Fig. 75.
Fig.75.—Nototherium mitchelli.Side view of skull. ×1⁄6. (After Owen.)
Of extinct American Diprotodonts the Epanorthidae, already referred to in connexion with the livingCaenolestes, were the most prominent forms. The genusEpanorthusoccurs in the Santa Cruz formation of Patagonia, which is believed to be Miocene. The incisors are three in the upper jaw; and the single incisor of each ramus of the lower jaw is a great chisel-shaped, cutting instrument.
Abderitesis also typically Diprotodont by reason of the large projecting incisors of the lower jaw. It has a large cutting tooth in the lower jaw, which appears to be the last premolar, and is thus comparable to the great cutting tooth of the lower jaw and of the upper jaw of the extinct Phalanger,Thylacoleo.It may also be comparable to the great premolar of such Multituberculata asPtilodusandPlagiaulax. It is, moreover, marked with vertical grooves.
An interesting form, which is unfortunately but little known, is the Australian and Pleistocene genusTriclis, with one species,T. oscillans. In having a minute canine tooth in the lower jaw it agrees with some Phalangeridae, and being otherwise closely allied toHypsiprymnodon, it unites the Macropodidae with the Phalangeridae.
In this mainly carnivorous or insectivorous division of the Marsupials the incisors are four or five on each side of the upper jaw, and one or two fewer in the lower jaw. Figs. 76 and 77 illustrate the Polyprotodont and Diprotodont dentitions. The canines are those of flesh-eaters and so are the molars, being as a rule sharply cuspidate. As a rule, which has an exception in the Peramelidae, there is no syndactylism of toes in the hind-foot. This sub-order is at the present day Australian and American in its range.
Fig. 76.
Fig.76.—Front view of the skull of Tasmanian Devil (Sarcophilus ursinus), showing Polyprotodont and carnivorous dentition. (After Flower.)
Fam. 1. Dasyuridae.—This family consists of Marsupials which are generally pentadactylous, but with occasionally the hallux missing. The tail is long but not prehensile. The pouch is present or absent. The teeth vary in the different genera, butthe upper incisors are never less than three, and may be as many as five in the upper jaw and six in the lower. The canines are trenchant. There is no caecum.
Fig. 77.
Fig.77.—Front view of skull of Koala (Phascolarctos cinereus), illustrating Diprotodont and herbivorous dentition. (From Flower.)
Fig. 78.
Fig.78.—Longitudinal section of the skull of the Thylacine (Thylacinus cynocephalus). × ½.a, Angular process of mandible;AS, alisphenoid;BO, basioccipital;BS, basisphenoid;cd, condyle of mandible;ET, ethmoturbinal;Ex.O, exoccipital;Fr, frontal;ME, ossified portion of mesethmoid;MT, maxilloturbinal;Mx, maxilla;Na, nasal;OS, orbitosphenoid;Pa, parietal;Per, periotic;Pl, palatine;PMx, premaxilla;PS, presphenoid;Pt, pterygoid;SO, supraoccipital;Sq, squamosal;Vo, vomer. (From Flower'sOsteology.)
The genusThylacinuscontains but a single species, which is now limited to Tasmania, and is generally known as the Tasmanian Wolf. It has the build of an ordinary Wolf, and is of about the same size. The hinder part of the body is marked with a series of black transverse bands. The hallux is entirely wanting; the pouch opens backwards. The marsupial bones are minute and unossified. The dental formula is I 4/3 C 1/1 Pm 3/3 M 4/4 = 46. There are four mammae. This animal, now confined to Tasmania,is getting rarer on account of its sheep-killing propensities, and the consequent war of extermination declared upon it by the colonists. It will, however, feed upon other animals; and it is related that the first specimen ever captured had in its stomach the remains of an Echidna! Mr. Thomas thinks that the persistence of this and of some of the other larger carnivorous Marsupials in Tasmania after their extinction in Australia is not unconnected with the advent of the Dingo. But it is stated that the Thylacine is quite capable of keeping even a pack of dogs at bay.
