This backdrop shows the Paleozoic: a shallow reef and a land surface going from bare ground to forest, composed from nine published results, more than any other backdrop.
Backdrop representing a shallow reef and a land surface passing from bare ground to forest cover. Nine published results govern the composition, more than for any other backdrop on the timeline.
What the evidence shows
The reef appears because the Devonian carried the largest metazoan reef ecosystem in the history of the Earth. The land is bare in the earlier part because Cambrian landscapes were dominated by braided rivers with mobile channels: the argument is sedimentological and not botanical, the absence of roots to hold the banks leaving watercourses to wander. Between 419 and 393 million years, the vegetation is low and treeless, trees not yet existing in the Early Devonian. Each of these propositions proceeds from a publication, and the composition follows all nine.
Bounds and conventions
This is the most constrained backdrop on the timeline, and nonetheless a composite: a Devonian reef, a bare Cambrian plain and a Carboniferous forest never coexisted. What is depicted is a succession of scenes varying with display scale and not an observable landscape.