Reconstructed setting· The columns of time
Cenozoic world
66 Ma → Today
Closed woodland that opens into grassland partway through, with trees left standing among the grass. The opening has a date, and the trees that remain are what the evidence insists on.
What the evidence shows
Grassland ecosystems assembled in stages rather than arriving whole: open-habitat grasses appear only in the Paleogene, and the habitats they dominate spread later still, which is why the backdrop is closed woodland in its older half. Open grassland is drawn from the Neogene onward, that is from 23 million years, following the spread of grass-dominated habitats. Trees remain scattered through it rather than disappearing, because the spread of grasses did not clear the land: it changed the proportions, which is a different claim and the one the evidence supports.
Bounds and conventions
A single scene for the 66 million years in which the modern world assembles. The transition it draws is real and dated, but it happened at different times on different continents, and the backdrop shows one schedule where there were several.