any trace of a flying membrane, and with the fifth digit of the manus
slightly shorter than the third. This genus is represented only by _G.
leadbeateri_ of Victoria, and according to Mr. Thomas, may be regarded
as the primitive form from which the specialised _Petaurus_ has been
developed.
[Illustration: FIG. 48.—Squirrel Flying-Phalanger (_Petaurus sciureus_).]
_Dromicia._[62]—Size small, and general appearance dormouse-like. Ears
large and thin, almost naked, and without internal or basal tufts. No
flying membrane. Digits of normal proportions, the relative lengths of
those of the manus in the order 3, 4, 2, 5, 1; fore claws rudimentary,
hind ones long and sharp. Tail mouse-like, cylindrical, furry at base,
the remainder scaly, with fine hairs, except at the tip, which is naked
and prehensile. Skull short and broad, with the hinder part of the
palate incomplete, and the auditory bullæ large, much inflated, and
transparent. Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ³⁄₃, _m_ ³⁻⁴⁄₃₋₄. First
upper incisor spatulate, and much longer than either of the others.
Canine large, placed at some distance behind the third incisor. Molars
(except the last) with evenly rounded crowns, carrying four small smooth
cusps.
This genus, which occurs in New Guinea, Western Australia, and Tasmania,
is represented by four species. It seems to be intermediate between
_Petaurus_ and _Acrobates_, and it has apparently had to yield place to
those more highly organised types in regions where they have come in
contact with one another.
_Distœchurus._[63]—Size small. Ears rather short, thinly covered with
hair, but with small tufts at the base. No flying membrane. Digits of
normal proportions, without expanded terminal pads. Claws curved and
sharp. Tail, skull, and dentition as in _Acrobates_, with the exception
that the fourth premolar is small in the upper, and absent in the lower
jaw.
The one species of Feather-tailed Phalanger (_D. pennatus_) is found in
New Guinea.
_Acrobates._[64]—Size very small. Ears moderate, thinly covered
with hair, but with small tufts round the base and on the internal
prominences. A narrow flying membrane, fringed with long hairs, running
from the elbow to the flank, and from the latter to the knee. Four
mammæ. Digits furnished with expanded and striated terminal pads, the
relative length of those of the manus being in the order 4, 3, 5, 2,
1. Claws sharp, although somewhat concealed by the terminal pads. Tail
short-haired above and below, with a broad fringe on either side. Skull
short, wide, and depressed. Posterior portion of palate very imperfectly
ossified; anterior palatal vacuities almost confined to the maxillæ.
Auditory bullæ low, rounded, and but slightly prominent. Dentition: _i_
³⁄₂, _c_ ¹⁄₀, _p_ ³⁄₃, _m_ ³⁄₃. Teeth sharp, and of an insectivorous
type. Upper canine long, and approximated to third incisor. The three
upper premolars large, functional, and taller than the molars. Molars
small and rounded, with smooth unridged cusps.
There is only one species in this genus, the beautiful little Pigmy
Flying-Phalanger (_A. pygmæus_), not so big as a Mouse, which is found
in Queensland, New South Wales, and Victoria, and feeds on the honey
it abstracts from flowers, and on insects. Its agility and powers of
leaping are exceedingly great, and it is said by Mr. Gould to make a most
charming little pet.
Subfamily =Phascolarctinæ=.—Teeth large, normal; no rudimentary premolars
before the last upper premolar, or any teeth between the first lower
incisor and fourth premolar. Tongue of ordinary structure. Distinct
cheek-pouches. Stomach with a special gland near the cardiac orifice.
Cæcum very long, and (with the upper portion of the colon) dilated and
provided with numerous longitudinal folds of mucous membrane. In many
anatomical characters, especially the possession of a special gastric
gland, this group resembles the _Phascolomyidæ_.[65]
[Illustration: FIG. 49.—Skeleton of right hind foot of Koala
(_Phascolarctus cinereus_), showing the stout opposable hallux, followed
by two slender toes, which in the living animal are enclosed as far as
the nails in a common integument.]
_Phascolarctus._[66]—Dentition: _i_ ³⁄₁, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ⁴⁄₄; total
30. Upper incisors crowded together, cylindroidal, the first much larger
than the others, with a bevelled cutting edge (Fig. 36). Canine very
small; a considerable interval between it and the premolar, which is as
long from before backwards but not so broad as the true molars, and has
a cutting edge, with a smaller parallel inner ridge. The molars slightly
diminishing in size from the first to the fourth, with square crowns,
each bearing four pyramidal cusps, with curved ridges radiating from
them, and having a structure very similar to these of _Pseudochirus_. The
lower incisors are semiproclivous, compressed and tapering, bevelled at
the ends. Premolars and molars in continuous series, as in the upper jaw.
Milk-tooth very minute, and almost functionless. Fore feet with the two
inner toes slightly separated from and opposable to the remaining three,
all with strong, curved, and much compressed claws. Hind foot (Fig. 49)
with the hallux placed very far back, large and broad, the second and
third (united) toes considerably smaller than the other two; the fourth
the largest. No external tail. Fur dense and woolly. Ears of moderate
size, thickly clothed with long hairs. Vertebræ: C 7, D 11, L 8, S 2, C
8. Ribs eleven pairs, a rare exception to the usual number (13) in the
Marsupialia.
There is but one species, the Koala or Native Bear of the Australian
colonists (_P. cinereus_), an animal of comparatively large size and
heavy build (Fig. 50), found in the south-eastern parts of the Australian
continent. It is about two feet in length, and of an ash-gray colour, an
excellent climber, and residing generally in lofty _Eucalyptus_ trees,
on the buds and tender shoots of which it feeds, though occasionally
descending to the ground in the night.
EXTINCT PHALANGEROIDS.
Numerous imperfect remains recently described by De Vis are regarded as
indicating large extinct types of _Phalangeridæ_, but further evidence
is required before all these determinations can be definitely accepted.
Thus part of an upper jaw is provisionally referred to a large species
of _Pseudochirus_, while part of a scapula is made the type of a genus
_Archizonurus_ which appears to be allied to the former. Another
fragmentary scapula is considered to indicate a large _Phalanger_.
Finally, part of a fibula, described under the name of _Koalemus_ is
regarded as affording evidence of the former existence of a large
ancestral form allied to the Koala, and it is suggested that an upper jaw
with teeth may belong to the same or an allied type.
[Illustration: FIG. 50.—The Koala (_Phascolarctus cinereus_). From
Sclater, _Proc. Zool. Soc._ 1880, p. 355.]
_Thylacoleo._[67]—Dentition of adult: _i_ ³⁄₁, _c_ ¹⁄₀, _p_ ³⁄₃, _m_ ¹⁄₂;
total 28. First upper incisor much larger than the others; canine and
first two premolars rudimentary. In the lower jaw the two small anterior
premolars are functionless, and often deciduous; posterior premolars of
both jaws formed on the same type as those of _Potorous_, but relatively
much larger; true molars rudimentary, tubercular. One species, _T.
carnifex_. This animal presents a most anomalous condition of dentition,
the functional teeth being reduced to one pair of large cutting incisors
situated close to the median line, and one great, trenchant, compressed
premolar, on each side above and below. It was first described as a
carnivorous Marsupial, and named, in accordance with its presumed habits,
“as one of the fellest and most destructive of predatory beasts”; but, as
its affinities are certainly with the _Phalangeridæ_ and _Macropodidæ_,
and its dentition completely unlike that of any known predaceous animal,
this view has been called in question.
[Illustration: FIG. 51.—Front view of skull of _Thylacoleo carnifex_,
restored. ¹⁄₃ natural size. From _Quart. Journ. Geol. Soc._ vol. xxiv. p.
312.]
The dentition is nearer to that of the existing _Phalangeridæ_ than to
that of the _Macropodidæ_, and the genus may be provisionally regarded as
the type of a distinct subfamily of the former.
_Family_ MACROPODIDÆ.
Dentition _i_ ³⁄₁, _c_ ⁰⁻¹⁄₀, _p_ ²⁄₂, _m_ ⁴⁄₄. Incisors sharp and
cutting, those of the lower jaw frequently having a scissor-like action
against one another; upper canine, if present, small. Penultimate
premolar shed with the fourth milk-molar, which is molariform and long
persistent. Molars wide, and either transversely ridged or bluntly
tuberculate. Premolars and molars moving forwards in the skull as the age
of the animal increases, this being most marked in the larger species.
Masseteric fossa of mandible hollowed out below into a deep cavity walled
in externally by a plate of bone, and communicating with the inferior
dental canal by a large foramen. Hind limbs usually larger than the
anterior ones, and progression generally saltatorial. Fore feet with five
digits; hind feet syndactylous, the fourth digit being very large and
strongly clawed; hallux usually absent. Tail generally long and hairy,
occasionally prehensile; stomach sacculated. Pouch large and opening
forwards.
[Illustration: FIG. 52.—Skeleton of right hind foot of Kangaroo.]
The _Macropodidæ_ or Kangaroos, taken as a whole, form a very well-marked
family, easily distinguished from the other members of the suborder by
their general conformation, and by peculiarities in the structure of
their limbs, teeth, and other organs. They vary in size from that of a
sheep down to a small rabbit. The head, especially in the larger species,
is small, compared with the rest of the body, and tapers forward to the
muzzle. The shoulders and fore limbs are feebly developed, and the hind
limbs usually of disproportionate strength and magnitude, which gives
them a peculiarly awkward appearance when moving about on all fours,
as they occasionally do when feeding. Rapid progression is, however,
performed only by the powerful hind limbs, the animal covering the ground
by a series of immense bounds, during which the fore part of the body is
inclined forwards, and balanced by the long, strong, and tapering tail,
which is carried horizontally backwards. When not moving they often
assume a perfectly upright position, the tail aiding the two hind legs
to form a sort of supporting tripod, and the front limbs dangling by
the side of the chest. This position gives full scope for the senses of
sight, hearing, and smell to warn of the approach of enemies, from which
these animals save themselves by their bounding flight. The fore paws
have live distinct digits, each armed with a strong curved claw.
The hind foot (Fig. 52), as being a typical example of the syndactylous
modification, may be noticed in some detail. It is extremely long and
narrow, and (with only one exception) without any hallux or great toe.
It consists mainly of one very large and strong toe, corresponding to
the fourth of the human or other typically developed foot, ending in a
strong, curved, and pointed claw. Close to the outer side of this lies
a smaller fifth digit, and to the inner side two excessively slender
toes (the second and third), bound together almost to the extremity in
a common integument. The two little claws of these toes, projecting
together from the skin, may be of use in scratching and cleaning the fur
of the animal, but the toes themselves must have quite lost all connexion
with the functions of support or progression.
The dentition of the Kangaroos, functionally considered, consists of
sharp-edged incisors, most fully developed near the median line of the
mouth, for the purpose of cropping the various kinds of herbage on which
they feed, and ridged and tuberculated molars for crushing it, there
being no tusks or canines for offensive or defensive purposes.
The number of vertebræ is—in the cervical region 7, dorsal 13, lumbar
6, sacral 2, caudal varying according to the length of the tail, but
generally from 21 to 25. In the fore limb the clavicle and the radius and
ulna are well developed, allowing of considerable freedom of motion of
the hand. The pelvis has large epipubic or “marsupial” bones. The femur
is short, and the tibia and fibula are of great length, as is the foot,
the whole of which is applied to the ground when the animal is at rest in
the upright position.
[Illustration: FIG. 53.—The Great Gray Kangaroo (_Macropus giganteus_).]
The stomach is of large size, and very complex, its walls being puckered
up by longitudinal muscular bands into a great number of sacculi, like
those of the human colon. The alimentary canal is long, and the cæcum
well developed. All the species have a marsupium or pouch formed by a
fold of the skin of the abdomen, covering the mammary glands with their
four nipples. In this pouch the young are placed as soon as they are
born; there their growth and development proceeds; and to it they resort
temporarily for the purpose of shelter, concealment, or transport, for
some time after they are able to run and jump about the ground and feed
upon the same herbage which forms the nourishment of the parent. During
the early period of their sojourn in the pouch, the blind, naked,
helpless young creatures (which in the Great Kangaroo [Fig. 53] scarcely
exceed an inch in length) are attached by their mouths to the nipples
of the mother, and are fed by milk injected into their stomach by the
contraction of the muscle covering the mammary gland.
The Kangaroos are all vegetable feeders, browsing on grass and various
kinds of herbage, the smaller species also eating roots. They are
naturally timid, inoffensive creatures; but the larger ones when hard
pressed will turn and defend themselves, sometimes killing a dog by
grasping it in their fore paws, and inflicting terrible wounds with the
sharp claws of their powerful hind legs, sustaining themselves meanwhile
upon the tail. A few aberrant forms are arboreal. The great majority are
inhabitants of Australia and Tasmania, forming one of the most prominent
and characteristic features of the fauna of these lands, and in the
scenery of the country, as well as the economy of nature, performing the
part of the deer and antelopes of other parts of the world, which are
entirely wanting in Australia. Kangaroos were very important sources of
food-supply to the natives, and are hunted by the colonists, both for
sport and with a view to their destruction, on account of the damage they
naturally do in consuming the grass, now required for feeding cattle and
sheep. Notwithstanding this, they have in some districts increased in
numbers, owing to the suppression of their former enemies, the aborigines
and the Dingo or native dog. A few species are found in New Guinea and
the adjacent islands, which belong, in the zoological sense, to the
Australian region.
Before noticing the various generic types of the _Macropodidæ_, a few
words are necessary in respect of the tooth-change, and we may here quote
the observations of Mr. O. Thomas on this subject. “The full dentition
of the members of this family consists, in the upper jaw, first of three
incisors, then of a small canine (often, however, suppressed, as in Fig.
