The Hipparion datum
Three-toed horses spread from North America across the Old World so fast they date the rocks.
- When
- —
- Duration
- 600 thousand years
- Known to
- ± 300 thousand years
- Era
- Miocene, Cenozoic
Around 11.1 million years ago, hipparionine horses cross the Bering land bridge and disperse across Eurasia and Africa within a geological instant. Because the arrival is abrupt, near-synchronous and unmistakable in the fossils, it functions as a continent-spanning time marker — one of the most useful single datums in terrestrial biostratigraphy. The dispersal coincides with major late Miocene climatic reorganisation, and the horses spread because the open habitats they needed were spreading too.