Millepedes. From the Coal-formation.
Fig. 126.—Millepedes. From the Coal-formation.
a,Xylobius sigillariæ(Dawson).b,Archiulus xylobioides(Scudder). Anterior segments. Enlarged,c,X. farctus(Scudder). Caudal portion. Enlarged.
The insects of the Carboniferous as yet known, belong to three out of the ten or more orders into which the class is divided. One of these is represented by a number of species of Cockroach, another by May-flies and a Dragon-fly, and another by some weevil-like Beetles. The Cockroach is characterised by Huxley as one of the “oldest, least modified, and in many ways most instructive forms of insects;” and both he and Rolleston take its anatomy as typical of that of the class. That these creatures should have abounded in the Coal-period we need not wonder, when we consider the habits of those that infest our houses, and when we further bear in mind the number of species, some of them two inches in length, that exist in tropical climates. So many species of this family have been found in the Coal-formation on both sides of the Atlantic,48that we may fairly regard them as constituting one of its most characteristic features, and as probablythe oldest representatives of the order to which they belong49(Fig. 127). There were also in the Coal-period insects allied to the Locusts and to the Mantids, a carnivorous group. One of the latter (Lithomantis), described by Woodward, is a magnificent insect, not unlike some modern tropical species. It was found in the Coal-formation of Scotland. A still larger species, probably the largest insect known, has been described by Brongniart. The May-flies (Ephemeridæ) are represented in the Carboniferous by several very large species. That of which the wing is shown inFig. 128must have been seven inches in expanse of wings. The habits of the modern May-flies show us how animals of this group, living as larvæ in the streams and lakes, must have afforded large supplies of food to fishes, and when mature must have emerged from the waters in countless myriads, filling the air for the brief term of their existence in the perfect state. The May-flies represent another insect order.50The Coal-measures of Saarbruck have afforded several species allied to the white ants (Termites), insects which must have found abundant scope for their activity in the dead treesof the carboniferous forests. The occurrence of beetles,51especially of the weevil family, which have as yet been found only in Europe, might have been expected, considering the habits and modern distribution of this group. It has been asserted that moths52have been found in the Carboniferous; but the proof of this, so far as known to me, is the occurrence of leaves, noticed by Sternberg, with markings similar to those made by the larvæ of minute leaf-mining moths. This, however, is uncertain evidence. If we consider the orders of insects not found in the Coal-formation, we can perceive good reasons for the absence of some of them. Those containing the lice and fleas, and other minute and parasitic insects, we can scarcely expect to find. The bees and wasps, and the butterflies and moths, are little likely to have been present where there were scarcely any flowering plants; but such groups as those of the two-winged flies, the plant-bugs and the ants, we might have expected, butfor the fact of their being highly specialised forms, and for that reason likely to have appeared later.53There are, indeed, as yet no haustellate or suctorial insects known in this early period. Plausible theories of the phylogeny of insects are not wanting; but they do not well suit the known facts as to their first appearance; and perhaps we may venture without much blame to apply to the insects of the Coal-period the remark made by Wollaston with reference to the rich insect fauna of the isolated rock of St. Helena: “To a mind which, like my own, can accept the doctrine of creative acts as not necessarily ‘unphilosophical,’ the mysteries [of the existence of these species in an island so remote from other lands], howevergreat, become at least conceivable; but those which are not able to do this may, perhaps, succeed in elaborating some special theory of their own, which, even if it does not satisfy all the requirements of the problem, may at least prove convincing to themselves.”
Wings of Cockroaches. From the Coal-formation.
Fig. 127.—Wings of Cockroaches. From the Coal-formation.
a,Archimulacris Acadicus(Scudder).b,Blattina Bretonensis(Scudder).c,B. Hesri(Scudder).
Wing of May-fly.
Fig. 128.—Wing of May-fly (Haplophlebium Barnesii, Scudder). From the Coal-formation.
A Jurassic Sphinx-moth.
