershof-West, with a marked slower growth and maturation. When these results are analyzed together with other evidence, the somewhat drier and more open conditions of Artesilla as a result of the effects of the MCO seem to be the explanation for the different life history and ecology between these Procervulus species. More generally, this study illustrates that life histories within a single genus evolve in response not only to internal constraints but also to the environments, as predicted by the Life History Theory.