RHINOCEROS, a name applied by the ancients to an animal the most striking external peculiarity of which is certainly the horn growing above its nose (______, nose-horn).
The various existing and extinct species are grouped into a family, Rhinocerotidse, which is a division of the Perissodactyle (odd-toed) section of the great order of Ungulata or hoofed mammals, of which section the tapirs and horses are the only other surviving members (see MAMMALIA, vol. xv. p. 428).
The following are the general characters applicable to all the members of the family.
First, as regards dentition. Incisors variable, generally reduced in number and often quite rudimentary, and early deciduous. Canines, in existing species, absent. Molar series, consisting of the full number of four premolars and three molars above and below, all in contact and closely resembling each other, except the first, which is much smaller than the rest and often deciduous. The others gradually increasing in size up to the penultimate. The upper molars have a very characteristic pattern of crown, having a much-developed flat or more or less sinuous outer wall, and two transverse ridges running obliquely inwards and backwards from it, terminating internally in conical eminences or columns, and enclosing a deep (middle) sinus between. The posterior sinus is formed behind the posterior transverse ridge, and is bounded externally by a backward continuation of the outer wall and behind by the cingulum. The anterior sinus is formed in the same manner, but is much smaller. The middle sinus is often intersected by vertical laminae (" combing plates ") projecting into it from the anterior sur-face of the posterior transverse ridge or from the wall, the development of which is a useful guide in discriminating the species, especially those no longer existing and known only by the teeth and bones. The depressions between the ridges are not filled up with cernentum as in the horse. The lower molars have the crown formed by a pair of crescents; the last has no third lobe or talon.
Head large, skull elongated, elevated posteriorly into a transverse occipital crest. No post-orbital processes or any separation between orbits and temporal fossae. Nasal bones large and stout, co-ossified, and standing out freely above the premaxillas, from which they are separated by a deep and wide fissure; the latter small, generally not meeting in the middle line in front, often quite rudimen-tary. Tympanies small, not forming a bulla. Brain cavity very small for the size of the skull. Vertebras :cervical,. 7 ; dorsal, 19-20 ; lumbar, 3 ; sacral, 4; caudal, about 22. Limbs stout, and of moderate length. Three completely developed toes, with distinct broad rounded hoofs on each foot. Mammas two, inguinal. Eyes small. Ears of moderate size, oval, erect, prominent, placed near the occiput. Skin very thick, in many species thrown into massive folds. Hairy covering scanty. All existing species have one or two median horns on the face.. When one is present it is situated over the conjoined nasal bones ; when two, the hinder one is over the frontals. These horns, which are of a more or less conical form and usually recurved, and often grow to a great length (three or even four feet), are composed of a solid mass of hardened epidermic cells growing from a cluster of long dermal papillas. The cells formed on each papilla consti-tute a distinct horny fibre, like a thick hair, and the whole are cemented together by an intermediate mass of cells which grow up from the interspaces between the papillas. It results from this that the horn has the appearance of a. mass of agglutinated hairs, which, in the newly growing part at the base, readily fray out on destruction of the softer intermediate substance; but the fibres differ from true hairs in growing from a free papilla of the derm, and not within a follicular involution of the same.
The Rhinocerotidx are all animals of large size, but of little intelligence, generally timid in disposition, though ferocious when attacked and brought to bay, using the nasal horns as weapons, by which they strike and toss their assailant. Their sight is dull, but their hearing and scent are remarkably acute. They feed on herbage, shrubs, and leaves of trees, and, like so many other large animals which inhabit hot countries, sleep the greater part of the day, being most active in the cool of the evening or even during the night. They are fond of bathing and wallowing in water or mud. None of the species have been domesti-cated. Animals of the group have existed in both the Old and New Worlds since the beginning of the Miocene period. In America they all became extinct before the end of the Pliocene period. In the Old World their distribution has become greatly restricted, being no longer found in Europe and North Asia, but only in Africa and in portions of the Indian and Indo-Malayan regions.
The existing species of rhinoceros are naturally grouped into three sections, which some zoologists consider of generic value.
I. Rhinoceros proper. The adults with a single large compressed incisor above on each side, and occasionally a small lateral one; below, a very small median, and a very large, procumbent, pointed lateral incisor. Nasal bones pointed in front. A single nasal horn. Skin very thick, and raised into strong, definitely arranged ridges or folds.
