LIFE × EVOLUTION

Before the Dinosaurs

~270 to 252 million years ago

Phanerozoic · Paleozoic · Permian

For twenty million years the large land animals were relatives of mammals: tusked dicynodont herbivores moving in herds, and gorgonopsians with sabre teeth hunting them. Whole basins in South Africa and Zambia are filled with their bones. Nearly every major group of them appears in less than ten million years, after a long stretch in which the lineage leaves no fossils at all.

Why it matters

This is the world the end-Permian extinction erased. Mammals then spent 150 million years small and nocturnal, and one could take that for their natural condition. It was not: through the whole of that earlier stretch, the same lineage had held the largest bodies on land. What left the survivors small was a catastrophe, not a rule of nature.

Dating & uncertainty

The middle Permian radiation is timed with relaxed clock models across a long ghost lineage, so the age of therapsid origins is fixed only loosely. A gorgonopsian from Mallorca, older than any specimen from Africa, points to a tropical rather than a temperate origin, which would make the Karoo record a late chapter rather than the opening one.

Sources

1. Kammerer et al. (2022), Journal of African Earth Sciences · The earliest gorgonopsians from the Karoo Basin of South Africa
2. Matamales-Andreu et al. (2024), Nature Communications · Early-middle Permian Mediterranean gorgonopsian suggests an equatorial origin of therapsids
3. Peecook et al. (2025), Journal of Vertebrate Paleontology · Successive assemblages of upper Permian vertebrates in the upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia

Earth history as one day

22:34:211 h 26 min before midnight

if Earth’s 4.54 billion years were compressed into a single day