The Geographical Distribution of Animals/Chapter 6
ON THE DISTRIBUTION OF EXTINCT ANIMALS.
THE EXTINCT MAMMALIA OF THE OLD WORLD.
Although it may seem somewhat out of place to begin the systematic treatment of our subject with extinct rather than with living animals, it is necessary to do so in order that we may see the meaning and trace the causes of the existing distribution of animal forms. It is true, that the animals found fossil in a country are very generally allied to those which still inhabit it; but this is by no means universally the case. If it were, the attempt to elucidate our subject by Palæontology would be hopeless, since the past would show us the same puzzling diversities of faunas and floras that now exist. We find however very numerous exceptions to this rule, and it is these exceptions which tell us of the past migrations of whole groups of animals. We are thus enabled to determine what portion of the existing races of animals in a country are descendants of its ancient fauna, and which are comparatively modern immigrants; and combining these movements of the forms of life with known or probable changes in the distribution of land and sea, we shall sometimes be able to trace approximately the long series of changes which have resulted in the actual state of things. To gain this knowledge is our object in studying the "Geographical Distribution of Animals," and our plan of study must be determined, mainly, by the facilities it affords us for attaining this object. In discussing the countless details of distribution we shall meet with in our survey of the zoological regions, we shall often find it useful to refer to the evidence we possess of the range of the group in question in past times; and when we attempt to generalise the phenomena on a large scale, with the details fresh in our memory, we shall find a reference to the extinct faunas of various epochs to be absolutely necessary.
The degree of our knowledge of the Palæontology of various parts of the world is so unequal, that it will not be advisable to treat the subject under each of our six regions. Yet some subdivision must be made, and it seems best to consider separately the extinct animals of the Old and of the New Worlds. Those of Europe and Asia are intimately connected, and throw light on the past changes which have led to the establishment of the three great continental Old World regions, with their various subdivisions. The wonderful extinct fauna recently discovered in North America, with what was previously known from South temperate America, not only elucidates the past history of the whole continent, but also gives indications of the mutual relations of the eastern and western hemispheres.
The materials to be dealt with are enormous; and it will be necessary to confine ourselves to a general summary, with fuller details on those points which directly bear upon our special subject. The objects of most interest to the pure zoologist and to the geologist—those strange forms which are farthest removed from any now living—are of least interest to us, since we aim at tracing the local origin or birthplace of existing genera and families; and for this purpose animals whose affinities with living forms are altogether doubtful, are of no value whatever.
The great mass of the vertebrate fossils of the tertiary period consist of mammalia, and this is precisely the class which is of most value in the determination of zoological regions. The animals of the secondary period, though of the highest interest to the zoologist are of little importance to us; both because of their very uncertain affinities for any existing groups, and also because we can form no adequate notion of the distribution of land and sea in those remote epochs. Our great object is to trace back, step by step, the varying distribution of the chief forms of life; and to deduce, wherever possible, the physical changes which must have accompanied or caused such changes. The natural division of our subject therefore is into geological periods. We first go back to the Post-Pliocene period, which includes that of the caves and gravels of Europe containing flint implements, and extends back to the deposit of the glacial drift in the concluding phase of the glacial epoch. Next we have the Pliocene period, divided into its later portion (the Newer Pliocene) which includes the Glacial epoch of the northern hemisphere; and its earlier portion (the Older Pliocene), represented by the red and coralline crag of England, and deposits of similar age in the continent. During this earlier epoch the climate was not very dissimilar from that which now prevails; but we next get evidence of a still earlier period, the Miocene, when a warmer climate prevailed in Europe, and the whole fauna and flora were very different. This is perhaps the most interesting portion of the tertiary deposits, and furnishes us with the most valuable materials for our present study. Further back still we have the Eocene period, with apparently an almost tropical climate in Europe; and here we find a clue to some of the most puzzling facts in the distribution of living animals. Our knowledge of this epoch is however very imperfect; and we wait for discoveries that will elucidate some of the mystery that still hangs over the origin and migrations of many important families. Beyond this there is a great chasm in the geological record as regards land animals; and we have to go so far back into the past, that when we again meet with mammalia, birds, and land-reptiles, they appear under such archaic forms that they cease to have any local or geographical significance, and we can only refer them to wide-spread classes and orders. For the purpose of elucidating geographical distribution, therefore, it is, in the present state of our knowledge, unnecessary to go back beyond the tertiary period of geology.
The remains of Mammalia being so much more numerous and important than those of other classes, we shall at first confine ourselves almost exclusively to these. What is known of the birds, reptiles, and fishes of the tertiary epoch will be best indicated by a brief connected sketch of their fossils in all parts of the globe, which we shall give in a subsequent chapter.
