Vestiges of the Natural History of Creation (Chapter 7)
by Robert Chambers
Era of the New Red Sandstone.
Terrestrial Zoology Commences with Reptile.
First Traces of Birds.
he next volume of the rock series refers to an era
distinguished by an event of no less importance than the commencement of
land animals. The New Red Sandstone System is subdivided into
groups, some of which are wanting in some places; they are pretty fully
developed in the north of England, in the following ascending order:—
1. Lower red sandstone; 2. Magnesian limestone; 3. Red and white sandstones
and conglomerate; 4. Variegated marls. Between the third and fourth there
is, in Germany, another group, called the Muschelkalk, a word expressing a
limestone full of shells.
The first group, containing the conglomerates already
adverted to, seems to have been produced during the time of disturbance
which occurred so generally after the carbonigenous era This new era is
distinguished by a paucity of organic remains, as might partly be expected
from the appearances of disturbance, and the red tint of the rocks, the
latter being communicated by a solution of oxide of iron, a substance
unfavourable to animal life.
The second group is a limestone with an infusion of
magnesia It is developed less generally than some others, but occurs
conspicuously in England and Germany. Its place, above the red sandstone,
shews the recurrence of circumstances favourable to animal life, and we
accordingly find in it not only zoophytes, conchifera, and a few tribes of
fish, but some faint traces of land plants, and a new and startling
appearance—a reptile of saurian (lizard) character, analogous to the
now existing family called monitors. Remains of this creature are found in
cupriferous (copper-bearing) slate connected with the mountain limestone,
at Mansfield and Glucksbrunn, in Germany, which may be taken as evidence
that dry land existed in that age near those places. The magnesia limestone
is also remarkable as the last rock in which appears the leptaena, or
producta, a conchifer of numerous species which makes a conspicuous
appearance in all previous seas. It is likewise to be observed, that the
fishes of this age, to the genera of which the names palmoniscus,
catopterus, platysomus, &c., have been applied, vanish, and henceforth
appear no more.
The third group, chiefly sandstones, variously coloured
according to the amount and nature of the metallic oxide infused into them,
shews a recurrence of agitation, and a consequent diminution of the amount
of animal life. In the upper part, however, of this group, there are
abundant symptoms of a revival of proper conditions for such life. There
are marl beds, the origin of which substance in decomposed shells is
obvious; and in Germany, though not in England, here occurs the
muschelkalk, containing numerous organic remains, (generally different from
those of the magnesian limestone,) and noted for the specimens of land
animals, which it is the first to present in any considerable abundance to
our notice.
These animals are of the vertebrate sub-kingdom, but of
its lowest class next after fishes,—namely, reptiles,—a portion
of the terrestrial tribes whose imperfect respiratory system perhaps fitted
them for enduring an atmosphere not yet quite suitable for birds or
mammifers.[1] The specimens found in the muschelkalk
are allied to the crocodile and lizard tribes of the present day, but in
the latter instance are upon a scale of magnitude as much superior to
present forms as the lepidodendron of the coal era was superior to the
dwarf club-mosses of our time. These saurians also combine some
peculiarities of structure of a most extraordinary character.
The animal to which the name ichthyosauru has
been given, was as long as a young whale, and it was fitted for living in
the water, though breathing the atmosphere. It had the vertebral column
and general bodily form of a fish, but to that were added the head and
breast-bone of a lizard, and the paddles of the whale tribes. The beak,
moreover, was that of a porpoise, and the teeth were those of a crocodile.
It must have been a most destructive creature to the fish of those early
seas.
The plesiosaurus was of similar bulk, with a
turtle-like body and paddles, shewing that the sea was its element, but
with a long serpent-like neck, terminating in a saurian head, calculated to
reach prey at a considerable distance. These two animals, of which many
varieties have been discovered, constituting distinct species, are supposed
to have lived in the shallow borders of the seas of this and subsequent
formations, devouring immense quantities of the finny tribes. It was at
first thought that no creatures approaching them in character now inhabit
the earth; but latterly Mr. Darwin has discovered, in the reptile-peopled
Galapagos Islands, in the South Sea, a marine saurian from three to four
feet long.
The megalosaurus was an enormous lizard—a
land creature, also carnivorous. The pterodaclyle was another
lizard, but furnished with wings to pursue its prey in the air, and varying
in size between a cormorant and a snipe. Crocodiles abounded, and some of
these were herbivorous. Such was the iguanodon, a creature of the character
of the iguana of the Ganges, but reaching a hundred feet in length, or
twenty times that of its modern representative.
There were also numerous tortoises, some of them
reaching a great size; and Professor Owen has found in Warwickshire some
remains of an animal of the batrachian order,[2] to
which, from the peculiar form of the teeth, he has given the name of
labyrinthidon. Thus, three of Cuvier's four orders of reptilia
(sauria, chelonia, and batrachia) are represented in
this formation, the serpent order (ophidia) being alone wanting.
The variegated marl beds which constitute the uppermost
group of the formation, present two additional genera of huge
saurians,—the phytosaurus and mastodonsaurus.