Fig. 129.—A Jurassic Sphinx-moth (Sphinx Snelleri, Weyenburgh).
An Eocene Butterfly.
Fig. 130.—An Eocene Butterfly (Prodryas persephone, Scudder). From Colorado.
The suctorial insects make their first certain appearance in the Jurassic; and the magnificent Sphinx Moth inFig. 129is an example of the magnitude and perfection to which that tribe attained in the age of the Solenhofen slate; though Weyenburgh, who describes it, fancies that he sees evidence that it may, unlike any modern moths, have been provided with a sting. The most perfect and beautiful fossil butterfly known to me is that represented inFig. 130, from a photograph kindly given to me by Mr. Scudder. It is from the Tertiary rocks of Western America, and is laid out in stone as neatly as if prepared by an entomologist, while its preservation is so perfect that even the microscopic scales on the wings can be made out. It belongs to one of the highest types ofmodern butterflies, that to which theVanessæbelong, but with some points of structure pointing to the lower group of the “Skippers” (Hesperiadæ). Scudder remarks that while the fore-wings resemble those of the former group, the hind-wings look more like those of the latter; and this seems to be a common character of two or three others of the few fossil species known, none of which are older than the Tertiary.
Abdominal part of a Carboniferous Scorpion.
Fig. 131.—Abdominal part of a Carboniferous Scorpion.54
We know too little of the spiders and scorpions of the Carboniferous to say more than that they closely resemble modern forms. Two of the scorpions are represented inFigs. 131 and 132; and the only spider certainly known, which is from Silesia, is said to belong to the group of the hunting or trap-door spiders (Lycosa).55
The Batrachians of the Coal are its most characteristic and remarkable air-breathers,—especially so as the precursors of the reptiles of the Mesozoic age. Cope in a recent summary enumerates no less than thirty-nine genera and about one hundred species; and to these have to be added at least a dozen more recently discovered in Europe; though it was only in 1841 that the first indications of such creatures were found, and were then regarded by geologists with the same scepticism which some of them still apply toEozoon. Thefirst trace ever observed of batrachians in the Carboniferous consisted of a series of small but well-marked footprints found by the late Sir W. E. Logan in the Lower Carboniferous shales of Horton Bluff, in Nova Scotia. In that year this painstaking geologist had examined the coal-fields of Pennsylvania and Nova Scotia, with the view of following up his important discovery of theStigmariæ, or roots ofSigillaria, as accompaniments of the coal-underclays. On his return he read a paper, detailing his observations, before the Geological Society of London. In this he mentioned the footprints in question; but the paper was published only in abstract, and the importance of the discovery was overlooked for a time, the anatomists evidently being shy to acknowledge the validity of the evidence for a fact so unexpected.Fig. 133is a representation of another slab subsequently found in beds of the same age in Nova Scotia, and which may serve to indicate the nature of Sir William’s discovery. In consequence of the neglect of this first hint by the London geologists, the discovery of bones of a batrachian by von Dechen at Saarbruck in 1844, and that of footprints by King in Pennsylvania in the same year, are usually represented as the first facts of this kind. My own earliest discovery of reptilian bones in Nova Scotia was made in 1844,though not published till some time afterward, and was followed up by further collections in company with Sir Charles Lyell in 1851, at which time also the earliest land-snail was found, and in the following year the first millepede. Since that time the progress of discovery has been astonishingly rapid, and has extended over most of the principal coal-areas on both sides of the Atlantic.
Carboniferous Scorpion.
Fig.132.—Carboniferous Scorpion (Eoscorpius carbonarius, Meek and Worthen). Illinois.
Footprints of one of the oldest known Batrachians.
Fig.133.—Footprints of one of the oldest known Batrachians, probably a species ofDendrerpeton. From the Lower Carboniferous of Parrsboro, Nova Scotia. Upper figure natural size.
