 CHAPTER IX. The Mammals form the highest and most important group of the vertebrates, broadly speaking, they correspond to the popular terms of quadruped, but also include man himself, and the whales, seals, and manatees. These reptiles have scales, and birds' feathers, mammals have hair, as their most obvious character. But the skin is often partly, rarely, wholly naked, and in a few mammals, scales or bony plates are also present, covering the surface more or less completely. The young are born alive and suckled by the mother. This is the primary distinguishing character. They are warm-blooded, air-breathing, the heart with four chambers, and lungs and heart are separated from the abdominal organs by a muscular diaphragm. The sense organs are more highly developed than in other vertebrates. The brain larger and more complex, the skull more consolidated. Teeth are nearly always present, and usually elaborated into various and often complex structures adapted to the various food requirements of the animal. The limbs and feet show an equally wide diversity in adaptation to various habits and modes of life. The tertiary period is often called the age of mammals. During that time the mammals assumed the dominant position among animals, previously held by reptiles, and evolved, mostly from small ancestors of uniform type, into the diverse and often gigantic species of the present day. Ancestral mammals had first evolved from primitive reptiles long before, probably before the close of the age of amphibians, and these small primitive ancestors had been living side by side with the gigantic dinosaurs during all the age of reptiles. They were rare and of minute size, probably tree-living animals, and it is not unlikely that their arboreal life, with its continual demands on intelligent action and readiness to grasp opportunities, stimulated the much higher grade of intelligence to which the mammals had attained when they first appeared in numbers at the opening of the tertiary period. These primitive ancestral mammals were small, long-tailed animals, which might be compared to the modern tree-shrews. They had flexible limbs and feet, slender body, moderately long neck, slender skull, and long jaws with teeth adapted to insect eating. The number of teeth was upward of forty-four. The toes were five on each foot, the digits flexible, clawed, the inner digit to some extent opposable, and with one less joint than the others. Small mammals have been found in great numbers and variety in the formations of successive epics of the tertiary period, and it is possible to trace the successive stages through which they evolved from these small primitive types into the various kinds of modern quadrupeds. Conversely, when the ancestral series of any modern quadruped is traced back, it is found leading down in every case toward this identical small primitive type, and when one examines and compares the structure and anatomy of any modern animal it is seen that it is most easily explained as a modification from this common primitive type in adaptation to one or another habit of life. Some races have become herbivorous, others carnivorous, others fruit-eating, and the teeth have been modified in accordance. Some have remained arboreal, others have become terrestrial, aquatic, or fosorial. Some have remained small, others have become large or even gigantic in size, and the limbs and feet have been modified to suit their various habits and size. In herbivorous mammals, the cheek teeth are used for crushing and grinding vegetable food, the front teeth for cropping. The trule molars are enlarged and complicated into a more or less elaborate pattern of crests or crescentic ridges which serve to chop or grind the food. The pre-molars either degenerate or become like the molars. The canines are sometimes enlarged into tusks for fighting, sometimes degenerate and disappear. The incisors are converted into spade-like teeth for nipping off food into large, gnawing teeth or degenerate and disappear. Grievous animals, on the other hand, the pointed canines used for seizing and holding the prey are large, sharp, and strong. The pre-molars used for cutting the food are well developed. While the molars used for grinding tend to degenerate or disappear or to become more like the pre-molars and to be used chiefly for cutting up the food. Even forgiverous animals, the cheek teeth are used for crushing fruits or nuts and become flat-topped. The pre-molars often degenerate. The front teeth, used for biting off the food, are converted into a row of little spade-shaped teeth. Animals of more mixed diet show various combinations of these characters in the dentition. The animals which have remained arboreal have retained and perfected the adaptation of limbs and feet to this purpose, but have departed less than any others from the primitive type. Among terrestrial mammals are found a variety of adaptations. Some have developed speed to escape from their enemies or pursue their prey. For this purpose they have taken to walking or running upon the fingers, or even upon the tips of the claws, instead of, as at first, upon the flat of the foot. In consequence the lower limbs and feet are lengthened. The joints of the feet made stronger and more compact, the side toes tend to degenerate, and the middle toes bear the weight of the body, and the claws are converted into broad, strong hoofs which finally support the whole weight. Other terrestrial races have depended upon their fighting capacity rather than upon speed. They have increased rapidly in size, developed horns, tusks, armor plates, or spines, for attack or defense, and the limbs have become adapted to bearing enormous weights with heavy bones, massive muscles, short, heavily padded feet. Fossorial mammals have developed short and exceedingly powerful limbs, and great digging claws upon the feet. In aquatic mammals, the feet become webbed and are finally converted into paddles, or in such as developed, a powerful swimming tail, the hind limbs, have degenerated and disappeared. Finally one group of aerial mammals appears, the bats, in which the forelimbs are converted into wings, by lengthening the fingers and developing a web between them, and the sides of body and tail. Various arboreal mammals also have web-like expansions of the skin which they stretch as parachutes in leaping from bow to bow. The quadrupeds are less dependent upon temperature and climate than most of the lower animals, while they are more strictly limited in their migrations by the boundaries of the continents and islands which they inhabit. Moreover, they are not so ancient as the invertebrates and lower vertebrates. Their evolution and dispersal over the world has mostly occurred during the tertiary period, when the distribution of land and water was not so very different from what it is at present. We find that the present general arrangement of the land areas, with the great central northern land mass and isolated peninsular continents stretching down into the southern hemisphere, is the key to the geographical distribution of mammals. They have spread out in successive waves of migration from one part or another of the whole Arctic region, and each new wave or higher stages of evolution in the different races has driven its more primitive predecessors before it toward the remotest confines of the southern continents and islands. This general tendency has been limited by the land connections with the southern continents and islands. The connection with South America was interrupted during a part of the tertiary, and during that interruption the South American animals evolved independently into races which were quite different from those of the northern world. When connection was resumed, the northern animals invaded South America, while some of the southern races invaded North America. But the superior quality of the animals evolved on the great northern land mass, enabling them to overcome and displace those of South American origin, which have nearly all become extinct. In Africa, and in peninsular India, the connection was also interrupted for a time and then restored with the same results, but the interruption did not last so long. India and the adjoining islands have been separated since before the tertiary period, and the higher mammals have never been able to reach those regions. In consequence, the more primitive mammals which reached there at an earlier period have evolved and specialized into a large and varied mammal fauna paralleling the higher mammals of the northern world. Some of the East Indian islands, now separated from the mainland only by shallow seas, have been united with it during the tertiary period, so that the great land animals could invade and occupy them. Other oceanic islands like Salibis, Madagascar, the West Indies, New Zealand, and many smaller islands are separated by deep oceans from the mainland. In these it is noted that land mammals are generally absent, or are peculiar types different from those of other regions, and probably developed on the islands themselves from such small animals as might, once in a long while, reach their shores on floating rafts drifted out from the mouths of rivers on the mainland. Small mammals, such as rodents, insectivores, or small lemurs, might once in a while gain a footing on the isolated island in this way, and once established in the absence of competition would evolve into a variety of larger races, as the marsupials did in Australia. In this way can be explained why Madagascar possesses none of the elephants, rhinoceroses, zebras, antelopes, dogs, cats, etc., of the adjoining coast of Africa, but does have a great number of lemurs not found elsewhere, a number of insectivores of a family centetidae peculiar to the island, two or three carnivores, related to the civets but of a very exceptional character. The bush-pigs may have been brought there by man. The pygmy hippopotami found fossil on the island may have reached it by swimming, but the absence of practically all the mainland animals, together with the presence of peculiar types which seem adapted to take their place, can scarcely be explained except by supposing that the island has been separated from the African mainland for a very long period. The problems of geographical distribution are a most fascinating branch of zoology and have attracted a large share of the attention of scientific men, especially in recent years. In the arrangement of this class of vertebrates, first must be set aside the egg-laying mammals of Australia as an exceedingly archaic type, to a great extent a connecting link between mammals and the primitive reptiles from which they are descended. As might be expected, these most ancient of mammals are found on the very outskirts of the mammalian domain, southern Australia and Tasmania, most