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TYLOPODA (Gr. for boss-footed, in ref...

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Originally appearing in Volume V27, Page 498 of the 1911 Encyclopedia Britannica.
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TYLOPODA (Gr. for See also:boss-footed, in reference to the See also:cushion-like pads forming the soles of the feet)  , the scientific name of the See also:section of ruminating artiodactyle ungulate mammals (see See also:ARTIODACTYLA) now represented by the Old See also:World camels (see See also:CAMEL) and the See also:South See also:American Llamas (see See also:LLAMA) Characters.—In the See also:skull there is a sagittal See also:crest; the tympanic bulla is filled with cancellous See also:tissue; the condyle of the See also:lower See also:jaw is rounded; and the premaxillae, or anterior bones of the tipper jaw, have the full number of incisor See also:teeth in the See also:young See also:state, the See also:outer-most of these being persistent through See also:life as an isolated tooth . The tusk-like canines are See also:present in both jaws, those of the lower jaw Mr F . W . D . See also:Brie (See also:English See also:Historical See also:Review, 1906) vol. xxi. advances the theory that See also:Tyler and See also:Straw are one and the same See also:person.being differentiated from the See also:long, See also:horizontal and spatulate incisors; in See also:form they are sub-erect and pointed . The crowns of the molars belong to the crescentic or selenodont type, and are tall-crowned or hypsodont; but one or more of the anterior premolars is usually detached from the See also:series, and of See also:simple pointed form . The hinder See also:part of the See also:body is much contracted, and the femur long and vertically placed, so that the See also:knee-See also:joint is lower in position, and 'the thigh altogether more detached from the See also:abdomen than in most mammals . The limbs are long, but with only two digits (the third and See also:fourth) See also:developed on each, no traces of any of the others being present . The trapezoid and magnum of the carpus, and the cuboid and navicular of the See also:tarsus are distinct . The two See also:cannon-bones of each See also:limb are confluent for the greater part of their length, though separated for a considerable distance at the lower end . Their lower articular surfaces, instead of being See also:pulley-like, with deep ridges and grooves, as in other Artiodactyla, are simple, rounded and smooth . The first phalanges are See also:expanded at their lower ends, and the wide, depressed See also:middle phalanges embedded in a broad cutaneous See also:pad, forming the See also:sole of the See also:foot, on which the See also:animal rests in walking instead of on the hoofs .

The terminal phalanges are small and nodular, not flattened on their inner or opposed surfaces, and not completely encased in hoofs, but bearing nails on their upper See also:

surface only . The See also:neck is long and curved, and its vertebrae are remarkable for the position of the See also:canal for the transmission of the vertebral artery, which does not perforate the transverse See also:process, but passes obliquely through the anterior part of the pedicle of the See also:arch . There are no horns or antlers . Though these animals ruminate, the See also:stomach differs considerably in the details of its construction from that of the See also:Pecora . The interior of the rumen or paunch has no tags or villi on its surface, and there is no distinct psalterium or manyplies . Both first and second compartments are remarkable for the presence of a number of pouches or cells in their walls, with See also:muscular partitions, and a sphincter-like arrangement of their orifices, by which they can be shut off from the See also:rest of the cavity, and into which the fluid portion only of the contents of the stomach is allowed to enter . The See also:placenta is diffuse, not cotyledonary . Finally, the See also:Tylopoda differ not only from other ungulates, but from all other mammals, In the fact that the red corpuscles of the See also:blood, instead of being circular in outline, are See also:oval as in the inferior vertebrate classes . Camels.—Of the two existing generic representatives of the Camelidae (as the See also:family in which they are both included is named), the Old World camels (Camelus) are characterized by their See also:great bodily See also:size, and the presence of one or two fleshy humps, which diminish or increase in size according to the See also:physical See also:condition of the animals themselves . There is a See also:total of 34 teeth, arranged as i . I, c . I, p .

, m . R . Of these the first upper premolar is a simple tooth placed See also:

close behind the premaxilla and separated by a long See also:gap from the two other teeth of the same series; while the lower incisors, of which the outermost is the largest, are directed partially forwards . The skull is elongated, with an overhanging occiput, See also:complete bony rims to the orbits, and the premaxillae separated from the arched and rather long nasals . The vertebrae are C . 7 . D . 12 . L . 7 . S . 4 and Ca .

