Alfred Russel Wallace

“ If to these two causes we add the difficulty of obtaining sufficient food for such large animals, and perhaps the injurious effects of changes of climate, we shall not find it difficult to understand how such a vast physical revolution as the Glacial epoch, with its attendant phenomena of elevations and subsidences, icy winds, and sudden floods by the bursting of lake barriers, might have led to the total extinction of a vast number of the most bulky forms of mammalia, while the less bulky were able to survive, either by greater hardiness of constitution or by becoming more or less modified. ”

“ The remains of land and fresh-water shells are not much more frequent than those of insects. Like them, too, their forms are very stable, continuing unchanged through several geological periods. In the Pliocene and Miocene formations, most of the shells are very similar to living species, and some are quite identical. In the Eocene we meet with ordinary forms of the genera Helix, Clausilia, Pupa, Bulimus, Glandina, Cyclostoma, Megalostoma, Planorbis, Paludina and Limnæa, some resembling European species, others more like tropical forms. ”

“ Compared with those of mammalia, the remains of birds are exceedingly scarce in Europe and America; and from the wandering habits of so many of this class, they are of much less value as indications of past changes in physical geography. ”

“ Tortoises are perhaps the most abundant of the Tertiary reptiles. They are numerous in the Eocene and Miocene formations both in Europe and North America. The genera Emys and Trionyx abound in both countries, as well as in the Miocene of India. Land tortoises occur in the Eocene of North America and in the Miocene of Europe and India, where the huge Colossochelys, twelve feet long, has been found. In the Pliocene deposits of Switzerland the living American genus Chelydra has been met with. ”

“ Not only are such diversified groups as Carnivora, Perrissodactyle and Artiodactyle Ungulates, Primates, Chiroptera, Rodents, and Marsupials already well marked, but in many of these there is a differentiation into numerous families and genera of diverse character. It is impossible therefore to doubt, that many peculiar forms of mammalia must have lived long anterior to the Eocene period ”

“ A large proportion of the remains belong to aquatic or wading types, and as these have now often a world-wide range, the occurrence of extinct forms can have little bearing on our present inquiry. There are, however, a few interesting cases of extinct land-birds belonging to groups now quite strangers to the country in which they are found; and others scarcely less interesting, in which groups now peculiar to certain areas are shown to have been preceded by allied species or genera of gigantic size. ”

“ The great comparative antiquity of the genera is however the important fact for us, and we shall have occasion often to refer to it, in endeavouring to ascertain the true bearing of the facts of insect distribution, as elucidating or invalidating the conclusions arrived at from a study of the distribution of the higher animals. ”

“ Extensive tracts of fertile land might have been submerged, and the consequent crowding of large numbers of species and individuals on limited areas would have led to a struggle for existence in which the less adapted and less easily modifiable, not the physically weaker, would succumb. ”

“ Even the oldest insects, from the Devonian rocks of North America, can mostly be classed as Neuroptera or Myriapoda, but appear to form new families.
We may consider it, therefore, as proved, that many of the larger and more important genera of insects date back to the beginning of the Tertiary period, or perhaps beyond it; but the family types are far older, and must have been differentiated very early in the Secondary period, while some of them perhaps go back to Palæozoic times. ”

“ Heer examined more than 5,000 specimens belonging to over 800 species, and many have been found in other localities in Switzerland; so that more than 1,300 species of Miocene insects have now been determined. Most of the orders are represented, but the beetles (Coleoptera) are far the most abundant. Almost all belong to existing genera, and the majority of these genera now inhabit Europe, only three or four being exclusively Indian, African, or American. ”

“ We must also remember the extreme specialization of many of the large animals that have become extinct—a specialization which would necessarily render modification in any new direction difficult, since the inherited tendency of variation would probably be to increase the specialization in the same directions which had heretofore been beneficial. ”

“ It is dependent on the fact, that large animals as compared with small ones are almost invariably slow breeders, and as they also necessarily exist in much smaller numbers in a given area, they offer far less materials for favourable variations than do smaller animals. ”

“ More remarkable, however, is the recent discovery in the carboniferous shales of Belgium, of the clearly-defined wing of a large moth (Breyeria borinensis) , closely resembling some of the Saturniidæ; so that we have now all the chief orders of Insects—including those supposed to be the most highly developed and the most recent—well represented at this very remote epoch. ”

“ There were also many ducks, some allied to the genus Dendrocygna; the Oriental genus of storks, Leptoptilus; Ibidipodia, a remarkable form allied to Ibis and Ciconia; Elornis, near Limosa; Pelagornis, a large bird allied to gannets and pelicans; Hydrornis, allied to the ducks and petrels; Dolichopterus, allied to plovers. Perhaps the most interesting of these extinct birds are, however, the flamingoes, represented by forms hardly distinguishable from living species, and by one extinct genus Palælodus, which had very long toes, and probably walked on aquatic plants like the tropical jacanas. ”

“ Hesperornis a gigantic diver; and Icthyornis a very low form, with biconcave vertebra, such as are only found in fishes and some reptiles—also from Cretaceous deposits.
South America.—The caverns of Brazil produced thirty-four species of birds, most of them referable to Brazilian genera, and many to still existing species. The most interesting were two species of American ostrich (Rhea) , one larger than either of the living species; a large turkey-buzzard (Cathartes) ; a new species of the very isolated South American genus Opisthocomus; and a Cariama, or allied new genus. ”