The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records
The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records
Unraveling the timing of the metazoan radiation is crucial for elucidating the macroevolutionary processes associated with the Cambrian explosion. Because estimates of metazoan divergence times derived from molecular clocks range from quite shallow (Ediacaran) to very deep (Mesoproterozoic), it has been difficult to ascertain whether there is concordance or quite dramatic discordance between the genetic and geologic fossil records. Here, using a range of molecular clock methods, we show that the major pulse of metazoan divergence times was during the Ediacaran, consistent with a synoptic reading of the Ediacaran macrobiota. These estimates are robust to changes in priors, and are returned with or without the inclusion of a palaeontologically-derived maximal calibration point. The two historical records of life both suggest, therefore, that although the cradle of Metazoa lies in the Cryogenian, and despite the explosion of ecology that occurs in the Cambrian, it is the emergence of bilaterian taxa in the Ediacaran that sets the tempo and mode of macroevolution for the remainder of geologic time.
Keywords: molecular clock, Cambrian explosion, fossil calibration, Ediacaran
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