window". It seems that the cause of this may have been ecological, at least in the root cause; a post-Cambrian changes in the amount of bioturbation in deeper-water low oxygen environments increased sedimentary porosity and thus enhanced microbial activity and accelerated rates of decay. These higher rates of decay after the Cambrian meant that many soft bodied organisms were destroyed before the opportunity for preservation arose. See also Taphonomy Notes References Paleobiology Evolutionary biology