Fig. 79.
Fig.79.—Tasmanian Devil.Sarcophilus ursinus.×1⁄10.
The genusSarcophilushas been frequently confounded with the next, but it is kept apart by Mr. Thomas, who follows Cuvier in this. An alternative generic name isDiabolus, which, like the first name, refers to the habits and character of the single species which this genus contains. The genus is more likeThylacinusthan isDasyurus. The hallux is wanting, and the teeth, though fewer in number (42), resemble those of the Thylacine more closely than do those of the Dasyure. The species is calledS. ursinus, the popular name being Tasmanian Devil. It is black with a variable number of white patches on the body. It is of about the size of a Badger, and is, like the Thylacine, a nocturnal animal. The Tasmanian Devil is said to be one of the most ferocious of animals, and to express its ferocity by a "yelling growl."
Fig. 80.
Fig.80.—Skull ofDasyurus. (Lateral view.)al.sph, Alisphenoid;ang, angular process of mandible;fr, frontal;ju, jugal;lcr, lachrymal;max, maxilla;nas, nasal;oc.cond, occipital condyle;par, parietal;par.oc, paroccipital process;p.max, premaxilla;s.oc, supraoccipital;sq, squamosal;sq′, zygomatic process of squamosal. (From Parker and Haswell'sZoology.)
Fig. 81.
Fig.81.—Dasyure.Dasyurus viverrinus. ×1⁄5. (After Vogt and Specht.)
The next genus of this family,Dasyurus, comprises five species, which range over the whole of the Papuan and Australian sub-regions. The general form is Viverrine, and the hallux is sometimes present though small. The dental formula is as in the last genus, but the teeth "are more insectivorous in their character." There are six or eight mammae. The members of this genus are grey or brown, and spotted with white; they are all arboreal, and feed largely upon birds and their eggs. Mr. Thomas has pointed out that in two species,D. viverrinusandD. geoffroyi, the striae upon the foot-pads are absent, and that therefore these at least are probably not so purely arboreal as the rest. The animals are not diurnal, and during the day hide themselves in the hollow trunks of trees. They are spoken of as "Native Cats," but have the general habits of Martens.D. maculatusis common in Tasmania, but is rare in Australia, thus "approaching the condition now exhibited by the Thylacine andTasmanian Devil, namely, complete extermination in Australia, where both once lived."D. hallucatusshows an approach toPhascologalein its five-toed hind-feet and slender build.
Phascologaleis a genus which, like the last, is usually arboreal (although notP. virginiaeof North Queensland), but is of much smaller size, the species not exceeding the dimensions of a rat. They have no spots, but there is sometimes a stripe down the back. There are thirteen species, which have the same range as the last genus. The hallux is present though small, but the pouch is "practically obsolete," though there is a small fold of skin behind the teats. The rhinarium is naked; the tail is long, "bushy, crested, or nearly naked." The mammae are four to ten in number. The dental formula is as inDasyurus, and the teeth are not very different in form; sometimes the last premolar is wanting. "The members of this genus," remarks Mr. Thomas, "evidently take the place in the Australian region filled in the Oriental by the Tupaiae, and in the Neotropical by the smaller Opossums."
The genusSminthopsiscomprises not more than four species, even smaller than the last. The largest species,S. virginiae, is only 125 mm. in length. The hallux is present, and there is a well-developed pouch. There are forty-six teeth, as in the Dasyures. The feet are narrow with granulated or hairy soles, whereas inPhascologalethey are broad with smooth soles. The mammae are eight or ten. The genus ranges through Australia and Tasmania.
The genusAntechinomyshas but a single species, which is a native of Queensland and New South Wales. The build is Jerboa-like, and the animal is, as might be inferred, terrestrial. The ears are very long, and the limbs elongated; the hallux is absent; the teeth are exactly as inSminthopsis.
