Page images
PDF
EPUB

the American Pliocene and Miocene periods, abounding in genera and species; whereas in Europe the group only exists in the Post-Pliocene or Lower Pliocene, with one Upper Miocene species of Camelus in N. India. The Anthracotheridae (extinct), found only in the Upper Miocene of France and India, reach even the Lower Eocene in America. These facts may be due, in part, to a want of strict co-ordination between the Tertiary deposits of Europe and North America, —in part to the imperfection of the record in the latter country. Yet it does not seem probable that they are altogether due to these causes, because the Miocene beds, which are by far the best known in America as in Europe, exhibit deficiencies of the same kind as the less known Eocene deposits. The fossil fauna of both countries is so rich, that we can hardly impute great and well marked differences to imperfect knowledge; yet we find such important families as the Civets, Hyaenas, Giraffes, and Hippopotami absent from America, with the Weasels, and Antelopes almost so; while America possesses almost all the Camelidae, two peculiar orders, Dinocerata and Tillodontia, and four remarkably peculiar families, Limnotheridae, Lemuravidae, Oreodontidae and Brontotheridae. If then the facts at present known represent approximately the real time-relations of the groups in question on the two continents, they render it probable that weasels, bears, true horses, swine, oxen, sheep and antelopes, originated on the Old World continent, and were transmitted to America during some part of the Miocene period; while camels originated in the New World, and somewhere about the same time passed over to Europe. Of the extinct families common to the two hemispheres, the Anthracotheridae alone seem to have had an American origin. Of the genera common to the two countries, almost all seem to have had a European origin, the only genera of equal date being the two rhinoceroses and three Anchitheridae; but if the Brontotheridae are allied to the Rhinocerotidae, these latter may have originated in America, although now an exclusively Old World type. These conclusions are not improbable when we consider the much greater size of the Old World continents, extending far into the tropics and probably always more or less united to the tropical areas; while the evidence of the extinct mammalia themselves shows, that South America has been for the most part isolated from the northern continent, and did not take part in the development of its characteristic Tertiary fauna. Before speculating further on this subject, it will be well to lay before our readers a summary of South American palaeontology, after which we shall be in a better position to draw correct inferences from the whole body of the evidence.

SOUTH AMERICA.

Unfortunately, our knowledge of the interesting fossil fauna of this continent, is almost wholly confined to the Post-Pliocene and Pliocene periods. A few remains have been discovered in deposits believed to be of Eocene age, but nothing whatever representing the vast intervening period, so rich in peculiar forms of animal life both in North America and Europe.

Fauna of the Brazilian caves—What we know of the PostPliocene period is chiefly due to the long-continued researches of Dr. Lund in the caves of Central Brazil, mostly situated in a district near the head waters of the San Francisco river in the Province of Minas Geraes. The caves are formed in limestone rocks, and are so numerous that Dr. Lund visited thousands, but only sixty contained bones in any quantity. These caves have a floor of reddish earth, often crowded with bones. In one experiment, half a cubic foot of this earth contained jaws of 400 opossums, 2,000 mice, besides remains of bats, porcupines and small birds. In another trial, the whole of the earth in a cavern was carried out for examination, amounting to 6,552 firkins; and, from a calculation made by measured samples, it was estimated to contain nearly seven millions of jaw-bones of cavies, opossums, porcupines, and mice, besides small birds, lizards, and frogs. This immense accumulation is believed to have been formed from the bodies of animals brought into the cavern by owls; and, as these are unsocial birds, the quantity found implies an immense lapse of time, probably some thousands of years. More than 100 species of Mammalia, in all, were obtained in these caves. Some were living species or closely allied to such; but the majority were extinct, and a considerable number, about one-fourth, belonged to extinct genera, or genera not now inhabiting South America. Stone implements and human remains were found in several of the caves with extinct animals. The following enumeration of these remains is from the corrected list of M. Gervais. Primates.—Extinct species of Cebus, Callithria, and Jacchus— South American genera of monkeys; with an extinct genus, Protopithecus—an animal of large size but belonging to the American family Cebidae. Chiroptera.--Species belonging to the South American Phyllostomidae, and to two South American genera of other families. Carnivora-Five species of Felis, some allied to living animals, others extinct; a species of the widespread extinct genus Machairodus ; and a small species referred to Cynaelurus, the genus containing the hunting leopard now found only in Africa and India. Canidae are represented by Canis and Icticyon (a living Brazilian species of the latter genus), and the extinct genus Speothos. Mustelidae are represented by extinct species of the South American genera Mephitis and Galictis. Procyonidae, by a species of Nasua. Ursidae, by Arctotherium, a genus closely resembling, if not identical with, that containing the “spectacled bear” of Chili. Ungulata.-Equus, Tapirus, Dicotyles, Auchenia, Cervus, Leptotherium, and Antilope, are the cave-genera of this order. Equus and Antelope are particularly interesting, as representing groups forming no part of existing South American zoology; while the presence also of Leptotherium, an extinct genus of antelopes, shows that the group was fairly represented in South America at this comparatively recent period. Proboscidea.—A species of Mastodon, found also in the Pliocene of La Plata, represents this order. Rodentia.-These abound. Dasyprocta, Caelogenys, Cavia, Kerodon, all living genera of Caviidae, are represented by extinct species. Cercolabes, the ‘tree porcupine' (Cercolabidae) has two species, one as large as a peccary; Myopotamus, Loncheres, Carterodon, are existing genera of spiny rats (Echimyidae); and there are two extinct genera of the same family, Lonchophorus and Phyllomys. Lagostomus (Chinchillidae), the viscacha of the Pampas, is represented by an extinct species. There is also an extinct species of Lepus; several species of Hesperomys and Oxymycterus; and a large Arvicola, a genus not living in South America.