55), and then of six cheek-teeth, of which the second in the series is
the only one which has a milk or deciduous predecessor, and is therefore
the one to be regarded as the last premolar of the typical mammalian
dentition. The special characteristics that render the development and
succession of the teeth in the _Macropodidæ_, and especially in the genus
_Macropus_, so puzzling to systematic zoologists, are: firstly, a general
progression forwards in the jaw of the whole tooth-row, comparable to
that found elsewhere only in the Elephants and some Sirenians; and,
secondly, the fact that before the tooth-change the first tooth of the
series (_p_ 3) and the single milk-tooth (_dm_ 4) placed next to it,
both of which fall out at the change, are respectively so very similar
in shape and size to the first and second teeth of the permanent series,
viz. the permanent premolar (_p_ 4) and the first molar (_m_ 1), as
to be most naturally mistaken for, or compared with, them in specific
descriptions.... The necessary knowledge as to the stage of dentition in
which any skull may be, can often be gained only by cutting open the bone
either above and behind the first tooth of the series to see if the true
permanent _p_ 4 be still buried there (in which case, of course, that
first tooth is only _p_ 3), or behind the last visible molar to see if
there be yet another tooth behind it, showing it to be _m_ 3 and not _m_
4. The first plan is, as a rule, the better, since _p_ 4 is generally by
far the most important tooth for diagnostic purposes, and its characters
have, therefore, in any case to be taken into account.”
The _Macropodidæ_ are divided into three well-marked sections: (1)
the true Kangaroos (_Macropodinæ_); (2) a group consisting of smaller
animals, commonly called Rat Kangaroos, or (improperly) “Kangaroo Rats,”
or sometimes Potoroos; and (3) the _Hypsiprymnodontinæ_, now represented
only by a single species.
Subfamily =Hypsiprymnodontinæ=.—Size very small. Claws small, feeble,
and subequal. Hind feet with an opposable hallux. Tail naked and scaly.
The fourth premolar twisted obliquely outwards, as in _Phalanger_. Other
teeth as in the _Potoroinæ_.
This subfamily is now represented only by the genus _Hypsiprymnodon_,[68]
which is a form of great interest, as showing a structure of foot
connecting that of the Kangaroos with that of the Phalangers. The
single known species, _H. moschatus_, was described by Ramsay from
specimens discovered in north-east Australia. It was described almost
simultaneously by Owen under the name of _Pleopus nudicaudatus_. From
the resemblance in the structure of the foot and the obliquity of the
premolars to the Phalangers Mr. Thomas has some hesitation as to which
family should receive this genus, but the macropine characters of the
mandible preponderate in favour of the _Macropodidæ_.
_Triclis._[69]—A lower jaw of a much larger form from the Pleistocene
deposits of Australia apparently indicates another member of this
subfamily, having the outwardly directed and grooved premolar
characteristic of _Hypsiprymnodon_. It differs, however, from that genus,
and also from all other known _Macropodidæ_, in having a small tooth
between the incisor and fourth premolar, which apparently represents a
canine, or perhaps an anterior premolar. This form indicates, therefore,
a closer connexion between the _Phalangeridæ_ and _Macropodidæ_ than any
other.
Subfamily =Potoroinæ=.—The second section or subfamily, the _Potoroinæ_,
have the first upper incisor narrow, curved, and much exceeding the
others in length (Fig. 54). Upper canines always persistent, flattened,
blunt, and slightly curved. Premolars of both jaws always having large,
simple, compressed crowns, with a nearly straight or slightly concave
free cutting edge, both outer and inner surfaces usually marked by a
series of parallel, vertical grooves and ridges, these teeth being either
set in the same line with the molars, or slightly bent outwards. Molars
with quadrate crowns, having a blunt, conical cusp at each corner,
the fourth notably smaller than the third, sometimes rudimentary, and
appearing early. Fore feet narrow; three middle toes considerably
exceeding the first and fifth in length; their claws long, compressed,
and but slightly curved. Hind feet as in _Macropus_. Tail long and hairy,
sometimes partially prehensile, being used for carrying bundles of grass
with which these animals build their nests.
[Illustration: FIG. 54.—Skull and teeth of Rat Kangaroo (_Bettongia
lesueuiri_). _c_, Upper canine. The other letters as in Fig. 51.]
The Potoroos or Rat Kangaroos are all small animals, none of them
exceeding a common rabbit in size. They inhabit Australia and Tasmania,
are nocturnal, and feed on the leaves of various kinds of grasses and
other plants, as well as roots and bulbs, which they dig up with their
fore paws. Nine species are known, presenting a considerable range of
diversity in minor characters, and admitting of being grouped in four
principal sections, which may be allowed the rank of genera. These are:
_Potorous._[70]—Head long and slender. Auditory bullæ somewhat inflated.
Ridges on premolars few and perpendicular. Large palatine foramina.
Tarsus short. Muffle naked. Three species, viz. _P. tridactylus_, _P.
gilberti_, and _P. platyops_; the last two being confined to West
Australia.
_Bettongia._[71]—Head comparatively short and broad. Ears short and
rounded. Auditory bullæ generally much inflated. Large palatine foramina.
Tarsus long. Ridges on premolars numerous and oblique. Tail more or less
prehensile, thickly haired, and the hairs on the upper surface longer
than those on the lower, and forming a crest. Muffle naked. Four species,
viz. _B. penicillata_, _B. cuniculus_, _B. gaimardi_, _B. lesueuiri_.
_Caloprymnus._[72]—Muffle naked, as in _Bettongia_, but the edge of
the hairy part less emarginate backwards in the middle line. Ears
short, rounded, and hairy. Auditory bullæ much inflated, and of large
size. Nasals larger and wider behind than in the other genera. Very
long anterior palatine foramina. Limbs as in _Bettongia_. Tail thin,
cylindrical, evenly coated with short hair, without trace of a crest.
Skull broad and flat, with a remarkably short and conical muzzle. The
sole representative of this genus is _C. campestris_ of South Australia,
originally referred to _Bettongia_.
[Illustration: FIG. 55.—Skull and Teeth of the Red-necked Wallaby
(_Macropus ruficollis_). _i¹_, _i²_, _i³_, First, second, and third upper
incisors; _pm_, fourth or posterior premolar (the penultimate or third
having been already shed); _m¹_, _m²_, _m³_, _m⁴_, the four true molars.
The last, not fully developed, is nearly concealed by the ascending ramus
of the jaw.]
_Æpyprymnus._[73]—Head short and broad. Auditory bullæ not inflated.
No palatine foramina. Tarsus long. Muffle partially hairy. Tail
evenly hairy, not crested above. Molars oblong, less distinctly
quadritubercular, and not decreasing so much in size posteriorly as in
the other genera. Represented only by _Æ. rufescens_.
Remains of _Æ. rufescens_ occur in the Pleistocene cave-deposits of New
South Wales.
Subfamily =Macropodinæ=.—This subfamily includes the largest forms.
The cutting edges of the upper incisors are nearly level, or the first
pair but slightly longer than the others (Fig. 55). The canines are
rudimentary and often wanting. The premolars are usually not longer
(from before backwards) than the true molars and less compressed than
in the last subfamily; they are placed in precisely the same line with
the molars. The crowns of the molars always have two prominent transverse
ridges; and these teeth increase in size from before backwards, the
fourth molar appearing very late. The fore limbs are small, with subequal
toes armed with strong, moderately long, curved claws. Hind limbs very
long and strongly made. Head small, with more or less elongated muzzle.
Ears generally rather long and ovate.
Upwards of forty-four existing species of this group have been described,
and many attempts have been made to subdivide them into smaller groups or
genera for the convenience of arrangement and description, but these have
generally been based upon such trivial characters that it is preferable
to speak of many of them as sections of the genus _Macropus_, reserving
generic rank only to forms somewhat aberrant in structure. According to
this arrangement the genera will be as follows:
_Lagostrophus._[74]—Represented only by the Banded Wallaby (_L.
fasciatus_) of Western Australia, which presents the following
distinctive features. Size small. Muffle naked. Hind feet covered with
long bristly hairs, concealing the claws. Lower part of back marked
by dark cross-bands. Skull with a narrow pointed muzzle and inflated
auditory bullæ; symphysis of mandible firmly united. No canine. Upper
incisive series meeting at a sharp angle, and diverging but slightly
behind. First incisor smaller in section than either of the others and
scarcely longer, bluntly pointed; second with a flattened oral surface;
third smaller, similarly flattened, but with a groove on oral surface
forming a notch at its postero-external angle. Fourth premolar short,
with a distinct inner ledge. Molars as in _Macropus_.
_Dendrolagus._[75]—General proportions of limbs and body normal and
unlike those of other members of the family. Muffle broad and only partly
naked. Fur on nape, and sometimes on back, directed forwards. Fore limbs
nearly as large as the hind; hind feet with the syndactylous second and
third digits relatively large; claws of fourth and fifth hind digits
curved like those of the manus. Tail very long, and thickly furred. Skull
stout, with a short and wide muzzle; the posterior part of the palate
fully ossified, and the auditory bullæ not inflated. A small canine.
Fourth premolar large, but much shorter antero-posteriorly than in the
next genus; molars as in the latter.
This genus includes four species of Tree-Kangaroos, three of which occur
in New Guinea, while _D. lumholtzi_ is found in North Queensland. They
differ greatly from all the other forms in being chiefly arboreal in
their habits, climbing with facility among the branches of large trees,
and feeding on the bark, leaves, and fruit. They are confined to the
tropical forests of the regions mentioned; and it would appear that we
must regard their resemblance in the proportions of the limbs and habits
to the Phalangers as having been independently acquired.
_Dorcopsis._[76]—Hind limbs relatively less large than in _Macropus_.
Muffle large, broad, and naked. Ears small. Fur on nape directed wholly
or partially forwards. Hind claws not concealed by hair. Tail with a
nearly naked tip. Skull long and narrow, with the auditory bullæ not
inflated. A well-developed canine. First upper incisor somewhat short;
second and third nearly equal, notched externally. Fourth premolar
greatly elongated antero-posteriorly, its length generally exceeding the
united lengths of the first and second molars; a distinct inner ledge,
and vertical grooves on both sides. Molars low and rounded, with the
median longitudinal bridge between the ridges almost or quite aborted,
and the talon in front of the first transverse ridge very narrow, and not
extending to the inner side. The two series of cheek-teeth parallel, or
nearly so, instead of converging at the extremities.
Three species of this genus are known, all of which are from New Guinea;
the type being _D. muelleri_. In the characters of the dentition, the
forward inclination of the fur on the nape, and other points, this genus
is allied to _Dendrolagus_; but _Dorcopsis macleayi_ connects the other
species with _Macropus_.
_Lagorchestes._[77]—Muffle entirely or partially covered with hair.
Fourth hind digit with a long claw, not concealed by hair. Tail rather
short, evenly furred, without a spur. Skull with short muzzle and
diastema, and inflated auditory bulla. Canine present, sometimes very
small. Fourth premolar large, not constricted in the middle, with a
continuous inner ledge.
This genus includes the Hare-Kangaroos, a group of small hare-like
animals, great leapers and swift runners, which mostly affect the open
grassy ridges, particularly those of a stony character, sleeping in forms
or seats like the common hare. Their limbs are comparatively small, their
claws sharp and slender, and their muffle is clothed with velvet-like
hairs. Three species—_M. leporoides_, _M. hirsutus_, _M. conspicillatus_.
The range extends over the whole of Australia, but does not embrace
Tasmania.
_Onychogale._[78]—Muffle hairy. Fourth hind claw long, narrow,
compressed, and sharp. Tail long and tapering, covered with short
hair, and furnished at the tip with a horny spur. Skull nearly as in
_Macropus_, with the auditory bullæ more or less inflated. Canine small
or wanting. Upper incisors small, decreasing in size from first to third.
Fourth premolar small, hour-glass shaped, and without inner ledge. Molars
as in _Macropus_.
This genus contains three species, having the same distribution as
_Lagorchestes_. Mr. O. Thomas observes: “The spur-tailed Wallabies form
a natural little group, distinguished both by the shape of the incisors
and the peculiar horny excrescence at the tip of the tail. The latter
character is altogether unique among Marsupials, and is only found among
other mammals in the Lion, which occasionally has a somewhat similar
horny spur at the end of its tail. In the case of the Wallabies it is
difficult to conceive what can be the use of this spur; and observations
on the living animal are much needed with regard to this interesting
point.”
_Petrogale._[79]—Muffle naked. Fur of nape directed backwards. Claw of
fourth hind digit very short. Tail long, cylindrical, thinner than in
_Macropus_, and thickly haired and pencilled at the extremity. Skull
as in the smaller species of _Macropus_, with large posterior palatal
vacuities, and the bullæ sometimes inflated. No canine. Upper incisors
small, the third resembling that of _Macropus_. Fourth premolar large
and stout, as in some of the Wallabies, with a continuous inner ledge,
and two or three indistinct vertical ridges externally. Molars as in the
Wallabies.
This genus is represented by six species, of which _P. penicillata_
is a well-known example, ranging over the whole of the mainland of
Australia. The Rock-Wallabies, as its members may be called, are very
closely allied to some of the true Wallabies; and some hesitation may be
expressed as to the advisability of accepting their generic separation
from _Macropus_. They inhabit rocky regions, making their retreats
in caverns and crevices, leaping with surprising agility from one
narrow ledge to another, and browsing upon the scanty herbage that the
neighbourhood of such situations affords. The species are _P. xanthopus_,
_P. penicillata_, _P. lateralis_, _P. concinna_, _P. brachyotis_, _P.
inornata_.
Remains of _P. penicillata_ are found in a fossil state in the
Pleistocene cave-deposits of New South Wales.
_Macropus._[80]—Muffle generally completely naked. Ears large. Fur on
nape (with an occasional exception in two species) directed backwards.
Claw of fourth hind digit very long. Tail thick, tapering, and evenly
furred. Four mammæ. Skull (Fig. 55) long, smooth, and rounded; the nasals
expanded behind; generally large palatal vacuities; and the auditory
bullæ not inflated. Canine minute, and shed at an early period. Incisor
series forming an open curve; the first the tallest, and the third nearly
always the longest antero-posteriorly, and generally with an infolding
of enamel near its postero-external angle. Fourth upper premolar with a
secant edge, and an inner basal ledge or tubercle; corresponding lower
tooth secant; both maybe longer or shorter than first molar. Molars
(except very occasionally) with a distinct longitudinal bridge connecting
transverse ridges. Lower incisors long and scalpriform, with inner secant
edges opposable, owing to the loose articulation of the mandibular
symphysis.