remote from the main center of the mammalian evolution in the north. These form the subclass prototheria. The rest of the mammals may be divided again into a small and a large group, the marsupials or pouched mammals, metatheria, in which the young are born alive but very immature and are carried for some time in a pouch on the underside of the mother's body until they are able to shift for themselves, and the placental mammals, eutherea, including all the rest. In the placentals, the young are more mature when born, and are never carried about in a pouch. Either they are able to follow the mother about or she remains with them in some suitably protected spot until they are well grown. There are of course numerous distinctions in the skeleton and soft anatomy to support this division of the mammals into prototherians, metatherians and euthereans, but from a modern point of view it is well to lay weight on these differences in the care of the young. For, as has been seen among invertebrates, the progressively greater care of the young, the prolongation of infancy, appears to be more than anything else the key to the possibilities of higher development. Among insects it is patent that the higher life of the social wasps and bees centers mainly about the care of the young. It is no less true among vertebrates. The most prominent feature in the life of birds and mammals is the care that they take of their young, and in the higher orders of mammals the period of infancy becomes progressively longer until it reaches its maximum in man. The mammalia are further divisible into twenty-three orders, as generally accepted in recent years. Their arrangement is as follows. One subclass prototheria, egg-laying mammals. One order of monotremata, ornithorhynchus, and echidna. Two subclass metatheria, pouched mammals. Two order of marsupalia, opossums, kangaroos, etc. Three subclass euthyria, placental mammals. Three order insectivora, hedgehogs, moles, etc. Four order edentata, sloths, armadillos, etc. Five order cetacea, whales, dolphins, etc. Six order serenia, manatee, and dugong. Seven order perisodactyla, horses, rhinoceroses, tapirs. Eight order arteriodactyla, pigs and ruminants. Nine order propocidia, elephants. Ten through sixteen orders condilarthra, amblypoda, toxodontia, liptoptaema, arsinoetheria, embrythopoda, astropotheria, extinct hoofed mammals. Seventeen order hierocodia, cones. Eighteen order rodentia, rats, mice, rabbits, etc. Nineteen through twenty, orders telodonta and teneodonta, extinct clod mammals. Twenty-one order of carnivora, dogs, cats, weasels, civets, etc. Twenty-two order chiropterra, bats. Twenty-three order primates, lemurs, monkeys, apes, man. The egg-laying mammals therefore must be treated first. These two little animals, the ornithorhincus, or duck-billed, and the echidna, or spiny anteater, inhabit southern Australia and Tasmania. They are the most archaic of all mammals, and from their geographic location may be regarded as the vanguard of the great mammalian dispersion, which is spread out in successive waves from the northern continental landmass. They are classed with mammals because of their hair-covered skin, solid skull, jaws all of one piece, and various features of their anatomy, but they retain numerous characters in the skeleton approaching those of the primitive reptiles of the coal period, from which the mammals are believed to be descended. Like the marsupials these animals are provided with a pouch, to which the eggs are transferred after they are laid. The eggs are hatched in the pouch, and the young animal remains there for some time, nourished by a secretion from the skin of the mother. The ornithorhincus lives and burrows along the margin of ponds and streams, feeding upon freshwater clams, crustaceans, etc. During the Australian winter, says Dr. Simon, from June till the end of August when the nights are cold, you may be sure to find the animals in the river at sunrise and sunset. If you are near the river early enough to watch the rising of the sun, you will see something flat, one or two feet in length, floating on the water, like a plank. As soon as the first sunbeams strike the river surface and allow you to discern single objects. Sometimes it lies motionless for a while, then it disappears, to reappear again after a few moments in quite a different place. This is an ornithorhincus seeking its breakfast in the mire of the river. The echidna, or spiny anteater, is a shy, nocturnal burrowing animal living in the dense and penetrable scrub and wild rocky parts of the country. On its nightly expeditions, says Simon again, the anteater seeks worms and insects of all kinds, which it extracts from their hiding places in earth holes between stones and in rotting bark, by means of its long, worm-like tongue. Its principal food, however, consists of ants, which it captures, like other anteaters, by thrusting its tongue into the antel, waiting till it is covered with ants, and then drawing it in quickly. It is interesting to note that the pouched mammals have a lower and less constant body temperature than any of the higher mammals. In this respect also, they approach the reptiles and other cold-blooded vertebrates. The marsupials are more or less intermediate between the monotremes and the placental mammals, but decidedly nearer in all respects to the latter. They lack a placenta, that particular internal organ which enables the young to be brought to a mature, more perfected state before birth. In consequence, they are born in a very rudimentary condition and are usually transferred to a pouch on the underside of the mother to complete their development. Teets are present, as in the higher mammals, and the little animal is suckled within the pouch. Marsupials are today chiefly found in Australia and the adjacent islands. The opossums of South and Central America, of which one species ranges northward into the United States and a rare little animal, Canolestes, recently discovered in the Andean Highlands, are the only living representatives of the order outside of Australasia, except that a few of the Australian marsupials also range northward into the East Indies. Formally, the marsupials were worldwide in their distribution. It is probable that most, if not all of the tiny shrew-like mammals which have been referred to as contemporaries of the gigantic dinosaurs during the Age of Reptiles were marsupials, or at least equivalent to them in their stage of evolution. But with the advent of the higher placental mammals at the beginning of the tertiary period, the marsupials gradually disappeared from the northern world, a few survivors having been found among the early tertiary mammals of Europe and North America, and they were abundant in South America until the later part of the tertiary period when the great invasion of the northern mammals swept them out of existence, save for the epossums and Canolestes. In Australia, however, they were undisturbed by northern competitors, as this continent remained isolated throughout the tertiary period. They were allowed, says Saman, to thrive unhindered to regard the bush forests, the riverbanks, the rocks and mountains, as their undisputed domain, adapting themselves more and more to the characters of their surroundings. Some feed on the grass of the bush like kangaroos and wallabies, others dig for roots and bulbs like the kangaroo rats, still others seek their food on eucalyptus trees like phasolarctus, the Australian epossum, and the flying marsupials. Bandicoats, paramellidae, and the shrew-like bush rats and bush mice, face collogally and teconomies, are mostly insectivorous. The native cat, the Tasmanian devil, and the pouched wolf carnivorous with teeth strongly reminding us of those of placentelia, as different as their food or the dwellings, the habits and the modes of locomotion in all these animals. Like jumping mice, the kangaroos hop over the level country. Some of them, for instance, the rock wallabies being able to execute their leaps also in mountainous country with the cleverness of a camois, while the tree kangaroo, dendrolegus, performs real climbing antics in the crowns of the highest trees. We see the Australian epossum and the couscous climb with the agility of squirrels. Petorus flits from tree to tree and is therefore erroneous called by the Australians flying squirrel. Fascolarctos, however, climbs along as lazily as any sloth. Slinking is the gate of the native cat and trotting that of the pouched wolf. In the grass, in rocky caves, on the ground or on trees, we find the hiding places and the layers of the marsupials. Like rabbits, the wombats dig long and deep burrows in the ground and quite subterranean are the life and habits of the blind notorites typhlops, which latter has but recently been discovered in the deepest interior of Australia and the mean and habits of which strongly remind us of our mole and still all these animals have nothing to do with moles, squirrels, flying squirrels, rats, jumping mice, shrew mice, cats and wolves. All of them are marsupials and related much more closely to each other than to any of the other placental mammals which they resemble as to looks, movements or habits and from which they derive their popular names. Further, we must not imagine that the placental beasts of prey have sprung from similar marsupial beasts of prey, the genuine jumping mice from kangaroos, moles from notorites and so on. It is more probable that the transition from marsupials to placentals took place only once and from a less specialized group of marsupials than now exists. The original group of placentals thence has differentiated into the distinct series like insectivora, rodents, hoofed animals, beasts of prey, lemurs, apes and men. The outer resemblance between certain groups of marsupials and placentals is a phenomenon of convergence and is produced by adaptation to similar conditions of life. It ought to be judged like the resemblance between woodlice and centipedes, fishes and whales, birds and bats. Outer resemblance is not always a proof of blood relationship. Echidna, porcupine and hedgehog are no wise related much as they resemble each other since the former is related to ornithorancus, the second to chinchella and the last to the mole. The marsupials are divided into two main groups. In the polyprotodonts, mostly carnivorous and insectivorous, the canine teeth are sharp and strong, the incisor teeth small and set in a traverse row, and the cheek teeth adapted to cutting flesh or insect food. In the diprotodonts, mostly herbivorous and frugivorous, the canine teeth are minute or absent, and one or two pair of the incisor teeth are enlarged somewhat as in rodents while the cheek teeth are fitted for crushing or chopping vegetation, fruit or nuts. In the first group, the feet have usually five separate