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irregular dark crossbands on the body. In some specimens the sides of the body
are, however, of a bright red. The form and arrangement of the scales on the
head, the presence of seven upper labial shields, and the arrangement of the body
scales in not more than twenty-nine rows, together with the uniformly coloured
under surface of the body, serve to distinguish the species from its congeners.
This snake is an inhabitant of the Antilles and Central America. During the
daytime it lies curled up in repose within the middle of the coils of the body,
ready to dart out with the rapidity of lightning on the approach of an enemy.

The mainland of South America is the home of two closely allied
Jararaca.

terrestrial representatives of the genus, respectively known as the

jararaca (T. jararaca) and the labaria (T. atrox), which are exceedingly difficult to
distinguish from one another. The former, which ranges from Amazonia south-
wards to San Paulo and westwards to Ecuador and Peru, has eight or nine upper
labial shields on the snout, and from twenty-five to twenty-seven rows of scales
on the body; the general colour of the upper-parts being grey or greyish brown,
with small dark brown crossbands, bordered by darker edges ; while the under-
parts are grey, with two or four irregular longitudinal rows of whitish or yellowish
spots. The labaria differs in having only seven upper labials, as well as in certain
details of coloration, the back showing dark lozenges alternating with X -shaped
markings, while the under-parts are darker, with sometimes two rows of white
spots, and from the eye to the corner of the mouth runs a broader dark brown
stripe. Inhabiting Eastern Brazil, this species extends as far north as Guiana,
while its southward range is less than that of the jararaca.

Writing of the latter, Bates states that in Brazil it is far more dreaded than
the jaguar or the alligator. " The individual seen by Lino lay coiled up at the
foot of a tree, and was scarcely distinguishable, on account of the colours of its
body being assimilated to those of the fallen leaves. Its hideous, flat, triangular
head, connected with the body by a thin "-ok, was reared and turned towards us;
Frazao killed it with a charge of shot, shattering it completely, and destroying its
value as a specimen. In conversing on the subject of jararaca as we walked
onwards, every one of the party was ready to swear that this snake attacks man



EXTINCT SCALED REPTILES. 249

without provocation, leaping towards him from a considerable distance when he
approaches. I met, in the course of my daily rambles through the woods, many
jararacas, and once or twice very narrowly escaped treading on them, but never
saw them attempt to spring. On some subjects the testimony of the natives of a
wild country is utterly worthless. The bite of the jararacas is generally fatal."

EXTINCT GROUPS OF SCALED REPTILES.

A brief reference may be made to two groups of extinct reptiles from the
rocks of the Secondary epoch, which must be included in the order Squamata.
Long-Necked The first of these groups is represented by a small snake-lizard, from
Lizards. the English Chalk, described under the name of Dolichosa/wrus, and
Forming a suborder (Dolichosauria) by itself. Whereas ordinary lizards have not
more than nine vertebrae in the neck, this strange reptile has upwards of from
iifteen to seventeen, while its hind-limbs are characterised by having the whole of
:he five metatarsal bones of the foot well developed, and its whole structure
reveals a very generalised type of organisation. The vertebrae have additional
articulations like those of snakes. It is probable that these reptiles form the
ancestral group from which the other suborders of scaled reptiles have originated.

Cretaceous A still more remarkable group of the order is formed by certain

Sea-Serpents, carnivorous marine reptiles from the Cretaceous rocks, many of which
attained gigantic dimensions, and may not inappropriately be designated extinct
sea-serpents. Commonly known as Mosasauroids, on account of the first described

nus (Mosasaarus), having been found on the banks of the Meuse, they form a
suborder technically known as the Pythonomorpha. They all had a much elon-
gated body, and a skull approximating in structure to that of the monitors among
existing lizards, the nasal and premaxillary bones being welded together, and the
quadrate very loosely attached to the skull. Teeth were present on some of the
bones of the palate, as well as on the margin of the jaws ; those of the latter series
being large, sharply pointed, and attached by expanded bases. The bones of the
shoulder-girdle and pelvis were more or less imperfectly developed ; and the limbs
were modified into paddles or flippers, with the toes enclosed in a common skin,
and devoid of claws. There were either nine or ten vertebrae in the neck ; and
whereas, in some cases, the vertebrae resembled those of snakes, in other instances
they lacked the additional articulations distinguishing the latter. It will be un-
necessary to particularise the various genera of these reptiles, but it may be
mentioned that while some of the better-known forms have been described as
Mosasaurus, others have received the names of Liodon and Clidastes. They appear
to have inhabited the Cretaceous seas of all parts of the world, having been
obtained from regions as far apart as England, New Zealand, and Argentina ; and
while some attained a length of between 25 and 30 feet, others were not more
than 8 or 10. Then, again, while in some cases the jaws were armed with power-
ful teeth to their extremities, other forms ^d a long, toothless beak.