Edentata.-These, which constitute the great feature of the existing South American fauna, were still more abundant and varied in the Cave period, and it is remarkable that most of them are extinct genera. The armadillos are alone represented by living forms, Dasypus, and Xenurus; Eurydon and Heterodon, are extinct genera of the same family, as well as Chlamydotherium—huge armadillos the size of a tapir or rhinoceros, and Pachytherium, which was nearly as large. The ant-eaters are represented only by Glossotherium, an extinct form allied to Myrmecophaga and Manis. The sloths were more numerous, being represented by the extinct genera Caelodon, Sphenodon and Ochotherium, the last of large size. The huge terrestrial sloths—Megatheridae, also abounded; there being species of Megatherium and Megalonya, as well as the allied Scelidotherium, supposed to have some affinity for the African Orycteropus.

Marsupials—No new forms of these appear, but numerous species of Didelphys, all closely allied to opossums still living in South America.

The preceding sketch of the wonderful cave fauna of Central Brazil, is sufficient to show that it represents, in the main, a period of great antiquity. Not only are almost the whole of the species extinct, but there are twenty extinct genera, and three others not now inhabitants of South America. The fact that so few remains of the living animals of the country are found in these caves, indicates that some change of physical conditions has occurred since they were the receptacles of so many of the larger animals; and the presence of many extinct genera of large size, especially among the Edentata and American families of Rodents, are additional proofs of a very high antiquity. Yet many of these cave animals are closely allied to those which are found in North America in the Post-Pliocene deposits only, so that we have no reason to suppose the cave-fauna to be of much earlier date. But the great amount of organic change it implies, must give us an enlarged idea of the vast periods of time, as measured by years, which are included in this, the most recent of all geological epochs.

Pliocene Period of Temperate South America.--We have now to consider the numerous remains of extinct animals found in various deposits in the Pampas, and in Patagonia, and a few in Bolivia. The age of these is uncertain; but as they are very similar to the cave-fauna, though containing a somewhat larger proportion of extinct genera and some very remarkable new forms, they cannot be very much older, and are perhaps best referred at present to the newer portion of the Pliocene formation. Carnivora.-The genus Machairodus or sabre-toothed tigers, represents the Felidae. There are several species of wolves (Canis); a weasel (Mustela); two bears of the Brazilian cavegenus Arctotherium; and the extinct European genus Hyaenarctos. Ungulata.-There are two species of Equus, found in the Pampas, Chili, and Bolivia; two of Macrauchenia, an extraordinary extinct group allied to the tapir and Palaeotherium, but with the long neck, and general size of a camel. A second species found on the highlands of Bolivia is much smaller. A more recent discovery, in Patagonia, is the almost perfect series of teeth of a large animal named Homalodontotherium; and which is believed by Professor Flower, who has described it, to have been allied to Rhinoceros, and still more to the Miocene Hyracodon from North America; and also to present some resemblances to Macrauchenia, and though much more remotely, to the curious genus Nesodon mentioned further on. The Artiodactyla, or even-toed Ungulates, are represented by a species of Dicotyles, or peccary, found in the deposits of the

« EelmineJätka »