There are two well-marked species of one-horned rhinoceroses. (1) The Indian Rhinoceros, R. unicornis of Linnaeus, the largest and best known, from being the most frequently exhibited alive in England, is at present only met with in a wild state in the terai region of Nepal and Bhutan, and in the upper valley of the Brahmaputra or province of Assam, though it formerly had a wider range.
FIG. 2.Indian Rhinoceros (Rhinoceros unicornis). This and the following woodcuts are reduced from drawings by J. Wolf, from animals living in the London Zoological Society's Gardens.
FIG. 3.Javan Rhinoceros (Rhinoceros sondaicus).
The first rhinoceros seen alive in Europe since the time when they, in common with nearly all the large remarkable beasts of both Africa and Asia, were exhibited in the Roman shows, was of this species. It was sent from India to Emmanuel, king of Portugal, in 1513 ; and from a sketch of it, taken in Lisbon, Albert Dürer composed his cele-brated but rather fanciful engraving, which was repro-duced in so many old books on natural history. (2) The Javan Rhinoceros, R. sondaicus, Cuvier, is distinguished by smaller size, special characters of the teeth and skull, and different arrangement of the plications of the skin (as seen in the figures); the horn in the female appears to be very little developed, if not altogether absent. This has a more extensive geographical range, being found in the Bengal Sunderbans near Calcutta, Burmah, the Malay Peninsula, Java, Sumatra, and probably Borneo.
II. Ceratorhinus. The adults with a moderate-sized compressed incisor above, and a laterally placed, pointed, procumbent incisor below, which is sometimes lost in old animals. Nasal bones narrow and pointed anteriorly. A well-developed nasal, and a small frontal horn separated by an interval. The skin thrown into folds, but these not so strongly marked as in the former section. The smallest living member of the family, the Sumatran Bhinoceros, R. sumatrensis, Cuv., belongs to this group. Its geo-graphical range' is nearly the same as that of the Javan species, though not extending into Bengal; but it has been found in Assam, Chittagong, Burmah, the Malay Peninsula, Sumatra, and Borneo. It is possible that more than one species have been confounded under this designation, as two animals now living in the London Zoological Gardens present considerable differences of form and colour. One of them, from Chittagong, has been named by Sclater R. lasiotis, the Hairy-Eared Rhinoceros, but until an opportunity is afforded for anatomical ex-amination, it is difficult to pronounce upon the value of the distinction.
III. Atelodus. In the adults, the incisors are quite rudimentary or entirely wanting. Nasal bones thick, rounded and truncated in front. Well-developed anterior and pos-terior horns in close contact. Skin without any definite permanent folds.
The two well-marked existing species are peculiar to the African continent.
lower jaw. It ranges through the wooded and watered districts of Africa, from Abyssinia in the north to the Cape Colony, but its numbers are yearly diminishing, owing to
1. The common Two-Horned Rhinoceros, R. bicornis, Linn., is the smaller of the two, with a pointed prehensile upper lip, and a narrow compressed deep symphysis of the the inroads of European civilization, and especially of English sportsmen. It feeds exclusively upon leaves and branches of bushes and small trees, and chiefly frequents the sides of wood-clad rugged hills. Specimens in which the posterior horn has attained a length as great as or greater than the anterior have been separated under the name of R. keitloa, but the characters of these appendages are too variable to found specific distinctions upon. The two-horned African rhinoceros is far more rarely seen in menageries in Europe than either of the three Indian species, but one has lived in the gardens of the London Zoological Society since 1868. Excellent figures from life of this and the other species are published in the ninth volume of the Transactions of the society, from which the accompanying woodcuts are reduced.