Historic Period.—In tracing back the history of the organic world we find, even within the limits of the historical period, that some animals have become extinct, while the distribution of others has been materially changed. The Rytina of the North Pacific, the dodo of Mauritius, and the great auk of the North Atlantic coasts, have been exterminated almost in our own times. The kitchen-middens of Denmark contain remains of the capercailzie, the Bos primigenius, and the beaver. The first still abounds farther north, the second is extinct, and the third is becoming so in Europe. The great Irish elk, a huge-antlered deer, probably existed almost down to historic times.
Pleistocene or Post-Pliocene Period.—We first meet with proofs of important changes in the character of the European fauna, in studying the remains found in the caverns of England and France, which have recently been so well explored. These cave-remains are probably all subsequent to the Glacial epoch, and they all come within the period of man's occupation of the country. Yet we find clear proofs of two distinct kinds of change in the forms of animal life. First we have a change clearly traceable to a difference of climate. We find such arctic forms as the rein-deer, the musk-sheep, the glutton, and the lemming, with the mammoth and the woolly rhinoceros of the Siberian ice-cliffs, inhabiting this country and even the south of France. This is held to be good proof that a sub-arctic climate prevailed over all Central Europe; and this climate, together with the continental condition of Britain, will sufficiently explain such a southward range of what are now arctic forms.
But together with this change we have another that seems at first sight to be in an exactly opposite direction. We meet with numerous animals which now only inhabit Africa, or South Europe, or the warmer parts of Asia. Such are, large felines—some closely related to the lion (Felis spelæa), others of altogether extinct type (Machairodus) and forming the extreme development of the feline race;—hyænas; horses of two or more species; and a hippopotamus. If we go a little further back, to the remains furnished by the gravels and brick-earths, we still find the same association of forms. The reindeer, the glutton, the musk-sheep, and the woolly rhinoceros, are associated with several other species of rhinoceros and elephant; with numerous civets, now abundant only in warm countries; and with antelopes of several species. We also meet here with a great extension of range of forms now limited to small areas. The Saiga antelope of Eastern Europe occurs in France, where wild sheep and goats and the chamois were then found, together with several species of deer, of bear, and of hyæna. A few extinct genera even come down to this late period, such as the great sabre-toothed tiger, Machairodus; Galeotherium, a form of Viverridæ; Palæospalax, allied to the mole; and Trogontherium, a gigantic form of beaver,
We find then, that even at so early a stage of our inquiries we meet with a problem in distribution by no means easy to solve. How are we to explain the banishment from Europe in so short a space of time (geologically speaking) of so many forms of life now characteristic of warmer countries, and this too during a period when the climate of Central Europe was itself becoming warmer? Such a change must almost certainly have been due to changes of physical geography, which we shall be better able to understand when we have examined the preceding Pliocene period. We may here notice, however, that so far as we yet know, this great recent change in the character of the fauna is confined to the western part of the Palæarctic region. In caves in the Altai Mountains examined by Prof. Brandt, a great collection of fossil bones was discovered. These comprised the Siberian rhinoceros and mammoth, and the cave hyæna; but all the others, more than thirty distinct species, are now living in or near the same regions. We may perhaps impute this difference to the fact that the migration of Southern types into this part of Siberia was prevented by the great mountain and desert barrier of the Central Asiatic plateau; whereas in Europe there was at this time a land connection with Africa. Post-pliocene deposits and caverns in Algeria have yielded remains resembling the more southern European types of the Post-pliocene period, but without any admixture of Arctic forms; showing, as we might expect, that the glacial cold did not extend so far south. We have here remains of Equus, Bos, Antilope, Hippopotamus, Elephas, Rhinoceros, Ursus, Canis, and Hyæna, together with Phacochœrus, an African type of swine which has not occurred in the European deposits.
It is perhaps to the earlier portion of this period that the Merycotherium of the Siberian drift belongs. This was an animal related to the living camel, thus supporting the view that the Camelidæ are essentially denizens of the extra-tropical zone.
Primates.—We here first meet with evidence of the existence of monkeys in Central Europe. Species of Macacus have left remains not only in the Newer Pliocene of the Val d'Arno in Italy, but in beds of the same age at Grays in Essex; while Semnopithecus and Cercopithecus, genera now confined to the Oriental and Ethiopian regions respectively, have been found in the Pliocene deposits of the South of France and Italy.
Carnivora.—Most of the genera which occurred in the Post-Pliocene are found here also, and many of the same species. Few new forms appear, except Hyænarctos, a large bear with characters approaching the hyænas, and Pristiphoca, a new form of seal, both from the Older Pliocene of France; and Galecynus, a fox-like animal intermediate between Canis and Viverra, from the Pliocene of Œninghen in Switzerland.
Cetacea.—Species of Balæna, Physeter, and Delphinus occur in the Older Pliocene of England and France, and with these the remains of many extinct forms, Balænodon and Hoplocetus (Balænidæ); Belemnoziphius and Choneziphius (Hyperoodontidæ), and Halitherium, an extinct form of the next order—Sirenia, now confined to the tropics, although the recently extinct Rytina of the N. W. Pacific shows that it is also adapted for temperate climates.
