Late Palaeocene – Recent
Their digestive system is more basic than the even-toed ungulates. A key difference between the two is that odd-toed ungulates digest plant cellulose in their intestines rather than in one or more stomach chambers as the even-toed ungulates do.
Horses, for example, get much less nutrition out of grass than bovines do. This has the consequence that horses have to stop and feed more often, which in turn makes them more liable to predators. However, horses are very well-adapted for running, more so than many oxen or other Artiodactyls.
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- Ronald M. Nowak: Walker's Mammals of the World. 6th edition. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9