CHAPTER VI.

THE REMAINING GROUPS OF REPTILES, Orders ICHTHYOPTERYGIA,
RHYNCHOCEPHALIA, AND ANOMODONTIA.

OF the three orders remaining for consideration, two are completely extinct, and
not known from deposits of later date than those of the Secondary period, while
the third is represented at the present day only by a single species from New
Zealand, although in former geological epochs it appears to have been abundant.
The first of the three for consideration is the group of

FISH-LIZARDS, Order ICHTHYOPTERYGIA.

More or less familiar to all from the beautifully preserved skeletons obtained
from the Lias of England and the Continent, specimens of which are exhibited in
almost every museum, the Fish-lizards, or Ichthyosaurs, were large marine reptiles,
with the naked body thick and whale-like, the neck extremely short, and the limbs
modified into paddles differing from those of all other members of the class in the
structure of their skeleton. The skull is produced into a long snout, generally
furnished with a full series of sharp teeth, and mainly formed in the upper jaw by the
premaxillary, or front jawbones; and the nostrils are consequently placed close to
the eyes, the latter, like those of birds, being provided with a ring of movable plates.
Superiorly, the skull has a hole or foramen, in the parietal bones ; while posteriorly
the upper and lower arches are connected behind the socket of the eye by a bone
known as the supratemporal, so that this portion of the skull is completely roofed
over, as we shall see to be the case in the Labyrinthodont Amphibians. Then,
again, the quadrate-bone, with which the lower jaw articulates, is firmly united to
the adjacent elements of the skull; while in the general relations of this bone
and the bones of the palate there is a marked agreement with the beaked reptiles.
The teeth are confined to the edges of the jaws, where they are implanted in
distinct sockets; and generally have conical and fluted crowns, although more
rarely they are compressed and smooth, with sharp cutting edges at the front and
back. The back-bone presents a nearly similar structure, the vertebra 1 , as shown
in the figure on p. 6, being short discs, which may be either deeply cupped or
neai-ly flat at the two ends. In the body and neck these vertebrae carry a pair of
tubercles on each side for the articulation of the forked ends of the ribs; but in
the tail there is but one such tubercle, the ribs bein<r single-headed Moreover, the

O c^

vertebrae are further remarkable for the absence of any body union between the
body or centrum (the part represented in the figure), and the arch enclosing the
spinal marrow, so that these two portions are always found detached. The bones



FISH-LIZARDS.



25*



of the shoulder-girdle much resemble those of lizards, the collar-bones being well-
developed, and the T-shaped interclavicle resting on the lower surface of these and
the metacoracoids. The limbs are quite unlike those of any other reptiles, the
upper bone (humerus in the fore-limb) being very short and thick, while below
this the whole of the bones, as shown in the accompanying figure, were polygonal,
and so articulated with one another that the skeleton of the paddles assumed a




SKELETON OF FISH-LIZARD, SHOWING YOUNG ONE WITHIN THE CAVITY OF THE RIBS (^ nat. size).

(From Gaudry.)

:ind of pavement-like or mosaic structure. In most kinds the front paddles were
inch larger than the hinder-pair ; and whereas, in some cases, two longitudinal
eries of bones originate from the bone marked i in the accompanying figure, thus

producing a very broad type of paddle,
in other forms (as shown in the skeleton
in the figure above), only a single series
articulated with that bone, and the whole
paddle was consequently much narrower.
Specimens like the one figured here show
that while the soft parts of the paddle
extended but a short distance in advance
of the front edge of the bones, on the
hinder -side they terminated in a wide
fringe, thus forming a structure admir-
ably adapted for swimming. Other
examples indicate that the back of these
reptiles was furnished with an upright
triangular fin somewhat like that of a
porpoise, behind which were a number
of small finlets, while the extremity of
the tail was expanded into a horizontal
fin, comparable to the flukes of a whale.
Many of these reptiles attained a length

from 30 to 40 feet; and they flourished throughout the whole of the Secondary
riod, that is to say, from the epoch of the Trias, or Red Sandstone, to that of the



I'AliT OK THE FORE-PADDLE 01




FISH-LIZARD.

hu, bone of upper arm ; r.u, bones of fore-arm ; the
her letters indicate the bones of the wrist, below
rh are the bones of the fingers.