well-developed toes. In the second, the toes are usually reduced in number, the fourth digit enlarged, the others enclosed in a common entanglement. Of the carnivorous marsupials, or polyprotodonts, the American opossums and the thylacine, or Tasmanian wolf, the Tasmanian devil, sarcophylus and desior, or native cat of Australia, are the best known living types. In the Australian regions, these take the place of true placental carnivora of other continents, which are unknown there, except for the dingo, or wild dog, probably introduced by man. But even in the short time that the dingo has been present on the main continent of Australia, his superiority as a hunter over his marsupial competitors is shown by the fact that the thylacine and devil, abundant in Australia in prehistoric times, have disappeared from the mainland and survive only in Tasmania, where dingoes have not been introduced. In South America, during the tertiary period, while it was an island continent, there were likewise no true carnivora, and there too the carnivorous marsupials developed into large wolf-like, lion-like, and smaller cat-like, or civet-like, forms, depending upon the various herbivora. When toward the end of the tertiary, the continent was united with North America. True carnivores invaded it from the North and soon caused the extinction of all the carnivorous marsupials, except the opossums, whose arboreal habits and more omnivorous, or insectivorous diet enabled them to survive to the present day. The remains of these extinct South American marsupial carnivores, discovered in recent years, show so much resemblance to the thylacines that they have been referred to the same family, and supposed to have migrated from Australia to South America by means of land connections with the Antarctic continent. In the present writer's opinion, the resemblance is better explained as due to similar adaptation from primitive opossum-like marsupials, originally derived with the rest of the South American and Australian mammals, from those primitive mammals which lived during the age of reptiles in the northern continents. These primitive marsupials, ancestors of the various living marsupials, and from which, at a somewhat earlier period, the remote ancestors of the higher, or placental mammals had branched off, are pretty closely represented in the living opossums, so that, one may, without very great straining of facts, place the opossum in the gallery of ancestral portraits and picture from him the sort of animal from which man, in common with all the quadrupeds, is remotely descended, little rat-like or shrew-like animals with long prehensile pale, with opposable thumb and great toe, insectivorous, living in trees and venturing out from their hiding places, mainly by night, alert and intelligent above their fellows of the reptilian era, but not by the higher standards of modern quadrupeds, such as far as can be judged, were the remote ancestors of the mammals, and such are the opossums today. The thylacine is a much larger animal, with teeth specialized for flesh-eating and feet for running. Its superficial resemblance to a wolf is well shown in the illustration. The striped rump suggests the tiger, also while the long stiff tail is an opossum character. It is now limited to the mountains of Tasmania, as is also the related Tasmanian devil, but both are found in the castle in Australia. The dasiaries are smaller, civet-like animals of Australia and Tasmania, which take the place of the smaller, predatious carnivora of other parts of the world. The bandicoots are small omnivorous or insectivorous marsupials, with teeth like those of the carnivorous group, but feet more like those of the herbivorous group. In the wombats the reverse is the case. The teeth being of the diprototent type, while the feet have five well-developed toes with strong claws. These animals, in their heavy clumsy build, short stubby tail, and shuffling walk, very much resemble small bears and are commonly known as native bears. The phalanges of small rhic marsupials are boreal in their habits and found throughout Australasia, ranging as far north and west as Ambuena and Salibas among the East Indian islands. The largest living marsupials are the kangaroos, which in Australia take the place of the hoofed quadrupeds of other continents. These animals, says Saimon, will always hold their own as the most characteristic feature of Australia. Everyone who has observed them in zoological gardens and menageries will have remarked that there exist larger and smaller kinds of this animal, but we are apt to lose sight of the many and considerable differences between the various species and genera in the simple fact that the general quaintness of their aspect, the peculiar structure of their extremities detail and the queer manner of their locomotion leads us to overlook everything else. Nevertheless these animals, apparently so uniform in structure show an astonishing variety in their more minute features their habits and their distribution. If we reckon only the genuine macro-potaday without the kangaroo rats we have to admit seven genera compromising 43 species. And of these 23 belong to the genus macropus the real kangaroo. The Australian colonists call all the larger kinds kangaroos the smaller kinds they call wallabies. The kangaroos for the most part prefer the open bush the level or undulating ground of which gives them occasion to exercise their splendid leaping powers. Besides offering them a rich pasture. The leaps of the bigger kinds have generally a length of several yards. When chased they heighten the extent of a single leap to ten yards or more. The jerk is produced by the hind legs without assistance from the tail as some think. This is easily proved by observing the track the animals leaps imprint upon the ground. The tail is flourished at every leap but hardly touches the earth. It seems to help the leaping animals to steer and to support its weight while resting. While the kangaroos are the largest of living marsupials the extinct Diprotodon and Nototherium which inhabited Australia during the Pleistocene Epic were gigantic animals equaling the Indian rhinoceros in bulk and curiously resembling the modern elephant in the long straight massive post-like limbs and short rounded stubby feet. They were related to the wombats and may in fact be regarded as a sort of gigantic development of this race adapted probably to a less arid climate and more abundant vegetation than now prevails in Australia. Numerous skeletons of these extinct giants have lately been found in the dried up lakes of west Australia north of Adelaide. End of Part 1 End of Section 13 Section 14 of the Science History of the Universe Volume 6 This is LibriVox recording while LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org The Science History of the Universe Volume 6 Edited by Francis Rult Wheeler Zoology Chapter 9 The Vertebrates Part 4 Mammals Part 2 The cetaceans are mammals which have become adapted to marine life and assumed to fish-like form lost their hair converted the forelimbs into paddles lost the hind limbs entirely and converted the tail into a swimming organ. They are only superficially like fish the skeleton and internal organs the quality of the muscles the teeth are all those of land mammals and widely different from fish they are warm-blooded bring forth their young alive and nurse them after the manner of land quadrupeds the brain is far superior to that of any fish and the intelligence is of a much higher order than that of fishes the intelligence of the dolphin seems to have been noticed by men in prehistoric times for it appears in Greek mythology as the friend and active helper of man. The cetaceans include the largest of known animals, living or extinct the whale bone whales and sperm whales and the numerous smaller active species of which the dolphins and porpoises are most familiar the order is divided into two groups the whale bone whales mysticite are toothless and provided with fringed plates of whale bone which act as a sieve to catch and retain in the mouth the minute crustaceans etc. upon which the animal feeds there are several kinds of these whales all of gigantic size in the right whales bellena the head is more arched and the whale bone plates and fringes longer in the roar quolls baleenoptera the whale bone plates are smaller and the animal is longer bodied the head less gigantic there is a dorsal fin on the right whales whence the name of finner and humpback apply to different species and the throat has a series of longitudinal furrows the species of bellena reach a length of 40 to 70 feet with an enormous bulk the roar quolls though somewhat less massive attain even greater size a large sulfur bottom whale will reach 75 to 85 feet in length and weigh about 75 tons a skeleton in the museum of Christchurch New Zealand is reported as measuring 87 feet in total length the skull alone being 21 feet long the danger and romance of whaling are departed and it has become a merciless butchery which bids fair soon to extinguish utterly the largest and most magnificent of living animals the whale bone which is now the only practical object of the pursuit seems epitifully inadequate compensation for their extinction the toothed cetaceans odontocetes have no baleen plates but the jaws are set with sharp pointed recurved teeth adapted to seize and hold the fish and other swift swimming marine animals on which they prey the sperm whale or cacolot attains a size almost rivaling the whale bone whales 55 to 60 feet is a conservative estimate of the length and of this nearly a third is the gigantic blunt snouted head in the cavities of the skull are stored vast quantities of fluid fat the spermisetti of commerce the sperm whale is also obtained the rare and valuable substance ambergris used in the preparation of perfumes unlike the whale bone whales which are confined to the cold temperature and arctic seas the sperm whale chiefly inhabits the tropical oceans its food is chiefly cuttlefish and it is said to especially seek the gigantic octopus which lives far beneath the surface of the deep seas and has so rarely been seen by man that it was till recently regarded as a fabulous monster bullen in the cruise of the cacolot has given a fascinating account of the combat between these giants of the deep the spermisetti, oil and amigris of the cacolot are the objects of a considerable fishery which however at present threaten the extinction of the animal the first two products are found in the other toothed cetaceans but in smaller quantities the dolphins in purposes and their allies are common in all parts of the world mostly marine but some of them inhabiting the great tropical rivers the largest of the dolphin group is the grampus or killer a fierce predatious species which reaches a