By about 25–20 million years ago, grass-rich habitats were expanding in several regions, with different regional histories. Many modern tropical C4 grasslands spread much later, especially around 8–3 million years ago. Climate, fire and grazing interacted, while herbivore adaptations did not always appear at the same time as open grasslands.
Annual surface temperature from CESM (T): a model estimate, not a direct observation of the past.
0 Ma: pre-industrial climate/CO₂; modern sea-level and O₂ references.
Glacial-interglacial cycles with 120m+ sea level swings. Homo sapiens spread from Africa across the globe, and most megafauna went extinct.
Annual model means · 0 Ma: pre-industrial
Mapped sample / window records · not abundance
0–2.5 Ma
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API records whose numeric ages miss the queried window are excluded from the map and counts, with exclusions retained in provenance.
Plate boundaries are a separate model comparison. Their reference frame differs from PALEOMAP terrain and coordinates; coastlines may not align.
· 0 Ma
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