Antechinomyshas thirteen dorsal and seven lumbar vertebrae; three sacrals and twenty-five caudals, the latter number being in excess of that of its allies. The stomach is nearly globular, with approximated orifices; the intestine measured 6.8 inches, a little more than twice the length of the animal itself.A. lanigerais a native of East Central Australia, and appears to be entirely terrestrial in habit, and to progress by a series of leaps—at any rate when going at full speed.
Professor Spencer, who found examples of this rare species, givesan interesting description of its habits.Antechinomyshas much the look of the Australian Rat,Hapalotis mitchelli; and as the two animals lead a similar kind of life, the resemblance is not unexpected. Professor Spencer wonders why these creatures are saltatory in habit. The country which they inhabit is arid, but with patches of grass and shrubs. For a big kangaroo the advantage of the power of leaping over such obstacles may be obvious, but not for the small and slenderAntechinomys. The chief foes of this rare Marsupial appear to be predatory birds; and Professor Spencer thinks that the saltatory mode of progression may be more baffling to such pursuers than even a rapid run.
The genusDasyuroideshas been lately instituted by Professor Spencer for a Marsupial from Central Australia somewhat intermediate betweenSminthopsisandPhascologale. As there is but one species, the generic will be considered with the specific characters.D. byrneiis an animal of about the size of the Common Rat. The hallux is absent. The tail is fairly thick, but not "incrassated." There are six mammae, and the pouch is but slightly developed, with two low lateral folds. The dentition is I 4/3 C 1/1 Pm 3/2 M 4/4. This Marsupial is nocturnal, and burrowing in habit. Its food consists of insects.[87]
Myrmecobiusis so different from the last-described genera (Dasyurinae) that it is usually separated from them as a sub-familyMyrmecobiinae. The animal is of a bright rufous colour, banded posteriorly with white. There is no hallux, though the metatarsal belonging to that digit is present. There are four mammae.[88]On the chest is a naked patch of some extent, upon which open the ducts of a complex gland, which has been described and figured by myself.[89]There is no pouch, but a tract of skin shows indications of a pouch-like structure. The teeth are extraordinarily numerous, fifty to fifty-four; the formula being I 4/3(4) C 1/1 Pm 3/3 M 5/6. Their resemblance to those of certain Jurassic Marsupials is dealt with on p.100.[90]In this matter lies ofcourse the chief interest of the genus, which may be "an unmodified survivor from Mesozoic times, and therefore from a time long before the Didelphyidae, Peramelidae, and Dasyuridae were differentiated one from the other." Another ancient feature (found in Jurassic mammals) is a mylo-hyoid groove upon the lower jaw, which, however, is not always present, and its existence has therefore been denied. The single species,M. fasciatus, is partly arboreal and partly terrestrial in habit, and feeds upon ants. It is a Western and Southern Australian form.
Fig. 82.
Fig.82.—Banded Australian Anteater.Myrmecobius fasciatus.×1⁄5.
Fam. 2. Didelphyidae.—All the members of this family are pentadactylous. The teeth are fifty in number, arranged thus: I 5/4 C 1/1 Pm 3/3 M 4/4. The caecum is small; the pouch is generally absent; the tail generally long and prehensile.
Fig. 83.
Fig.83.—Virginian Opossum.Didelphys virginiana.×1⁄5. (After Vogt and Specht.)
The genusDidelphyscontains most of the forms belonging to this family, including as it does some twenty-three species. The Opossums are mainly arboreal animals, insectivorous in their food; but the larger species eat reptiles, birds, and their eggs. Several of the small species carry their young, when able to leave the teats, ontheir back, the tails of the young being wrapped round that of the mother. It is not only the pouched species which carry their young in something of this fashion. Azara's Opossum, an animal as big as a cat, is said to carry its eleven young ones (themselves as large as rats) on the back, though their foothold does not appear to be strengthened by intertwining the tails. Even with this huge family on her back, the mother can climb trees with considerable alacrity. The mammae are seven to twenty-five in number. The genus has been lately split up into a number of genera,Marmosa,Dromiciops,Peramys, etc.