Ungulata.—The Pliocene deposits are not very rich in this order. The horses (Equidæ) are represented by the genus Equus; and here we first meet with Hipparion, in which small lateral toes appear. Both genera occur in British deposits of this age. A more interesting fact for us is the occurrence of the genus Tapirus in the Newer Pliocene of France and in the older beds of both France and England, since this genus is now isolated in the remotest parts of the eastern and western tropics. The genera Rhinoceros, Hippopotamus, and Sus, occur here as in the preceding epoch.
We next come to the deer genus (Cervus), which appears to have been at its maximum in this period, no less than eight species occurring in the Norwich Crag, and Forest-beds. Among the Bovidæ, the antelopes, ox, and bison, are the only forms represented here, as in the Post-Pliocene period. Passing on to the Proboscidea, we find three species of elephants and two of Mastodon preserved in European beds of this period, all distinct from those of Post-Pliocene times.
Rodentia.—In this order we find representatives of many living European forms; as Cricetus (hamster), Arvicola (vole), Castor (beaver), Arctomys (marmot), Hystrix (porcupine), Lepus (hare), and Lagomys (pika); and a few that are extinct, the most important being Chalicomys, allied to the beaver; and Issiodromys, said to come nearest to the remarkable Pedetes of South Africa, both found in the Pliocene formations of France.
General Conclusions as to Pliocene and Post-Pliocene Faunas of Europe.—This completes the series of fossil forms of the Pliocene deposits of Europe. They show us that the presence of numerous large carnivora and ungulates (now almost wholly tropical) in the Post-Pliocene period, was due to no exceptional or temporary cause, but was the result of a natural succession from similar races which had inhabited the same countries for long preceding ages. In order to understand the vast periods of time covered by the Pliocene and Post-Pliocene formations, the works of Sir Charles Lyell must be studied. We shall then come to see, that the present condition of the fauna of Europe is wholly new and exceptional. For a long succession of ages, various forms of monkeys, hyænas, lions, horses, hipparions, tapirs, rhinoceroses, hippopotami, elephants, mastodons, deer, and antelopes, together with almost all the forms now living, produced a rich and varied fauna such as we now see only in the open country of tropical Africa. During all this period we have no reason to believe that the climate or other physical conditions of Europe were more favourable to the existence of these animals than now. We must look upon them, therefore, as true indigenes of the country, and their comparatively recent extinction or banishment as a remarkable phenomenon for which there must have been some adequate cause. What this cause was we can only conjecture; but it seems most probable that it was due to the combined action of the Glacial period, and the subsidence of large areas of land once connecting Europe with Africa. The existence, in the small island of Malta, of no less than three extinct species of elephant (two of very small stature), of a gigantic dormouse, an extinct hippopotamus, and other mammalia, together with the occurrence of remains of hippopotamus in the caves of Gibraltar, indicate very clearly that during the Pliocene epoch, and perhaps during a considerable part of the Post-Pliocene, a connection existed between South Europe and North Africa in at least these two localities. At the same time we have every reason to believe that Britain was united to the Continent, what is now the German Ocean constituting a great river-valley. During the height of the Glacial epoch, these large animals would probably retire into this Mediterranean land and into North Africa, making annual migrations northwards during the summer. But as the connecting land sank and became narrower and narrower, the migrating herds would diminish, and at last cease altogether; and when the glacial cold had passed away would be altogether prevented from returning to their former haunts.
We now come to a period which was wonderfully rich in all forms of life, and of which the geological record is exceptionally complete. Various lacustrine, estuarine, and other deposits in Europe, North India, and North America, have furnished such a vast number of remains of extinct mammalia, as to solve many zoological problems, and to throw great light on the early distribution and centres of dispersal of various groups of animals. In order to show the bearing of these remains on our special subject, we will first give an account of the extinct fauna of Greece, of the Upper Miocene period; since this, being nearest to Africa and Asia, best exhibits the relations of the old European fauna to those countries. We shall then pass to the Miocene fauna of France and Central Europe; and conclude with the remarkable Siwalik and other Indian extinct faunas, which throw an additional light on the early history of the animal life of the great old-world continents.
Extinct Animals of Greece.
These are from the Upper Miocene deposits at Pikermi, near Athens, and were collected by M. Gaudry a few years ago. They comprise ten living and eighteen extinct genera of mammalia, with a few birds and reptiles.
Primates.—These are represented by Mesopithecus, a genus believed to be intermediate between the two Indian genera of monkeys, Semnopithecus and Macacus.