252 BEAKED LIZARDS.

Chalk, most or all of the forms from the first-named deposits being of a more
generalised type than those of later date.

In external appearance the fish -lizards must have presented a marked
resemblance to whales, the place of which they seem to have filled in the old sens.
Like these animals, they were obliged to come periodically to the surface of the
water for the purpose of breathing ; and they were likewise carnivorous, as is
attested not only by the conformation of their teeth, but likewise by the petrified
remains of their prey. Occasionally specimens are met with, in which entire
skeletons of one or more young individuals of the same species are preserved within
the cavity of the ribs, thus proving that in these reptiles the eggs were hatched
within the body of the females, and the offspring produced in a living condition.



THE BEAKED LIZARDS.
Order RHYNCHOCEPHALIA.

The tuatera, which seems to be confined to the small islands off the north-east
of New Zealand, is not only the most remarkable of all existing reptiles to which
the term lizard can be applied, but is the sole living representative of a distinct
family, as well as of an entire order ; and the difference between it and an ordinary
lizard immeasurably exceeds that by which the latter is separated from a serpent..-
As an order, the beaked reptiles may be provisionally characterised as follows.
Externally most of these reptiles appear to have been more or less lizard-like ;
and, as in their living representative, the body was probably covered above with
small granular scales intermingled with tubercles. The skull differs essentially
from that of lizards in having the quadrate-bone immovably fixed by the upper
end to the adjacent bones; and likewise by having both an upper and a lower
temporal arch. The hind portion of the palate is formed by the union of the
pterygoid bones, which, generally at least, extend forwards to meet the vomers,
and thus divide the palatines ; while the anterior upper jawbones, or pre-
maxillaa, remain separate from each other. The teeth are not implanted in
distinct sockets, and are usually welded to the summits of the jaws. In the trunk,
the ribs articulate to the vertebrae by single heads, and may have hook-like:
processes similar to those of birds ; while on the lower surface of the body,
so-called abdominal ribs are always developed, forming a shield composed of 4<
number of segments, and comparable to the plastron of the tortoises. The
vertebrae may be either hollowed at both articular ends, or the hinder surface
may be cupped and the front one ball-like. That the beaked reptiles form a very\,
primitive group is clear, not only from their structure, but from their antiquity;;
representatives of the order occurring in the Permian strata, immediately ovefl
lying the Carboniferous or coal-bearing rocks. While some of these early forme"
appear to connect the order very closely with the Sauropterygians, others indicate
an equally close relationship with the under-mentioned Anomodonts.

The single existing representative of the order (Xnlenodoiti

The Tuatera. J

pu/ncldtn*) forms a family (Sphenodontidce) by itself, and likewutM

is the representative of a distinct suborder (Rhynchocephalia Vera), characterised!



TUATKK.l. 253

by each .segment of the shield on the lower surface of the body being formed of
' only three elements, of which the middle one is chevron-shaped, and likewise by
the fifth nietatarsal bone of the hind-foot being reduced in length and thickened
in the same manner as in lizards. The group is further characterised by the
double nostrils, the union of the two branches of the lower jaw by cartilage, and
the deeply hollowed articular surfaces of the vertebrae. From its extinct allies the
family is distinguished by having a perforation on each side of the lower
extremity of the humerus, or upper bone of the fore-limb; by the presence of
hook-like processes to the ribs, as well as of so-called intercentra, or additional
segments between the bodies of the vertebras; and likewise by the beak-like
premaxillary bones carrying a pair of somewhat chisel-like teeth, and the presence




NEW XEALAND TUATEUA (\ lUlt. SJXc) ;



of only a single row of teeth on the palate, which are separated by a groove from
the row affixed to the edge of the upper jaw. Into this groove is received the
teeth and upper edge of the lower jaw, which in very old individuals becomes as
hard and polished as the teeth themselves; the latter being more or less completely
worn away in extreme old age. On the upper surface of the skull is a large
vacuity, or foramen, in the parietal bones. In external appearance the tuatera is
lizard-like, the body being slightly and the long tail strongly compressed ; while
the limbs carry five toes, all furnished with claws, and connected at their bases by
webs. There is no external opening to the ear, and the large eye has the pupil
vertical. On the upper-parts the creature is clothed with small granular scales,
intermixed with tubercles ; and a crest of spine-like scales runs from the hinder-
part of the head clown the middle of the back, continued in a smaller degree of



254



BEAKED LIZARDS.