Fig. 84.
Fig.84.—Thick tailed Opossum.Didelphys crassicaudata.×1⁄5.
Chironectesis hardly different fromDidelphys. It has webbed hind-feet, and is aquatic in habit. The one species of the genus is known as the Yapock, and is a Central and South American form. It is of about the size of a large rat, and appears to be an expert diver after the fish upon which it lives.
Fam. 3. Peramelidae.—The Bandicoots, although clearly belonging to the Polyprotodont Marsupials, yet agree with the Diprotodonts in the fact that the second and third toes of the feet are bound up in a common integument, which is not the case with the DiprotodontCaenolestes. The hind-feet are longer than the front; of the former limb, two or three of the fingers alone are long and functional; the others are rudimentary or absent. Tail long, hairy, and non-prehensile. Dentition I 5/3 C 1/1 Pm 3/3 M 4/4 = 48, or sometimes, owing to the absence of a pair of upper incisors, 46. There is a caecum.
Fig. 85.
Fig.85.—Bones of manus.A, ofChoeropus castanotis. × 2.B, of Bandicoot (Perameles). × 1½.c, Cuneiform;l, lunar;m, magnum;R, radius;s, scaphoid;td, trapezoid;tm, trapezium;u, unciform;U, ulna;I-V, digits. (From Flower'sOsteology.)
Fig. 86.
Fig.86.—Rabbit Bandicoot.Peragale lagotis.×1⁄5.
The genusPeragale, the Rabbit-Bandicoots, consists of two species entirely Australian in range. The enormous ears (whence "Rabbit" Bandicoot) distinguish this genus fromPerameles. The pouch opens backwards, and there are eight mammae.P. lagotis, the only species about whose ways of life anything isknown, burrows in the soil, whence it extracts grubs; it is also a grass-feeder, and it is said that its likeness to a Rabbit in appearance is strengthened by its similarity in flavour!
Peramelesis a genus consisting of twelve species, which are found in Tasmania, Australia, and New Guinea. Like the last genus, from which it does not widely differ in other points,Peramelesconsists of species which combine insectivorous and vegetarian habits. One species is said to become in captivity an expert in catching mice. The pouch opens backwards, and there are six or eight mammae.
Fig. 87.
Fig.87.—Pig-footed Bandicoot.Choeropus castanotis.× ⅓.
The last genus of this family isChoeropus, containing but one species,Ch. castanotis. It is confined to the Australian continent. It is to be distinguished from the last two by the fact that there are only two functional digits, the second and third, in the fore-limb; the fourth is rudimentary; the other two are absent. It burrows, and is omnivorous like its allies. The two metacarpals that are developed are very long and closely apposed; they have hence a remarkably pig-like aspect, and justify its name. The pouch opens backwards, and there are eight mammae.
Fam. 4. Notoryctidae.—This family contains but a single genus and species, the recently-discoveredNotoryctes typhlops.[91]
We may regard as family-characters the pentadactyle limbs, the existence of three pairs of incisors in the lower and four in the upper jaw; and the tritubercular nature of the upper molars.Notoryctes typhlops, the "Marsupial Mole" as it has been termed, was originally discovered by Professor Stirling in Central South Australia. It is a burrowing creature, clothed in a silky fur of a pale golden red, without external ears. It has been compared in appearance withChrysochloris, the Cape Golden Mole, and the eminent palaeontologist, Professor Cope, has even insisted upon a real genetic affinity. Edentate affinities have also been suggested. ButNotorycteshas a small pouch opening backwards as in other Polyprotodonts,[92]and as it also possesses marsupial bones it must undoubtedly be referred to the Marsupialia. The animal shows many curious adaptations to its underground mode of life. Certain of the vertebrae in the neck and in the lumbar region are firmly welded together, giving of course a strength of push, and suggesting the Armadillos; the claws of the third and fourth front-toes are greatly enlarged, and must be efficient digging organs. The track of the animal is like that of a railway in mountainous country; it burrows for a short distance, emerges, and then descending beneath the surface re-emerges. The red colour of the fur is said to be in harmony with the arid soil in which it lives. The native name of the creature is "Urquamata." It feeds upon ants and other insects.