It is in the upper beds of the red sandstone that beds
of salt first occur. These are sometimes of such thickness, that the mine
from which the material has been excavated looks like a lofty church. We
see in the present world no circumstances calculated to produce the
formation of a bed of rock salt; yet it is not difficult to understand how
such strata were formed in an age marked by ultra-tropical heat and
frequent volcanic disturbances. An estuary, cut off by an upthrow of trap,
or a change of level, and left to dry up under the heat of the sun, would
quickly become the bed of a dense layer of rock salt. A second shift of
level, or some other volcanic disturbance, connecting it again with the
sea, would expose this stratum to being covered over with a layer of sand
or mud, destined in time to form the next stratum of rock above it.
The plants of this era are few and unobtrusive.
Equiseta, calamites, ferns, Voltzia, and a few of the other families found
so abundantly in the preceding formation, here present themselves, but in
diminished size and quantity.
This seems to be the proper place to advert to certain
memorials of a peculiar and unexpected character respecting these early
ages in the sandstones. So low as the bottom of the carboniferous system,
slabs are found marked over a great extent of surface with that peculiar
corrugation or wrinkling which the receding tide leaves upon a sandy beach
when the sea is but slightly agitated; and not only are these ripple-marks,
as they are called, found on the surfaces, but casts of them are found on
the under sides of slabs lying above. The phenomena suggests the time when
the sand ultimately formed into these stone slabs, was part of the beach of
a sea of the carbonigenous era; when, left wavy by one tide, it was covered
over with a thin layer of fresh sand by the next, and so on, precisely as
such circumstances might be expected to take place at the present day.
Sandstone surfaces, ripple-marked, are found throughout the subsequent
formations: in those of the new red, at more than one place in England,
they further bear impressions of rain-drops which have fallen upon
them—the rain, of course, of the inconceivably remote age in which the
sandstones were formed. In the Greensill sandstone, near Shrewsbury, it has
even been possible to tell from what direction the shower came which
impressed the sandy surface, the rims of the marks being somewhat raised on
one side, exactly as might be expected from a slanting shower falling at
this day upon one of our beaches. These facts have the same sort of
interest as the season rings of the Craigleith conifers, as speaking of a
parity between some of the familiar processes of nature in those early ages
and our own.
In the new red sandstone, impressions still more
important in the inferences to which they tend, have been,—namely, the
footmarks of various animals. In a quarry of this formation, at Corncockle
Muir, in Dumfriesshire, where the slabs incline at an angle of thirty-eight
degrees, the vestiges of an animal supposed to have been a tortoise are
distinctly traced up and down the slope, as if the creature had had
occasion to pass backwards and forwards in that direction only, possibly in
its daily visits to the sea. Some slabs similarly impressed, in the
Stourton quarries in Cheshire, are further marked with a shower of rain
which we know must have fallen afterwards, for its little hollows
are impressed in the footmarks also, though more slightly than on the rest
of the surface, the comparative hardness of a trodden place having
apparently prevented so deep an impression being made. At Hessberg, in
Saxony, the vestiges of four distinct animals have been traced, one of
them a web-footed animal of small size, considered as a congener of the
crocodile; another, whose footsteps having a resemblance to an impression
of a swelled human hand, has caused it to be named the
cheirotherium. The footsteps of the cheirotherium have been found
also in the Stourton quarries above mentioned. Professor Owen, who stands
at the head of comparative anatomy in the present day, has expressed his
belief that this last animal was the same batrachian of which he has found
fragments in the new red sandstone of Warwickshire. At Runcorn, near
Manchester, and elsewhere, have been discovered the tracks of an animal
which Mr. Owen calls the rynchosaurus, uniting with the body of a reptile
the beak and feet of a bird, and which clearly had been a link
between these two classes.
If geologists shall ultimately give their approbation to
the inferences made from a recent discovery in America, we shall have the
addition of perfect birds, though probably of a low type, to the animal
forms of this era. It is stated to be in quarries of this rock, in the
valley of Connecticut, that footprints have been found, apparently produced
by birds of the order grallae, or waders. " The footsteps appear in regular
succession on the continuous track of an animal, in the act of walking or
running, with the right and left foot always in their relative places. The
distance of the intervals between each footstep on the same track is
occasionally varied, but to no greater amount than may be explained by the
bird having altered its pace. Many tracks of different individuals and
different species are often found crossing each other, and crowded, like
impressions of feet upon the shores of a muddy stream, where ducks and
geese resort."[3]
Some of these prints indicate small animals, but others
denote birds of what would now be an unusually large size. One animal,
having a foot fifteen inches in length, (one-half more than that of the
ostrich,) and a stride of from four to six feet, has been appropriately
entitled, ornithichnites giganteus.
Notes
The immediate effects of the slow respiration of
the reptilia are, a low temperature in their bodies, and a slow consumption
of food. Requiring little oxygen, they could have existed in an atmosphere
containing a less proportion of that gas to carbonic acid gas than what now
obtains.
The order to which frogs and toads belong.
Dr. Buckland, quoting an article by Professor
Hitchcock, in the American Journal of Science and Arts, 1836.
| |
[ Robert Chambers,
Vestiges of the
Natural History of Creation, 1st edition, 1844; Reprinted in James Secord,
ed., Chicago: University of Chicago Press, 1994, pp. 94-104. ]
Home Page |
Further Reading |
Site Map |
Send Feedback