We may, for convenience, call these animals reptiles, but they are regarded as belonging to that lower grade of reptilian animals, the Amphibians or Batrachians, which includes the modern frogs and newts and water-lizards.56Still it would be doing great injustice to the carboniferous reptiles not to say,that while related to this low type, they presented a much greater range of organisation than it shows at present, evincing a capability to fill most of the places now occupied by the true reptiles. Some of them were aquatic, and with limbs rudimentary or little developed, but many of them walked on the land, and were powerful and predaceous creatures. They had large and complex teeth, they were protected by external bony plates, and some of them had in addition a beautiful covering of horny plates and spines, and ornamental lappets. Many had well-developed ribs, indicating a condition of respiration much in advance of that in the ribless batrachians. Some of them attained to size and strength rivalling those of the modern alligators, while some of the smallest species exhibit characters approaching in some respects to the lizards.
Perhaps the most fish-like of these animals are those first discovered by von Dechen (Archegosaurus,Fig. 134). Their long heads, short necks, supports for gills, feeble limbs and long flat tail, show that they were aquatic creatures presenting many points of resemblance to the Ganoid fishes which must have been their companions. Yet they show what no fish can exhibit, fore and hind limbs with proper toes, and the complete series of bones that appear in our own arms and legs, while they must have had true lungs and breathed through nostrils. So different are they from the fish in details, that a single limb bone, a vertebra, a rib, or a fragment of a skull bone, suffices to distinguish them. Much has been said recently of the genesis of limbs; and here, as far as now known, we have the first true limbs; but it is scarcely too much to say that the feet ofArchegosaurusdiffer more from the fins of any carboniferous fish than they do from the human hand; while it is certain that the feet which made the impressions represented inFig. 133, on the lowest beds of the Carboniferous, or that from the upper coal-formation represented inFig. 139, were not less typical or perfectly formed feet than those of modern lizards.
Leaving these fish-like forms, we find the remainder of the carboniferous reptiles to diverge from them along three lines.
Archegosaurus Decheni.
Fig.134.—Archegosaurus Decheni.Head and anterior limb reduced. Coal-field of Saarbruck.
Ptyonius. A Snake-like Amphibian.
Fig.135.—Ptyonius.A Snake-like Amphibian. Coal-measures of Ohio.—After Cope.
The first leads to snake-like creatures, destitute of limbs, and which must have been functionally the representatives of the serpents in the Palæozoic, though batrachian in their affinities (Fig. 135). They are found both in Europe and America; and Huxley describes one from Ireland more than twenty-one inches long, and with over one hundred vertebræ.57Some extraordinary traces are found on the sandstones of the coal-formation,58which appear to indicate that there may havebeen species of this type much larger than any represented by skeletons, and with bodies perhaps six inches in diameter. It is not unlikely that they had the habits of the modern water snakes.
A large Carboniferous Labyrinthodont.
Fig.136.—A large Carboniferous Labyrinthodont (Baphetes planiceps, Owen).
a, Anterior part of the skull, viewed from beneath. One-sixth natural size,b, One of the largest teeth, natural size.
A second line leads upward to large crocodile-like creatures, with formidable teeth, strong bony armour, and well-developed limbs (Labyrinthodontia,Figs. 136, 137). Some of them must have attained a length of ten feet. They were lizard-like in form, could walk well, as is seen from the footprints of some of the species which present a considerable stride, and moved over mud without the belly touching the ground. Their tails were long, and probably useful in swimming. Their heads were flat and massive, and their teeth were strengthened by a remarkable folding inward of the outer plate of enamel (Fig. 137b). The belly was protected by bony plates and closely imbricated scales. In some of the species at least the upper parts were clothed with horny scales, and the throat and sides were ornamented with pendent scaly fringes or lappets.59Their general aspect and mode of life must have resembledthose of modern alligators; and in the vast swamps of the Coal-period, full of ponds and sluggish streams swarming with fish, they must have found a most suitable abode. While rigid anatomy may ally these animals rather with the batrachians than the true reptiles, it is evident that their great size, their capacity for walking with the body borne well above the ground, their bony and scaly armour, their powerful teeth and their capacious chests, with well-developed ribs, indicate conditions of respiration and general vitality quite comparable with those of the highest modern members of the class Reptilia.