Fig. 88.
Fig.88.—Australian Marsupial Mole.Notoryctes typhlops.× ¼.
Extinct Polyprotodonts.—Of extinct Polyprotodonts (apart from those Mesozoic forms which are considered on p.100) extinct species ofThylacinusandDasyurusare known fromAustralia. The most interesting fact in connexion with the Tertiary Polyprotodonts is the existence in South America of such genera asProthylacinusandAmphiproviverra, which are not merely Polyprotodonts but definitely Dasyures, and not referable to the Didelphyidae.
These forms have been included in an order,Sparassodonta. But it is not by any means certain whether these forms are rightly placed in the neighbourhood of the carnivorous Marsupials; it is possible that they ought to be relegated to the Creodonta or to their allies. Their structure is in fact somewhat intermediate between those two groups. The teeth seem to be carnivorous and Marsupial-like in form; but as already mentioned, in connexion with the general structure of teeth, more than a single premolar is replaced. These animals in fact, in so far as regards their teeth, are midway between the Marsupials and the typical Eutheria. The angle of the lower jaw is inflected, but the palate is not marked by deficient ossification. At least this is not the case with all the members of the group. Whether the smallMicrobiotherium, which is made the type of a family, is rightly referred here is not certain. This animal had palatine vacuities as well as an inflected angle to the lower jaw.
Terrestrial, partly subterranean, or arboreal creatures of quite small to gigantic size (some extinct genera), with frequently a covering of scales or bony scutes. Limbs clawed. Teeth either totally absent or, if present, imperfect in structure, being without enamel, and not forming a complete series; incisors and canines being as a rule absent. Teats axillary, pectoral, or inguinal.[93]Retia mirabilia very common in the extremities.
To this group the name of Bruta was given by Linnaeus, but then it included not only the families which we now place in the modern order Edentata, but also the Elephant and the genusTrichechus. Mr. Thomas has proposed to change the name into Paratheria, which name is suggestive of what he and some others think concerning the systematic position of the group,i.e.that it is not to be placed in the Eutherian group of mammals at all, but represents a separate twig which has arisen with the Eutheria from a low mammalian stock. This view can hardly be accepted if the Ganodonta—which will be treated of presently—be really ancestral Edentates, for they are not in any way a Prototherian mammalian group, so far as their remains enable us to judge.
The Edentata contain the Sloths, Ant-bears, Armadillos,ManisandOrycteropus, among living forms. The great Ground-Sloths,Megatherium, etc., and Armadillos,Glyptodon, etc., represent the extinct forms.
The name that has been applied to this group is inappropriateinasmuch as many Edentates have teeth. It is, however, by a number of small tooth-characters that the order can be defined. Thus if teeth are present they are simple in structure, without enamel in the adult condition, though a rudimentary enamel-organ has been discovered in an Armadillo. The teeth, moreover, are not found in the anterior part of the mouth, and they grow from persistent pulps; neither is there much differentiation among them. It is not possible, however, to speak of the Edentates as quite homodont, since inOrycteropusthere are large cheek-teeth; but there is at any rate not a marked heterodonty in that or in any other Edentate. It used to be said that the Edentates were monophyodont. But the ArmadilloTatusiawas subsequently found to possess a second suppressed dentition, and after this discovery Mr. Thomas proved thatOrycteropusis also diphyodont. Since then other Armadillos have been shown to be diphyodont; and the whole group therefore, so far as concerns those members that have teeth, may in all probability be regarded as typically mammalian in this respect.