This genus includes the true Kangaroos and Wallabies, the size of the
individual existing species varying from that of a Rabbit to that of a
Man. There are no less than twenty-three existing species, which may be
divided into three groups, as well as many extinct ones. The genus is
found in Australia and New Guinea, as well as in the eastern half of the
Austro-Malayan transitional region.
The first group, or true Kangaroos, comprises the largest existing forms,
which are generally of a uniform and sombre colour.
The skull is of a large and massive type, with the palate more or less
well ossified posteriorly, while the molars frequently have a median
longitudinal bridge connecting the first transverse ridge with the
anterior talon, and no antero-external bridge between the same ridge and
talon. The history of the discovery of the typical representative of this
group, as being of considerable interest, may be given at some length.
When Captain Cook, during his first memorable voyage of discovery, was
detained for the purpose of refitting his ship at Endeavour river on
the north-east coast of Australia, a strange-looking animal, entirely
unknown to them, was frequently seen by the ship’s company; and it is
recorded in the annals of the voyage that, on the 14th of July 1770,
“Mr. Gore, who went out this day with his gun, had the good fortune
to kill one of the animals which had been so much the subject of our
speculation, ... and which is called by the natives kanguroo,” a name
which, though it does not appear to be now known to any of the aboriginal
tribes of the country, has been adopted for this animal in all European
languages, with only slight modifications of spelling. With the exception
of a passing glimpse in the beginning of the same century by the Dutch
traveller Bruyn of some living examples of an allied species, this was
the first introduction to the civilised world of any member of a group
of animals now so familiar. The affinities of the species, skins of
which were brought home by Captain Cook and subsequent voyagers, were
recognised by Schreber as nearer to the American opossums (then the
only known Marsupials) than to any other mammals with which zoologists
were acquainted, and consequently it was placed by him, in his great
work on the Mammalia, then in the course of publication, in the genus
_Didelphys_, with _gigantea_ for a specific designation,—the latter
having been bestowed upon it by Zimmermann under the impression that
it was a huge species of jerboa. Soon afterwards (1791) Dr. Shaw very
properly formed a new genus for its reception, which he named _Macropus_,
in allusion to the peculiar length of its hind foot. By the name thus
formed, _Macropus giganteus_, this kind of Kangaroo has ever since been
known in zoological literature. It is the common Gray Kangaroo, called
“boomer,” “forrester,” or “old man” by the colonists, and frequents the
open grassy plains of the greater part of eastern Australia and Tasmania;
a figure being given in the woodcut on p. 160. The muffle is partly
covered with hair, and the fourth premolar very short. Several varieties
are known.
A sub-group, distinguished from the above by the naked muffle, includes
some very large and handsome species, which principally dwell in rocky
mountain ranges, as _M. rufus_, the great Red Kangaroo, _M. antilopinus_,
and _M. robustus_. The fourth premolar is of large or medium size in
these forms. Remains of _M. giganteus_ occur fossil in the Pleistocene
of Australia, where we also find the allied extinct _M. titan_, which
attains somewhat larger dimensions. _M. robustus_ also dates from the
same geological epoch, where it was accompanied by two allied types known
as _M. altus_ and _M. cooperi_.
The second group includes the larger Wallabies, which are smaller than
the true Kangaroos, with a brighter and more variegated coloration. The
palate is generally more incomplete than in the typical group; and in the
molars the anterior talon is connected with the first transverse ridge
by an external instead of a median longitudinal bridge. The members of
this group are frequenters of forests and dense impenetrable brushes and
scrubs, and hence are often called Brush Kangaroos, though a native name,
“Wallaby,” is now generally applied to them. There are several species,
of which _M. ruficollis_, _M. ualabatus_, _M. parryi_, and _M. agilis_
are the best known.
_M. ualabatus_ and _M. parryi_ are found fossil in the Pleistocene
deposits of Australia. In those beds we also meet with remains of several
very large extinct species, which appear to be allied to those Wallabies
in which the fourth premolar is large and elongated, all of them agreeing
with the Wallabies in the absence of the median bridge between the first
ridge and talon of the molars. These fossil forms comprise _M. brehus_,
in which the skull was probably about one foot in length, and _M.
rœchus_, and _M. anak_, which were of somewhat inferior dimensions. In
the last-named species the length of the fourth upper premolar is equal
to that of the first and half of the second molar.[81]
The third and last group of the genus includes the small Wallabies,
which are small and lightly-built animals, in some instances not larger
than a Rabbit. Their muffles are always naked, and in the skull the
anterior palatine foramina are small and the posterior vacuities very
large, while the posterior expansion of the nasals is very marked. The
third upper incisor is smaller than in the last group. This group extends
farther into the tropics than either of the others, being found in the
New Britain and Aru islands, as well as in New Guinea. _M. brachyurus_
is remarkable for its comparatively short and slender tail and small
ears. The earliest known species of Kangaroo, referred to before, _M.
bruni_, belongs to this section. Several examples were seen by Bruyn in
1711 living in captivity in the garden of the Dutch governor of Batavia,
and described and figured in the account of his travels (_Reizen over
Moskovie_, etc.) under the name of “Filander.” It was quite lost sight
of, and its name even transferred by S. Müller to another species
(_Dorcopsis muelleri_), until rediscovered in 1865 by Rosenberg, who
sent a series of specimens to the Leyden Museum from the islands of Aru
and Great Key, thus determining its true habitat. _M. thetidis_ is a
well-known Australian representative of this group.
_Extinct genera._—In addition to the fossil forms already mentioned which
can be referred to existing genera, there are others from the Australian
Pleistocene indicating extinct generic types of _Macropodidæ_, to which
brief reference may now be made. The first of these is _Sthenurus_,[82]
represented by a single large species (_S. atlas_), and characterised by
the presence of a complete inner lobe to the fourth upper premolar, and
of an outer one in the opposing lower tooth, so that these teeth present
a flat and oval grinding surface when worn. The median longitudinal
bridge connecting the transverse ridges of the molars is very imperfect;
and in the upper molars there is no bridge between the first ridge and
talon. In _Procoptodon_[83] the premolars resemble those of _Sthenurus_,
but the molars are elongated, and usually have their enamel thrown into
numerous vertical foldings. The most distinctive feature is, however, the
complete ankylosis of the mandibular symphysis; the mandibular rami being
deep, and the diastema in the dental series short. The lower incisors are
nearly cylindrical, and the palate has large vacuities. Three species are
known. The largest representation of the whole family is the type of the
genus _Palorchestes_[84] (_P. azael_), in which the length of the skull
is estimated at sixteen inches. It is distinguished from _Procoptodon_
by the longer mandibular symphysis and diastema, and the spatulate lower
incisors. The true molars have no distinct anterior talon, and are not
grooved, while the palate was fully ossified.
EXTINCT FAMILIES.
Here may be noticed two genera of extinct Marsupials, the remains of
which have been found in the Pleistocene deposits of Australia, which
agree with the _Macropodidæ_ and the _Phalangeridæ_ in having ³⁄₁
incisors, those of the lower jaw being very large and proclivous. As the
whole of their structure, especially that of the hind feet, is not yet
known, their precise affinities cannot be determined.
_Diprotodon._[85]—Dentition: _i_ ³⁄₁, _c_ ⁰⁄₀, _p_ ¹⁄₁, _m_ ⁴⁄₄; total
28. The first upper incisor very large and scalpriform (Fig. 56). True
molars with prominent transverse ridges, as in _Macropus_, but wanting
the longitudinal connecting bridge. Anterior and posterior limbs less
disproportionate than in the Kangaroos. Humerus elongated, and differing
from that of nearly all Marsupials in the absence of an entepicondylar
foramen. The palate is fully ossified, and there is no pit or perforation
in the masseteric fossa of the mandible. _D. australis_ is the largest
known Marsupial, being fully equal in bulk to a Rhinoceros. It may be
regarded as the type of a family—_Diprotodontidæ_—having affinity on the
one hand with the Phalangers and on the other with the Kangaroos.
[Illustration: FIG. 56.—Left lateral aspect of the skull of _Diprotodon
australis_; from the Pleistocene of Australia. ⅒ natural size. _i_,
Incisors; _p_, premolar; _m_, molars. (After Owen.)]
_Nototherium._[86]—Represented by a species of somewhat smaller size
than the type of _Diprotodon_, with a shorter skull, in which the
zygomatic arches are very wide and the nasals curiously expanded at
their extremities. The mandibular symphysis is ankylosed; and, as in
_Diprotodon_, there appears to have been no tooth-change. The humerus
probably referable to _Nototherium_ is of a short and widely expanded
type, with a large entepicondylar foramen, and coming nearer to that of
the Wombat than to that of any other existing form. The _Nototheriidæ_
may apparently be regarded as a distinct family connecting the
_Diprotodontidæ_ with the _Phascolomyidæ_ and _Phalangeridæ_.
_Bibliography of Marsupialia._—G. R. Waterhouse, _Nat. Hist. of
the Mammalia_, vol. i. “Marsupiata,” 1846; J. Gould, _Mammals
of Australia_, 1863; R. Owen, article “Marsupialia,” in
_Cyclop. of Anatomy and Physiology_, and various memoirs “On
Extinct Mammals of Australia” in _Philosophical Transactions_;
W. H. Flower, “On the Development and Succession of the Teeth
in the Marsupialia,” _Phil. Trans._ 1867; O. Thomas, “On the
Homologies and Succession of the Teeth in the Dasyuridæ,”
_Phil. Trans._ 1887; and “Catalogue of Marsupialia and
Monotremata in the British Museum,” 1888.
CHAPTER VII
THE SUBCLASS EUTHERIA AND THE ORDER EDENTATA
The whole of the remaining groups of mammals are included in a single
subclass, known by the names Eutheria, Monodelphia, or Placentalia.[87]
The one distinctive feature they have in common (from which the
last-mentioned name is derived) is the presence of an allantoic placenta
by means of which the fœtus is nourished within the uterus of the mother.
Throughout the entire subclass, as a general rule, the urino-genital
organs open quite independently of the rectum; the corpus callosum of the
brain is well developed; the mandible does not show a marked inflection
of its angle; and distinct epipubic bones are not attached to the
anterior margin of the pubic symphysis. In those cases where there is a
heterodont and diphyodont dentition the dental formula can be reduced to
some modification of the one given on p. 25, there being only one known
genus where four true molars occur, and even that not invariably. As
in the Metatheria, the coracoid is reduced to a mere appendage of the
scapula, and the acetabular cavity of the pelvis is imperforate. While
the survivors of the other subclasses have probably been for a long time
in a stationary condition, these have, as there is already good evidence
to show throughout all the Tertiary geological age, and by inference
for some time before, been multiplying in numbers and variations of
form, and attaining higher stages of development and specialisation in
various directions. They consequently exhibit far greater diversity of
external or adaptive modification than is met with in either of the other
subclasses,—some being fitted to live as exclusively in the water as
fishes, and others to emulate the aerial flight of birds.
To facilitate the study of the different component members of this large
group, it is usual to separate them into certain divisions which are
called “orders.” In the main zoologists are now of accord as to the
general number and limits of these divisions among the existing forms,
but the affinities and relationships of the orders to one another are
far from being understood, and there are very many extinct forms already
discovered which do not fit at all satisfactorily into any of the orders
as commonly defined.
Commencing with the most easily distinguished, we may first separate
a group called Edentata, composed of several very distinct forms, the
Sloths, Anteaters, and Armadillos, which under great modifications of
characters of limbs and digestive organs, as well as habits of life,
have just enough in common to make it probable that they are the very
specialised survivors of an ancient group, most of the members of
which are extinct, although the researches of palæontology have not
yet revealed them to us. The characters of their cerebral, dental, and
in many cases of their reproductive organs show an inferior grade of
organisation to that of the generality of the subclass. The next order,
about the limits of which there is no difficulty, is the Sirenia,—aquatic
vegetable-eating animals, with complete absence of hind limbs, and low
cerebral organisation,—represented in our present state of knowledge by
but two existing genera, the Dugongs and Manatees, and by a few extinct
forms, which, though approaching a more generalised mammalian type, show
no special characters allying them to any of the other orders. Another
equally well-marked and equally isolated, though far more numerously
represented and diversified order, is that of the Cetacea, composed of
the various forms of Whales, Dolphins, and Porpoises. In aquatic habits,
external fish-like form, and absence of hind limbs, they resemble the
last, though in all other characters they are as widely removed as are
any two orders among the Eutheria.
All the remaining orders are more nearly allied together, the steps by
which they have become modified from one general type being in most cases
not difficult to realise. Their dentition especially, however diversified
in detail, always responds to the formula already alluded to, and,
although the existing forms are broken up into groups in most cases easy
of definition, the discoveries already made in palæontology have in great
measure filled up the gaps between them.
Very isolated among existing Eutheria are the two species of Elephant
constituting the group called Proboscidea. These, however, are now known
to be the survivors of a large series of similar animals, Mammoths,
Mastodons, and Dinotheres, which as we pass backwards in time gradually
assume a more ordinary or generalised type; and the interval which was
lately supposed to exist between even these and the rest of the class
is partially bridged over by the discovery in American Eocene and early
Miocene formations of the gigantic Dinocerata, evidently offshoots of
the great group of hoofed animals, or Ungulata, represented in the
actual fauna by the Horses, Rhinoceroses, Tapirs, Swine, and Ruminants.
