Review of paleo-humidity parameters in fossil rodents (Mammalia): Isotopic vs. tooth morphology approach

Paleoecology of fossil rodents is frequently inferred from the dental pattern of the teeth, attributing the habitat conditions of extant rodents to fossil species with similar dental pattern. This technique is common practice and has been in use for several decades. A relatively new technique is based on the carbon and oxygen isotope composition of the incisor enamel of fossil rodents to reconstruct paleoenvironmental scenarios. We combine these two methods, studying material from two Early Miocene Spanish sections, one in the Mediterranean coastal area and one in Northcentral inland Spain. Comparison of the humidity values obtained by means of these two proxies reveals discrepancies. Therefore, we analyzed the habitat preferences, especially humidity, of extant rodents and found that dental pattern is not very reliable to reconstruct the humidity preferences of fossil rodents and this kind of interpretation has to be taken with caution. We conclude that the isotopic composition of enamel of fossil teeth is a more reliable proxy in the studied sections.