These characters are slender enough, but there seem to be no others by means of which the members of this order can be satisfactorily linked together. The fact is, that we have here a polymorphic order which contains in all probability representatives of at least two separate orders. We have at present a very few, and these perhaps highly modified, descendants of a large and diverse group of mammals. For convenience' sake they will be all treated of under the head of Edentata.
Although for the probable reasons already stated it is a hard matter to frame such a definition as will include all existing Edentates, it is easy enough to define two groups in this heterogeneous order; to define one group we should say, rather, and then to regard the leavings as forming another not so easily definable a group.
The perfectly-definable group is that which includes the American Anteaters, the Armadillos, and the Sloths. In all these creatures, which may certainly be regarded as representing on their own account as many family types, there are a number of important and highly-characteristic anatomical features which they share in common. So exceedingly different are these three types in general appearance and (correlated with that) in way of life that these common characters acquire increased importance.
Fig. 89.
Fig.89.—Great Anteater (Myrmecophaga jubata).A, Side view of twelfth and thirteenth thoracic vertebrae.B, Posterior surface of second lumbar vertebra.C, Anterior surface of third lumbar vertebra, × ⅔.az, Anterior zygapophysis;az1,az2,az3, additional anterior, articular facets;cc, facet for capitulum of rib;m, metapophysis;pz, posterior zygapophysis;pz1,pz2,pz3, additional posterior articular facets;t, transverse process;tc, facet for articulation of tubercle of rib. (From Flower'sOsteology.)
The first of these characters is the series of additional zygapophyses on the posterior dorsal and lumbar vertebrae; these are very clear in the Anteaters and Armadillos; less clear, but still obviously represented, in the Sloths. In the second place, they all possess a clavicle, rudimentary, it is true, in the Great Ant-bear, but still present. Thirdly, the testes are abdominal throughout life, a character which they share with such lowly-organised animals as the Monotremata and the Whales. Finally, and this is by no means a matter to be overlooked, not only are all the existing members of this group American in range, but there is no evidence to prove that they have ever existed elsewhere. No European or Old-Worldrepresentatives have as yet been discovered which can be referred to the Anteater, Armadillo, or Sloth type with certainty.[94]
Of these American forms, which will be treated of first, the Armadillos are further apart from either Sloths or Anteaters than the last two are from each other. The nameXenarthrahas been suggested for the American Edentates with "abnormal" vertebral articulations; the correspondingNomarthraincludes the Old-World forms.
Fig. 90.
Fig.90.—Right scapula and clavicle of Two-toed Sloth (Choloepus hoffmanni). × 1⅔.a, Acromion;af, prescapular fossa;c, coracoid;cl, clavicle;csf, coraco-scapular foramen;gc, glenoid cavity;pf, postscapular fossa. (From Flower'sOsteology.)
Between the Sloths and Anteaters the extinctMegatheriumand some of its allies are to a certain extent intermediate. But it may be pointed out in the first place that there are certain important resemblances between the living forms. In both, retia mirabilia are developed in the tail (in spite of its reduction in the Sloths) and in the limbs. But, as is well known, retia are also found in other mammals far removed in the series from these under consideration. The reproductive organs generally are very similar, and they have both a dome-shaped and deciduate placenta. The latter character they share with the Armadillos and with the Aard Vark;Manishaving a non-deciduate placenta which is, like that of the Carnivora, zonary in form. The Edentates, at any rate the American forms, have a double vena cava posterior and no azygos vein. This condition is also met with among Whales.
Osteologically the Sloths and Anteaters are united by the fact that the coracoid becomes fused with the coracoid border of the scapula, thus forming a foramen; the importance of this character is, however, discounted by its occurrence in three genera of Cebidae.
The above facts embody the views of Sir William Flower.[95]
A subsequent study of the brain and of the muscles of these animals has led to results not entirely in harmony with these views.