length of 30 feet the killer preys upon seals and purposes and several will combine to attack one of the larger whales another remarkable form is the narwhal in which the teeth are reduced to a single long twisted tusk projecting forward from the head to a length of 6 or 7 feet the purpose of this twisted tusk is not certainly known among the numerous fossil cetaceans the most interesting are the zooglodonts a primitive group which serve to connect the cetacea with the land quadrupeds of the early tertiary especially with primitive carnivora and carnivorous insectivores although marine and fish like in form the teeth and skull characters to those of early carnivorous land mammals from which they were no doubt derived they have been found in the eocene formations of alabama and more recently in Egypt among the living relics of prehistoric animals preserved to this day in the isolated southern continents the so called edentates are not the least interesting the tree sloths are sluggish stupid creatures covered with long greenish brown hair which inhabit the brazilian forests hanging upside down from the trees by their long curved claws feeding upon leaves and moving slowly and cautiously from bow to bow and protected by their likeness and color and appearance to the mossy green leech and covered branches around them the armadillos are covered by plates embedded in the skin forming a rigid buckler at each end of the body with bands of movable plates between so that the animal can roll up into an armor covered ball they are phosaurial animals active diggers and are found in old parts of south america and as far north as southern texas the anteaters also south american are covered with long hairy hair toothless with long snouts and slender protrusible tongue and powerful claws to tear down the nests of the ants on which they are especially adapted to feed these creatures are all of moderate size the largest being the great anteater seven feet in length including the long bushy tail the term edentates toothless animals applies strictly to the anteaters only the others have teeth although they lack enamel the living edentates are the remnants of a race which flourished greatly in south america during the age of mammals while that region was an island continent protected by ocean barriers from the incursions of the more highly developed mammals of the northern world some of the extinct edentates the great ground sloths and gliptodonts attained gigantic size the megatherium almost rivaled an elephant in bulk and was extraordinarily massive in skeleton its allies, the myelodonts were somewhat smaller these huge animals were nearest to the tree sloths in structure but were much too large to have lived in trees they are supposed to have used their gigantic claws in digging up and uprooting trees upon whose foliage they fed the gliptodonts or tortoise armadillos were covered with armor a massive solid carapace without the movable bands of the armadillo and the feet hoofed instead of clawed they had very efficient grinding teeth and were presumably raising animals some of them equaled rhinoceros in bulk certain of these gigantic animals appeared to have survived in Patagonia almost to historic time and to have been actually domesticated by the Indians of that region the native legends tell of gigantic animals which correspond not very accurately with the myelodon as it must have appeared in life and in a cave at last hope inlet Patagonia they were recently found parts of the skin well preserved and almost fresh together with the dropping of a myelodon and chopped grass on which it is supposed to have been fed the indications being that the animals were kept confined in a part of the cave the order insectivora includes the hedgehogs moles, shrews and many less familiar animals the living insectivores are the scattered remnants of an ancient race of mammals from whose earlier members were evolved the higher and more intelligent races which have mostly displaced them in the struggle for existence the survivors are protected by spiny armor or nauseous taste or by burrowing habits or else inhabit remote fringes of the continents or large islands where they have escaped from the competition of higher types all the insectivora are small or minute animals with teeth adapted to a diet of insects which form their principal food the best known of the insectivores are the hedgehogs covered with a prickly coat and like the armadillos able to roll themselves up into a ball which defies the assaults of any ordinary beast of prey the moles strictly subterranean and almost blind the four limbs converted into a very powerful and efficient digging instrument and the shrews less specialized for burrowing but protected by their nocturnal habits and nauseous taste few birds or animals will touch a shrew the owl is almost the only one that preys upon it hedgehogs, moles and shrews inhabit the northern continents hedgehogs being restricted to the old world various other insectivores more or less related to these but mostly less specially protected are found in south and west africa in the east and west indies and in Madagascar and one species at least formally existed in south america in the early part of the age of mammals the insectivores were far more numerous and some larger in their size and they had not then developed the various extreme specializations by which the surviving members of the order have managed to prolong their existence the higher mammals in the opinion of Huxley were probably derived from some of these very primitive unspecialized insectivores the bats order chiroptera are usually regarded as chiroptera but they are the most isolated and highly specialized of all mammals in relation to their habits of flight in adaptation to this purpose the forelimbs and especially the fingers are greatly elongated the hind limbs reduced and slender twisted around so that the knee projects backward and a thin flexible wing membrane and from the front of the forearm to the hind limbs and usually to the tail the pectoral muscles which move the wings are greatly enlarged as they are in flying birds the thumb and the five toes of the hind foot are tipped with slender curved claws by which the animal suspends himself when at rest generally hanging upside down Dr. W. L. Hahn who has recently studied the habits of cave bats observes they have no nests, dens or fixed homes they have few enemies consequently fear is little developed about five sixths of the bats entire existence is spent in a dormant condition a large amount of fat is favorable to torpor in the caves where conditions of light and temperature are constant bats come to the cave entrance with their intervals the length of time between these intervals depends upon the amount of surplus fat stored in the body food consists of insects that are caught on the wing hearing and the tactile sense are chiefly relied upon to perceive and locate food bats are more helpless on their feet than most birds in the air they have greater agility they can check their momentum very quickly in flight they can secure the surface only slightly rough with a single thumb or with one foot neither sight nor the external ears are necessary for the perception of obstacles during flight such are perceived chiefly through the sense organs located in the internal ear but the body hairs have probably a sensory function as well perception is probably due to the condensation of the atmosphere between the moving animal and the object which it is approaching it is difficult to explain how they find their way by means of the five senses familiar to us the presence of a sixth sense that of direction will explain all the facts but it has not been conclusively shown that such a sense exists there are two principal groups of bats the large fruit bats inhabit the East Indies, Africa and Madagascar, Australia and many of the Pacific islands feeding upon fruit and hanging from branches of trees when not on the wing the smaller insectivorous bats are much better known and are cosmopolitan in their distribution the ears are large and complex and many kinds possess peculiar leafy outgrowths from the nostrils which aid in perception of objects around somewhat as do the antennae events save that it is the sense that is elaborated instead of that of smell while most of them live on insects a few are frugivorous or carnivorous and the South American Desmodus the true vampire bat is a blood sucker fastening upon men or animals during sleep and inflicting severe wounds with serious loss of blood without awakening the sleeper by means of its keen damaged front teeth the cave haunting habits of modern bats are familiar and their fossil remains have been found in ancient cave and crevice formations as far back as the early part of the tertiary period all the extinct species are closely related to modern kinds and show nothing of the evolution of this singular group of mammals they are probably of very ancient origin next above insectivores in the scale of life may be placed the rodents including the rats and mice, squirrels, porcupines rabbits, etc this group of mammals although comparatively low in scale of organization is very abundant and varied and highly successful in the battle of life their success may be ascribed to their great fecundity their adaptability to changing conditions of life and their readiness to combine together in social relations not generally very complex yet each serving to assist the others to a considerable extent whatever be the reasons the rodents are by far the most numerous of the orders of mammals both as to species and individuals nearly all are of small size they are distributed all over the world a few even reaching Australia and are terrestrial arboreal fosorial or amphibious in their habits none of them is marine and none is able to fly although some have membranous expansions of the skin which can be stretched like parachutes in taking long soaring leaps from tree to tree the limbs and feet are mostly of primitive type five-toed tipped with claws and the animal walks on the sole of the foot the teeth are peculiar in the conversion of one pair of incisors in each jaw into gnawing teeth in disappearance of all the other front teeth the cheek teeth are adapted to crushing or grinding rodents live mainly upon seeds roots, nuts, fruits or upon grasses or the bark of trees but they are by no means averse to insect or animal food more than half of the living species of mammals belong to this order it is divided into four groups of which the squirrels porcupines rats and rabbits serve as types the squirrel group includes the squirrels marmots beavers rocket gophers and their allies the arboreal squirrels are the most intelligent and attractive of rodents and are found all over the world save in Australia and Madagascar their long