Integrative approaches to fossil cephalopod macroevolution

Cephalopods are among the most iconic taxonomic groups for palaeontological research due to their excellent fossil record and high evolutionary rates. However, despite their historical relevance, phylogenetic studies have been lagging behind when compared to other fossil groups. Only recent years have seen an increase in these studies, with the application of modern quantitative methods such as Bayesian inference and particularly the fossilised birth-death model. This has allowed a clearer understanding of the evolutionary history of different groups of fossil cephalopods. Building upon this, it is also necessary to expand research efforts into novel, as well as traditional directions. For example, comparative phylogenetic tools allow to target specific characters for ancestral state reconstructions or their rate of changes across the tree. This can be used for geochemical proxy data, allowing to link population-level palaeoenvironmental conditions with macroevolutionary patterns, for which the term “phylogeochemistry” was recently established. Other studies have provided new insights into biomineralization strategies, microstructures and chemical composition of fossil cephalopods, as well as improved knowledge on the 3D morphology of internal shell structures. Last but not least, core taxonomic work remains crucial, as it forms the basis of palaeobiological research, but many uncertainties and problems persist. All previous aspects provide information that can be fed back into morphological character matrices or further explore cephalopod macroevolutionary patterns through downstream analyses. In conclusion, fossil cephalopods can serve as an excellent example how diverse tools allow for an integrative perspective on the evolution and palaeobiology of a clade.