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Updated: May 3, 2025
But the Cheiroptera are extreme modifications of the Insectivora, just as the Cetacea are extreme modifications of the Carnivorous type; and therefore it is to my mind incredible that monodelphous Insectivora and Carnivora should not have been abundantly developed, along with Ungulata, in the Mesozoic epoch.
Among the twelve or fourteen species of Mammalia which are said to have been found in the Purbecks, not one is a member of the orders Cheiroptera, Rodentia, Ungulata, or Carnivora, which are so well represented in the Tertiaries. No Insectivora are certainly known, nor any opossum-like Marsupials.
And at that point the separation is insuperable. Certain forms of Carnivora and Ungulata seem to be for ever apart not only the two great orders, but even subdivisions within them. Reptiles and birds, on the other hand, unlike as they at first sight seem, have no type line drawn to separate them; that, at least, is one of the more recent conclusions of biological science.
Within the last few years this has been done fully in the case of the horse, less completely in the case of the other principal types of the ungulata and of the carnivora; and all these investigations tend to one general result, namely, that, in any given series, the successive members of that series present a gradually increasing specialisation of structure.
With the case of the Horses before us, justifying a belief in the production of new animal forms by modification of old ones, I see no escape from the necessity of seeking for these ancestors of the Ungulata beyond the limits of the Tertiary formations. I could as soon admit special creation, at once, as suppose that the Perissodactyles and Artiodactyles had no five-toed ancestors.
M. Gaudry has arranged the species of Hyoenidoe, Proboscidea, Rhinocerotidoe, and Equidoe in their order of filiation from their earliest appearance in the Miocene epoch to the present time, and Professor Rütimeyer has drawn up similar schemes for the Oxen and other Ungulata with what, I am disposed to think, is a fair and probable approximation to the order of nature.
And many other characters are found to go with this obvious one. Even the very earliest Ungulata show this distinction, which is completely developed and marked even in the Eocene palæotherium and anoplotherium found in Paris by Cuvier. Now, the macrauchenia, from the first relics of it which were found, was thought to belong, as has been said, to the even-toed division.
The same moral is inculcated by the study of every other order of Tertiary monodelphous Mammalia. Each of these orders is represented in the Miocene epoch: the Eocene formation, as I have already said, contains Cheiroptera, Insectivora, Rodentia, Ungulata, Carnivora, and Cetacea.
It can thus obtain food beyond the reach of the other Ungulata or hoofed animals inhabiting the same country; and this must be a great advantage to it during dearths. The Niata cattle in South America show us how small a difference in structure may make, during such periods, a great difference in preserving an animal's life.
The zoologist classifies them under many heads. The field mouse and rabbits are rodentia, the deer ungulata, the kangaroos marsupialia. In my museum they are all one family, and their labels are their ears. In these days of international conferences, parliaments of religion, pan-everything-in-turn councils, might we not arrange for a great catholic congress of distinguished ears?
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