Macroevolution of Animal Body Plans: Is There Science after the Tree?

摘要

A renewed emphasis on the gaps in organization that exist between the crown-group body plans of higher-level animal taxa is a hallmark of the emerging consensus in metazoan phylogenetics. Bridging these gaps is the greatest hurdle that stands in the way of translating our knowledge of phylogeny into a renewed understanding of the macroevolution of animal body plans. Unless a good fossil record is available, there is little hope that we will be able to bridge many of these gaps empirically. We have, therefore, little choice but to resort to our more-or-less informed imagination to produce the historical narratives that are the ultimate goal of our studies of animal evolution. Only by fully engaging with the challenges of devising testable scenarios will we be able to tell where along the spectrum of science and fiction our understanding of animal body plan evolution will finally come to rest