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On the physical side it includes a very considerable rise of the land over the greater part of the globe, and the formation of lofty chains of mountains; on the botanical side it means the reduction of the rich Mesozoic flora to a relatively insignificant population, and the appearance and triumphant spread of the flowering plants, on the zoological side it witnesses the complete extinction of the Ammonites, Deinosaurs, and Pterosaurs, an immense reduction of the reptile world generally, and a victorious expansion of the higher insects, birds, and mammals; on the climatic side it provides the first definite evidence of cold zones of the earth and cold seasons of the year, and seems to represent a long, if irregular, period of comparative cold.
The chronicle of the later Cretaceous is a story of devastation. The reduction of the cyeads is insignificant beside the reduction or annihilation of the great animals of the Mesozoic world. The skeletons of the Deinosaurs become fewer and fewer as we ascend the upper Cretaceous strata. The Ichthyosaurs and Plesiosaurs vanish from the waters.
On the other hand, a branch of the vegetarian Ornithopods developed heavy armour, for defence against the carnivores, and became, under the burden of its weight, the quadrupedal and monstrous Stegosauria and Ceratopsia. Taking this instructive general view of the spread of the Deinosaurs as the best interpretation of the material we have, we may now glance at each of the orders in succession.
It will be remembered that the last of the Deinosaurs and the Ammonites also exhibited some remarkable developments in their last days. These facts have suggested to some writers the idea that expiring races pass through a death-agony, and seem to die a natural death of old age like individuals.
It had two pairs of paddles so that the name of sea-serpent is very imperfectly applicable and four rows of formidable teeth on the roof of its mouth. Like the Deinosaurs and Pterosaurs, the order was doomed to be entirely extinguished after a brief supremacy in its environment.
Indeed when we consider the extraordinary compactness and rotundity of the modern cetaceans, as compared with the tall limbs and straggling skeleton of the huge Jurassic deinosaurs, I am inclined to believe that the tonnage of a decent modern rorqual must positively exceed that of the gigantic Atlantosaurus, the great lizard of the west, in propria persona.
With the dawn of the tertiary period, the reign of the reptiles begins to wane, and the reign of the mammals to set in at last in real earnest. In place of the ichthyosaurs we get the huge cetaceans; in place of the deinosaurs we get the mammoth and the mastodon; in place of the dominant reptile groups we get the first precursors of man himself.
They were, however, sluggish and stupid monsters, with smaller brains even than the Sauropods. Such, in broad outline, was the singular and powerful family of the Mesozoic Deinosaurs.
We have seen that there were leaping reptiles with hollow bones, and although the intermediate forms are missing, there is little doubt that the Pterosaur developed from one or more of these leaping Deinosaurs.
New Zealand seems to have been cut off from the southern continent at the close of the Permian or beginning of the Triassic, and so preserved for us that very interesting relic of Permian life. From some primitive level of this group, it is generally believed, the great Deinosaurs arose.
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