Carnivora.—These were abundant. Of Felis there were four species, ranging from the size of a cat to that of a jaguar, a large hyæna, and a large weasel (Mustela). Besides these there were the huge Machairodus, larger than any existing lion or tiger, and with enormously developed canine teeth; Hyænictis and Lycæna, extinct forms of Hyænidæ; Thalassictis=Ictitherium, an extinct genus of Viverridæ but with resemblances to the hyænas, represented by three species, some of which were larger than any existing Viverridæ; Promephitis, an extinct form of Mustelidæ, having resemblances to the European marten, to the otters, and to the S. African Zorilla; and lastly, Simocyon, an extraordinary carnivore of the size of a small panther, but having the canines of a cat, the molars of a dog, and the jaws shaped like those of a bear.
Ungulata.—These are numerous and very interesting. The Equidæ are represented by the three-toed Hipparion, which continued to exist till the Older Pliocene period. There are three large species of Rhinoceros, as well as a species of the extinct genus Leptodon of smaller size. Remains of a very large wild boar (Sus) were found. Very interesting is the occurrence of a species of giraffe (Camelopardalis) as tall as the African species but more slender; and also an extinct genus Helladotherium, not quite so tall as the giraffe but much more robust, and showing some approach to the Antilopidæ in its dentition. Antelopes were abundant, ranging from the size of the gazelle to that of the largest living species. Three or four seem referable to living genera, but the majority are of extinct types, and are classed in the genera Palæotragus, Palæoryx, Tragocerus, and Palæoreas; while Dremotherium is an ancient generalized form of Cervidæ or deer.
Proboscidea.—These are represented by two species of Mastodon, and two of Dinotherium, an extraordinary extinct form supposed to be, to some extent, intermediate between the elephants and the aquatic manatees (Sirenia.)
Rodentia.—This order is represented by a species of Hystrix, larger than living porcupines.
Edentata.—This order, now almost confined to South America, was represented in the Miocene period by several European species. Ancylotherium and Macrotherium, belonging to an extinct family but remotely allied to the African ant-bear (Orycteropus), occur in Greece.
Birds.—Species of Phasianus and Gallus were found; the latter especially interesting as being now confined to India.
Reptiles.—These are few and unimportant, consisting of a tortoise (Testudo) and a large lizard allied to Varanus.
Summary of the Miocene Fauna of Greece.—Although we cannot consider that the preceding enumeration gives us by any means a complete view of the actual inhabitants of this part of Europe during the later portion of the Miocene period, we yet obtain some important information. The resemblance that appeared in the Pliocene fauna of Europe, to that of the open country of tropical Africa, is now still more remarkable. We not only find great felines, surpassing in size and destructive power the lions and leopards of Africa, with hyænas of a size and in a variety not to be equalled now, but also huge rhinoceroses and elephants, two forms of giraffes, and a host of antelopes, which, from the sample here obtained, were probably quite as numerous and varied as they now are in Africa. Joined with this abundance of antelopes we have the absence of deer, which probably indicates that the country was open and somewhat of a desert character, since there were deer in other parts of Europe at this epoch. The occurrence of but a single species of monkey is also favourable to this view, since a well-wooded country would most likely have supplied many forms of these animals.
Miocene Fauna of Central and Western Europe.
We have now to consider the Miocene fauna of Europe generally, of which we have very full information from numerous deposits of this age in France, Switzerland, Italy, Germany, and Hungary.
Primates.—Three distinct forms of monkeys have been found in Europe—in the South of France, in Switzerland, and Wurtemberg; one was very like Colobus or Semnopithecus; the others—Pliopithecus and Dryopithecus—were of higher type, and belonged to the anthropomorphous apes, being nearest to the genus Hylobates or gibbons. Both have occurred in the South of France. The Dryopithecus was a very large animal (equal to the gorilla), and M. Lartet considers that in the character of its dentition it approached nearer to man than any of the existing anthropoid apes.
Insectivora.—These small animals are represented by numerous remains belonging to four families and a dozen genera. Of Erinaceus (hedgehog) several species are found in the Upper Miocene; and in the Lower Miocene of Auvergne two extinct genera of the same family—Amphechinus and Tetracus—have been discovered. Several species of Talpa (mole) occur in the Upper Miocene of France, while the extinct Dinylus is from Germany, and Palæospalax from the Lower Miocene of the Isle of Wight. The Malayan family Tupaiidæ or squirrel-shrews, is believed to be represented by Oxygomphus, a fossil discovered in South Germany (Wiesenau) by H. von Meyer. The Soricidæ or shrews, are represented by several extinct genera—Plesiosorex, Mysarachne and Galeospalax; as well as by Amphisorex and Myogale still living. Echinogale, a genus of Centetidæ now confined to Madagascar, is said to occur in the Lower Miocene of Auvergne, a most interesting determination, if correct, as it would form a transition to the Solenodon of the Antilles belonging to the same family; but I am informed by Prof. Flower that the affinities of the animals described under this name are very doubtful.