bushy tails neat, smooth, fur and often handsome coloring and their restless activity and chatter offset their occasional depredations on birds' nests and hermits woodchucks, gophers, prairie dogs, etc are nearly related to the tree squirrels but terrestrial and more or less burrowing in habit adapted to live in open country and in temperate or arctic climates the beavers are more distantly related they are a small group of highly specialized habits large brained and intelligent for rodents there are only two living species the European and American beaver as is well known they live in colonies in artificial lakes which they construct by damming streams with logs, brush and mud each family making a nest or burrow in or beside the shallow waters of the pond accessible by an underwater entrance both species have been hunted almost to extinction for their fur a large extinct relative of the beaver castoroidus lived in North America during the glacial epic equaling the black bear in size but nothing is known of its habits except that it remains are mostly found in ancient swamps and pond bottoms during the tertiary period small animals related to the beaver stenofiber were common both in Europe and North America but their habits were like those of the modern prairie dogs they constructed elaborate winding corkscrew like burrows and the remains of these burrows filled in by sand and petrified are known in the west as devil's corkscrews it is not easy to see how the peculiar habits of the aquatic beavers could have evolved from those of burrowing ancestors but they were perhaps a side branch not directly ancestral the pocket gophers and pocket mice of North America are intermediate between the squirrel and rat groups of rodents they get their name from the large cheek pockets in which they carry food and transport earth from their burrows the pocket gophers are completely subterranean equaling the mole in their digging powers and vegetable food the pocket mice are terrestrial and some of them active leavers the gerboas and their relatives are also specialized for leaping rather than running but are more nearly related to the rats and porcupines than to the squirrels they inhabit the northern continents and Africa mostly living in open plains or desert regions the most abundant of the rodent groups and mice and their relatives these are found all over the world a few have even penetrated to Australia and to various oceanic islands which few or none of the other mammals have contrived to reach they are nearly all of small size living upon all kinds of plant food and often more or less omnivorous adapting themselves very readily to varying conditions of life and endowed with great fecundity their depredations upon crops upon stored grain upon household supplies the damage they do by girdling trees for the edible inner bark cause enormous losses in various fields of human activity so that they rank with noxious insects in their economic importance birds of prey are their natural enemies more efficient in general than any artificial check on their increase the porcupine group of rodents are represented by two or three large spiny coated species in the northern continents but their headquarters are in South America where they include the cavies and chintillas viscaches agoutis, capybaras and many others of which the largest, the capybara reaches the size of a pig quite a number of this group of rodents inhabit Africa and during the tertiary period they were the only rodents in South America and one extinct genus is estimated to have attained the size of an ox much beyond that of any other rodent the last group of rodents are the hares, rabbits, and pikas worldwide in distribution but most familiar and abundant in the north temperate and subarctic regions in Australia and New Zealand they have been introduced by the white settlers and have thriven and multiplied exceedingly so as to be a serious pest in the absence of their natural enemies their limbs and feet are more specialized for speed than in most rodents although the rabbit-like cavies and chinchillas of South America show a corresponding adaptation End of Chapter 9 Part 2 End of Section 14 Section 15 of the Science History of the Universe Volume 6 This is a LibriVox recording all LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org The Science History of the Universe Volume 6 Edited by Francis Rold Wheeler Zoology Chapter 9 The Verdebrates Part 4 Mammals Part 3 Under the name of Hooft Mammals or Oungulata are commonly grouped together several orders of mammals which are not in fact nearly related to each other They are all herbivorous adapted to terrestrial life using the feet only for walking or running and in all of them the claws have been thickened and broadened into hoofs serving for support but useless for grasping or climbing So far as can be judged they are derived from several stocks of primitive clawed ancestors in each of which the hoofs have been independently evolved in adaptation to similar habits of life the horses, tappers and rhinoceroses are derived from one primitive stock the pigs in ruminance from another the elephants from a third while there are several extinct races of hoofed mammals derived from still other primitive stocks The Oungulates are all medium to large sized mammals they are all medium gigantic none of them very small their brains are mostly of high type and in intelligence they rank with the carnivora decidedly above any of the orders that we have considered except the Cetacea and exceeded only by the higher primates monkeys, apes and men the two most important groups are the perisodactyls or odd toad and the artyodactyls and toad hoofed mammals in the former the number of toes in the hind foot at least is three or one the axis of symmetry passing through the middle digit in the latter the number of toes is four or two the axis of symmetry passing between the two middle digits there are numerous other points of difference in the structure of teeth skeleton and soft anatomy which show that these two groups are distinct that while animals so different as the horse and rhinoceros are derived from a common ancestral stock the tapper and the pig or the rhinoceros and the hippopotamus are derived from different primitive stocks of placental mammals these relationships are fully confirmed by what is known of the geological history of the various races of ungulates owing to their large size and comparative abundance fossil hoofed mammals are more common and better known than any of the other groups and the geological history and evolution of many of the ungulate races is quite fully known the horse wrote the small boy in an essay is a square animal with a leg at each corner a definition that might perhaps be improved upon but in fact the horse needs no definition of it before the eye of man woman or child its graceful proportions compact well-knit body long head and arched neck its flowing mane and tail its slender limbs and one-toed feet tipped each by a broad solid hoof these are the ideal proportions of the swift running hoofed mammal designed to cover long distances at a high rate of speed true horses are practically unknown in a wild state the so-called wild horses being for the most part descended from animals which have escaped from domestication the Zowalski horse of the deserts of central Asia is however believed to be a truly wild species the closely related asses and zebras occur in the wild state in western Asia and in Africa they differ from the horse chiefly in size and color pattern and are all included in the genus equus in a broad way all of them may be called horses the structure of the feet and teeth in the horse using the word in this broader sense is unique among modern animals the foot has but a single toe corresponding to the middle state of man but the second and fourth digits are represented by small rudiments splint bones which lie closely pressed against the back of the cannon bone corresponding to the third metacarpal bone of the palm in the human hand or the third metatarsal bone of the instep in the foot these rudiments are all that is left of the second and fourth toes of the first and fifth there is no trace at all the big teeth are equally peculiar they are long square columns growing at the base and pushing up from the jaws they wear off at the surface in grinding the food they are composed of enamel dentine and cement the enamel which forms the covering of the usual type of mammal tooth is infolded into a complicated pattern it's worn edges supported on one side by the dentine which underlies in the normal mammal tooth and on the other by cement a special substance slightly softer than the dentine deposited on what is at first the outer side of the enamel before the tooth pushes up through the gum by this means the grinding surface of the tooth at any stage of wear is composed of a complex pattern of hard enamel ridges braced on either side by the somewhat softer dentine and cement this forms the most efficient instrument for grinding and triterating the hard dry grasses which are the natural food of the horse in the successive formations of the tertiary period in the great plains region of the western united states have been found a series of evolutionary stages leading up to the modern horse from small ancestors no larger than a cat with four toes on the four foot and three on the hind foot and with grinding teeth of the primitive bunodont type such as are still retained by man and many other mammals these little four-toed horses are scarcely distinguishable from the contemporary ancestors of tapirs and rhinoceroses the successive stages of the divergent lines of evolution which led up into the three widely different modern types have been found in the successive formations of the American tertiary about a dozen successive stages are known nearly all form complete fossil skeletons besides numerous incomplete ones which illustrate the gradual transition from the little four-toed horse to his modern descendant in the Eocene the ancestors of the horse complete toes in the four foot three in the hind foot all resting on the ground in the oligocene they had but three complete toes on four or hind foot all resting on the ground but the side toes are slender and the middle digit larger the outside toe of their Eocene ancestors is represented by a rudiment or splint in the myocene the central toe is more enlarged it's also a very slender and can no longer touch the ground but are like the dew claws of a dog or deer in the Pliocene the side toes are still more slender and the bones of the middle digit have more clearly the proportions of those of a horse and in the old world it is seen that there were already one-toed horses in which the dew claws had disappeared all horses were one-toed like those of today and at that