13 to 15 . The ears are See also:

short and rounded; the toes of the broad feet very imperfectly separated ; the tail is well developed, with a terminal tuft; and the straight See also:hair is not woolly . Llamas.—Although the name llama properly applies only to one of the domesticated breeds, zoologically it is taken to include all the South American representatives of the Camelidae, which form the genus Lama . In this sense, llamas are characterized as follows . The dentition in the adult is i. c. if, p . , in . I; total 32 . In the upper jaw there is a compressed, See also:sharp-pointed, tusk-like incisor near the See also:hind edge of the premaxilla, followed in the male at least by a moderate-sized, pointed, curved canine in the anterior part of the maxilla . The isolated canine-like premolar which follows in the camels is not present . The teeth of the cheek-series which are in contact with each other consist of two small premolars (the first almost rudimentary) and three broad molars, constructed generally like those of Camelus . In the lower jaw the three incisors are long, spatulate and horizontal, with the outer one the smallest . Next to the latter is a curved, sub-erect canine, followed after an See also:interval by an isolated See also:minute and often See also:deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of See also:recent See also:species of Camelus in having a small See also:accessory See also:column at the anterior outer edge .

The skull generally resembles that of Camelus, the relatively larger See also:

brain-cavity and orbits and less developed See also:cranial ridges being due to its smaller size . The nasal bones are shorter and broader, and are joined by the premaxillae . Vertebrae: C . 7, D . 12, L . 7, S . 4, Ca . 15 to 20 . Ears rather long and pointed . No hump . Feet narrow, the toes being more separated than in the camels, and each with a distinct plantar pad . Tail short .

Phoenix-squares

Hairy covering long and woolly . Size smaller and See also:

general form lighter than in the camels . Llamas are now confined to the western and southernmost parts of South See also:America, though fossil remains have been found in the caves of See also:Brazil, and in the See also:pampas of the See also:Argentine See also:Republic . (See also See also:ALPACA; See also:GUANACO; LLAMA and VICUGNA.) Fossil See also:History.—As regards the past history of the See also:group, remains of fossil species of Camelus have been obtained from the superficial deposits of various parts of See also:Russia, See also:Rumania, and See also:Siberia, and others from the Lower See also:Pliocene of See also:northern See also:India; the molar teeth of these latter presenting the additional column referred to above as distinguishing those of the llamas from those of See also:modern camels . In addition to these Dr M . See also:Schlosser has described remains of a large camel-like animal from See also:China, with apparently generalized See also:affinities, for which the name of Paracamelus is proposed . Mme Pavlow, of See also:Moscow, has brought to See also:notice a fossil camel-skull of great See also:interest, which was collected in the See also:district Alexandrie, of the See also:government of See also:Kherson, Russia . Unfortunately, the precise See also:age of the formation from which it was obtained is unknown, but it is considered probable that it See also:dates from the later See also:Tertiary . Although it has the deciduous dentition, Mme Pavlow considers herself justified in referring the Kherson skull to the genus Procamelus previously known only from the Lower Pliocene or Upper See also:Miocene strata of See also:North America, and differing from modern camels, among other features, by the retention of a See also:fuller series of premolar teeth . Part of the cannon-See also:bone of a camel from another district in Russia is provisionally assigned to the same species . Possibly this See also:Russian camel (Procamelus khersonensis), as it is called, may form the connecting See also:link between the typical Procamelus of North America and the fossil camel (Camelus sivalensis) of the Siwalik Hills of India . Be this as it may, the See also:identification of a North American type of camel from the Tertiary strata of eastern See also:Europe forms another connecting link between the See also:extinct faunas of the northern See also:half of the Old World and North America, and thus tends to show that the claim of America to be the exclusive birthplace of many Old World types may have to be reconsidered .