Almost as isolated as the Proboscidea among existing mammals are the
few small species constituting the family _Hyracidæ_, and in their case
palæontology affords no help at present, and therefore, pending further
discoveries, it has been thought advisable in most recent systems to
give them the honour of an order to themselves, under the name of
Hyracoidea. But the number of extinct forms already known allied to
the Ungulata, though not coming under the definition of either of the
two groups (Artiodactyla and Perissodactyla) under which all existing
species range themselves, is so great that either many new orders must
be made for their reception or the definition of the old order Ungulata
so far extended as to receive them all, in which case both Proboscidea
and Hyracoidea may be included within it. Again, the Rodentia or gnawing
animals—Rabbits, Rats, Squirrels, Porcupines, Beavers, etc.—are, if
we look only at the present state of the class, most isolated. No one
can doubt what is meant by a Rodent animal, or have any difficulty
about defining it clearly, at least by its dental characters; yet our
definitions break down before the extinct South American _Typotherium_,
half Rodent and half Ungulate, which leads by an easy transition to
the still more truly Ungulate _Toxodon_, for the reception of which a
distinct order (Toxodontia) has been proposed. It has also been suggested
that the Rodents are connected by some of the extinct Tillodontia (or
Tæniodontia) with the Edentates. The Insectivora and the Carnivora
again are at present quite distinct orders, but they merge into one
another through fossil forms, and are especially connected by the large
group of primitive Carnivora, so abundantly represented in the Eocene
deposits both of America and Europe, to which Cope has given the name
of Creodonta. The Carnivora also appear to have been closely connected
with the primitive Ungulates as represented by the extinct group called
Condylarthra. In another direction the step from the Insectivores to
the Lemurs is not great, and in past times the transition was probably
complete. The Bats or Chiroptera are allied to the Insectivora in all
characters except the extraordinary modification of their anterior
extremities into wings; but this, like the want of the hind limbs in the
Cetacea and Sirenia, makes such a clear distinction between them and all
other mammals that, in the absence of any knowledge of any completely
intermediate or transitional forms, they can be perfectly separated,
and constitute as well-defined an order as any in the class. We have,
however, an inkling of the mode in which the Insectivora were modified
into Chiroptera shown us by the so-called Flying Lemur (_Galeopithecus_).
Finally, we have the important and well-characterised group called
Primates, including all the Monkeys and Man; and the question is not yet
solved as to how and through what forms this is linked on to the other
groups. It is commonly assumed that the Lemurs are nothing more than
inferior Primates, but the interval between them in the actual fauna of
the world is very great, and our knowledge of numerous extinct types
recently discovered in America, said to be intermediate in characters,
is not yet sufficient to enable us to form a definite opinion upon the
subject.
The Edentata may be taken first as standing in some respects apart from
all the others; and the Primates must be placed at the head of the
series. The position of the others is quite arbitrary, as none of the
hitherto proposed associations of the orders into larger groups stand
the test of critical investigation, and palæontological researches have
already gone far to show that they are all modifications of a common
heterodont, diphyodont, pentadactylate form.
_Order_ EDENTATA.
The name assigned to this group (which some zoologists think ought
rather to be ranked as a subclass[88] than an order) by Cuvier is often
objected to as inappropriate—for although some of the members are
edentulous, others have very numerous teeth—and the Linnæan name Bruta
is occasionally substituted. But that term is quite as objectionable,
especially since the group to which Linnæus applied it is by no
means equivalent to the order as now understood, as the names of the
genera contained in it, viz. _Elephas_, _Trichechus_, _Bradypus_,
_Myrmecophaga_, _Manis_ and _Dasypus_, indicate. It contained, in fact,
all the animals then known which are comprised in the modern groups
of Proboscidea, Sirenia and Edentata together with the Walrus, one
of the Carnivora. If retained at all, it should rather belong to the
Proboscidea, as _Elephas_ stands first in the list of genera in the
_Systema Naturæ_. Cuvier’s order included the _Ornithorhynchus_ and
_Echidna_, the structure of which was then imperfectly known, and which
are now by common consent removed to an altogether different section
of the class; but otherwise its limits are those now adopted. The name
Edentata is so generally used, and its meaning so well understood, that
it would be undesirable to change it now; in fact similar reasons might
be assigned for ceasing to use nearly all the other current ordinal
designations, for it might be equally well objected that all Carnivora
are not flesheaters, many of the Marsupialia have not pouches, and so
forth.
If the teeth are not always absent, they invariably exhibit certain
imperfections, which are indeed almost the only common characters
binding together the various extinct and existing members of the order.
These are—that they are homodont and, with the remarkable exceptions
of _Tatusia_ and _Orycteropus_, monophyodont; they are never rooted,
but have persistent pulps; except in some fossil forms, they are always
deficient in one of the constituents which enter into the formation of
the complete mammalian tooth, the enamel; and, at least among living
forms, are never present either in the upper or lower jaw in the fore
part of the mouth, the situation occupied by the incisors of other
mammals.[89]
The peculiar nature of the dentition in the aberrant _Orycteropus_ will
be noticed under the heading of that genus. As a rule, the coracoid
process of the scapula of the Edentates is more developed than in other
Eutheria.
The degree of development of the brain varies considerably in the
different families, the hemispheres being in some cases almost or quite
smooth (Fig. 57), with a small corpus callosum, and large anterior
commissure; while in other instances the hemispheres are convoluted, and
the corpus callosum is larger.
[Illustration: FIG. 57.—Upper surface of the brain of the Broad-banded
Armadillo (_Xenurus unicinctus_). The large olfactory lobes are seen at
the anterior extremity (left of figure); the hemispheres have only three
sulci. (From Garrod, _Proc. Zool. Soc._ 1878, p. 230).]
There is so great a difference in structure and habits between some of
the existing animals assigned to this order that, beyond the negative
characters just mentioned, there seems little to connect them. The Sloths
and Anteaters, for instance, in mode of life, general conformation of
limbs, structure of digestive organs, etc., appear at first sight almost
as widely separated as any mammals. Palæontology has, however, thrown
great light upon their relations, and proved their real affinities.
Perfectly intermediate forms have been discovered in the great Ground
Sloths of America, which have the dentition and general form of the
head of the Sloths, combined with the limbs and trunk of the Anteaters.
It is, indeed, highly probable that the existing members of this order
are very much differentiated representatives of a large group, the
greater number of which are now extinct, and have become so without ever
attaining a high grade of organisation. The great diversity of structure
in the existing families, the high degree of specialisation to which many
have attained, the paucity of species and even of individuals, their
limited area of distribution, and their small size compared with known
ancestral forms, all show that this is an ancient and a waning group, the
members of which seem still to hold their own either by the remoteness
and seclusion of their dwelling-places, by their remarkable adaptation
of structure to special conditions of life, or by aid of the peculiar
defensive armature with which they are invested. Their former history
can, however, only be thus surmised, rather than read, at present; for,
though we have ample evidence of the abundance and superior magnitude of
certain forms in the most recent or Pleistocene geological age, yet we
have at present no definite evidence as to their origin, or relationship
to other orders of mammals.
The existing members of the order readily group themselves into five
distinct families, the limits of which are perfectly clear. These are
(1) _Bradypodidæ_, or Sloths; (2) _Myrmecophagidæ_, or Anteaters;
(3) _Dasypodidæ_, or Armadillos; (4) _Manidæ_, Pangolins or Scaly
Anteaters; and (5) _Orycteropodidæ_, Aard-varks or African Anteaters.
The geographical distribution of these families coincides with their
structural distinction, the first three being inhabitants of the New
and the last two of the Old World. It has been usual to arrange these
families into two large groups or suborders: (1) the Phyllophaga,
leaf-eaters, also called Tardigrada, containing the _Bradypodidæ_ alone;
and (2) the Entomophaga, insect-eaters, or Vermilingua, containing
all the other families, from which sometimes the _Orycteropodidæ_
are separated as a third suborder under the name of Effodientia, or
Tubulidentata. Such an arrangement is, however, an artificial one,
founded on superficial resemblance. The bonds which unite the _Manidæ_
to the _Myrmecophagidæ_ are mainly to be found in the structure of the
mouth, especially the extensile character of the tongue, the great
development of the submaxillary glands, and the absence of teeth.
These characters are exactly analogous to those found in the Echidna
among Monotremes, the Woodpeckers among Birds, and the Chameleon among
Reptiles,—the fact probably being that in countries where Termites and
similar insects flourish various distinct forms of vertebrates have
become modified in special relation to this abundance of nutritious
food, which could only be made available by a peculiar structure of the
alimentary organs. A close study of the more essential portions of the
anatomy of these animals[90] leads to the belief that all the American
Edentates at present known, however diversified in form and habits,
belong to a common stock. Thus the _Bradypodidæ_, _Megatheriidæ_, and
_Myrmecophagidæ_ are certainly allied, the modifications seen in the
existing families relating only to food and manner of life. The ancestral
forms may have been omnivorous, and gradually separated into the purely
vegetable and purely animal feeders; from the former are developed
the modern Sloths, from the latter the Anteaters. The Armadillos
(_Dasypodidæ_) are another modification of the same type, retaining some
generalised characters, as those of the alimentary organs, but in other
respects, as in their defensive armature, remarkably specialised. The
two Old World families _Manidæ_ and _Orycteropodidæ_ are so essentially
distinct, both from the American families and from each other, that it
may even be considered doubtful whether they are derived from the same
primary branch of mammals, or whether they may not be offsets of some
other branch, the remaining members of which have been lost to knowledge.
Further remarks on this point are recorded under the description of the
_Orycteropodidæ_.[91]
_Family_ BRADYPODIDÆ.
Externally clothed with long, coarse, crisp hair. Head short and rounded.
External ears inconspicuous. Teeth ⁵⁄₄ in each jaw, subcylindrical, of
persistent growth, consisting of a central axis of vaso-dentine, with a
thin investment of hard dentine, and a thick outer coating of cement;
without (so far as is yet known) any succession. Clavicles present. Fore
limbs greatly longer than the hind limbs. All the extremities terminating
in narrow, curved feet; the digits never exceeding three in number,
encased for nearly their whole length in a common integument, and armed
with long strong claws. Tail rudimentary. Stomach complex. No cæcum.
Uterus simple and globular. Placenta deciduate, dome-like, composed of an
aggregation of numerous discoidal lobes. Strictly arboreal in habits,
vegetable feeders, and limited geographically to the forest regions of
South and Central America.
[Illustration: FIG. 58.—Two-toed Sloth (_Cholœpus hoffmanni_).]
The Sloths, as the animals of this family are called on account of the
habitual sluggishness of their movements, are the most strictly arboreal
of all mammals, living entirely among the branches of trees, usually
hanging under them, with their backs downwards (Fig. 58), and clinging
to them with the simple hook-like organs to which the terminations of
all their limbs are reduced. When they are obliged from any cause to
descend to the ground, which they rarely, if ever, do voluntarily, their
limbs, owing to their unequal length and the peculiar conformation of the
feet—which allows the animals to rest only on the outer edge—are most
inefficient for terrestrial progression, and they crawl along a level
surface with considerable difficulty. Though generally slow and inactive,
even when in their natural haunts, Sloths can on occasions travel with
considerable rapidity along the branches; and, as they do not leap, like
most other arboreal creatures, they avail themselves of the swaying of
the boughs by the wind to pass from tree to tree. They feed entirely on
leaves and young shoots and fruits, which they gather in their mouth, the
fore limbs aiding in dragging boughs within reach, but not being used
like hands, as they are by monkeys, squirrels, etc. When sleeping they
roll themselves up in a ball, and, owing to the dry shaggy character of
their hair, are very inconspicuous among the mosses and lichens with
which the trees of their native forests abound; the concealment thus
afforded being heightened in some species by the peculiar greenish tint
of the outer covering—very uncommon in mammals. This is not due to the
colour of the hair itself, but to the presence upon its surface of an
alga, the lodgment of which is facilitated by the fluted or rough surface
of the exterior of the hair, and the growth of which is promoted by the
dampness of the atmosphere in the gloomy tropical forests, as it soon
disappears from the hair of animals kept in captivity in England. Sloths
are nocturnal, silent, inoffensive, and solitary animals, and usually
produce but one young at birth. They appear to show an almost reptilian
tenacity of life, surviving the most severe injuries and large doses of
poisons, and exhibiting longer persistence of irritability of muscular
tissue after death than other mammals.
In the _Bradypodidæ_, as well as in the _Myrmecophagidæ_, the testes
are placed close to each other, lying on the rectum between it and the
bladder; the penis is quite rudimentary, consisting of a pair of small
corpora cavernosa, not directly attached by their crura to the rami
of the ischia, and having a glans scarcely larger than that of the
clitoris of most mammals, and, as in birds and reptiles, without any
true corpus spongiosum. In the females of both families the uterus is
simple and globular; and the vagina, at least in the virgin state, is
divided into two channels by a strong median partition. The deciduate
placenta of _Cholœpus_ is composed of a number of lobes aggregated into a
dome-like mass; and it does not appear that the placenta of the Anteaters
departs in any important characters from this type. According to the
late Professor W. K. Parker, the embryos of the Sloths, Anteaters, and
Pangolins have the stapes of the middle ear in the form of a rod, thus
showing affinities with a very primitive type of mammalian organisation.
The Sloths were all included in the Linnæan genus _Bradypus_, but Illiger
very properly separated the species with but two claws on the fore feet,
under the name of _Cholœpus_, leaving _Bradypus_ for those with three.
_Bradypus._[92]—Three-toed Sloths. Teeth usually ⁵⁄₄ on each side; no
tooth projecting greatly beyond the others; the first in the upper jaw
much smaller than any of the rest; the first in the lower jaw broad and
compressed; the grinding surfaces of all much cupped. Vertebræ: C 9, D
and L 20 (of which 15 to 17 bear ribs), S 6, C 11. All the known species
present the remarkable peculiarity of possessing nine cervical vertebræ,
_i.e._ nine vertebræ in front of the one which bears the first thoracic
rib (or first rib connected with the sternum, and corresponding in its
general relations with the first rib of other mammals); but the ninth,
and sometimes the eighth, bears a pair of short movable ribs. The arms
or fore limbs are considerably longer than the hind legs. The bones of
the fore arm are complete, free, and capable of pronation and supination.
The hand is long, very narrow, habitually curved, and terminates in three
pointed curved claws, in close apposition with each other. The claws are,
in fact, incapable of being divaricated, so that the hand is reduced to
the condition of a triple hook, fit only for the function of suspension
from the boughs of trees. The foot closely resembles the hand in its
general structure and mode of use; the sole being habitually turned
inwards, so that it cannot be applied to the ground in walking. The
tongue is short and soft, and the stomach large and complex, bearing some
resemblance to that of the ruminating Ungulates. The windpipe or trachea
has the remarkable peculiarity among mammals—not unfrequent among birds
and reptiles—of being folded on itself before it reaches the lungs. The
mammæ are two, and pectoral in position.
“Ai” is the common name given in books to the Three-toed Sloths. They
were all comprised by Linnæus under the species _Bradypus tridactylus_.