time there were species of wild horse in Europe Asia, Africa, North and South America since that time the geographic range of horses has been much restricted they disappeared wholly from the new world to be reintroduced by European settlers in the North and South Americas they are no longer found in the wild state in Europe nor in most parts of Asia and the zebras and wild asses are rapidly disappearing the domesticated breeds which are believed to be crosses of Asiatic, North African and perhaps a native European wild horses have been introduced everywhere that civilized man has made his home and feral races escaped from domestication have re-peopled the high plains of both Americas the evolution of the horses to be regarded as an adaptation to changing conditions of climate and geography which favored more and more the development of swift running types and open grassy plains at the beginning of the tertiary period the plains of western America lay near to sea level had a moist subtropical climate and were heavily forest clad throughout this period they were being slowly elevated the climate was becoming colder and more arid and the forests were disappearing to be replaced by extensive grassy plains of the original population of animals some were treated southward with the changing climate and their descendants are today to be found in the tropical forests some became extinct and are known to us only from their fossil remains some, like the horses were able to adapt themselves to the changing conditions and their descendants, much changed in form and habits, still survive hand in hand with the changes in foot structure adapting them to swift running when changes in the teeth adapting them to feed upon the hard dry upland grasses the steady increase in size is a common feature in many races of animals especially of ungulates the taphirs afford an example of a race which has followed the climate southward instead of altering its habits and structure tapirs today inhabit the forests of tropical America and the Malayan Peninsula they retain the primitive construction of the feet four toes in the forefoot three in the hind foot and their teeth are not greatly changed from the primitive type of the Eocene ancestors of horses, tapios and rhinoceroses except for increased size and bulk and the development of a short flexible proboscis they have changed but little during the early part of the tertiary period tapios inhabited all the northern continents but their range was gradually restricted further and further to the south the history of the rhinoceroses is much the same as of the tapios in the early tertiary their ancestors had four toes on the front foot and primitive short crowned monodont teeth like the early horses these ancestral rhinoceroses lost the outer digit in the forefoot and began to lengthen out the crowns of the teeth making them more efficient grinders but they got no further than these first steps and then like the tapirs they followed the changing climate southward in preference to adapting themselves to new conditions of life rhinoceroses were common in Europe northern Asia and North America as far as Canada during the early and middle tertiary but by the end of the tertiary they had disappeared from the northern regions except for a few survivors in Europe and Asia and today they are found only in the tropical regions of the old world in India and some of the east Indian islands in Africa as far south as Cape Colony in the new world they have become wholly extinct other races of the early perisodactyls have become entirely extinct such were the titanothiars of tertiary north America huge massive rhinoceros like animals with humped back like the bison and paired bony horns at the front of the solidly built skull the paleothiars of the European tertiary smaller, horneless tapio-like in size and proportion but with only three front toes and most peculiar of all the calico-tares an odd combination of horse and rhinoceros in proportions but with a hooves we converted into large powerful claws used probably to dig around trees and uproot them in order to feed upon their foliage in reviewing the historical development of the perisodactyls it must be deemed an order that has passed its prime and is tending toward extinction it was represented during the tertiary period by a great number and variety of members both small and large its living representatives are few in number of large size scattered widely diverse in form and habits and except for the horses confined to tropical regions even the horses the most successful in adapting themselves to modern conditions of life do not appear to maintain themselves in competition with their numerous and varied rivals of the ruminant group which are by far the most abundant among modern hoofed mammals the order artiodactyla includes two principal groups first the non-ruminants pigs, peccaries, and hippopotami with the primitive bonadont type of teeth and with four separate digits in each foot although the sides of toes are sometimes much reduced second the ruminants camels, deer, antelope, sheep and cattle in which the cheek teeth are adapted for grinding although with a wholly different pattern from the grinders of horses and there are only two complete digits on each foot the metapodials of which are fused into a single cannon bone although the toes remain separate and the side toes are rudimentary dew claws or altogether absent the first group retain more nearly the ancestral characters of teeth and feet and have survived owing to certain unusual habits of life or special means of defense which have affected them against competition the second group is the progressive and dominant group of herbivorous mammals the pigs of the old world and the peccaries of the new are provided with bristly hair thick skin and very efficient canine tusks they are compact bodied bold and active fighters dangerous adversaries whom their carnivorous enemies or herbivorous rivals may well hesitate to attack nevertheless their ranks and numbers have been much decreased since the middle tertiary several large kinds of peccary inhabited North America as far north at least as the Canadian border up to the Pleistocene epic there is now but a single genus which ranges from southern Texas to Brazil in Europe there were also a number of true pigs some of large size during the later tertiary the wild boar is the only surviving type in temperate regions but in tropical Africa and the East Indies there are several others the warthog red riverhog babarusa and a number of species of pigs the pigs like the tapirs and rhinoceroses have followed the tropical forest from it southward in its gradual disappearance from the temperate zone the hippopotamus is among the largest of living quadrupeds thick skin almost hairless its broad short feet with four toes of nearly equal size its huge jaws and long heavy tusks adapted to root in the mud of river bottoms chiefly aquatic in its habits it can remain underwater for some time or coming up to breathe it is found today only in the rivers of central Africa but had formerly a much wider range inhabiting Madagascar and southern Asia and ranging northward into Europe nine tenths of the hoofed animals belong to the ruminants a section of the artiodactyls they are distinguished especially by the peculiar complexity of the stomach which enables them to chew the cud it is divided into four chambers the first and largest or paunch serving to contain the hastily swallowed food which is laid to return to the mouth thoroughly masticated at leisure and passes to the other divisions of the stomach for digestion the advantage of this habit of chewing the cud to an herbivorous animal whose food requires thorough chewing are very considerable food can be obtained hastily, where rich and plentiful while the necessary mastication can be continued while en route from the feeding grounds or during rest or deferred till a place of safety is reached the limbs and feet of ruminants are highly specialized both for speed and endurance almost if not quite as much as in the horse padded hoof really two separate hoofs closely paired gives them a better footing on rough or irregular ground among living ruminants the camels and llamas stand apart as a primitive and peculiar race specialized for desert life the long loose jointed limbs and padded feet lack the speed adaptation of the higher races but are well fitted to traverse the loose desert sand the stomach is less complex but peculiarly specialized to carry a supply of water which enables the animal to go without drinking for several days at a time although the camels are now found only in the Central Asian and North African deserts and the llamas in the arid regions of South America they were during the tertiary period a peculiarly North American family and the evolution of the race has been traced almost as completely as the evolution of the horse back to little ancestors no larger than a cat with four separate digits on each foot they disappeared from North America before the appearance of civilized man like the Native American horses and the preservation of camel in the old world is perhaps like the preservation of the Asiatic horse due to their being domesticated by man it is doubtful whether any truly wild camels exist either in Asia or Africa if these domesticated races be set aside it will be found that camels and horses have both disappeared from the northern continents where they were abundant during the age of mammals but are preserved in the outlying southern continents the peculiarly American camels in South America the cosmopolitan horses in southern Africa looking at the matter in this way it may reasonably be supposed that they were driven into the outlying southern regions through their inability to contend with the more perfected ruminants whose center of dispersal was in the great northern landmass both camels and llamas have been domesticated by man and used as beasts of burden the Bactrian or two-hummed camel in Central Asia the Dromedary in North Africa the llama was the only beast of burden in ancient Peru while the smaller alpaca was kept for its fleece and meat the wild races of these two species still exist in the high plains of South America under the names of Guanaco and Vecunia before taking up the typical ruminants or Pecorra allusion may be made to the chevrotane of the dense forests of the East Indies and the water chevrotane of the equally dense forests of West Africa both regions the refuge of many primitive survivors of the tertiary fauna these two genera are grouped together because of the less perfected foot structure and lack of horns and represent quite nearly the early tertiary stage in the evolution of the ruminants as it is found fossil in Europe and North America the true ruminants or Pecorra are undoubtedly