Baphetes planiceps.
Fig.137.—Baphetes planiceps(Owen).
a, Fragment of maxillary bone showing sculpture, four outer teeth, and one inner tooth. Natural size.b, Section of inner tooth. Magnified,c, Dermal scale. Natural size.
The third line of progress leads to some slender and beautiful creatures (Microsauria), chiefly known to us by remains found in erect trees, and which resembled in form and habits the smaller modern lizards. They have simple teeth, a well-developed brain-case, limbs of some length, and bony andscaly armour, the latter in some cases highly ornate.60They were probably the most thoroughly terrestrial, and the most active of the coal batrachians, if indeed they were not strictly intermediate between them and the lizards proper.Fig. 138shows some fragments of one of these animals; and the animal represented inFig. 139, recently figured by Fritsch, probably belongs to this group.
A lizard-like Amphibian.
Fig.138.—A lizard-like Amphibian (Hylonomus aciedentatus).
a, Maxillary bone; enlarged.
b, Mandible; enlarged.
c, Teeth; magnified, showing front and side view of ordinary tooth and grooved anterior tooth.
d, Section of tooth; magnified.
e, Scale; natural size and magnified.
f, Pelvic bone (?); natural size.
g, Rib; natural size.
h, Scapular bone (?); natural size.
i, Palate; natural size.
Stelliosaurus longicostatus.
Fig.139.—Stelliosaurus longicostatus(Fritsch). Upper Coal-formation of Bohemia.
The Labyrinthodonts of the Carboniferous continue upward into the Permian, where they meet with the true reptiles; and in the earlier Mesozoic some of the largest and most typicalexamples are found.61But here their reign ceases, and they give place to reptiles of more elevated type, whose history we must consider in the next chapter.
Nothing can be more remarkable than the apparently sudden and simultaneous incoming of the batrachian reptiles in the Coal-formation. As if at a given signal, they came up like the frogs of Egypt everywhere and in all varieties of form. If, as evolutionists suppose, they were developed from fishes, this must have been by some sudden change, occurring at once all over the world, unless indeed some great and unknown gap separates the Devonian from the Carboniferous—a supposition which seems quite contrary to fact—or unless in some region yet unexplored this change was proceeding, and at a particular time its products spread themselves over the world—a supposition equally improbable. In short, the hypothesis of evolution, as applied to these animals, is surrounded with geological improbabilities.
A remarkable picture of the conditions of Palæozoic land life is presented by the occurrence of remains of reptiles, millepedes and land-snails in such erect trees as that represented inFig. 140. In the now celebrated section of the South Joggins in Nova Scotia, trees of this kind occur at more than sixty different levels; but only in one of these have they as yet been found to be rich in animal remains. Fortunately this bed is so well exposed and so abundant in trees, that I have myself, within a few years, removed from it about twenty of them, the greater number affording remains of land animals.
Section showing the position of an erect Sigillaria.
Fig.140.—Section showing the position of an erectSigillaria, containing remains of land animals.
1. Underclay, with rootlets of Stigmaria, resting on gray shale, with two thin coaly seams.
2. Gray sandstone, with erect trees,Calamites, and other stems: 9 feet.
3. Coal, with erect tree on its surface: 6 inches.
4. Underclay with Stigmaria rootlets.
a,Calamites.
b, Stem of plant undetermined.
c, Stigmaria roots.
d, Erect trunk, 9 feet high.
