James D. Schiffbauer¹, John Warren Huntley¹, Gretchen R. O’Neil¹**, Simon A.F. Darroch², Marc Laflamme³, Yaoping Cai⁴

1 Dept. of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA
2 Dept. of Earth and Environmental Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
3 Dept. of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
4 State Key Laboratory of Continental Dynamics and Dept. of Geology, Northwest University, Xi’an, 710069, China

Abstract

As signposted by the fossil record, the early Cambrian period chronicles the appearance and evolutionary diversification of most animal phyla in a geologically rapid event, traditionally termed the Cambrian Explosion. The uniqueness of this event pleads for a cause, and over the years, numerous biotic and abiotic factors have been offered as possible triggers. Many such explanations, however, either fail to correspond in time or do not provide a functional mechanism to explain the evolutionary pattern of animal diversification. We support the notion that a series of requisite biotic and abiotic events ushered in the Cambrian Explosion, wherein each event was necessary for the implementation of later events but did not guarantee their occurrence. The evolution of the terminal Ediacaran vermiform fauna was integral in the construction of the Eltonian pyramid, fostered an escalation of ecosystem engineering and macropredation, and represented a turning point in benthic ecosystems from those governed primarily by competition for space and resources to those also shaped by these novel pressures.

**Now at North Dakota State University, Dept. of Geosciences, Stevens Hall, 1340 Bolley Drive #201, Fargo, North Dakota 58102, USA.

Manuscript received 24 Sept. 2015; accepted 16 May 2016

doi: 10.1130/GSATG265A.1