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Updated: May 28, 2025
Most of them fall into two large orders: the Condylarthra, the ancestral herbivores from which we shall find our horses, oxen, deer, elephants, and hogs gradually issuing, and the Creodonta, the patriarchal carnivores, which will give birth to our lions and tigers, wolves and foxes, and their various cousins.
From the description of the Tertiary world which we have seen in the last chapter we understand the rapid evolution of the herbivorous Condylarthra.
They are then barely distinguishable from the Condylarthra and Creodonta, and seem only recently to have issued from a common ancestor with those groups. In the course of the Tertiary we find them especially in South America, which was cut off from the North and its invading Carnivores during the Eocene and Miocene developed into large sloths, armadilloes, and anteaters.
The clumsy early Condylarthra failed to meet the tests, and perished; the other branches of the race were more plastic, and, under the pressure of a formidable enemy, were gradually moulded into the horse, the deer, the ox, the antelope, and the elephant. We can follow the evolution of our mammals of this branch most easily by studying the modification of the feet and limbs.
The Condylarthra seem to have gone out of existence before the time of the middle Eocene, but before this they had become separated into the two great divisions of odd-toed and even-toed ungulates, into which all truly hoofed beasts now living fall.
In the opinion of many palaeontologists, the ancestors of the present hoofed beasts, or ungulates, were contained among these Condylarthra, as they were named by Prof. Cope.
The extinction of these races of the early Condylarthra, and the survival of those races whose descendants share the earth with us to-day, are quite intelligible. The hand of natural selection lay heavy on the Tertiary herbivores.
Even to an uncritical eye, the differences between ungulates and carnivores of to-day are many and obvious, but as we trace them back into the past we follow on converging lines, and in our search for the prototypes of the carnivora we are led to the Creodonta, contemporary with Condylarthra, which we have seen giving origin to hoofed beasts, but outlasting them into the succeeding age.
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