Abstract

ROS, Sonia  and  DE RENZI, Miquel. Preservation biases, rates of evolution and coherence of databases: Bivalvia as a study case. Ameghiniana [online]. 2005, vol.42, n.3, pp.549-558. ISSN 1851-8044.

Several hypotheses about the influence of preservation on Bivalvia rates of evolution estimates (marine and freshwater families) were tested in a previous paper. However, the database used for those tests had a patchy quality and our results were provisional. Now an improved database dealing with only marine families has been used in order to test again those hypotheses. We removed freshwater families from the early database and we test the statistical hypotheses on these two data sources. Diversification patterns remain stable in general with these different databases; however, only the improved database shows the mass extinction at the end of the Triassic times. Statistical conclusions in the previous paper are generally confirmed in the present study. Since the presence of taxa having shell biominerals with different stability (aragonite or calcite) is not independent from geologic time (as expression of the fossil record rarefaction), the estimates of rates of evolution will be biased by these two factors. The influence of the mode of life, however, has been reinterpreted since it is mainly associated with mineralogical compositions. As a consequence, the mode of life does not influence preservation. In addition, age-sea character (aragonitic or calcitic seas) has significantly no influence on preferential preservation of the corresponding CO3Ca polymorph. Some significant statistical results are better interpreted in evolutionary terms.

Keywords : Databases; Fossil record; Preservation biases; Bivalves; Rates of evolution.