Carnivora.—Besides Felis and Machairodus, which extend back to the Upper Miocene, there are two other genera of Felidæ, Pseudælurus in the Upper Miocene of France, and Hyænodon, which occurs in the Upper and Lower Miocene of France, named from some resemblance in its teeth to the hyænas, and considered by some Palæontologists to form a distinct family, Hyænodontidæ. The Viverridæ, or civets, were very numerous, consisting of the living genus Viverra, and three extinct forms—Thalassictis=Ictitherium, as large as a panther, and Soricictis, a smaller form, occurring both in France and Hungary. Of Hyænidæ, there was the living genus Hyæna, and the extinct Hyænictis, which has occurred in Hungary as well as in Greece. The Canidæ, or wolf and fox family, were represented by Pseudocyon, near to Canis; Hemicyon, intermediate between dogs and gluttons; and Amphicyon, of which several species occur in the Upper and Lower Miocene of France, some of them larger than a tiger. The Mustelidæ, or weasels, were represented by five genera, the existing genera Lutra (otter) and Mustela (weasel); Potamotherium, an extinct form of otter; Taxodon, allied to the badger and otter; Palæomephitis in Germany, and the Promephitis (already noticed) in Greece. The bears were represented only by Hyænarctos, which has been noticed as occurring in the Pliocene, and first appears in the Upper Miocene of France. Seals are represented by a form resembling the Antarctic Otaria, remains of which occur in the Upper Miocene of France.
Cetacea (whales).—These occur frequently in the Miocene deposits, four living, and five extinct genera having been described; but these marine forms are not of much importance for our purpose.
Sirenia (sea-cows).—These are represented by two extinct genera, Halitherium and Trachytherium. Several species of the former have been discovered, but the latter has occurred in France only, and its affinities are doubtful.
Ungulata.—Horses are represented by Hipparion and Anchitherium, the latter occurring in both Upper and Lower Miocene and Eocene; while Hipparion, which is more nearly allied to living horses, first appears in the Upper Miocene and continues in the Pliocene.
Hippotherium, in the Upper Miocene of the Vienna basin, forms a transition to Paloplotherium, an Eocene genus of Tapiridæ or Palæotheridæ. Tapirs, allied to living forms, occur in both Upper and Lower Miocene. Rhinoceroses are still found in the Upper Miocene, and here first appear the four-toed hornless rhinoceros, Acerotherium. The Suidæ (swine) are rather numerous. Sus (wild boar) continued as far back as the Upper Miocene; but now there first appear a number of extinct forms which have been named Hyotherium, Palæochœrus, Chœromorus, all of a small or moderate size; Hyopotamus, nearly as large as a tapir; and Anthracotherium, nearly the size of a hippopotamus and, according to Dr. Leidy, the type of a distinct family. Listriodon, from the Upper Miocene of the Vienna basin, is sometimes classed with the tapirs.
We now come to a well-marked new family of Artiodactyle or even-toed Ungulata, the Anoplotheriidæ, which consisted of more slender long-tailed animals, allied to the swine but with indications of a transition towards the camels. The only genera that appear in the Miocene formation are, Chalicotherium, nearly as large as a rhinoceros, of which three species have been found in Germany and France; and Synaphodus, known only from its teeth, which differ somewhat from those of the Anoplotherium which appears earlier in the Eocene formation. Another extinct family, Amphimericidæ or Xiphodontidæ, is represented by two genera, Cainotherium and Microtherium, in the Miocene of France. They were of very small size, and are supposed to be intermediate between the Suidæ and Tragulidæ.
The Camelopardalidæ, or giraffes, were represented in Europe in Miocene times by the gigantic Helladotherium, which has been found in the south of France, and in Hungary, as well as in Greece. The chevrotains (Tragulidæ) are represented by the extinct genus Hyomoschus.
The Cervidæ do not seem to have appeared in Europe before the Upper Miocene epoch, when they were represented by Dorcatherium and Amphimoschus, allied to Moschus, and also by true Cervus, as well as by small allied forms, Dremotherium, Amphitragulus (in the Lower Miocene), Micromeryx, Palæomeryx, and Dicrocerus.
The Bovidæ, or hollow-horned ruminants, were not well represented in Central Europe in Miocene times. There were no sheep, goats, or oxen, and only a few antelopes of the genus Tragocerus, and one allied to Hippotragus; and these all lived in the Upper Miocene period, as did the more numerous forms of Greece.
Proboscidea.—The true elephants do not extend back to the Miocene period, but they are represented by the Mastodons, which had less complex teeth. These first appear in the Upper Miocene of Europe, five species being known from France, Germany, Switzerland, and Greece. Dinotherium, already noticed as occurring in Greece, extended also to Germany and France, where remains of three species have been found.
