“Trias” is an arbitrary term applied in geology to the upper division of
a vast series of red loams, shales, and sandstones, interposed between
the lias and the coal, in the midland and western counties of England.
This series is collectively called the “New Red Sandstone formation,” to
distinguish it from the “Old Red Sandstone formation,” of similar or
identical mineral character, which lies immediately beneath the coal.
The animals which have been restored and placed on the lowest formation
of the Secondary Island, are peculiar to the “triassic,” or upper
division of the “New Red Sandstone” series, which division consists, in
England, of saliferous (salt-including) shales and sandstones, from 1000
to 1500 feet thick in Lancashire and Cheshire, answering to the
formation called “Keuper-sandstone” by the German geologists; and of
sandstone and quartzose conglomerate of 600 feet in thickness, answering
to the German “Bunter-sandstone.”
The largest and most characteristic animals of the trias are reptiles of
the order
Batrachia.
The name of this order is from the Greek word _batrachos_, signifying a
frog: and the order is represented in the present animal-population of
England by a few diminutive species of frogs, toads, and newts, or
water-salamanders. But, at the period of the deposition of the new red
sandstone, in the present counties of Warwick and Cheshire, the shores
of the ancient sea, which were then formed by that sandy deposit, were
trodden by reptiles, having the essential bony characters of the
Batrachia, but combining these with other bony characters of crocodiles
and lizards; and exhibiting both under a bulk which is made manifest by
the restoration of the largest known species, (No. 16), occupying the
extreme promontory of the Island, illustrative of the lowest and oldest
deposits of the secondary series of rocks. The species in question is
called the—
No. 18.—Labyrinthodon Salamandroides.
or the Salamander-like Labyrinthodon; the latter term being from the
Greek, signifying the peculiar structure of the teeth, which differ from
all other reptiles in the huge Batrachia in question, by reason of the
complex labyrinthic interblending of the different substances composing
the teeth. The skull of the Labyrinthodon is attached to the neck-bones
by two joints or condyles, and the teeth are situated both on the proper
jaw-bones, and on the bone of the roof of the mouth called “vomer:” both
these characters are only found at the present day in the frogs and
salamanders. The hind-foot of the Labyrinthodon was also, as in the toad
and frog, much larger than the fore-foot; and the innermost digit in
both was short and turned in, like a thumb.
[Illustration: No. 18. Labyrinthodon Salamandroides.]
Consecutive impressions of the prints of these feet have been traced for
many steps in succession (as is accurately represented in the new red
sandstone part of the Secondary Island) in quarries of that formation in
Warwickshire, Cheshire, and also in Lancashire, more especially at a
quarry of a whitish quartzose sandstone at Storton Hill, a few miles
from Liverpool. The foot-marks are partly concave and partly in relief;
the former are seen upon the upper surface of the sandstone slabs, but
those in relief are only upon the lower surfaces, being, in fact,
natural casts, formed on the subjacent foot-prints as in moulds. The
impressions of the hind-foot are generally eight inches in length and
five inches in width: near each large footstep, and at a regular
distance—about an inch and a half—before it, a smaller print of the
fore-foot, four inches long and three inches wide, occurs. The footsteps
follow each other in pairs, each pair in the same line, at intervals of
about fourteen inches from pair to pair. The large as well as the small
steps show the thumb-like toe alternately on the right and left side,
each step making a print of five toes.
Foot-prints of corresponding form but of smaller size have been
discovered in the quarry at Storton Hill, imprinted on five thin beds of
clay, lying one upon another in the same quarry, and separated by beds
of sandstone. From the lower surface of the sandstone layers, the solid
casts of each impression project in high relief, and afford models of
the feet, toes, and claws of the animals which trod on the clay.