More recently Dr. Gray described as many as eleven species, ranged in two
genera, _Bradypus_ and _Arctopithecus_; but the distinctions which he
assigned both to species and genera do not bear close examination. Some
are covered uniformly with a gray or grayish-brown coat; others have a
dark collar of elongated hairs around the shoulders (_B. torquatus_);
some have the hair of the face very much shorter than that of the rest
of the head and neck; and others have a remarkable-looking patch of soft
short hair on the back between the shoulders, consisting, when best
marked, of a median stripe of glossy black, bordered on each side by
bright orange, yellow, or white. There are also structural differences in
the skulls, as in the amount of inflation of the pterygoid bones, which
indicate real differences of species; but the materials in our museums
are not yet sufficient to correlate these with external characters and
geographical distribution. The habits of all are apparently alike. They
are natives of Guiana, Brazil, and Peru, and one if not two species (_B.
infuscatus_ and _B. castaneiceps_) extend north of the Isthmus of Panama
as far as Nicaragua. Of the former of these Dr. Seeman says that, though
generally silent, a specimen in captivity uttered a shrill sound like a
monkey when forcibly pulled away from the tree to which it was holding.
_Cholœpus._[93]—Teeth ⁵⁄₄; the most anterior in both jaws separated by
an interval from the others, very large, caniniform, wearing to a sharp,
bevelled edge against the opposing tooth, the upper shutting in front of
the lower when the mouth is closed (Fig. 59), unlike the true canines
of heterodont mammals. Vertebræ: C 6 or 7, D 23-24, L 3, S 7-8, C 4-6.
One species (_C. didactylus_) has the ordinary number of vertebræ in
the neck; but an otherwise closely allied form (_C. hoffmanni_) has but
six. The tail is very rudimentary. The hand generally resembles that of
_Bradypus_; but there are only two functional digits with claws—those
answering to the second and third of the typical pentadactylate manus.
The structure of the hind limb generally resembles that of _Bradypus_,
the appellation “two-toed” referring only to the anterior limb, for
in the foot the three middle toes are functionally developed and of
nearly equal size. _C. didactylus_, which has been longest known, is
commonly called by the native name of _Unau_. It inhabits the forests
of Brazil. _C. hoffmanni_ (Fig. 58) has a more northern geographical
range, extending from Ecuador through Panama to Costa Rica. Its voice,
which is seldom heard, is like the bleat of a sheep, and if the animal is
seized it snorts violently. Both species are very variable in external
coloration.
[Illustration: FIG. 59.—Skull of Two-toed Sloth (_Cholœpus didactylus_).
From _Proc. Zool. Soc._ 1871, p. 432.]
_Nothropus._[94]—The only fossil form which has been referred to this
family is indicated by a lower jaw, described by Dr. Burmeister, from the
Pleistocene of Argentina, which appears to have belonged to an animal
of about double the dimensions of _Cholœpus didactylus_. Professor Cope
states, however, that this jaw really belongs to a Glyptodont; while it
is referred by Dr. Ameghino to the next family.
_Family_ MEGATHERIIDÆ.
[Illustration: FIG. 60.—Section of upper molar teeth of _Megatherium
americanum_. × ⅓. _p_, pulp-cavity; the other letters explained in the
text. (After Owen.)]
The members of this family are all extinct. Their characters, so far as
is known from the well-preserved remains of many species found abundantly
in deposits of Pleistocene age in both North and South America, were
intermediate between those of the existing _Bradypodidæ_ and the
_Myrmecophagidæ_, combining the head and dentition of the former with
the structure of the vertebral column, limbs, and tail of the latter.
Almost all the known species are of comparatively gigantic size, the
smallest, _Nothrotherium escrivanense_, exceeding the largest existing
Anteater, and the Megatherium being larger than a Rhinoceros. The femur
has no third trochanter, and the odontoid process of the axis vertebra
has a peculiar facet on the ventral surface. The dentition is usually
⁵⁄₄ on each side, as in the Sloths, but ⁴⁄₃ in _Nothrotherium_.[95]
This genus, and in a still more marked degree _Megatherium_, differ
from all the others in the details of the structure of the teeth. They
are very deeply implanted, of prismatic form (quadrate in transverse
section), and the component tissues—hard dentine (Fig. 60, _d_), softer
vaso-dentine (_v_), and cement (_c_)—are so arranged that, as the tooth
wears, the surface always presents a pair of transverse ridges, thus
producing a triturating apparatus comparable to the “bilophodont” molar
of _Dinotherium_, _Tapirus_, _Manatus_, _Macropus_, and others, though
produced in a different manner. In all the other genera the teeth are
more or less cylindrical, though sometimes laterally compressed or even
longitudinally grooved on the sides, and on the grinding surface the
prominent ridge of hard dentine follows the external contour, and is
surrounded only by a thin layer of cement, as in the existing Sloths.
The Ground Sloths, as the members of this family may be conveniently
designated, agree with the Sloths and Anteaters, and thereby differ from
all other mammals, in that the coracoid process of the scapula and the
coracoidal border of the same unite over the coraco-scapular notch, which
is thus converted into a foramen. Large clavicles are present.
_Megatherium._[96]—The typical genus _Megatherium_, as being the longest
known representative of the family, may be noticed in some detail. A
nearly complete skeleton, found on the banks of the River Luxan, near
Buenos Ayres, and sent in 1789 to the Royal Museum at Madrid, long
remained the principal if not the only source of information with regard
to the species to which it belonged, and furnished the materials for
many descriptions, notably that of Cuvier, who determined its affinities
with the Sloths.[97] In 1832 an important collection of bones of the
Megatherium was discovered near the Rio Salado, and secured for the
Museum of the College of Surgeons of England; and these, with another
collection found at Luxan in 1837, and now in the British Museum,
supplied the materials for the complete description of the skeleton
published by Sir R. Owen in 1861. Other skeletons have subsequently been
received by several of the Continental museums, as Milan and Paris, and
also by those in South America; and consequently our knowledge of the
organisation of the Megatherium, so far as it can be deduced from the
bones and teeth, is as complete as that of any other animal, recent or
extinct.
[Illustration: FIG. 61.—Oral surface of mandible of _Megatherium
americanum_. _a_, Condyle; _b_, masseteric process; _c_, angle; _d_,
symphysis. (After Owen.)]
The remains hitherto spoken of are all referred to one species,
_Megatherium americanum_ of Blumenbach (_M. cuvieri_ of Desmarest), and
are all from the newest or Pleistocene geological formations of the
Argentine Republic and Paraguay, or the lands forming the basin of the
Rio de la Plata. Dr. Leidy has described, from similar formations in
Georgia and South Carolina, bones of a closely allied species, about
one-fourth smaller, which he has named _M. mirabile_. Three other South
American species have been described; but _M. laurillardi_, of Lund,
founded upon remains found in Brazil, has been made the type of the genus
_Ocnopus_.
[Illustration: FIG. 62.—Skeleton of _Megatherium_, from the specimen in
the Museum of the Royal College of Surgeons. × ¹⁄₂₅.]
The following description will apply especially to the best-known
South American form, _Megatherium americanum_. In size it exceeded any
existing land animal except the elephant, to which it was inferior only
in consequence of the comparative shortness of its limbs; for in length
and bulk of body it was its equal, if not superior. The full length of
a mounted skeleton (Fig. 62), from the fore part of the head to the end
of the tail, is 18 feet, of which the tail occupies 5 feet. The head,
which is small for the size of the animal, presents a general resemblance
to that of the Sloth; the anterior part of the mouth is, however, more
elongated, and the jugal bone, though branched posteriorly in the same
way as that of the Sloth, meets the zygomatic process of the squamosal,
thus completing the arch. The lower jaw has the middle part of its
horizontal ramus curiously deepened, so as to admit of implantation of
the very long-rooted teeth, the peculiar structure of which has been
already described. A skull recently discovered shows that, instead of the
wide gap between the extremity of the nasals and the premaxillæ exhibited
in Fig. 62, there was a prenasal bone, towards which a process extended
upwards and backwards from the extremity of the upper surface of the
premaxillæ.
The vertebral column consists of seven cervical, sixteen dorsal, three
lumbar, five sacral, and eighteen caudal vertebræ. The spinous processes
are much better developed than in the Sloths, and are all directed
backwards, there being no reversing of the inclination near the posterior
end of the dorsal series, as in most active-bodied mammals. In the lumbar
region, the accessory zygapophyses, rudimentary in Sloths, are fully
developed, as in the Anteaters.
The tail is large, and its basal vertebræ have strong lateral and spinous
processes and chevron bones, indicating great muscular development.
The scapula resembles that of the Sloths in the union of the acromion
with the coracoid, and in the bridging over of the suprascapular notch.
The clavicle is complete and very large, much resembling that of man
on a large scale. The fore limbs are longer than the hind limbs. The
humerus has no entepicondylar foramen. The radius and ulna are both
well developed, and have a considerable amount of freedom of movement.
The hand is singularly modified. The pollex is represented only by
a rudimentary metacarpal, but the next three digits are large, and
terminate in phalanges adapted for the support of immense claws, the
middle one being especially large. The outer or fifth digit has no claw,
and it may be considered as certain that the weight of the foot was, in
standing and walking, chiefly thrown upon this one, which was protected
by a callous pad below, as in the existing great Anteater, while the
other toes were curved inwards towards the palm, and only came in contact
with the ground by their outer surfaces. The mechanical arrangements by
which the weight of the body was thrown entirely upon the outer side of
the foot are very curious, and are fully described in Owen’s memoir. The
pelvis is remarkably wide, even more so than that of the Elephant, but it
is formed on the same principle as in the Sloths. The femur is extremely
broad and flattened; the tibia and fibula are short and strong, and
united together at each end. The hind foot, contrary to the usual rule
in the Edentata, is even more singularly modified than the hand. Thus
the ankle-joint is formed upon a peculiar plan, quite unlike that of the
Sloths, or of any other mammal, except the Megatherium’s nearest allies;
and the calcaneum projects nearly as far backwards as the fore part of
the foot does forwards. There is no trace of great toe or hallux, or of
its corresponding cuneiform bone; the second toe is rudimentary; while
the third has an enormous ungual phalanx, which, as in those of the hand,
is remarkable for the immense development of the bony sheath reflected
from its proximal end around the base of the claw. The two outer toes
have large and very peculiarly-shaped metatarsals, but only small
phalanges, and no claws. The creature probably walked upon the outer edge
of the sole, so that the great falcate claw of the third toe did not come
into contact with the ground, and so was kept in a state of sharpness
ready for use. The foot was therefore formed upon quite a different
principle from that of the Anteaters or Sloths, though somewhat like the
latter in having two of the toes aborted.
Taking all the various points of its structure together, they clearly
indicate affinities both with the existing Sloths and with the
Anteaters, the skull and teeth more resembling those of the former, and
the vertebral column and limbs the latter. It is also not difficult
to infer the food and habits of this enormous creature. That it was a
leaf-eater there can be little doubt; but the greater size and more
complex structure of its teeth might have enabled it to crush the smaller
branches as well as the leaves and succulent shoots which form the food
of the existing Sloths. It is, however, very improbable that it climbed
into the branches of the trees like its diminutive congeners, and it is
far more likely that it obtained its subsistence by tearing them down
with the great hook-like claws of its powerful prehensile fore limbs,
being easily enabled to reach them by raising itself up upon the massive
tripod formed by the two hind feet, firmly fixed to the ground by the one
huge falcate claw, and the stout, muscular tail. The whole conformation
of the hinder part of the animal is strongly suggestive of such an
action. There can also be little doubt but that all its movements were as
slow and deliberate as those of its modern representatives.
An idea at one time prevailed that the Megatherium was covered externally
with a coat of bony armour like that of the Armadillos; but this
originated in dermal plates belonging to the Glyptodon having been
accidentally associated with bones of the Megatherium. Similar plates,
on a smaller scale, have indeed been found in connection with the
skeleton of the Mylodon, but never yet with the Megatherium, which we may
therefore imagine with a covering of coarse hair like that of its nearest
living allies, the Sloths and Anteaters.
_Scelidotherium_, _Mylodon_, etc.—Of the more important remaining
genera of this family a briefer notice will suffice. _Scelidotherium_
(in which _Platyonyx_ may be included) comprises several species of
considerably smaller dimensions than the Megatherium, and is in some
respects intermediate between that genus and _Mylodon_. The teeth have
an oval cross-section, like those of the Sloths, while the skull, in
which the length of the nasals is subject to great variation in the
different species, approximates more or less closely to that of the
_Myrmecophagidæ_. The humerus generally has an entepicondylar foramen;
and the form and relations of the bones of the feet differ considerably
from those obtaining in the type genus. _S. leptocephalum_, the type of
the genus, occurs in Patagonia and Argentina but other species are found
in Brazil and Chili. The genus _Mylodon_, in its widest sense, may be
taken to include a number of comparatively large Edentates, some of which
have been described under the names of _Grypotherium_, _Lestodon_, and
_Pseudolestodon_. The teeth of the upper jaw are generally of an oval or
subtriangular section; and in the more typical forms the first and second
teeth are separated by a short interval, the former being horizontally
worn. In other species, however, like _M. (Lestodon) armatus_, there is
a considerable space between the first and second teeth, and the first
is worn obliquely. The skull is exceedingly like that of the Sloths in
general contour; and there is not the descending process at the angle of
the mandible found in _Megatherium_. The humerus has no entepicondylar
foramen. The species represented in Fig. 63 is from the Pleistocene of
South America; but the type of the genus is _M. harlani_, from beds
of corresponding age in Kentucky. The Patagonian _M. (Grypotherium)
darwini_ is a remarkable form, characterised by the presence of a
bony arch connecting the premaxillæ with the nasals, of which, as
already mentioned, there is an incomplete development in _Megatherium_.
_Megalonyx_, from the Pleistocene of Kentucky, differs from _Mylodon_ by
the long interval between the first and second teeth, and also by the
presence of an entepicondylar foramen in the humerus. _Nothrotherium_
is a smaller form, occurring in the deposits of the Brazilian caves, of
which the dental features have been already mentioned. The osteological
characters of these and other allied genera have been fully described
in the works of Cuvier, Owen, Burmeister, Leidy, Ameghino, Gervais,
Reinhardt, and others.
[Illustration: FIG. 63.—Skeleton of _Mylodon robustus_ (Pleistocene,
South America). From Owen.]
