The History of Earth rules out microbial mat fossils being part of it.
 Microbial mats help to preserve soft-bodied fossils  by:Capturing corpses on the sticky surfaces of mats and thus preventing them from floating or drifting away
 As a result of this Cambrian substrate revolution, marine microbial mats are confined to environments in which burrowing is non-existent or negligible: very harsh environments, such as hyper-saline lagoons or brackish estuaries, which are uninhabitable for the burrowing organisms that broke up the mats; rocky "floors" which the burrowers cannot penetrate; the depths of the oceans, where burrowing activity today is at a similar level to that in the shallow coastal seas before the revolution

