ABSTRACT
The origin of the bilaterian phyla is one of the classic areas of conflict between molecular dates and the fossil record. Here we examine possible sources of bias in the fossil record, and conclude that on several grounds, not least broad stratigraphic and phlyogenetic congruence, it is hard to see the Cambrian fossil record as representing anything but a broadly ‘real-time’ event. Refinements of molecular estimates of the dating of bilaterian origins have increasingly cut the gap between fossil and molecular estimates, and a rapprochement must be hoped for in the next few years. Further refinements of our understanding of this event must increasingly focus on better phylogenies, and a consideration of the ecology and biogeography of the event.