Allied Families.



development down the tail ; while inferiorly there are large squarish scales arranged
in transverse rows. Attaining a length of about 20 inches, the tuatera is olive or
blackish in ground-colour, upon which are small yellowish dots, while the lobes of
the crest on the neck and back are likewise of the latter colour. The perforation
in the parietal bones of the skull just referred to covers a rudimentary eye, which
although now functionless was probably a working organ in the ancestors of
the Vertebrates. In the young tuatera this pineal eye can be seen through the
translucent skin, but in the adult this skin becomes opaque.

In the Jurassic rocks of Europe there occur remains of reptiles
allied to the tuatera, but constituting a distinct family (Honueosan ,-

idee) typically represented by the genus
Homoeosawrus. These have no tusk-like
teeth in the front of the jaws, and the lower
end of the humerus lias a perforation only
on its inner side, and there are no inter-
centra between the vertebras of the back,
and no hook-like processes to the ribs. A
third family (Rhynchosauridce) is typified
by the genus Rhynchosaurus, from the Trias
or New Red Sandstone of England, and is
characterised by the beak being toothless
and probably sheathed in horn ; the palate
having two or more longitudinal rows of
teeth separated by a groove. From the
preceding families these reptiles differ by
having only a single aperture to the nostrils,
and by the bony union of the two branches
of the lower jaw ; while the articular
surfaces of the vertebrae are nearly flat.
Moreover, there is no vacuity in the middle
SKULL OF THE Hyperodapedm (J nat. size). Q f the top Q f t] ie ^11 J u the typical gel i us

The upper figure shows the superior aspect; the there is a single 1'OW of teeth on the il mel-
lower one on the left the palate, and the right lower . ,
one the under surface of the front of the lower jaw. Slde of the gTOOVG Oil the palate, but in

Hyperodapedon, there were numerous ro\vs,

as is shown in the illustration. The extremity of the beak in each jaw formed
two curved tusk-like processes, which diverged in the lower one.

The Permian rocks of Europe yield remains of genera, sucli as
Proterosaurus and Palceohatteria, differing markedly from the Tore-
going, and constituting a second suborder (Proterosauria), characterised by the
complex nature of the bones forming the shield on the lower surface of thebody,
by the fifth metatarsal bone of the hind-foot being of an ordinary type, and like-
wise by the lower bones of the pelvis being expanded into large flattened plates,
instead of comparatively narrow. The last feature allies the group to the earlier
Sauroptcrygians. In the genus first named the vertebras of the neck have cup-
shaped articular surfaces behind and balls in front, and there are no intercentra
between the vertebra of the back, but in the other the articular surfaces of the




Oldest Types.



A NO MO DO NTS.



vertebrae are slightly cupped at each end throughout the series, and intercentra
are present.

THE ANOMODONTS, OR MAMMAL-LIKE REPTILES.
Order ANOMODONTIA.

The last order of Reptiles, which is entirely extinct and confined to the
Triassic and Permian epochs, is of especial interest to the evolutionist as being
nearly allied to the ancestral stock from which Mammals have originated, and also
equally closely related to certain extinct Amphibians noticed in the sequel, which
were themselves evidently not far removed from the type whence sprang both
Reptiles and Mammals. It should be observed, however, that these Anomodonts
show the nearest relationship to the Egg-laying Mammals, and until we know the
true affinity of
the latter to the
other members
of the same class,
it is of course
impossible to at-
tempt to define
the genealogy
more exactly.
The Anomodonts
are the only
iv] i tiles which
agree with the
Egg- laying
Mammals in
having three dis-
tinct bones on
each side of the
true shoulder-
girdle ; that is

to say, a blade-bone, or scapula, above, and a coracoid and metacoracoid below.
Then the pelvis is very mammal-like, not only in that its three elements are
united, but likewise in the small size of the vacuity, or foramen (of) between
the pubis and ischium. It will also be seen from the two figures here given how
close is the resemblance between the pelvis and shoulder-girdle of these reptiles,
each having one bone above and two below. Even still more marked is the
similarity between the upper arrn-bone or humerus of the Anomodonts and that
of the Egg-laying Mammals ; each having a perforation on the inner border of
the lower end, whereas in those existing reptiles which possess such a perfora-
tion (with the exception of the tuatera, where there is one on each side), it is
situated on the outer border. As a rule, the Anomodonts further resemble
Mammals in the absence of abdominal ribs ; and there are important similarities
in the structure of the skull.