Dr. Elliot Smith is of opinion,[96]after an exhaustive study of the Edentate brain, that in this region of the body the present group shows very decided points of likeness to the Carnivora; that is, so far as concerns the Anteaters. On the other hand,Orycteropusis as distinctly comparable with a primitive Ungulate type, such as is exemplified byMoschus. "If the brain ofOrycteropus," he remarks, "were given to an anatomist acquainted with all the other variations of the mammalian type of brain, there is probably only one feature which would lead him to hesitate in describing it as an exceedingly simple Ungulate brain. That one feature is the high degree of macrosmatism.[97]Manis, on the other hand, does not come especially near toOrycteropus. The brain ofManisconforms to a simple type of architecture, which agrees in many points with both those ofOrycteropusand the American Edentates; there is not sufficient evidence to show which type it really favours." Elliot Smith would, in fact, agree with Max Weber that it is better, if a division is to be made, to divide the group into three orders:—the Xenarthra (Sloths, Anteaters, and Armadillos), Tubulidentata (Orycteropus), and Squamata (Manis), instead of into Xenarthra and Nomarthra.
Messrs. Windle and Parsons[98]are disposed to see in muscular similarities reasons for unitingManiswith the American Edentates, though they confess to being unable to placeOrycteropus; in this animal, they say, "we are more struck by the generalised mammalian arrangement of its muscles than by any special Edentate characters. There are, however, two muscles inOrycteropuswhich show peculiarities not found elsewhere than in the Edentates";—the triceps, which has more than one scapular head, and the tibialis posticus, which is double. They conclude thatOrycteropus"presents some feeble claims to be taken into the order."
We shall here adopt the following divisions.
Fam. 1. Myrmecophagidae.—The family Myrmecophagidae contains three genera, all South American in range. These genera,Myrmecophaga,Tamandua, andCycloturus, agree greatly in their outward form. They are all without teeth, and have long snouts and long protrusible tongues. The fur is thick, and they have powerful claws wherewith to break down the strong ant-hills upon whose inhabitants they feed.TamanduaandCycloturusare arboreal,Myrmecophagais terrestrial in habit. The claws of the arboreal forms are useful to destroy the bark, and thus bring to light insects which lurk in such situations.
Fig. 91.
Fig.91.—Great Anteater.Myrmecophaga jubata.×1⁄10.
The genusMyrmecophagacontains but one species, the Great Anteater,Myrmecophaga jubata. It is a large and handsome animal, with long, shaggy, greyish-black hair and a broad white stripe across the shoulder. The coloration is similar in the two sexes. Including the long and bushy tail it reaches a length of over 7 feet. It is on account of its long tongue and greatly developed salivary glands that this and the allied genera were originally placed withManis. It is the submaxillary glands which are so enormous; they extend back over the chest, and open by three distinct ducts, of which two unite just before the external orifice.Along their course these ducts are provided with a sphincter muscle, which squeezes the secretion towards the external orifice into the mouth-cavity. The stomach is somewhat gizzard-like. The intestine has no caecum.[99]
The Anteater's great claws are not only serviceable in tearing up the ground to get at its food; armed with them he does not fear, as Mr. Waterton remarked, "the fatal pressure of the serpent's fold or the teeth of the famished jaguar." An Anteater, too, is more than a match for a big dog, and will rip open its belly with the claws while the dog is vainly trying to make an impression with its teeth upon the shaggy hair.
Tamanduais a smaller animal thanMyrmecophaga, and, as has been stated, is arboreal; associated with this habit is a prehensile tail. Like the last genus,Tamanduahas a rudimentary clavicle, this bone being well developed in the littleCycloturus.
Fig. 92.
