TRIASSIC AND CENOZOIC PALAEOBIOGEOGRAPHY: TWO CASE STUDIES IN QUANTITATIVE MODELLING USING IDL®

Abstract

This work presents two examples of palaeobiogeographic reconstruction using the Interactive Data Language® (IDL). Although this meta-language is devoted to geoscientists and offers an array of easily usable tools, few palaeontologists actually use it. Our purpose is to illustrate how the IDL can be used to generate clear and direct visualizations of simulation results and interpolation methods for personal Geographic Information Systems (GIS). The first example is a paleogeographic simulation of the biodiversity evolution of planktonic species (and especially ammonoids) in the Early Triassic. Principal results of this global scale simulation are that the formation of a marine latitudinal gradient of species richness depends on the shape and magnitude of the Sea Surface Temperature (SST) gradient, and the geographic location of the group’s ancestor. Thus, the recovery pattern of Early Triassic ammonoids species richness can be simulated and explained by a general increasing trend in steepness of the SST gradient. The second example describes a custom-designed GIS for large European Neogene continental mammals. Species richness and ecomorphologic parameters are interpolated, monitored in several ways, and discussed. Comparisons with the presentday distribution of large European mammals are also drawn and allow us to recognize that a broad North/South aridity gradient already existed by the Late Miocene with more open environments in Southern Europe.