THE LIFE OF MAMMALS 
beginning; but whether or not they were covered with horny sheaths is 
not known. The various forms have been named Dinoceras, Tinoceras, 
Loxolophodon, Uintatherium, etc. These amblypods became extinct at 
the close of the Eocene, and the last ones, though greatly superior in bulk 
and armament, had smaller and less useful brains than had their earlier 
forbears. The group degenerated and ended in failure — the machine 
became too big and unwieldy for the engineer in charge. 
Another primitive ungulate suborder, Ancylopoda, widespread 
in Miocene and earlier times, contained large beasts shaped 
Ancylo- somewhat like hyenas, and having curiously huge- 
pees: clawed feet and other features which make their 
true place undeterminable as yet. The most typical ones 
are Chalicotherium and Macrotherium.** The Typotheria 
and Toxodontia are other extinct primitive suborders some- 
what approaching the Elephants (Proboscidea), and a part 
of that amazing early Tertiary fauna of the Argentine pampas 
disclosed by the labors of Lydekker, Ameghino, and Scott. 
Toxodon was a prominent representative genus of a group of 
great rhinoceroslike, marsh-loving, hoofed creatures such as 
the nesodons (yet some were smaller), with massive heads and 
high hindquarters, having in much of their structure a most 
curious resemblance to rodents. Some of them were armed 
with self-sharpening tushes like a huge boar. 
None of the foregoing seem to have been successes, so to 
speak; that is, they were unable to change with the gradually 
altering conditions of climate and vegetation as time advanced, 
and were crowded out by the more adaptable progenitors of 
modern hoofed mammals. 
All existing ungulates except the elephants and conies fall 
Ungulate Within one of two suborders, according to the struc- 
Distinevions ure ef their fect, namely : — 
I. Artiodactyla — even-toed, or split-hoofed ungulates. 
I. Perissodactyla — odd-toed, or solid-hoofed ungulates. 
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