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“Early horses, Hyracotherium, are superabundant at midlatitudes. But they don’t make it” to the Arctic.

After hiking for about an hour across the flat desert, they came across boulder-strewn hollows where they uncovered a cache of mammalian fossils, including teeth from the extinct five-toed horse Hyracotherium.

And if, for example, we were to call the Hyracotherium a Hyrax beast it would not be a name, but a description, and not a bit more intelligible.

From Hyracotherium, which is closely related to the Eocene representatives of the ancestral stocks of the other three branches of the Perissodactyla, the transition is easy to Phenacodus, the representative of the common ancestor of all the Ungulata.

The evolution of the horse through such forms as Hyracotherium, Pachynolophus, Eohippus, &c., appears to have proceeded along parallel lines in Eurasia and America, but the true horse did not arrive until later.