THE 1UGHT SIDE OF THE PELVIS (A) AND SHOULDER-GIRDLE (B) OF AN ANOMODONT.

il, haunch-bone, or ilium ; is, iscliium ; pb t pubis ; of, foramen between ischium and
pubis ; sc, blade-bone, or scapula ; p.cor, coracoid ; cor, metacoracoid ; gl, cavity for head
of upper arm-bone, or humerus.



256



ANOMODOMS.



Anomodonts arc met with in the Triassic rocks, and are represented by at
least four well-marked subordinal types. In the first group, known as Mammal -





SKULL AND TEETH OF CAI.ESAUR



UPPER SURFACE OK THE SKULL OF A PAVEMENT-
TOOTHED ANOMODONT (^ nat. .size).



toothed (Theriodont) Reptiles, the teeth,
as exemplified in the figure of the skull
of the African galesaur, are differentiated
into incisors, tusks, and cheek-teeth ; the
latter frequently having three cusps
ranged in a longitudinal series. Whether,
however, this marked mammalian type
of dentition is indicative of genetic affinity
with Mammals, may be open to doubt, as it is quite as likely to be due to parallelism
in development. Another modification is presented by the Dicynodonts of England,
Africa, and India, in which the jaws formed a horny beak, either destitute of
teeth, as in the tortoises, or provided with a huge pair of tusks in the upper

jaw; some of these reptiles being of
gigantic size. A third group, known as
Pavement-toothed, or Placodont Reptiles,
which should probably be included in the
order, are characterised by the presence
of broad, flattened teeth on the palate and
jaws, as shown in the figure on p. 5 ; the
skull being very short and more or less
triangular, with the double nostrils situated
near the extremity of the mu/zle, some
distance in advance of the sockets of
eyes, which occupy a nearly central
tion. In all these forms, the skull has
large temporal fossae in the hinder part

the upper surface ; but in the Wall-toothed or Pariasaurian Anomodonts, as sho\
in the cut, the hinder part of the skull was roofed over by bone, in the main
characterising the Labyrinthodorit Amphibians, to which these reptiles were allie<
a peculiar sculpturing of the surface of the skull being another point of resem-
blance. In the species, of which the skull is figured, a number of spines surmounted
the head; but these were wanting in the African pariasaur, which was a gigantic
creature, with a somewhat frog-like head, an apology for a tail, and powerful
short limbs, in which the toes were armed with long claws.




UPPER SURFACE OF THE SKULL OF A WALL-TOOTHED

ANOMODONT (J nat. size).




FIRE-BELLIED FKOGS (liat. size).



AMPHIBIANS.



CHAPTER I.

GENERAL CHARACTERISTICS, Class Amphibia.
FROGS AND TOADS, Order ECAUDATA.

IN popular estimation frogs and toads, together with their near relatives the newts
and salamanders, are regarded as Reptiles, but they are really very different, and
constitute a class by themselves, being in many respects intermediate between
Reptiles and Fishes. From the mode of life of its members the very appropriate
name of Amphibians has been proposed for the class, and is the one which should
be adopted, although the term Batrachians, which more properly applies to frogs
and toads alone, is not unfrequently used in the same sense. Agreeing with the
higher Vertebrates in the structure of their limbs, which are divided into the same
number of segments as in Mammals and Reptiles, and supported by corresponding
bones, existing Amphibians are distinguished from Reptiles by the absence of any
ossification in the basioccipital region of the lower surface of the hinder-part of
the skull, in consequence of which the latter is articulated to the first vertebra by
means of two condyles formed exclusively by the exoccipital bones. A further
important point of distinction is afforded by the absence in the embryo of those,
membranous structures known as the amnion and allantois. Moreover, the great
majority of Amphibians pass through a metamorphosis, or rather a series of

VOL. V. 17



258 AMPHIBIANS.



Online LibraryRichard LydekkerThe new natural history (Volume 5) → online text (page 27 of 62)