the dominant group of herbivore today they are a group of comparatively recent evolution geologically and first appear in the middle tertiary developing out of primitive artyodactyls meaning in the old world their center of diffusion was apparently North Asia whence they spread to Europe on one hand to North America on the other reaching Africa and South America at a later date probably toward the end of the tertiary period they include three main sections first the giraffes in which the horns are bony excrescences covered with a skin pad second the deer in which the horns, antlers are covered with a skin pad the velvet only when newly formed and are shed annually third the antelopes, sheep and cattle in which the horn cones are covered with a heavy solid and puff true horn which is permanent during the lifetime of the animal the giraffes may be regarded as the most primitive of these three sections they are today limited to Africa the giraffe being adapted to the semi-desert plains where its long neck enables it to feed upon the succulent upper foliage of memoses and other thorny bushes while its ally the recently discovered okapi inhabits the deep forests of central Africa fossil giraffes have been found in the late tertiary of Asia and southern Europe and nearly related forms of the ethereum etc were of greater bulk although not so tall and had the horns much larger and more branched end of chapter 9 part 3 end of section 15 section 16 of the science history of the universe volume 6 this is a LibriVox recording while LibriVox recordings are in the public domain for more information or to volunteer LibriVox.org the science history of the universe volume 6 edited by Francis Rold Wheeler zoology chapter 9 the vertebrates part 4 mammals part 4 the deer are especially adapted to forest life the teeth short crowned and suited for browsing they inhabit all the forest regions of Europe Asia, North Africa and the two Americas but have been prevented from reaching the Ethiopian region by the wide stretch of the Saharan desert and the arid mountainous country to the east of it the largest and most progressive of the deer are found as one might expect in the arctic and cold temperate zones of the north the wopiti and red deer the reindeer and caribou the moose and European elk being the highest development of the family the smallest and most primitive members live in southern Europe in southeastern Asia the East Indies and in Central and South America the earliest deer were of small size at first hornless like the modern musk deer the Malias and water deer of China or the fawn of any of the larger deer then with a single spike like the Central American Brockets or the second year of the larger deer to which the term Brocket originally belonged then with two, three or more times all the stages being paralleled both by the adults of different species of modern deer and by the annual changes in the young of the larger northern deer the antelopes sheep and cattle are primarily adapted to living on open plains the teeth are mostly long crowned and in many of them the grinding edges of the enamel are braced by a heavy deposit of cement as in the horses they are thus suited to feed upon the hard dry plains grass which require very thorough chewing before their nutrition becomes available antelopes is a broad term that covers all the various races except two the sheep and goats and the cattle which on account of their domestication by man are of special importance and have received special names from the zoological point of view they are not more different from antelopes than the different races of antelopes are from each other but they may fairly be considered as the highest and most progressive of the various antelope groups the antelopes are today most abundant and varied in Africa in Europe and Asia where they were numerous during the later tertiary they have been mostly displaced by the sheep and oxen but are still found in large numbers in India in Arabia and Syria and a few in the more central parts of Asia except for one or two little known extinct species they do not appear ever to have reached the new world the so called antelope pronghorn of the western plains is a solitary survivor of a distinct race intermediate between deer and antelopes in its affinities especially characteristic of North America the smallest antelope is a little meduca or a pygmy antelope of east Africa no larger than a hare not much larger are the duker box cephalophus of south and east Africa so called from the dexterity and quickness with which they duck or dive into the tall grass or bushes to escape from their pursuers in these the horns are small straight spikes the gazelles with longer ringed horns delicate head with large soft eyes slender neck and long limbs are generally admitted to be the most graceful of the hoofed quadrupeds and unsurpassed in speed in the larger antelopes the horns are either ringed or spirally twisted mostly projecting upward with a slight backward curve but in the gnu they are depressed on the side of the head is in the sheep some of the larger antelopes such as the african eland or indian nilgai have nearly the size and proportions of domestic cattle the goats, sheep and cattle are the latest of the antelope groups to appear in geological history and the wild species are today predominantly asiatic in their distribution the cattle however are widely distributed throughout africa, india and the east india islands and in north america are represented by the bison and musk ox the big horn and mountain goat of north western north america are the only new world representatives of the sheep and goats a single species of wild sheep is found in north africa otherwise they are all palearctic a few such as the ibex and camois inhabiting the mountainous regions of europe most of them the highlands of asia while the cattle are especially plains and lowland types the sheep and goats are preeminently mountain dwellers active climbers sure-footed and able to endure severe cold the domesticated species of cattle, sheep and goats are of enormous economic importance and have contributed very largely to shaping the development of old world civilization besides the ancestors of the modern pigs and ruminants there were various races of this order of hoofed animals that have not survived the eloteers were large animals with huge skulls cheek teeth like those of pigs front teeth more like carnivorous mammals feet strictly toed as in camels and ruminants but the metapodials not united into a cannon bone they inhabited the northern continents in the middle part of the tertiary period the skull of the largest of them dynoeus is over 3 feet long the animal as large as a hippopotamus longer legs and short massive body proportion more like the bison the oreodonts very abundant in north america at the same time have been called ruminating hogs as they combine the foretoed feet of the pigs with a ruminating type of teeth they must have resembled peccaries in appearance and habits but with shorter snout the contemporary anoploteers took the place of the oreodonts in the old world the anthrocodethiers pig-like in proportions with teeth partly intermediate between those of pigs and ruminants are regarded as more or less directly ancestral to the hippopotamus the elephants are the most gigantic of living quadrupeds and the most singular in appearance the elongation of the snout into a long flexible trunk serving much the same purposes as the hands in man set them apart from all the other ungulates as in this respect at least a higher mechanical adaptation for there can be no doubt that the development of the hand into an effective organ of prehension released from the functions of locomotion has played an important part in the evolution of intelligent life in man and in the elephant we see an entirely different organ serving the same purpose almost as effectively to find the elephant ranking as the most intelligent of hoofed animals there is what might be expected the limbs are long straight and massive the feet short rounded, heavily padded with five small hooves on each this construction is best adapted to support the gigantic weight of the body five to fifteen thousand pounds and all very large land animals approach it more or less nearly the teeth are very highly specialized one pair of upper incisors is enlarged and lengthened into tusks all the other front teeth have disappeared of the cheek teeth only the molars remain are high crown composed of alternating transverse plates of enamel, dentine and cement the three molars come into use one after another dropping out as they wear down to the roots and in a fully adult elephant only one grinding tooth is left on each side of the upper or lower jaw four grinders and two tusks constitute the entire adult dentition and even the tusks are absent in the female the skull and jaws are extremely short and large in proportion giving room for the attachment of the powerful muscles necessary to wheel the trunk and tusks and grind the food leaves, twigs, fruits and forest grasses unlike other long-limbed animals accepting man the neck is very short as the trunk makes it unnecessary to reach the ground the average height of elephants is from 8 to 10 feet but the African species at least sometimes reaches 12 feet in height Jumbo was 11 feet high his weight 6.5 tons the Indian species is more massive but not so tall as the African one its forehead is higher and grinders larger with more numerous and closely set plates the tusks are smaller and often absent in males as well as females elephants have been tamed since the days of the ancients both Indian and African species those brought by Hannibal from Carthage must have been African elephants but the Greeks and Romans were more familiar with the Indian species the two modern species of elephants are the last survivors of a race that was readily distributed in prehistoric times the mammoths were simply a species of elephant the mastodons were a nearly related genus but with shorter crown and more numerous teeth and other primitive characters these during the Pleistocene epic ranged over all the northern continents mammoth remains have been found in all parts of Europe and in Asia northward to the Leacof Islands in the Arctic Ocean where vast quantities of their tusks and bones are preserved in the frozen soil in America the mammoths of different species ranged from Siberia to Mexico the mastodons were of even wider range penetrating into South America as far as the Argentine plains the Arctic species of elephants were covered with a shaggy coat of reddish brown wool and longer black hairs in Siberia and Alaska carcasses of these animals more or less complete have been found preserved in the frozen soil the southern mammoths were more probably naked skinned like the