_Promegatherium._—Two genera from the infra-Pampean beds of Argentina,
described as _Promegatherium_ and _Promylodon_, are respectively
distinguished from _Megatherium_ and _Mylodon_ by the presence of bands
of enamel on the teeth, which points to the descent of the Edentates from
mammals with enamelled teeth.
The Tertiary North American forms described as _Moropus_ and
_Morotherium_,[98] and originally regarded as Edentates, would appear to
be aberrant Ungulates.
_Family_ MYRMECOPHAGIDÆ.
Externally clothed with hair. No teeth. Head elongated. Mouth tubular,
with a small terminal aperture, through which the long, vermiform tongue,
covered with the viscid secretion of the enormous submaxillary glands,
is rapidly protruded in feeding, and withdrawn again with the adhering
particles of aliment, which are then sucked into the pharynx. Clavicles
rudimentary. In the manus, the third toe is greatly developed, and has
a long falcate claw, the others are reduced or suppressed. The pes has
four or five subequal digits with claws. Posterior dorsal and lumbar
vertebræ, with additional interlocking zygapophyses. Tail long, sometimes
prehensile. Uterus simple. Placenta dome-like or discoidal. Brain fairly
convoluted, and with a large corpus callosum and anterior commissure.
The animals of this family are the “Anteaters” _par excellence_. They
feed exclusively on animal substances, mostly insects. One species is
terrestrial, the others arboreal; none burrow in the ground. They are all
inhabitants of the Neotropical region.
The reproductive organs, as noticed on p. 181, are of the same general
type as in the _Bradypodidæ_.
_Myrmecophaga._[99]—Skull greatly elongated and narrow, its upper
surface smooth and cylindriform. Anteriorly the face is produced into a
long, tubular rostrum, rounded above and flattened below, with terminal
nares, and composed of the mesethmoid ossified for more than half its
length, the vomer, the maxillæ, and the long and narrow nasal bones,
the premaxillæ being extremely short and confined to the margin of the
anterior nares. The zygomatic arch is incomplete, the styliform jugal
only articulating with the maxilla in front, and not reaching to the
very short zygomatic process of the squamosal. The lachrymal foramen is
in front of the margin of the orbit. There are no postorbital processes
to the frontals, or any other demarcation between the orbits and the
temporal fossæ. Palate extremely elongated, and produced backwards as
far as the level of the external auditory meatus by the meeting in
the middle line of the largely developed pterygoids. The glenoid fossa
a shallow oval facet, with its long diameter from before backwards.
Mandible very long and slender with an exceedingly short symphysis, no
distinct coronoid process, and a slightly elevated, elongated, flattened,
condylar articular surface. Vertebræ: C 7, D 15-16, L 3-2, S 6, C 31.
Clavicles rudimentary. In the manus the first digit is very slender, the
second also slender, with compressed phalanges of nearly equal length.
The third digit is immensely developed; though its proximal phalanx is
extremely short, its ungual phalanx is so long that the entire length of
the digit exceeds that of the second. The fourth has a long and rather
slender metacarpal, and three phalanges diminishing in size, the ungual
phalanx being very small. The fifth has the metacarpal nearly as long,
but not so stout, as the fourth, and followed by two small phalanges, the
last rudimentary and conical. Claws are developed upon all but the fifth.
In walking the toes are kept strongly flexed, and have their points
turned upwards and inwards, the weight being supported upon a callous pad
over the end of the fifth digit, and by the dorsal surfaces of the third
and fourth digits. The hind feet are short and rather broad, with five
subequal claws, the fourth the longest, the first shortest; the whole
sole is placed on the ground in walking. Body rather compressed, clothed
with long, coarse hair. Tail about as long as the body, and covered with
very long hair; not prehensile. Ears small, oval, erect. Eyes very small.
Stomach consisting of a subglobular, thin-walled, cardiac portion, and
a muscular pyloric gizzard with dense epithelial lining. No ileo-colic
valve, and a short wide ill-defined cæcum. Mammæ two, pectoral.
There is one species,[100] _M. jubata_, the Great Anteater, or Ant Bear
(Fig. 64), measuring 4 feet in length without the tail, and upwards of
2 feet in height at the shoulder. Its prevailing colour is gray, with
a broad black band, bordered with white, commencing on the chest, and
passing obliquely over the shoulder, diminishing gradually in breadth
as it approaches the loins, where it ends in a point. It is extensively
distributed in the tropical parts of South and Central America,
frequenting low swampy savannas along the banks of rivers, and the depths
of the humid forests, but is nowhere abundant. Its food consists mainly
of termites, to obtain which it opens their nests with its powerful sharp
anterior claws, and as the insects swarm to the damaged part of their
dwelling, it draws them into its mouth by means of its long, flexible,
rapidly-moving tongue covered with glutinous saliva. The Great Anteater
is quite terrestrial in its habits, being never known to climb trees,
nor does it burrow underground like the Armadillos. Though generally an
inoffensive animal, when attacked it can defend itself vigorously and
effectively with its sabre-like anterior claws. The female bears but a
single young at a birth.
The union of the pterygoids in the middle line to prolong the narial
passage is a character found elsewhere among existing mammals only in the
next genus, in one Armadillo (_Tatusia_), and in certain Cetacea. The
contrast in length between the skull of the Great Anteater and that of
the Sloth is, as Professor Parker observes, very marked indeed; the one
being relatively the longest and the other almost the shortest in the
whole class. The small size and incomplete development of the jugal bone
in the zygomatic arch affords another striking contrast to the Sloths
(Fig. 59).
[Illustration: FIG. 64.—The Great Anteater (_Myrmecophaga jubata_). (From
Sclater, _List of Animals in Zoological Society’s Gardens_, 1883, p.
190.)]
_Tamandua._[101]—This genus closely resembles the last in anatomical
structure, but the head is much less elongated, the fur is short and
bristly, the tail tapering, prehensile, with the under side throughout
and the whole of the terminal portion naked and scaly. The stomach is
similar to that of _Myrmecophaga_, but with the muscular pyloric gizzard
not quite so strongly developed. There is a distinct ileo-colic valve and
a short globular cæcum. The fore foot has a very large claw on the third
toe, moderate-sized claws on the second and fourth, a very minute one on
the first, and none on the fifth, which is entirely concealed within the
skin. The hind foot has five subequal claws. Vertebræ: C 7, D 17, L 2, S
5, C 37. There are very rudimentary clavicles.
[Illustration: FIG. 65.—Tamandua Anteater (_Tamandua tetradactyla_). From
_Proc. Zool. Soc._ 1871, pl. xliii.]
The Tamandua (Fig. 65) is much smaller than the Great Anteater, and
differs essentially from it in its habits, being mainly arboreal. It
is an inhabitant of the dense primeval forests of South and Central
America. As different individuals vary much in their coloration, it is
possible that there may be more than one species. The usual colour is
yellowish-white, with a broad black lateral band, covering nearly the
whole of the side of the body.
[Illustration: FIG. 66.—Cæca of the Two-toed Anteater (_Cycloturus
didactylus_). _i_, Ileum; _c_, colon.]
_Cycloturus._[102]—The skull is much shorter even than in _Tamandua_, and
is arched considerably in the longitudinal direction. It differs from
that of the other members of the family mainly in the long canal for
the posterior nares not being closed by bone below, as the greater part
of the palatines and the pterygoids do not meet in the middle line. The
mandible has a prominent, narrow, recurved coronoid, and a well-developed
angular process; it is strongly decurved in front. Vertebræ: C 7, D 16, L
2, S 4, C 40. Ribs remarkably broad and flat. Clavicles well developed.
Manus remarkably modified, the third digit being greatly developed at the
expense of all the others, and having a stout short metacarpal and but
two phalanges, of which the most distal is large, compressed, pointed,
and much curved, and bears a very strong hook-like claw. The second digit
has the same number of phalanges, and bears a claw, but is very much more
slender than the third. The fourth is represented only by the metacarpal
and one nailless phalanx, the first and fifth only by very rudimentary
metacarpals. The pes is also completely modified into a climbing organ.
The hallux is rudimentary, consisting of a metatarsal and one phalanx,
concealed beneath the skin; but the other four toes are subequal and
much curved, with long pointed compressed claws. The tuber calcanei is
directed towards the plantar surface, and parallel with it and extending
to about double its length is a greatly elongated sesamoid ossicle.
These together support a prominent calcarine cushion, to which the nails
are opposed in climbing. Stomach pyriform, with muscular walls, but no
distinct gizzard-like portion, as in the foregoing genera. Commencement
of the colon provided with two small cæca (Fig. 66), resembling those
of many birds, narrow at the base, and rather dilated at their terminal
blind ends, and communicating with the general cavity by very minute
apertures. Tail longer than the body, tapering, bare on the under
surface, and very prehensile. Fur soft and silky.
This genus has also but one species certainly known, the Little or
Two-toed Anteater (_C. didactylus_), an animal not larger than a Rat, of
a general yellowish-colour, and exclusively arboreal in its habits. It is
a native of the hottest parts of South and Central America.
_Family_ DASYPODIDÆ.
The greater part of the skin strongly ossified. On the back and sides
the union of numerous quadrate or polygonal scutes forms a hard shield,
usually consisting of an anterior (scapular) and posterior (pelvic)
solid portion (which overhang on each side the parts of the body they
respectively cover, forming chambers into which the limbs are withdrawn),
and a variable number of rings between, connected by soft flexible skin
so as to allow of curvature of the body. The top of the head has also a
similar shield (cephalic), and the tail is usually encased in bony rings
or plates. The outer or exposed surfaces of the limbs are protected by
irregular bony scutes, not united at their margins; but the skin of the
inner surface of the limbs and under side of the body is soft, and more
or less clothed with hair. Hairs also in many species project through
apertures between the bony scutes of the back. The ossified dermal scutes
are everywhere covered by a layer of horny epidermis. Teeth numerous,
simple, of persistent growth, and usually monophyodont, but in one
genus (_Tatusia_) a succession of teeth has been observed. Zygomatic
arch of skull complete. Cervical vertebræ with extremely short, broad,
and depressed bodies. The atlas free, but the second and third, and
often several of the others, ankylosed together both by their bodies
and arches. Lumbar vertebræ with accessory zygomatic processes, and
very large metapophyses, supporting the bony carapace. Clavicles well
developed. A third trochanter on the femur. Tibia and fibula ankylosed
at their distal extremities. Fore feet with strongly developed, curved
claws, adapted for digging and scratching—three, four, or five in
number. Hind feet plantigrade, with five toes, all provided with nails.
Tongue long, pointed, and extensile, though to a less degree than in
the Anteaters. Submaxillary glands largely developed. Stomach simple.
Uterus simple. Placenta discoidal, deciduate. The brain is generally
characterised by the large size of the olfactory lobes (Fig. 57), and the
slight development of sulci on the hemispheres; the sylvian fissure being
represented only by a very open and shallow angle. From the earliest
stage of development the stapes is stirrup-shaped, thus showing a nearer
affinity to the higher mammals than is presented by the Sloths.
The animals of this family are commonly called Armadillos, a word
of Spanish origin, having reference to their armour-like covering.
The existing species are all of small or moderate size. They are
mostly, though not universally, nocturnal in their habits, and are all
omnivorous, feeding on roots, insects, worms, reptiles, and carrion.
Armadillos are harmless and inoffensive creatures, offering no resistance
when caught, their principal means of escape from their enemies being
the extraordinary rapidity with which they can burrow in the ground, and
the tenacity with which they retain their hold in their subterranean
retreats. Notwithstanding the shortness of their limbs they can run with
great rapidity. Most of the species are esteemed good eating by the
natives of the countries in which they live. They are all inhabitants
of the open plains or the forests of the tropical and temperate
parts of South America, with the exception of one species (_Tatusia
novemcincta_), which ranges as far north as Texas. Of the existing
genera, _Chlamydophorus_ stands apart from the rest in the formation
of its external covering; but in all other respects _Tatusia_ is the
most aberrant form, exhibiting a peculiar type of structure of the fore
feet, which in all the others show modifications, though in very varying
degrees, of a single and different type.
The reproductive organs of the _Dasypodidæ_ differ from those of the
Sloths and Armadillos in the presence of a largely developed copulating
organ in the male, and of a simple vagina of corresponding length in
the female. The testes are still abdominal, although not in the same
position; and the penis still wants both the glans and bulb. The uterus
is nearly or quite as simple as in the Sloths and Anteaters; and there is
no reason to believe that the placentation is essentially different from
that obtaining in the other groups.
Subfamily =Chlamydophorinæ=.—In most anatomical characters, especially
the structure of the fore foot, this little group resembles the
_Dasypodinæ_; but it differs remarkably from all other known Armadillos,
living or extinct, in the peculiar modification of the dermal armour.
_Chlamydophorus._[103]—Teeth ⁸⁄₈₋₉, subcylindrical, somewhat compressed,
moderate in size, smaller at each end (especially in front) than at
the middle of the series. Skull broad and rounded behind, pointed in
front. Muzzle subcylindrical and depressed. A conspicuous rounded,
rough prominence on the frontal bone, just before each orbit. Tympanic
prolonged into a tubular auditory meatus, curving upwards round the base
of the zygoma. Vertebræ: C 7, D 11, L 3, S 10, C 15. Upper part of head
and trunk covered with four-sided horny plates (with very small thin
ossifications beneath), forming a shield, free, and overhanging the
sides of the trunk, and attached only along the middle line of the back.
The plates are arranged in a series of distinct transverse bands, about
twenty in number between the occiput and the posterior truncated end, and
not divided into solid thoracic and pelvic shields with movable bands
between. The hinder end of the body is abruptly truncated and covered by
a vertically-placed, strong, solid, bony shield, of an oval (transversely
extended) form, covered by thin epidermic plates. This shield is firmly
ankylosed by five bony processes to the hinder part of the pelvis.
Through a notch in the middle of its lower border the tail passes out.
The latter is rather short, cylindrical in its proximal half, and
expanded and depressed or spatulate in its terminal portion, and covered
with horny plates. The dorsal surfaces of the fore and hind feet are also
covered with horny plates. The remainder of the limbs and under surface
and sides of the body beneath the overlapping lateral parts of the dorsal
shield are clothed with rather long, very soft, silky hair. Eyes and ears
very small, and concealed by the hair. Extremities short. Feet large,
each with five well-developed claws, those on the fore feet very long,
stout, and subcompressed, the structure of the digits being essentially
the same as those of _Xenurus_ and _Priodon_. Nipples two, pectoral.