2. Burchell's or the Square-Mouthed Rhinoceros (R. sirnus), sometimes called the White Rhinoceros, though the colour (dark-slate) is not materially different from that of .the last species, is the largest of the whole group, and differs from all the others in having a square truncated upper lip and a wide, shallow, spatulate symphysis to the lower jaw. In conformity with the structure of the mouth, this species lives entirely by browsing on grass, and is therefore more partial to open countries or districts where there are broad grassy valleys between the tracts of bush. It is only found in Africa south of the Zambesi, and of late years has become extremely scarce, owing to the persecutions of sportsmen; indeed, the time of its complete extinction cannot be far off. No specimen of this species has ever been brought alive to Europe. Mr E. C. Selous gives the following description of its habits from extensive personal observation :
" The square-mouthed rhinoceros is a huge ungainly-looking beast, with a disproportionately large head, a large male standing 6 feet 6 inches at the shoulder. Like elephants and buffaloes they lie asleep during the heat of the day, and feed during the night and in the cool hours of early morning and evening. Their sight is very bad ; but they are quick of hearing, and their scent is very keen; they are, too, often accompanied by rhinoceros birds, which, by running about their heads, flapping their wings, and screeching at the same time, frequently give them notice of the approach of danger. When disturbed they go off at a swift trot, which soon leaves all pursuit from a man on foot far behind ; but if chased by a horseman they break into a gallop, which they can keep up for some distance. However, although they run very swiftly, when their size and heavy build is considered, they are no match for an average good horse. They are, as a rule, very easy to shoot on horseback, as, if one gallops a little in front of and on one side of them, they will hold their course, and come sailing past, offering a magnificent broadside shot, while under similar circumstances a prehensile-lipped rhinoceros will usually swerve away in such a manner as only to present his hind-quarters for a shot. When either walking or running, the square-mouthed rhinoceros holds its head very low, its nose nearly touching the ground. When a small calf accompanies its mother, it always runs in front and she appears to guide it by holding the point of her horn upon the little animal's rump ; and it is perfectly wonderful to note how in all sudden changes of pace, from a trot to a gallop or vice versa, the same position is always exactly main-tained. During' the autumn and winter months (i.e., from March to August) the square-mouthed rhinoceros is usually very fat; and its meat is then most excellent, being something like beef, but yet having a peculiar flavour of its own. The part in greatest favour among hunters is the hump, which, if cut off whole and roasted just as it is in the skin, in a hole dug in the ground, would, I think, be difficult to match either for juiciness or flavour."Proc. Zool. Soc, 1381, p. 726
Extinct Species of Rhinoceros.The family once contained many more species, wdiich were far more widely distributed than at present. As in similar cases, our knowledge of them is as yet but fragmentary, though constantly augmenting, especially by dis-coveries made in the Tertiary deposits of North America, a region in which they all died out long ago, though, judging from the evidence at present available, this was the locality in which they first made their appearance. In the Eocene formations of the Rocky Mountains are found the remains of numerous modifications of the primitive Perissodactyle type, from which the rhinoceroses may have originated. In the Lower Miocene a form called Hyracodon by Leidy already presented many of the characteristics of the family, though, especially as regards the dentition, in a very generalized condition. The next stage of specialization is represented by Aceratherium. found in the Miocene of both Europe and America, which still, like the last, shows no sign of having possessed a nasal horn. It differed from the existing species also in having four toes on the anterior limb, instead of only three. At the same period forms occurred (Dicera thorium, Marsh) which show a pair of lateral tubercles on the nasal bones, apparently supporting horns side by side. These, however, soon disappeared and gave way in the Old World to species with one or two horns in the median line, a stage of development which apparently was never reached in America. In the Pliocene and Pleistocene of Europe and Asia numerous modifications of the existing types have been found. The present African two-horned type was represented in the Early Pliocene of Greece by R. pachygnathus, the skeleton of which is described by Gaudryas intermediate between the existing R. bicomis and R. simus. As many as three species were inhabitants of the British Isles, of which the best known is the Tichorhine or Woolly Rhinoceros, R. antiquitatis of Blumenbach, nearly whole carcases of wdiich, with the thick woolly external covering, have been discovered associated with those of the mammoth, preserved in the frozen soil of the north of Siberia, and which, in common with some other extinct species, had a solid median wall of bone supporting the nasals, from which it is inferred that the horns were of a size and weight surpassing that of the modern species. The one-horned Indian type was well represented under several modifications (R. sivalensis, paleeindicus, he), in the Pliocene deposits of the sub-Himalayan region, and forms more allied to the African bicorn species have also been found in India. R. schleirmacheri of the late European Miocenes was in some respects allied to the existing Sumatran rhinoceros, possessing incisor teeth and two horns. (W. H. F.)
In some extinct species a small outer toe is present on the forefoot.
Many authors use Cuvier's name, R. indicus, in preference to this, on the ground that there are more than one species with one horn, forgetting that the name substituted is equally inconvenient, as more than one species live in India. The fact of a speeilic name being applicable to several members of a genus is no objection to its restriction to the first to which it was applied ; otherwise changes in old and well-received names would constantly have to be made in consequence of new discoveries.