Equidae in the Pliocene
Quagga, member of the genus Equus (left),
Equus foelimb (right, modified from McFadden 1992)
The genus
Equus appeared in the Pliocene approximately 4 million years ago
(Hunt 1995). The land bridges that had recently formed allowed Equus
to migrate from North America to Asia and South America approximately 3 million
years ago (MacFadden 1994), and to replace the South American equids and
drive them to extinction (Clabby 1976). This was also when Equus
moved into the warmer climates of Africa, eventually resulting in the evolution
of the modern zebras seen today (Hunt 1995). By the end of the Pliocene,
Equus was the only surviving genus of the family in the northern
hemisphere (MacFadden 1994).