modern elephants which they somewhat exceeded in height and bulk a skeleton in the Paris Museum is slightly over 3 meters 13 feet in height the mastodons were also covered with hair the tusks in some of these mammoths and mastodons were of enormous size curling inward and crossing at the tips some of these fossil tusks was 13 feet in length and 9 inches in thickness like the tusks of modern elephants they are composed of ivory or dentine only the enamel being lacking during the latter half of the tertiary period primitive mastodons confotherium inhabited Europe, Asia and North America they were much smaller than the Pleistosteen mastodons and elephants with tusks in both upper and lower jaws and shorter limbs longer skull and much shorter trunk the lower tusks are short and straight or in the earliest forms curving slightly downward and with a strip of enamel on the face of the tusk in a related genus dynoetherium the upper tusks were absent the lower ones large and curving downward and in this animal the grinding teeth were more numerous five on each side of the jaw while the gumpotherium like the true mastodon had but three a complete series of intermediate stages between the primitive mastodons and the modern elephants is found in the successive formations of the latter tertiary in Europe and Asia the early history of the probosidians was unknown until very recently when the explorations in the Phaeum district of Egypt disclosed an early tertiary fauna which included among other large quadrupeds new to science the early stages in the evolution of mastodons and elephants these carried back the ancestry of the elephant to a small animal morotherium about as large as a cow with a nearly complete series of teeth short crowned grinders one pair of incisors enlarged and somewhat like the gnawing teeth of rodents with long head, no trunk and short limbs Phaeum mastodon was intermediate between this type and the primitive mastodons reference has been made to the various extinct relatives of the perosodactyls artyodactyls and probosidians but during the age of mammals there were a number of groups of hoofed mammals not related to any of the living orders and some of remarkable portions in gigantic size in North America during the Eocene epoch lived the euentotarium or dinocerous a huge creature larger than an Indian rhinoceros with elephantine limbs and feet its head armed with three pairs of bony horns and great saber-like upper tusks in Africa about the same time or a little later lived the Arseneuetherium equally huge an elephantine in limbs and feet and with a pair of great sharp horns at the front of the skull South America during the long period that it remained an island continent developed a great variety of hoofed mammals unrelated to those of the northern continents but sometimes paralleling them to a remarkable extent in the South American Eocene is found a great elephantine quadruped the pyroetherium singularly like the ancestral mastodons in many respects but probably not closely related to them in the myocene lived another huge beast the astropotherium again with elephantine limbs and feet and apparently provided with a shorter trunk but with tusks like those of pigs and peckeries only of larger size and with grinding teeth that bear a general resemblance to those of the rhinoceros at the same time lived smaller animals the nestodons proportioned somewhat on the lines of a small hornless rhinoceros and a little typotheries rabbit or coni-like in size and proportions but in fact related to the nestodons the most interesting members of the myocene fauna of South America were the lipopterna some of which paralleled the horses in their foot structure with extraordinary closeness although not at all horse-like in the skull or teeth the side toes were reduced to dew claws as in the later three-toed horses and finally disappeared leaving only the central pole with a rudimentary nodule of bone to represent each side toe like the splint of the modern horse that the foot bones threw out becomes singularly like that of the true horses other lipopterna retained three well-developed toes like the rhinoceroses but their limbs had rather the shambling build of the camel than the more compact proportions of rhinoceroses or tapir at the end of the tertiary still other gigantic ungulates developed in South America Nezodons gave rise to the huge massive toxodon exceeding a rhinoceros in size the three-toed lipopterna to the camel-like macrochenea all these extinct groups of ungulates were evolved in North America in South America and in Africa during epics when these regions were cut off from the main center of mammals the great landmass of northern and central Asia the corresponding forms evolved in this larger central region were subject to severe and wider competition were more advanced intelligent active or hardy than the quadrupeds evolved in the smaller isolated areas consequently when these areas were joined to the central landmass its fauna invaded them and swept out of existence all the competing autoctonic types the manatee and dugong are the remnants of a group of herbivorous mammals nearly related to the ancestors of the elephants like the cetacea they have adopted an aquatic life and become more or less fish-like in form losing the hind limbs developing the tail into a swimming organ and the forelimbs into fin-like paddles and entirely losing the hair unlike cetaceans they are sluggish slow-moving bottom feeders living on the aquatic vegetation of tidal rivers or upon seaweeds the dugong of the Red Sea and East Indies and the manatee of the Atlantic coasts are the only survivors a larger form Stellar's sea cow inhabited some of the illusion islands until 1758 and in the tertiary formations of Europe and North Africa various ancestral stages have been discovered the name sirenia may seem singularly inappropriate for such peculiarly ugly animals yet it is not unlikely that some of the older reports of mermaids were based upon the dugong owing to the custom of the parent holding the young to her breast with her flippers the round heads of both being raised out of the water the carnivora are the beasts of prey specially adapted for flesh-eating and nutritious habits for the most part they are exceptionally active, strong and restless of high intelligence and perfect bodily mechanism insofar as perfection consists in mechanical adaptation to an active and varied life the carnivora may indeed be regarded as the highest of living animals man indeed of his mental powers stands far above the rest of creation but as an all-around athlete he must yield the palm to the carnivores besides the land carnivora this order includes the seals and walruses adapted to a marine life and again partially assuming a fish-like form although they have retained their furry covering and in the absence of a heavy tail their limbs have been converted into a propelling organ instead of disappearing as they have done in cetaceans or sirenians the forelimbs are converted into flippers and the teeth mimic those of the early toothed whales in their adaptation to fish-eating but seals and walruses are not as helpless on land as are dolphins or whales their adaptation to marine life is not so complete the great rookeries in which seals congregate for breeding purposes and the long migrations which they undertake each season are remarkable features of their life the terrestrial carnivora are more numerous and familiar their teeth are specialized for seizing their prey and for cutting flesh the canine teeth are large and sharp and strong one pair of cheek teeth is enlarged and converted into stout shearing blades which act like a pair of scissors these are termed carna sails and the cheek teeth in front of them are usually of cutting type while the molars behind are used for crushing or are entirely absent the feet have either four or five digits the claws usually sharp sometimes retractile so that they can be drawn back out of the way while walking and extended only in seizing their prey they walk either upon the entire sole of the foot or upon the under surface of the toes the sole or palm being held free of the ground but never upon the tips of the toes as do the hoofed animals most of the carnivora are good climbers some live mostly or altogether in trees all of them are of high intelligence and keen perceptions the senses of light, smell and hearing very highly developed they are divided usually into seven families one canadae, dogs, wolves foxes and jackals partly omnivorous, adapted to swift running and very often hunting in packs cosmopolitan prosionidae raccoons omnivorous and arboreal found only in the new world three, ursidae bears omnivorous, terrestrial and all of large size cosmopolitan except australian region four, mustelidae weasels, martins, skunks badgers and otters mostly predatious and of small or medium size found everywhere except in the australian region five viviridae civets, mongooses et cetera mostly predatious and of small or medium size confined to the old world exclusive of australia the few species of carnivora in Madagascar all belong to this family six hyenidae predatious and of large size found only in africa and south asia seven filidae including the lion, tiger and various smaller cats strictly predatious large or of medium size cosmopolitan except australia the dog family are more adapted for speed than any other carnivora and the larger species often hunt in packs and run down their prey in the open they are equally expert in tracking their prey the sense of smell being very highly developed unlike most carnivora the claws are blunt and are used only for locomotion and they are quite unable to climb trees their range extends from the arctic regions to the equator and southward to patagonia and the focland islands the true wolves and foxes are mostly found in the northern continents the jackals are oriental and african while the south american canids belong to a somewhat primitive group known as dog foxes the dingo is the only member of the carnivora which is ender australia but whether introduced by a primitive man or naturally is certainly proven all of the family are much alike in structure differing mainly in size color and habits they are all included in the genus canis except four or five species inhabiting india africa and south america the raccoons of the new world are more or less related to the dogs but are boreal forest living nocturnal and omnivorous the well-deserved reputation for cleverness and cunning qualities shared by the less known members of the family the coyotee, caxomissel and the kinkajou of the central and south american forests the last name is the most strictly arboreal of the carnivora it's tale prehensile like the monkeys which it resembles in habits and food end of chapter 9 part 4 end of section 16