Rodentia.—A considerable number of generic forms of this order have been obtained from the Miocene strata. The principal genera are Cricetodon, allied to the hamsters, numerous in both the Upper and Lower Miocene period of France; Myoxus (the dormice) in France, and an allied genus, Brachymys, in Germany. The beavers were represented by the still living genus Castor, and the extinct Steneofiber in France. The squirrels by the existing Sciurus and Spermophilus; and by extinct forms, Lithomys and Aulacodon, in Germany, the latter resembling the African genus Aulacodes. The hares, by Lagomys and an extinct form Titanomys. Besides these, remains referred to the South American genera, Cavia (cavy) and Dasyprocta (agouti), have been found, the former in the Upper Miocene of Switzerland, the latter in the Lower Miocene of Auvergne. Palæomys, allied to the West Indian Capromys, has been found in the same deposits; as well as Theridomys, said by Gervais to be allied to Anomalurus and Echimys, the former now living in W. Africa, the latter in S. America.
Edentata.—These are only represented by the Macrotherium and Ancylotherium of the Grecian deposits, the former occurring also in France and Germany in Upper Miocene strata.
Marsupials.—These consist of numerous species related to the opossums (Didelphys), but separated by Gervais under the name Peratherium. They occur in both Upper and Lower Miocene beds.
Upper Miocene Deposits of the Siwalik Hills and other Localities in N. W. India.
These remarkable fresh-water deposits form a range of hills at the foot of the Himalayas, a little south of Simla. They were investigated for many years by Sir P. Cautley and Dr. Falconer, and add greatly to our knowledge of the early fauna of the Old World continent.
Primates.—Remains of the genera Semnopithecus and Macacus were found, with other forms of intermediate character; and some teeth indicated animals allied to the orang-utan of Borneo, and of similar size.
Carnivora.—These consisted of species of Felis and Machairodus of large size; Hyæna, Canis, Mellivora, and an allied genus Ursitaxus; Ursus, in the deposits of the Nerbudda valley (of Pliocene age); Hyænarctos as large as the cave bear; Amphicyon of the size of a polar bear (in the deposits of the Indus valley, west of Cashmere); Lutra, and an extinct allied genus Enhydrion.
Ungulata.—These are very numerous, and constitute the most important feature of this ancient fauna. Horses are represented by a species of Equus from the Siwalik Hills and the Irawaddy deposits in Burmah, and by two others from the Pliocene of the Nerbudda Valley; while Hippotherium—a slender, antelope-like animal, found in the Siwalik Hills and in Europe—is supposed to form a transition from the Equidæ to the Tapiridæ. These latter are found in the Upper Indus deposits, where there is a species of Tapirus, and one of an extinct genus Antelotherium. Of Rhinoceros, five extinct species have been found—in the Siwalik Hills, in Perim Island, and one at an elevation of 16,000 feet in the deserts of Thibet. Hippopotamus occurs in the Pliocene of the Nerbudda, and is represented in the older Miocene deposits by Hexaprotodon, of which three species have been found in various parts of India. Another remarkable genus, Merycopotamus, connects Hippopotamus with Anthracotherium, one of the extinct European forms allied to the swine. These last are represented by several large species of Sus, and by the extinct European genus Chœrotherium.
The extinct Anoplotheridæ are represented by a species of the European genus Chalicotherium, larger than a horse.
An extinct camel, larger than the living species, was found in the Siwalik Hills.
Three species of deer (Cervus) have been found in the Siwaliks, and one in the Nerbudda deposits.
A large and a small species of giraffe (Camelopardalis) were found in the Siwalik Hills and at Perim Island.
The Bovidæ are represented by numerous species of Bos, and by the extinct genera Hemibos and Amphibos. There are also three species of antelopes, one of which is allied to the African Alcephalus.
We now come to an extraordinary group of extinct animals, probably forming a new family intermediate between the antelope and the giraffe. The Sivatherium was an enormous four-horned ruminant, larger than a rhinoceros. It had a short trunk like a tapir, the lower horns on the forehead were simple, the upper pair palmated. The Bramatherium, an allied form from Perim Island, showed somewhat more affinity for the giraffe.
Proboscidea.—No less than seven species of elephants and four of mastodons ranged over India, their remains being found in all the deposits from the Siwalik Hills to Burmah. A large Dinotherium has also been found at Perim Island.
Reptiles.—Many remains of birds were found, but these have not been determined. Reptiles were numerous and interesting, the most remarkable being the huge tortoise, Colossochelys, whose shell was twelve feet long and head and neck eight feet more. Other small tortoises of the genera Testudo, Emys, Trionyx and Emydida were found, the Emys being a living species. There were three extinct and one living species of crocodile, and one of them was larger than any now living. The only other reptile of importance was a large lizard of the genus Varanus.