The history of one of these trees may be shortly stated thus. It was aSigillaria, perhaps two feet in diameter, and its stem had a dense and imperishable outer bark, a soft cellular inner bark liable to rapid decay, and a slender woody axis not very durable. It grew on the surface of a swamp, now represented by a bed of coal. By inundations and by subsidence, thisswamp was exposed to the invasion of muddy and sandy sediment, and this went on accumulating until the stem of the tree was buried to the height of about nine feet, before which time it was no doubt killed. After a time the top decayed and fell, leaving the buried stump imbedded in the sandy soil, which had now become dry, or nearly so. The trunk decayed, its inner bark and axis rotting away and falling in shreds into the bottom of the cylindrical hole, about nine feet deep, once occupied by the stem, and now kept open like a shaft or well by the hard resisting outer bank. The ground around this opening became clothed with ferns and reed-likeCalamites, partly masking and concealing it. And now millepedes and land snails made the buried trunk a home, or fell into it in their wanderings; and small reptiles sporting around, in pursuit of prey, or themselves pursued, stumbled into the open pitfall, and were unable to extricate themselves, though I have found in some of the layers in these trees trails which show that theseimprisoned reptiles had wearily wandered round and round, in the vain search for means of exit, till they died of exhaustion and famine. The bones of these dead reptiles, shells of land-snails and crusts of millepedes, accumulated in these natural coffins, and became mixed with vegetable debris falling into them, and with thin layers of mud washed in by the rains; and this process continued so long that a layer of six inches to a foot in thickness, full of bones, was sometimes produced. At length a new change supervened, the area was again inundated and drifted over with sand, and the hollow trunk was filled to the top and buried under many feet of sediment, never to be re-opened till, after the whole had been hardened into sandstone and elevated to form a part of the modern coast, when the old tree and its forest companions which had shared the same fate with it, are made to yield up their treasures to the geologist. This history is no fancy picture. It represents the results of long and careful study of the beds holding these erect trees, and of the laborious extraction of great numbers of them, and the breaking-up of their contents into thin flakes, to be carefully examined with the lens under a bright light in search of the relics they contained.Fig. 11in Chap. I. represents the extraction of one of these trees, which happened to be partially exposed by the wasting of the cliff; but many others had to be laboriously mined out of the rock by blasting with gunpowder.
Section of base of erect Sigillaria.
Fig.140a.—Section of base of erectSigillaria, containing remains of land animals.
a, Mineral charcoal.b, Dark-coloured sandstone, with plants, bones, &c.c, Gray sandstone, withCalamitesandCordaites.
It is evident that the combination of circumstances referred toabove could not often occur; and it is therefore not wonderful that only in one place and one bed has evidence of it been found, and that even in this some of the trees have been filled up at once by sand and clay, or so crushed by falling in or lateral pressure, that they could receive no animal remains. In one respect this is a striking evidence of the imperfection of the geological record, since, but for what may be called a fortunate accident, many of the most interesting inhabitants of the coal forests might have been altogether unknown to us. On the other hand, it shows how strange and unexpected are the ways in which the relics of the old world have been preserved for our inspection, and that there is probably scarcely any animal or plant that has ever lived of which some fragment does not exist, did we know where to look for it.
It may be well to remark, in closing this chapter, how many new forms of life, air-breathing and otherwise, make their first appearance in the Carboniferous, and have continued to prevail until now. Here we find the first specimens of Amphibians, Spiders, Myriapods, Orthopterous and Coleopterous Insects, and of the Crabs among ten-footed Crustaceans. In the latter group Woodward has recently described the oldest known crab, from the Coal-formation of Belgium.
Inhabitants of the English Seas in the Age of Reptiles.
Inhabitants of the English Seas in the Age of Reptiles.
Pliosaurus,Ichthyosaurus,Plesiosaurus,Mososaurus, andTeleosaurus.
