Fig. 12.—Hypohippus, a forest-living
horse, rear view, showing
large lateral digits on the fore and hind feet, adapted
to prevent the animal from sinking into the soft soil.
Fig. 13.—Neohipparion, a plains-living horse with very slender limbs and lateral digits small and well raised from the ground, adapted to a dry, hard soil.
Laws of Local Adaptive
Radiation and Polyphyletic
Evolution, illustrated
by two Upper Miocene
Horses of the Plains Region
of North America. These
horses are of the same
geologic age (Upper
Miocene) and were found in
the same geographic region
(South Dakota, U.S.A.).
One is supposed to have
lived in the forests along
the stream borders, and the
other in the open plains.
(Illustrations reproduced bypermission of the AmericanMuseum of NaturalHistory, New York.)
Fig. 14.—Restoration of Hypohippus. (From a drawing by Charles R. Knight,made under the direction of Professor Osborn.)
Fig. 15.—Restoration of Neohipparion. (From a drawing by Charles R. Knight,made under the direction of Professor Osborn.)