Remains of camels (C. thomasi) have also been found in the See also:

Pleistocene strata of See also:Oran and Ouen Seguen, in See also:Algeria; and certain remains from the Isle of See also:Samos have been assigned to the same genus, although the reference requires See also:confirmation . The Algerian Pleistocene camel was doubtless the See also:direct ancestor of the living See also:African species, which it serves to connect with the extinct C. sivalensis . In North America, apart from certain still older and more See also:primitive mammals, with teeth of the tubercular type, the earliest known form which can definitely be included in the camel-series is Protylopus, of the Uinta or Upper See also:Eocene . In this creature, which was not larger than a See also:European See also:hare, there was the full number of 44 teeth, which formed a See also:regular series, without any long gaps, and with the canines but little taller than the incisors, while the hinder cheek-teeth, although of the crescentic type, were See also:low-crowned . In both jaws the anterior front-teeth were of a cutting and compressed type . Unfortunately, the skull is incomplete, and the rest of the See also:skeleton very imperfectly known; but sufficient of the former remains to show that the socket of the See also:eye was open behind, and of the latter to indicate that in the hind-foot, at any See also:rate, the upper bones of the two functional toes had not coalesced into a cannon-bone . The lateral hind-toes (that is to say the second and fifth of the typical series) had, however, become rudimentary; although it is probable that the corresponding digits of the fore-limb were functional, so that this foot was four-toed . In old individuals the bones of the forearm (See also:radius and ulna) became welded together about half-way down, although they remained See also:free above . On the other See also:hand it appears that the smaller bone of the See also:leg (fibula) was welded to the larger one (See also:tibia), and that its upper portion had disappeared . Nothing is known of the neck vertebrae . It is, of course, evident that there must have been an earlier form in which all the feet were four-toed, and the bones of the forearm and lower part of the leg See also:separate . A See also:stage higher in the series, viz. in the Oligocene, we meet with Poebrotherium, in which a distinct increase in bodily size is notice-able, as also in the relative length of the two bones which unite in the higher types to form the cannon-See also:hone .

Moreover, the crowns of the hinder cheek-teeth are taller, and more distinctly crescentic, both feet are two-toed, the ulna and radius are fused, end the fibula is represented only by its lower part . In the vertebrae of the neck the distinctive cameloid characters had already made their See also:

appearance . On the other hand, the skull was short and See also:rabbit-like, showing none of the characteristic features of modern camels . In the Lower Miocene occurs Protomeryx or Gomphotherium, in which there is a considerable increase in the See also:matter of bodily size, the two metacarpal and metatarsal bones (or those which unite in the latter forms to constitute the cannon-bones) being See also:double the length of the corresponding elements in Protylopus . These bones, although separate, have their adjacent surfaces more closely applied than is the See also:case in the latter; while in this and the earlier genera the terminal toe-bones indicate that the foot was of the normal hoofed type . In the "skull the socket of the eye is surrounded by hone; while the dentition begins to approximate to the camel type—notably by the circumstance that the lower canine is either separated by a gap from the outermost incisors, or that its See also:crown assumes a backwardly curved shape . In Protolabis of the Middle Miocene, while no cannon-bone is formed, the first and second pairs of incisor teeth are retained, and the limbs and feet are short and disproportionately small . In the Upper Miocene we come to a distinct type—Procamelus—which is entitled to be regarded as a camel, and approximates in size to a small llama . Here themetacarpals and metatarsals have partially See also:united to form cannon-bones, the skull has assumed the elongated form characteristic of modern camels, with the loss of the first and second pairs of upper incisors, and the development of gaps in front of and behind each of the next three teeth, that is to say, the third incisor, the canine and the first cheek-tooth . The approximately contemporaneous Pliauchensa makes another step by the loss of the second lower cheek-tooth . Both these genera have the toe-bones of the irregular nodular form distinctive of modern camels, so that we may safely infer that the feet themselves had assumed the See also:cushion-type . In one species of Procamelus the metacarpals and metatarsals coalesced into See also:canon-bones See also:late in life; but when we come to the Pleistocene Camelops such See also:union took See also:place at an See also:early stage of existence, and was thoroughly complete .