Hadwe lived in the Carboniferous period, we might have supposed that the line of the great Labyrinthodont Batrachians would have been continued onward and elevated, perhaps, in the direction of the Mammalia, to which some features of their structure point. But we should have been mistaken in this. The Labyrinthodonts, it is true, extend into the Trias; but there is perhaps a sign of their coming degradation in the appearance in the Permian of the first known mud-eel, a humble Batrachian form allied to the Newts and Water-lizards.62Their special peculiarities are dropped in the Mesozoic in favour of those of certain small and feeble lizard-like animals, appearing first in the Carboniferous, and more manifestly in the Permian, and which are the true forerunners, though they can scarcely be the ancestors, of the magnificent reptilian species of the Mesozoic, which have caused this period to be called “the age of reptiles.”
The leading reptilian animal from the European Permian has long been theProterosaurus, from the copper slates of Thuringia (Fig. 141), a reptile of lizard-like form, with well-developed limbs, and attaining a length of three or four feet. It resembles more nearly those large modern lizards known as“Monitors,” than any other existing form. The fore-limb represented in the figure foreshadows very closely the bones of the human arm and hand. Besides this we find in the Permian certain lizards (Theriodontsof Owen) which present the remarkable and advanced peculiarity already predicted by some Carboniferous Microsauria,63of having distinct canine teeth, producing a division into incisors, canines, and molars, in the manner of the Carnivorous quadrupeds, which they seem also to have resembled in some other parts of their skeletons. It is not impossible that the footprints in the Permian sandstones of Scotland, which have been referred to tortoises, were those of animals of this type. Cope has recently described from the Permian of Texas a number of reptiles which have the complex dentition of the Theriodonts, and others which simulate that of Herbivorous mammals, by the possession of flat grinding teeth supposed to be adapted to vegetable food.64The teeth of all these Permian reptiles were set in sockets, also an advanced peculiarity. Thus already in the Permian, before the final decadence of the Carboniferous flora, and while the Palæozoic invertebrates still lingered in the sea, the age of reptiles dawned, and gave promise of its future greatness by the assumption on the part of reptilian species of structures now limited to the Mammalia.
Arm of Proterosaurus Speneri.
Fig. 141.—Arm ofProterosaurus Speneri. Reduced. Permian.
But the great Mesozoic reptiles were not fully enthroned, till the Permian, an unsettled and disturbed age, characterised by great earth movements, had passed away, and until that period of continental elevation, with local deserts and desiccation, and much volcanic action, which we call the Trias, had also passed.
Then in the Jurassic and early Cretaceous the reptiles culminated, and presented features of magnitude and structural complexity unrivalled in later times. At the same time the Labyrinthodonts disappear, or are degraded into the humble stations which the modern Batrachians now occupy.
To understand the reptiles of this age, it will be necessary to notice the subdivisions of their modern representatives. The true reptiles now existing constitute the following orders:—1, the Turtles and Tortoises (Chelonia); 2, the Snakes (Ophidia); 3, the Lizards (Lacertilia); 4, the Crocodiles and Alligators (Crocodilia). All of these, except the snakes, are well represented among Mesozoic fossils; but we have in this middle age of the earth’s geological history to add to them from five to seven orders now altogether extinct, and these not of low and inferior organisation, but including species far in advance of any now existing both in elevation and magnitude, and constituting the veritable aristocracy of the reptile race. It will best serve our purpose here to consider chiefly these perished orders and their history, and then to notice very shortly those that now survive.
Skeleton of Ichthyosaurus. Lias. England.
Fig. 142.—Skeleton ofIchthyosaurus. Lias. England.
The first of the extinct orders is that of the great Sea-lizards,65of which the now familiarIchthyosaurusandPlesiosaurusof the English seas, to be seen in all museums and text-books, are the types (Figs. 142, 142aand 142b). These were marine animals of large size, but not fishes or amphibians. They were true air-breathing reptiles, but with paddles for swimming instead of feet, and some of them with long flattened tails for steering and propulsion. They bore, in short, preciselythe same relation to the other members of the class Reptilia which the Whales and Porpoises bear to the ordinary quadrupeds. Some of these animals are believed to have been fifty or sixty feet in length, thus rivalling the Whales, while others were of smaller dimensions, like the Porpoises and Dolphins. Some, like theIchthyosaurusandPliosaurus(Fig. 142a), were strongly built and powerful swimmers, and able to destroy the largest fishes, while others, likePlesiosaurus, had the body short and compact, the head small, and the neck long and flexible, and probably preyed on small animals near the borders of the waters. Catalogues of British fossils alone include about thirty species of Enaliosaurs, which haunted the coasts of Mesozoic Europe, a wonderful fact, when we consider the absence of these creatures from the modern seas, and the probability that only a fraction of the species are yet known to us.
