Named By: Richard Owen - 1869.
Classification: Chordata, Mammalia, Perissodactyla, Equidae.
Species: H. principale, H. saldiasi.
Size: 1.4 meters high at the shoulders.
Known locations: Across South America.
Time period: Gelasian of the Pliestocene through to early Holocene.
Fossil representation: Multiple specimens.
is one of the first known horses to actually enter South America, but
interestingly while it has been regarded as being directly descended
from primitive forms such as Pliohippus,
more modern analysis
actually draws a link to the Equidae, the group that includes modern
One thing that makes Hippidion stand out from its North American relatives is the delicately domed nasal bone which likely allowed for an enlarged nasal area. This has been suggested as allowing for an increased sense of smell, although this would be a very curious adaptation for a herbivore to make, especially for a grazing animal. It is more likely that this enlarged nasal system was a climatic adaptation since Hippidion would have been living in ecosystems where the air was both cold and dry. By passing the air through a set of enlarged and possibly more complex air passages before reaching the lungs, Hippidion could beat the cooling effects of the chill air as well as significantly reduce the amount of moisture lost through respiration. With the lungs protected from drying out, Hippidion would then avoid having to deal with the ailments associated with long term exposure to dry air.
Hippidion is estimated to have died out at some point around the last ten thousand years, a time that saw much of the other South American megafauna disappear. This disappearance coincides with the arrival of the first people in South America and hunting may have been a significant factor in the decline of the South American megafauna at this time, although perhaps not the single root cause of this mass extinction. The next wave of horses to colonise South America would not happen till the sixteenth century when they were brought over by European explorers.