Visceral anatomy closely resembling that of _Dasypus_, the cæcum being
broad, short, and bifid.
The Pichiciago (_C. truncatus_), a small burrowing animal, about 5 inches
long, inhabits the sandy plains of the western part of the Argentine
Republic, especially the vicinity of Mendoza. Its horny covering is of
a pinkish colour, and its silky hair snow white. It is rare, and its
habits are but little known. A second species, _C. retusa_, from Bolivia,
has been described by Burmeister. It is of rather larger size, and has
the dorsal shield attached to the skin of the back as far as its edge,
instead of only along the median line.
Subfamily =Dasypodinæ=.—Fore feet usually with all five digits developed
and with nails, though the first and fifth may be suppressed. The
first and second long and slender, with the normal number and relative
length of phalanges. The others stout, with short broad metacarpals,
and the phalanges greatly reduced in length and generally in number
by coalescence. The ungual phalanx of the third very large, that of
the others gradually diminishing to the fifth. _Dasypus_, as now
restricted, has the most normal form of manus, but the modifications so
markedly developed in all the others (and culminating in _Tolypeutes_)
are foreshadowed, as it were, in it. Ears wide apart. Mammæ one pair,
pectoral.
_Dasypus._[104]—Teeth ⁹⁄₁₀ or ⁸⁄₉, of which the anterior in the upper
jaw is usually implanted in the premaxillary bone. The series of teeth
extends posteriorly some distance behind the anterior root of the
zygoma, almost level with the hinder edge of the palate. They are large,
subcylindrical, slightly compressed, diminishing in size towards each
end of the series; the anterior two in the mandible much smaller, and
more compressed than the others. Cranial portion of the skull broad and
depressed. Facial portion triangular, broad in front and much depressed.
Auditory bulla completely ossified, perforated on the inner side by the
carotid canal, and continued externally into an elongated bony meatus
auditorius, with its aperture directed upwards and backwards. (In all the
remaining genera of _Dasypodinæ_ the tympanic bone is a mere half ring,
loosely attached to the cranium.) Mandible with a high ascending ramus,
broad transversely-placed condyle, and high slender coronoid process.
Vertebræ: C 7, D 11-12, L 3, S 8, C 17-19. Head broad and flat above.
Muzzle obtusely pointed. Ears of moderate size or rather small, placed
laterally, far apart. Body broad and depressed. Carapace with six or
seven movable bands between the scapular and pelvic shields, each plate,
or scute, being marked by a regular ellipse formed of widely separated
punctures. Tail shorter than the body, tapering, covered with plates
forming distinct rings near the base. Fore feet with five toes; the first
much more slender than the others, and with a smaller ungual phalanx and
nail; the second, though the longest, also slender. The third, fourth,
and fifth gradually diminishing in length, all armed with very strong,
slightly curved, compressed claws, sloping away from an elevated rounded
inner border to a sharp, outer, and inferior edge. The hind foot rather
short, with all five toes armed with stout, compressed, slightly curved,
obtusely pointed claws—the third the longest, the second nearly equal to
it, the fourth the next, the first and fifth shorter, and nearly equal.
To this genus belongs one of the best known-species of the group, the
Six-banded Armadillo or Encoubert (_D. sexcinctus_) of Brazil and
Paraguay. A very similar species, _D. villosus_, the Hairy Armadillo,
replaces it south of the Rio Plata. There are also two very small
species—_D. vellerosus_, from the Argentine Republic and North Patagonia,
and _D. minutus_ from La Plata. The latter differs from the other three
in having no tooth implanted in the premaxillary bone. Remains apparently
referable to _D. villosus_ occur in the Pleistocene cavern-deposits of
Brazil.
_Xenurus._[105]—Teeth ⁹⁄₉ or ⁸⁄₈, of moderate size and subcylindrical.
The most posterior placed a little way behind the anterior root of the
zygoma, but far from the hinder margin of the palate. Cranium somewhat
elongated, much constricted behind the orbits, and immediately in front
of the constriction considerably dilated. Mandible slender; coronoid
process very small and sharp-pointed, sometimes obsolete. Vertebræ: C
7, D 12-13, L 3, S 10, C 18. Head broad behind. Ears rather large and
rounded, wide apart. Movable bands of carapace 12-13; the scutes being
marked by an obscurely granular sculpture. Tail considerably shorter
than the body, slender, and covered with nearly naked skin, with but a
few small, scattered, dermal bony plates, chiefly on the under surface
and near the apex. On the fore feet the first and second toes are long
and slender, with small claws and the normal number of phalanges; the
other toes have but two phalanges; the third has an immense falcate
claw; the fourth and fifth similar but smaller claws. The hind feet are
comparatively small, with five toes, bearing small, triangular, blunt
nails; the third longest, the first shortest. The best known species of
this genus, the Tatouay or Cabasson, _X. unicinctus_, is, after _Priodon
gigas_, the largest of the group. It is found, though not abundantly, in
Surinam, Brazil, and Paraguay, its remains occurring in the Pleistocene
cavern-deposits of Brazil. Others, _X. hispidus_ and _lugubris_, have
been described, but little is as yet known of them.
_Priodon._[106]—Teeth variable in number, and generally differing on
the two sides of each jaw, usually from 20 to 25 on each side above and
below, so that as many as 100 may be present altogether; but as life
advances the anterior teeth fall out, and all traces of their alveoli
disappear. The series extends as far back as the hinder edge of the
anterior root of the zygoma. The teeth are all very small; those in the
anterior half of each series being strongly compressed, with flat sides
and a straight free edge; the posterior ones are more nearly cylindrical,
with flat truncated, free surfaces. Vertebræ: C 7, D 12, L 3, S 10, C
23. Head small, elongated, conical. Ears moderate, ovate. Carapace with
12-13 movable bands. Tail nearly equal to the body in length, gradually
tapering, closely covered with quadrangular scales, arranged in a
quincunx pattern. Fore feet with five toes, formed on the same plan as
those of _Xenurus_, but with the claw of the third of still greater size,
and that of each of the others, especially the fifth, proportionately
reduced. Hind foot short and rounded, with five very short toes, with
short, broad, flat, obtuse nails. The only known species, the Great
Armadillo (_P. gigas_), is by far the largest of existing members of the
family, measuring rather more than 3 feet from the tip of the nose to the
root of the tail, the tail being about 20 inches long. It inhabits the
forests of Surinam and Brazil. The powerful falcate claws of its fore
feet enable it to dig with great facility. Its food consists chiefly
of termites and other insects, but it is said to attack and uproot
newly-made graves for the purpose of devouring the flesh of the bodies
contained in them.
_Tolypeutes._[107]—Teeth ⁹⁄₉ or ⁸⁄₉, rather large in proportion to the
size of the skull, the hinder end of the series reaching nearly to the
posterior margin of the palate. Vertebræ: C 7, D 11, L 3, S 12, C 13.
Ears placed low on the sides of the head, rather large, broadly ovate.
Carapace with its scapular and pelvic shields very free at the sides of
the body, forming large chambers into which the limbs can be readily
withdrawn. Only three movable bands; sculpture of scutes in the form
of subconcentrically arranged granules. Tail short, conical, covered
with large bony tubercles. The fore feet formed on the same type as in
the last genus, but the peculiarities carried out to a still greater
extent. The claw of the third toe is very long and falcate, the first and
fifth greatly reduced and sometimes wanting. On the hind foot the three
middle toes have broad, flat, subequal nails, forming together a kind of
tripartite hoof; the first and fifth much shorter, with more compressed
nails.
The Armadillos of this genus have the power of rolling themselves up into
a perfect ball, the shield on the top of the head and the tuberculated
dorsal surface of the tail exactly fitting into and filling up the
apertures left by the notches at either end of the carapace. This
appears to be their usual means of defence when frightened or surprised,
as they do not burrow like the other species. They run very quickly,
with a very peculiar gait, only the tips of the claws of the fore feet
touching the ground. Three species are described:—_T. tricinctus_, the
Apar; _T. conurus_, the Matico; and _T. muriei_. Remains apparently
referable to _T. conurus_ are of not uncommon occurrence in the Brazilian
cavern-deposits.
Subfamily =Tatusiinæ=.—This group contains but one genus, _Tatusia_.[108]
Teeth ⁸⁄₈ or ⁷⁄₇, very small subcylindrical. The first and second
subcompressed, the last considerably smaller than the others. They
present the remarkable peculiarity (elsewhere found among Edentates,
so far as is yet known, only in _Orycteropus_) of all being, with the
exception of the last, preceded by two-rooted milk teeth, which are not
changed until the animal has nearly attained its full size. Vertebræ:
C 7, D 9-11, L 5, S 8, C 20-27. Head narrow, with a long, narrow,
subcylindrical, obliquely-truncated snout; pterygoids meeting in the
middle line below the nasal passage. Ears rather large, ovate, and
erect, placed close together on the occiput. Carapace with seven to nine
distinct movable bands; sculpture on scutes consisting of pits arranged
in a V-shape. Body generally elongated and narrow. Tail moderate or long,
gradually tapering; its dermal scutes forming very distinct rings for
the greater part of its length. Fore feet with four visible toes, and
a concealed clawless rudiment of the fifth. Claws all long, slightly
curved, and very slender, the third and fourth subequal and alike, the
first and fourth much shorter. Hind feet with five toes, all armed with
strong, slightly curved, conical, obtusely-pointed nails. The third
longest, then the second and fourth; the first and fifth much shorter
than the others.
[Illustration: FIG. 67.—The Peba Armadillo (_Tatusia novemcincta_).]
This genus differs from all the other Armadillos in having a pair of
inguinal mammæ, in addition to the usual pectoral pair, and in producing
a large number (four to ten) of young at a birth, all the others having
usually but one or two.
The Peba Armadillo, _T. novemcincta_ (Fig. 67), is a well-known species,
having an extensive range from Texas to Paraguay. It is replaced in the
more southern regions of South America by a smaller species, with shorter
tail, the Mulita (_T. hybrida_), so called from the resemblance of its
head and ears to those of a mule. _T. kappleri_ is a large species from
Surinam.
A rare Armadillo from Peru described under the names of _Cryptophractus
pilosus_ and _Praopus hirsutus_, but which evidently belongs to
_Tatusia_, is of some interest owing to the thick coat of hair with
which it is covered. This animal appears to be closely allied to _T.
novemcincta_, from which it mainly differs by having the whole of the
carapace covered with a thick coating of light brown, fine, but rather
stiff hair, about an inch and a half in length. Similar hair is found
on the cheeks, the proximal portions of the limbs, and (although less
abundantly and shorter) on the under surface of the body. The cephalic
shield, snout, feet, and the tail, with the exception of the root, are
bare. The coating of hair on the back and sides completely conceals
the carapace, except near the margin of the scapular region; but by
separating the hairs the bands and scutes are rendered visible.[109]
In the Pleistocene cavern-deposits of Brazil have been found remains
of _T. novemcincta_, and also of _T. punctata_, which appears to be an
extinct form nearly allied to _T. kappleri_, but of somewhat larger size.
_Extinct genera._—In addition to remains referable to existing genera,
the above-mentioned deposits have also yielded evidence of the former
existence of extinct generic types of Armadillos, some of which attained
very large dimensions. Of these _Eutatus_ was a large form distinguished
from all existing genera by the circumstance that the whole of the
carapace was composed of movable bands, which were thirty-three in
number. _Dasypotherium_ was a still larger form, furnished with eight
teeth, of which the second seems to have been larger than the others;
this genus is regarded as connecting the modern Armadillos with the next
one. The gigantic _Chlamydotherium_, the scutes of which are common in
the Brazilian caves, is considered to have been as large as a Rhinoceros;
the carapace has several movable bands, but the teeth approximate in
structure to those of the next family, so that the genus tends to connect
the Armadillos with the Glyptodonts.
_Family_ GLYPTODONTIDÆ.
[Illustration: FIG. 68.—Tooth of _Glyptodon_ from the side, and from the
grinding surface. (After Owen.)]
In the Pleistocene cavern-deposits of Brazil, but still more abundantly
in the fluviatile deposits which cover the country in the neighbourhood
of Buenos Ayres, are found the remains of some of the most remarkable
forms of mammals yet discovered, the Glyptodonts, which may be regarded
as forming a separate extinct family. They differ from the existing
_Dasypodidæ_ in their large size, and in having the carapace composed of
a solid piece (formed by the union of a multitude of bony dermal scutes)
without any movable rings, and in usually having also a ventral piece or
plastron. The facial portion of the skull is very short. A long process
of the maxillary bone descends from the anterior part of the zygomatic
arch. The ascending ramus of the mandible is remarkably high. The teeth
are ⁸⁄₈ in the known species, all much alike, having two deep grooves or
flutings on each side, so as to divide them into three nearly distinct
lobes (Fig. 68). The vertebral column is almost entirely ankylosed into
a solid tube, and there is a complex joint at the base of the neck, to
allow of the head being retracted within the carapace. The limbs are
very strong, and the feet short and broad, resembling externally those
of an elephant or tortoise. This family is mainly characteristic of the
southern half of the American continent, but some species of the type
genus ranged into Texas and Mexico. Many species of the family have
been described and figured, especially by Burmeister (in the _Annales
del Museo publico de Buenos Aires_), among which the following may be
noticed. _Hoplophorus_ is characterised by the sculptured and frequently
thin scutes of the carapace, those of the periphery being flat, and
not raised into prominences. The caudal sheath has several overlapping
movable rings at the base, and ends in a long subcylindrical terminal
tube similar to the one represented with the carapace of _Glyptodon_
in Fig. 69, which in all probability really belongs to the genus under
consideration. Each foot has four complete digits, and the humerus has
an entepicondylar foramen. Most of the species are of medium size. Part
of a caudal tube from Uruguay described as _Eleutherocercus_ indicates,
however, a much larger allied form, in which the tail appears to have
had a number of stout bristles protruding from the joints between the
scutes. _Panochthus_ comprises very large Glyptodonts, distinguished by
the great thickness of the scutes of the carapace, which are ornamented
with tubercles. The termination of the caudal sheath forms a tube bearing
large radiated tubercles. _Euryurus_ is distinguished by the radiate
sculpture of the scutes of the carapace. _Dœdicurus_, of which one
species was about twelve feet in length, also has a rugose sculpture
on the carapace; but the termination of the caudal tube is expanded
into a club-like shape, flattened from above downwards, and covered
with tubercles mingled with a few large radiate discs, which, as in
_Panochthus_, probably carried horny spines in the living condition. The
typical genus _Glyptodon_ has each scute of the carapace ornamented with
a rosette-like sculpture, the peripheral scutes being raised into conical
prominences (Fig. 69). The caudal sheath, instead of being like the one
represented in the figure, was entirely composed of a series of movable
rings, ornamented with large tubercles. The manus had five digits, and
the pes four; and there was an entepicondylar foramen to the humerus. A
species of this genus, which attained very large dimensions, was made the
type of _Schistopleurum_, on the supposition that the tail of _Glyptodon_
was of the type represented in Fig. 69. The genus _Thoracophorus_,
of the Pleistocene of South America, as well as _Carioderma_, of the
Pliocene of Texas, differ from all the preceding in having the scutes of
the carapace in the form of disconnected nodules. Glyptodonts also occur
in South American beds of earlier age than the Pleistocene, some of these
forms having enamel bands on the teeth. “Why such a form as the Glyptodon
should have failed to keep his ground is,” as the late Professor W. K.