In the living members of the group it occurs before See also:

birth . The species of Camelops were probably fully as large as llamas, and some, at any rate, resembled these animals as regards the number of teeth, the incisors being reduced to one upper and three lower pairs, and the cheek-teeth to four or five in the upper and four in the lower jaw; the total number of teeth thus being 28 or 30 in place of the 44 of Poebrotherium . The sole difference between Camelops and Llama seems to consist in certain structural details of the lower cheek-teeth . An allied extinct genus (Eschatius) is also distinguished by certain features in the dentition . Apart from Procamelus the foregoing genera are exclusively North American . A lower jaw from the Pleistocene deposits of that See also:continent has, however, been referred to the Old World Camelus . In addition to the above there is an extraordinary North American Miocene See also:giraffe-necked camel (Alticamelus), a creature of the size of a giraffe, with similarly elongated neck and limbs, and evidently adapted for browsing on trees . The feet and number of teeth were generally similar to those of Procamelus . Unlike the giraffe, the length of the limbs is due to the See also:elongation of their upper segments, and that of the neck to the lengthening of only the hinder vertebrae . In caverns and superficial deposits of South America occur re-mains of extinct species more or less closely related to modern llamas; but previous .to the Upper Pliocene the group is unknown in South America, which it reached from the north . All the foregoing genera are included in the sub-family Camelidae . Parallel to this is, however, the North American family Leptomerychidae (Hypertragulidae), as represented by Leptomeryx, Camelomeryx and Leptoreodon, which presents remarkable resemblances; especially in the type genus, to the Tragulina (see See also:CHEVROTAIN); camel-like features being, however, apparent in the two genera last mentioned .

Generalized features are also displayed by the Oligocene Hypisodus, which in its short skull and large orbits presents a curious approximation to the African dik-dik antelopes of the genus Madoqua (see See also:

ANTELOPE) . Again, the remarkable horned North American Oligocene genus Protoceras, while displaying resemblances to Leptomeryx and Leptoreodon, presents also points of similarity to the Tragulina and Pecora (q.v.) . The North American genus See also:Oreodon typifies a second family included by See also:Professor W . B . See also:Scott in the Tylopoda and generally known as the Oreodontidae . As Oreodon is, however, antedated by Merycoidodon, the latter name is properly entitled to stand, in which case the family should be called Agriochoeridae . It is not easy to point out the characters in which the family approximates to the Camelidae, and only its general characteristics can be indicated . The family ranges in North America from the Upper Eocene to the Lower Miocene, but Oreodon (or Merycoidodon), which is typified by an animal of the size of a See also:sheep, is Oligocene . In the Oreodontinae or typical section of the family, which includes several genera nearly allied to Oreodon, the skull is shorter and higher than in the camels, with a swollen brain-case, a preorbital gland-See also:pit, the condyle of the lower jaw transversely elongated, the tympanic bulla hollow, and the See also:orbit surrounded by bone . The dentition comprises the typical 44 teeth, of which the molars are short-crowned, with four crescentic cusps on those of the upper jaw (selenodont type) . The most characteristic dental feature is, however, the See also:assumption of the form and See also:function of a canine by the first lower premolar; the lower canine being incisor-like . The tail is very long; and the feet have five functional toes, with complete but short metacarpals or metatarsals .

In the Miocene A griochoerus, which typifies a second sub-family (Agriochoerinae), there is no gland-pit in the skull, of which the orbit is open behind ; while the upper incisors are wanting in the adult and the terminal toe-bones are claw-like rather than of the hoofed type . The molars are less completely selenodont than in the type genus . It is See also:

note-worthy that a molar from the Tertiary of India has been referred to Agriochoerus, a determination which if correct probably indicates the occurrence of Oreodonts in the unknown Tertiary deposits of Central See also:Asia . It may be added that in the Oreodontidae the vertebral artery pierces the transverse processes of the cervical vertebrae in the normal manner . The earliest representatives of the Tylopoda according to Professor Scott is the Middle Eocene genus Homacodon, typifying the family Homacodontidae, which is regarded as the See also:common ancestor of both Camelidae and Oreodontidae, with resemblances to the European Oligocene genus Dichobune (see ARTIODACTYLA) . Homacodon was an animal of the size of a rabbit, with five toes (of which only five were functional to each foot) and 44 teeth, of which the molars are tuberculated (bunodont), with six columns on those of the upper jaw; the premolars being of a cutting type . It should be added that this generalized animal is not unfrequently classed among the ancestral pigs, but its cameline affinities are strongly emphasized by Professor Scott . (R .

End of Article: TYLOPODA (Gr. for boss-footed, in reference to the cushion-like pads forming the soles of the feet)
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