Similar foot-prints were first observed in Saxony, at the village of
Hessberg, near Hillburghausen, in several quarries of a gray quartzose
sandstone, alternating with beds of red sandstone, and of the same
geological age as the sandstones of England that had been trodden by the
same strange animal. The German geologist, who first described them,
proposed the name of _Cheirotherium_ (Gr. _cheir_, the hand, _therion_,
beast), for the great unknown animal that had left the foot-prints, in
consequence of the resemblance, both of the fore and hind feet, to the
impression of a human hand, and Dr. Kaup conjectured that the animal
might be a large species of the opossum-kind. The discovery, however, of
fossil skulls, jaws, teeth, and a few other bones in the sandstones
exhibiting the footprints in question, has rendered it more probable
that both the footprints and the fossils are evidences of the same kind
of huge extinct Batrachian reptiles.
An entire skull of the largest species discovered in the new red
sandstones of Wurtemberg; a lower jaw of the same species found in the
same formation in Warwickshire; some vertebræ, and a few fragments of
bones of the limbs, have served, with the indications of size and shape
of the trunk of the animal yielded by the series of consecutive
foot-prints, as the basis of the restoration of the _Labyrinthodon
salamandroides_, in the Secondary Island. It is to be understood,
however, that, with the exception of the head, the form of the animal is
necessarily more or less conjectural.
Nos. 19 & 20.—Labyrinthodon pachygnathus.
This name, signifying the Thick-jawed Labyrinthodon, was given by its
discoverer to a species of these singular Batrachia, found in the new
red sandstone of Warwickshire, and which bears to the largest species
the proportion exhibited by the head and fore-part of the body, as
emerging from the water, for which parts alone the fossils hitherto
discovered justify the restoration.[6]
[Illustration: Nos. 19 & 20. Section of Tooth of Labyrinthodon.
_a_ Pulp-cavity: _b b_ inflected folds of ossified capsule of
tooth.]
Nos. 21 & 22.—Dicynodon.
In 1844 Mr. Andrew G. Bain, who had been employed in the construction of
military roads in the colony of the Cape of Good Hope, discovered, in
the tract of country extending northwards from the county of Albany,
about 450 miles east of Cape Town, several nodules or lumps of a kind of
sandstone, which, when broken, displayed, in most instances, evidences
of fossil bones, and usually of a skull with two large projecting teeth.
Accordingly, these evidences of ancient animal life in South Africa were
first notified to English geologists by Mr. Bain under the name of
“Bidentals;” and the specimens transmitted by him were submitted at his
request to Professor Owen for examination. The results of the
comparisons thereupon instituted went to show that there had formerly
existed in South Africa, and from geological evidence, probably, in a
great salt-water lake or inland sea, since converted into dry land, a
race of reptilian animals presenting in the construction of their skull
characters of the crocodile, the tortoise, and the lizard, coupled with
the presence of a pair of huge sharp-pointed tusks, growing downwards,
one from each side of the upper jaw, like the tusks of the mammalian
morse or walrus. No other kind of teeth were developed in these singular
animals: the lower jaw was armed, as in the tortoise, by a trenchant
sheath of horn. Some bones of the back, or vertebræ, by the hollowness
of the co-adapted articular surfaces, indicate these reptiles to have
been good swimmers, and probably to have habitually existed in water;
but the construction of the bony passages of the nostrils proves that
they must have come to the surface to breathe air.
Some extinct plants allied to the Lepidodendron, with other fossils,
render it probable that the sandstones containing the Dicynodont
reptiles were of the same geological age as those that have revealed the
remains of the Labyrinthodonts in Europe.
The generic name Dicynodon is from the Greek words signifying “two tusks
or canine teeth.” Three species of this genus have been demonstrated
from the fossils transmitted by Mr. Bain.
The _Dicynodon lacerticeps_, or Lizard-headed Dicynodon, attained the
bulk of a walrus; the form of the head and tusks is correctly given in
the restoration (No. 21); the trunk has been added conjecturally, to
illustrate the strange combination of characters manifested in the head.
A second species, with a head so formed as to have given the animal
somewhat of the physiognomy of an owl, has been partially restored at
No. 22.
[Illustration: No. 8. Dinornis.]