Parker remarks, “a great mystery; nature seems to have built him, as Rome
was built, for eternity.”
[Illustration: FIG. 69.—_Glyptodon clavipes_ (Pleistocene, South
America). From Owen. The tail is incorrectly restored, and it is probable
that the figured portion belongs to _Hoplophorus_. The left lower corner
shows an upper and a lower view of the skull, and the right a section of
the caudal sheath.]
_Family_ MANIDÆ.
Covered externally (except the under surface of the body and inside
of the limbs) with large imbricated horny scales, and scattered
hairs growing in the intervals. No teeth. Tongue long, vermiform,
and protractile. No accessory articular processes to the lumbar
vertebræ, but the anterior zygapophyses largely developed and deeply
concave, completely embracing the semicylindrical surfaces of the
posterior zygapophyses. Limbs short, with five complete digits on each
foot. Scaphoid and lunar bones of carpus united. Uterus bicornuate.
Placenta diffused and non-deciduate. All the existing forms belong to
the Ethiopian and Oriental regions of the Old World. The absence of
additional articular processes to the lumbar vertebræ is a character in
which this and the following family differ from all the preceding forms.
_Manis._[110]—Skull somewhat of the form of an elongated cone, with the
small end turned forwards; very smooth and free from crests and ridges.
No distinction between the orbits and temporal fossæ. The zygomatic arch
usually incomplete, owing to the absence of the jugal bone. No distinct
lachrymal bone. Palate long and narrow. The pterygoids extend backwards
as far as the tympanics, but do not meet in the middle line below.
Tympanic ankylosed to the surrounding bones, and more or less bullate,
but not produced into a tubular auditory meatus. Rami of mandible very
slender and straight, without any angle or coronoid process. From near
the anterior extremity of the upper edge a sharp, conical, tooth-like
process projects upwards and outwards. No clavicles. No third trochanter
to the femur. Ungual phalanges bifid at their terminations. Caudal
vertebræ with very long, strong transverse processes and numerous
chevron bones. Tongue long, vermiform, flattened towards the tip; its
retractor or sterno-glossal muscles arising from the hinder extremity
of the immensely prolonged ensiform cartilage of the sternum. Stomach
with thick lining membrane and muscular walls, and a special gland near
the middle of the great curvature, consisting of a mass of complex
secreting follicles, the ducts of which terminate in a common orifice.
No cæcum. A gall-bladder. Head small, depressed, narrow, pointed in
front, with a very small mouth-opening. Eyes and pinna of ear very small.
Body elongated, narrow. Tail more or less elongated, convex above,
flat underneath. The whole of the upper surface of the head, the upper
surface and sides of the body, the whole of the tail, and the outer sides
of the extremities covered with large, overlapping, horny scales, but
usually with a few stiff hairs growing between and projecting beyond
them. The sides and under surface of the head, the under surface of the
body, and the inner sides of the limbs without scales, but with a rather
scanty covering of hair. Limbs short. In walking the dorsal surface and
outer sides of the phalanges of the two outer digits of the front feet
alone rest on the ground, the points of the nails turning upwards and
inwards. The third toe the longest, with a powerful compressed curved
claw; the second and fourth with similar but smaller claws, that of the
pollex often almost rudimentary. Hind feet plantigrade, with the hallux
very short, and the four other toes subequal, with moderate, curved,
subcompressed nails.
The reproductive organs of _Manis_ are of a totally different type from
those of the families already noticed. The testes lie in the inguinal
canal; and the penis is external and well developed. The uterus is
truly bicornuate, the vagina not divided, and the placenta diffused and
non-deciduate. All the organs and fœtal membranes are, indeed, formed
very much on the plan of those of the Ungulates, without any trace of the
special peculiarities obtaining in the typical American Edentates.
The animals of this genus, which includes all the existing forms, are
called Pangolins or Scaly Anteaters, and are all of small or moderate
size, terrestrial and burrowing, and feed mainly on termites. Several
of them can climb trees. Their length varies from 1 to 5 feet. They can
roll themselves up in a ball when in danger. Their peculiar elongated
form, short limbs, long, gradually-tapering tail, and scaly covering give
them on a superficial inspection more the appearance of reptiles than of
mammals. The species are not numerous, and may be divided into two groups
distinguished by a few not very important external characters; these
groups also coinciding with the present geographical distribution of the
genus. These two groups, according to Mr. O. Thomas, may be distinguished
as follows.
The Asiatic pangolins are characterised by having the central series of
body-scales continued quite to the extreme end of the tail, by having
many isolated hairs growing up between the scales of the back, and by
their small external ears. They all have a small naked spot beneath
the tip of the tail, which is said to be of service as an organ of
touch. There are three species, viz. _Manis javanica_, ranging from
Burma, through Malacca and Java, to Borneo; _M. aurita_, found in China,
Formosa, and Nipal; and the common Indian Pangolin, _M. pentadactyla_,
distributed over the whole of India and Ceylon. The African species have
the central series of scales suddenly interrupted and breaking into
two at a point about 2 or 3 inches from the tip of the tail; they have
no hair between the scales, and no external ear-conch. The following
are the four species belonging to this group:—the Long-tailed Pangolin
(_M. macrura_), which has a tail nearly twice as long as its body, and
containing as many as forty-nine caudal vertebræ, being the largest
number known among mammals; the White-bellied Pangolin (_M. tricuspis_),
Fig. 70, closely allied to the last, but with longer and tricuspid
scales, and white belly hairs. These two, like the Indian species, have
a naked spot beneath the tail tip, a character probably correlated with
the power of climbing, and they are, moreover, peculiar in having the
outer sides of their fore legs clothed with hair, all the other species
being scaly there as elsewhere. Lastly, the Short-tailed and the Giant
Pangolins (_M. temmincki_ and _gigantea_), both of which have their
tails covered entirely with scales, and evidently never take to arboreal
habits. All the four species of the second group are found in the West
African region, one only, _M. temmincki_, extending also into south and
eastern equatorial Africa.
[Illustration: FIG. 70.—The White-bellied Pangolin (_Manis tricuspis_).]
According to Professor W. K. Parker,[111] who remarks upon the peculiarly
aberrant nature of the group, the horny scales of the Pangolins really
consist of cemented hairs. This writer states that “in the early embryo
lozenge-shaped tracts of skin are seen all over its body, with lines of
thinner cuticle between. Under the microscope, sections of these thicker
tracts show that they are composed of fine hairs, cemented together by a
copious growth of epidermic cells; here and there larger hairs are seen,
but these fail to reach the surface, turning again towards the inside,
like nails driven into wood that is too hard for their points.”
The same author also observes[112] that there are occasional instances of
the presence of eight cervical vertebræ in the Pangolins—a feature which
has been considered to indicate some former genetic connection between
this family and the Sloths.
The following account of the habits of _Manis tricuspis_ is given by Mr.
L. Fraser in his _Zoologia Typica_:—
“During my short residence at Fernando Po I succeeded in procuring two
living specimens of this animal. The individuals, judging from the bones,
were evidently not adult; the largest measured 30 inches in length,
of which the head and body were 12 inches and the tail 18 inches. I
kept them alive for about a week at Fernando Po, and allowed them the
range of a room, where they fed upon a small black ant, which is very
abundant and troublesome in the houses and elsewhere. Even when first
procured they displayed little or no fear, but continued to climb about
the room without noticing my occasional entrance. They would climb up
the somewhat roughly hewn square posts which supported the building
with great facility, and upon reaching the ceiling would return head
foremost; sometimes they would roll themselves up into a ball and throw
themselves down, and apparently without experiencing any inconvenience
from the fall, which was in a measure broken upon reaching the ground by
the semi-yielding scales, which were thrown into an erect position by the
curve of the body of the animal. In climbing, the tail, with its strongly
pointed scales beneath, was used to assist the feet; and the grasp of
the hind feet, assisted by the tail, was so powerful that the animal
would throw the body back (when on the post) into a horizontal position,
and sway itself to and fro, apparently taking pleasure in this kind of
exercise. It always slept with the body rolled up; and when in this
position in a corner of the building, owing to the position and strength
of the scales, and the power of the limbs combined, I found it impossible
to remove the animal against its will, the points of the scales being
inserted into every little notch and hollow of the surrounding objects.
The eyes are very dark hazel, and very prominent. The colonial name for
this species of _Manis_ is ‘Attadillo,’ and it is called by the Boobies,
the natives of the island, ‘Gahlah.’ The flesh is said to be exceedingly
good eating, and is in great request among the natives.”
The Indian species is said to live in pairs, and to give birth to one or
two young at a time in the spring. Their burrow reaches a depth of some
twelve feet, and terminates in a large chamber, which may be as much as
six feet in diameter. A faint hiss appears to be the only sound emitted
by these animals.
Remains of a large species of _Manis_, which are indistinguishable from
the corresponding bones of the existing West African _M. gigantea_,
are found fossil in cave-deposits in the Karnul district of Madras.
This is one among several instances of the close connection between the
Pleistocene and Pliocene mammalian fauna of India with the existing
African fauna.
_Palæomanis._[113]—The lower Pliocene deposits of the Isle of Samos, in
the Turkish Archipelago, have yielded remains of a Pangolin fully three
times the dimensions of _M. gigantea_, upon the evidence of which the
genus _Palæomanis_ has been established.
_Family_ ORYCTEROPODIDÆ
External surface scantily covered with bristle-like hairs. Teeth
numerous, apparently heterodont, diphyodont, and of peculiar and complex
structure, being traversed by a number of parallel vertical pulp-canals.
Lumbar vertebræ with no accessory zygapophyses. Femur with a third
trochanter. Fore feet without pollex, but all the other digits well
developed, with strong moderate-sized nails, suited to digging, the
plantar surfaces of which rest on the ground in walking. Hind feet with
five subequal toes. Mouth elongated and tubular. Tongue subvermiform.
Uterus bicornuate. Placenta broadly zonular. Feeding on animal
substances. Terrestrial and fossorial in habits. Now mainly limited to
the Ethiopian region.
_Orycteropus._[114]—The total number of permanent teeth appears to be
from eight to ten in each side of the upper, and eight in the lower jaw;
but they are never all in place at one time, as the small interior teeth
are shed before the series is completed behind. In the adult they number
usually five on each side above and below, of which the first two are
simple and compressed, the next two larger and longitudinally grooved at
the sides, the most posterior simple and cylindrical. The last three in
either jaw having no milk-predecessors, may be regarded as true molars.
The structure of all these teeth is quite peculiar among mammals, though
resembling that of some fishes. Their summits are rounded before they are
worn; their bases do not taper to a root, but are evenly truncated and
continually growing. Each tooth is made up of an aggregation of parallel
dental systems, having a slender pulp-cavity in the centre, from which
the dentinal tubes radiate outwards, and being closely packed together
each system assumes a polygonal outline as seen in transverse section.
The small anterior teeth have milk-predecessors which are fully noticed
below. Skull moderately elongated. The facial portion subcylindrical
and slightly tapering. The zygoma complete and slender. The palate ends
posteriorly in the thickened transverse border of the palatines, and is
not continued back by the pterygoids. The tympanic is annular, and not
ankylosed to the surrounding bones. The mandible is slender anteriorly,
but rises high posteriorly, with a slender recurved coronoid, and an
ascending pointed process on the hinder edge below the condyle, which
is small, oval, and looks as much forwards as upwards. Vertebræ: C 7,
D 13, L 8, S 6, C 27. The large number of lumbar vertebræ is peculiar
among Edentates. Tongue less vermiform than in _Myrmecophaga_, being
thick and fleshy at the base, and gradually tapering to the apex. The
salivary apparatus is developed much in the same manner as in that genus,
but the duct of the submaxillary gland has no reservoir. The stomach
consists of a large subglobular cardiac portion, with a very thick, soft,
and corrugated lining membrane, and a smaller muscular, pyloric part,
with a comparatively thin and smooth lining. There is a very distinct
ileo-cæcal valve, and a considerable-sized cæcum; also a gall-bladder.
Head elongated, with a tubular snout, terminal nostrils, and small
mouth-opening. Ears large, pointed, erect. Tail nearly as long as the
body, cylindrical, very thick at the base, tapering to the extremity.
The reproductive organs and placentation of _Orycteropus_ are formed upon
a principle unknown in the more typical Edentates, or, in combination,
in any other mammals. Thus the testes, in the one described example,
were inguinal, but appeared to descend, at all events temporarily, into
a scrotum; but the penis is scarcely larger than that of the Great
Anteater. The uterus is still more fully bicornuate than in _Manis_,
with its two lateral chambers opening separately into the vagina, as in
certain Rodents. The placenta is broadly zonary, but it is not known
whether it is deciduate or not. It might readily be derived from the
diffused placenta of _Manis_ by the abortion of the fœtal villi at the
two poles of the ovum.