General Observations on the Miocene faunas of Europe and Asia.—Comparing the three faunas of approximately the same period, and allowing for the necessarily imperfect record of each, we find a wonderful similarity of general type over the enormous area between France on the west and the Irawaddy river in Burmah on the east. We may even extend our comparison to Northern China, where remains of Hyæna, Tapir, Rhinoceros, Chalicotherium, and Elephas, have been recently found, closely resembling those from the Miocene or Pliocene deposits of Europe or India, and showing that the Palæarctic region had then the same great extent from west to east that it has now. Of about forty genera comprised in the Indian Miocene fauna, no less than twenty-seven inhabited Central and Western Europe during the same epoch. The Indian Miocene fossils are much what we should expect as the forerunners of the existing fauna, the giraffes and hippopotami being the only additions from the present Ethiopian fauna. The numerous forms of the restricted bovine type, show that these probably originated in India; while the monkeys appear to be altogether of Oriental types.
In Europe, however, we meet with a totally different assemblage of animals from those that form the existing fauna. We find apes and monkeys, many large Felidæ, numerous civets and hyænas, tapirs, rhinoceros, hippopotamus, elephants, giraffes, and antelopes, such as now characterise the tropics of Africa and Asia. Along with these we meet with less familiar types, showing relations with the Centetidæ of Madagascar, the Tupaiidæ of the Malay Islands, the Capromys, of the West Indies, and the Echimys of South America. And besides all these living types we have a host of extinct forms,—ten or twelve genera allied to swine; nine genera of tapir-like animals; four of horses; nine of wolves; with many distinct forms of the long-extinct families of Anoplotheridæ, Xiphodontidæ, and the edentate Macrotheridæ. It is almost certain that during the Miocene period Europe was not only far richer than it is now in the higher forms of life, but not improbably richer than any part of the globe now is, not excepting tropical Africa and tropical Asia.
The deposits of Eocene age are less numerous, and spread over a far more limited area, than those of the Miocene period, and only restricted portions of them furnish any remains of land animals. Our knowledge of the Eocene mammalian fauna is therefore very imperfect and will not occupy us long, as most of the new types it furnishes are of more interest to the zoologist than to the student of distribution. Some of the Eocene mammalia of Europe are, however, of interest in comparison with those of North America of the same age; while others show that ancestral types of groups now confined to Australia or to South America, then inhabited Europe.
Primates.—The only undoubted Eocene examples of this order, are the Cænopithecus lemuroides from the Jura, which has points of resemblance to the South American marmosets and howlers, and also to the Lemuridæ; and a cranium recently discovered in the Department of Lot (S.W. France), undoubtedly belonging to the Lemuridæ, and which most resembles that of the West African "Potto" (Perodicticus). This discovery has led to another, for it is now believed that remains formerly referred to the Anoplotheridæ (Adapis and Aphelotherium from the Upper Eocene of Paris) were also Lemurs. Some remains from the Lower Eocene of Suffolk were at first supposed to be allied to Macacus, but were subsequently referred to the Ungulate, Hyracotherium. There is still, however, some doubt as to its true affinities.
Chiroptera.—In the Upper Eocene of Paris remains of bats have been found, so closely resembling living forms as to be referred to the genus Vespertilio.
Carnivora.—The only feline remains, are those of Hyænodon in the Upper Eocene of Hampshire, and Pterodon, an allied form from beds of the same age in France; with Ælurogale, found in the South of France in deposits of phosphate of lime of uncertain age, but probably belonging to this period. Viverridæ (civets) are represented by two genera, Tylodon, the size of a glutton from the Upper Eocene, and Palæonyctis, allied to Viverra, from the Middle Eocene of France. The Canidæ (wolves and foxes) appear to have been the most ancient of the existing types of Carnivora, five genera being represented by Eocene remains. Of these, Galethylax and Cyotherium were small, and with the existing genus Canis are found in the Upper Eocene of France. Arctocyon, about the size of a wolf, is a very ancient and generalised form of carnivore which can not be placed in any existing family. It is found in the Lower Eocene of France, and is thus the oldest known member of the Carnivora.
Ungulata.—These are more numerous. Equidæ (horses) are represented by the Miocene Anchitherium in the Lower, and by a more ancient form, Anchilophus, in the Middle Eocene of France. Tapiridæ and Palæotheridæ were very numerous. Palæotherium and the allied genus Paloplotherium, were abundant in France and England in Upper Eocene times. They somewhat resembled the tapir, with affinities for the horse and rhinoceros. A new genus, Cadurcotherium, allied to the rhinoceros and equally large, has been found in the same deposits of phosphate of lime as the lemur and Ælurogale. In the Middle Eocene of both England and France are found Lophiodon allied to the tapir, but in some of the species reaching a larger size; Propalæotherium and Pachynolophus of smaller size and having affinities for the other genera named; and Plagiolophus, a small, slender animal which Professor Huxley thinks may have been a direct ancestor of the horse. In the Lower Eocene we meet with Coryphodon, much larger than the tapir, and armed with large canine teeth; Pliolophus, a generalised type, allied to the tapir and horse; and Hyracotherium, a small animal from the Lower Eocene of England, remotely allied to the tapir.
