Implicaciones etologicas y significado de la estereotipicidad de Oichnus Bromley durante el plioceno en la cuenca del bajo Guadalquivir (SO España)

Abstract

The analysis of the stereotypy in the Oichnus-type borings on Bivalvia (epi and infaunal) from different Pliocene stratigraphic horizons in the Southwestern sector of the Guadalquivir Basin, has allowed to show sorne changes about the predatory behaviour. These have an effect on two levels: on a small scale, when the changes between juvenil and mature state of the preys are considered and on a larger scale, when the environmental conditions of every stratigraphic horizons are estimated. The variability on the first case are due to internal factors to the predatory-prey system: morphology, size and ornamentation of the preys. On the second one, are related with loss or increase in external factors on system: environmental selective pressure (kind of substrate, energy, ecologic competition). Wel1 defined behaviour patterns have been revealed by differences in the stereotypy of several Oichnus-type (O. paraboloides Bromley and O. simplex Bromley). This fact establish also various trace-makers for the latter.