Fig.92.—Skull of Anteater (Myrmecophaga). Lateral view,al.sph, Alisphenoid;cond, condyle of mandible;cor, coronoid process of mandible;ex.oc, exoccipital;ext.aud, external auditory meatus;fr, frontal;ju, jugal;lcr, lachrymal;max, maxilla;nas, nasal;occ.cond, occipital condyle;pal, palatine;par, parietal;p.max, premaxilla;s.oc, supraoccipital;sq, squamosal;ty, tympanic. (From Parker and Haswell'sZoology).
The skull of the Anteater[100]is very long and low; the fore-part is tubular, and there appear to be no traces of teeth. The premaxilla is very small; the zygomatic arch is imperfect, and does not reach the squamosal behind. A curious feature of this genus, which it shares with some Dolphins and other Whales, is that the pterygoid bones develop palatine plates which meet each other in the middle line, and thus shift the opening of theposterior nares backwards. This is also, of course, a character of various lower vertebrates. Another Whale-like character in the skull is the weak character of the mandible, which does not give off a marked coronoid process. But then in neither group is there much mastication. The tympanic, periotic and squamosal are ankylosed together. A peculiarity of the cervical vertebrae is that (as in the Camels) the vertebrarterial canal of several of the vertebrae perforates the pedicle obliquely. There are fifteen or sixteen dorsal and three or two lumbar vertebrae. The additional zygapophyses upon the former have been already referred to. The mode of articulation of the ribs is highly singular.
Fig. 93.
Fig.93.—Skull of Anteater (Myrmecophaga). Ventral view. Letters as in Fig. 92. In addition,b.oc, basioccipital;glen, glenoid surface for mandible;pter, pterygoid. (From Parker and Haswell'sZoology.)
Fig. 94.
Fig.94.—Side view of three mesosternal segments of a young Anteater (Tamandua), showing the mode of articulation of the sternal rib (sr).mst, The upper or inner surface of the mesosternal segment;sy, the synovial articulation between the segments. (From Flower'sOsteology, after Parker.)
Each segment of the sternum (of which there are eight) is separated from the next by a synovial membrane: and it has on either side two facets for articulation with the ribs. The way inwhich these latter bones are connected with the sternum is curiously like their mode of connexion with the spinal column at their other end. With this may be possibly compared the double articulation of the single rib (which articulates with the sternum) in the Rorquals. InCycloturusthis mode of articulation does not occur.
The manus ofMyrmecophagais five-fingered. Of these the third digit (as in Perissodactyles) is the most prominent; it is at least double the width of the second or third finger; the pollex is very slender. In the littleCycloturusthis is carried to a greater extent: the third digit is relatively enormous; the first and the fourth have become quite rudimentary; while the fifth is only just recognisable as a minute ossification.
Fig. 95.
Fig.95.—A, Manus of Great Anteater (Myrmecophaga jubata). × ⅓.B, Manus of Little Anteater (Cycloturus didactylus). × 2.c, Cuneiform;l, lunar;m, magnum;p, pisiform;s, scaphoid;td, trapezoid;tm, trapezium;u, unciform;I-V, digits. (From Flower'sOsteology.)
The chevron-bones in the tail surround a well-developed rete mirabile, a rete being found in precisely the same position in the EasternManis.Tamanduahas also retia, which are also found in the Spider-monkeys.
Cycloturusis by far the smallest of the Anteaters. It hasonly two toes on the fore-feet. It is to be distinguished, anatomically, from its larger relatives by the complete clavicle, and by the fact that the pterygoids do not meet in the middle line of the skull. The ribs, too, are unusually wide, as in the WhaleNeobalaena, and form a bony encasement for the body. It has two small caeca. Of fossil Anteaters but little is known. The most interesting form isScotaeops, interesting because it has two small back teeth, which are totally lost in its living allies. The huge Patagonian extinct birdPhororhacos, first known by a lower jaw, was at one time regarded as a member of this group on account of the form and edentulous character of the jaw.
Fig. 96.
Fig.96.—Unau, or Two-toed Sloth.Choloepus didactylus.×1⁄5. (After Vogt and Specht.)