Among the Artiodactyla, or even-toed ungulates, the swine are represented by several extinct genera, of moderate or small size—Acotherium, Chœropotamus, Cebochœrus and Dichobune, all from the Upper and the last also from the Middle Eocene of France; but Eutelodon, from the phosphate of lime deposits is large. The Dichobune was the most generalised type, presenting the characters of many of the other genera combined, and was believed by Dr. Falconer to approach the musk-deer. The Cainotherium of the Miocene also occurs here, and an allied genus Plesiomeryx from the same deposits as Eutelodon.
The Eocene Anoplotheridæ were numerous. The Anoplotherium was a two-toed, long-tailed Pachyderm, ranging from the size of a hog to that of an ass; the allied Eurytherium was four-toed; and there are one or two others of doubtful affinity. All are from the Upper Eocene of France and England.
Rodentia.—Remains referred to the genera Myoxus (dormouse) and Sciurus (squirrel) have been found in the Upper Eocene of France; as well as Plesiarctomys, an extinct genus between the marmots and squirrels. The Miocene Theridomys is also found here.
Marsupials.—The Didelphys (opossum) of Cuvier, now referred to an extinct genus Peratherium, is found in the Upper Eocene of France and England.
General Considerations on the Extinct Mammalian Fauna of Europe.—It is a curious fact that no family, and hardly a genus, of European mammalia occurs in the Pliocene deposits, without extending back also into those of Miocene age. There are, however, a few groups which, seem to be late developments or recent importations into the Palæarctic region, as they occur only in Post-Pliocene deposits. The most important of these are the badger, glutton, elk, reindeer, chamois, goat, and sheep, which only occur in caves and other deposits of Post-Pliocene age. Camels only occur in the Post-Pliocene of Siberia (Merycotherium), although a true Camelus of large size appears to have inhabited some part of Central Asia in the Upper Miocene period, being found in the Siwalik beds. The only exclusively Pliocene genera in Europe are Ursus, Equus, Hippopotamus, Bos, Elephas, Arvicola, Trogontherium, Arctomys, Hystrix and Lepus; but of these Equus, Hippopotamus, Bos, and Elephas are found in the Miocene deposits of India. Owing, no doubt, in part to the superior productiveness of the various Miocene beds, large numbers of groups appear to have their origin or earliest appearance here. Such are Insectivora, Felidæ, Hyænidæ, Mustelidæ, Ursus, Equidæ, Tapirus, Rhinocerotidæ, Hippopotamidæ, Anthracotheridæ (extinct), Sus, Camelopardalidæ, Tragulidæ, Cervidæ, Bovidæ, Elephantidæ, and Edentata.
Groups which go back to the Eocene period, are, Primates allied to South American monkeys, as well as some of the Lemuridæ; bats of the living genus Vespertilio; Hyænodontidæ, an ancestral form of Carnivore; Viverridæ; Canidæ (to the Upper Eocene), and the ancestral Arctocyonidæ to the Lower Eocene; Hyænarctos, an ancestral type of bears and hyænas; Anchitheridæ, ancestral horses, to the Middle Eocene; Palæotheridæ, comprising numerous generalised forms, ancestors of the rhinoceros, horse, and tapir; Suidæ, with numerous generalised forms, to the Middle Eocene; Anoplotheridæ and Xiphodontidæ, ancestral families of even-toed Ungulates, connecting the ruminants with the swine; and lastly, several groups of Rodents, and a Marsupial, in the Upper Eocene. We thus find all the great types of Mammalia well developed in the earliest portion of the tertiary period; and the occurrence of Quadrumana, of the highly specialized bats (Vespertilio), of various forms of Carnivora, and of Ungulates, clearly differentiated into the odd and even-toed series, associated with such lower forms as Lemurs and Marsupials—proves, that we have here hardly made an approach towards the epoch when the mammalian type itself began to diverge into its various modifications. Some of the Carnivora and Ungulates do, indeed, exhibit a less specialised structure than later forms; yet so far back as the Upper Miocene the most specialised of all carnivora, the great sabre-toothed Machairodus, makes its appearance.
The Miocene is, for our special study, the most valuable and instructive of the Tertiary periods, both on account of its superior richness, and because we here meet with many types now confined to separate regions. Such facts as the occurrence in Europe during this period of hippopotami, tapirs, giraffes, Tragulidæ, Edentata, and Marsupials—will assist us in solving many of the problems we shall meet with in reviewing the actual distribution of living forms of those groups. Still more light will, however, be thrown on the subject by the fossil forms of the American continent, which we will now proceed to examine.