Head of Pliosaurus.
Fig. 142a.—Head ofPliosaurus. Jurassic. Much reduced.
Paddle of Plesiosaurus Oxoniensis.
Fig. 142b.—Paddle ofPlesiosaurus Oxoniensis. Jurassic.—After Phillips. One-tenth natural size.
Another remarkable group is that to which Cope has given the name ofPythonomorpha, and which he regards as allied to the serpents, or as gigantic sea-serpents provided with swimming paddles, but which Owen considers more nearly connected with the lizards. In either case they constitute a group by themselves, remarkable not only on account of their anatomical affinities with animals so unlike them in general port, but also for their enormously extended length and formidable dentition (Fig. 143). Such animals as theMososaurusof Maestricht andClidastesof Western America may have exceeded in length the largest Ichthyosaurs and the most bulky of living Cetaceans, though their slender forms and numerous vertebræ remind one of the semi-fabulous sea-serpent, rather than of any known animal of our modern age. They were characteristic of the Later Mesozoic, more especially of the Cretaceous period, and must have been formidable enemies to the fishes of their time.
Owen has formed two orders66for the reception of some remarkable extinct reptiles of this age, found especially in South Africa and India, but also in Europe and America. The first includes large lizard-like animals having horny jaws like those of turtles, and in some of the species with great defensive tusks (Fig. 144). Their mode of life is not well known, but they may have been peaceable and harmless vegetable feeders. The second has been already referred to, in connection with the Permian, where it first appears, though it is continued in the Trias (Fig. 145). The resemblance of the skulls of these creatures to those of Carnivorous mammals is very striking, and nothing can be more singular than their early appearance and their decadence before the advent of those Tertiary mammals which in more modern times occupy their place.
Skeleton of Clidastes.
Fig. 143.—Skeleton ofClidastes. A great Mososauroid Sea Reptile of the Cretaceous.—After Cope, much reduced.
An Anomodont Reptile of the Trias
Fig. 144.—An Anomodont Reptile of the Trias (Dicynodon lacerticeps, Owen). Reduced.
A Theriodont Reptile of the Trias
Fig. 145.—A Theriodont Reptile of the Trias (Lycosaurus).—After Owen. Reduced.
Skeleton of Pterodochylus crassirostris.
Fig. 146.—Skeleton ofPterodochylus crassirostris. Jurassic of Solenhofen. Reduced.
Restoration of Rhamphorhyncus Bucklandi.
Fig. 147.—Restoration ofRhamphorhyncus Bucklandi. Jurassic of England.—After Phillips.
a, One of the teeth. Natural size.
Perhaps the most extraordinary of all the Mesozoic modifications of the reptilian type was that of the flying reptiles, orPterodactyls. These were, in short, lizards modified for flight, somewhat in the same manner with the bats among the mammals. If the bat may be likened to a flying shrew-mouse, a Pterodactyl may in like manner be compared to a flying lizard; but the modification in the latter case is by much the more remarkable, inasmuch as the lizard is a cold-blooded animal, and far less likely to be endowed with the active circulation and muscular power necessary to flight than is the mouse. In point of fact, there can be no doubt that the Pterodactyls must have been provided with some approach to a mammalian or ornithic heart, as they certainly were with great breast-muscles attached to a keel in the breast-bone for working their large membranous wings. These wings were also somewhat original in their construction. They were not furnished with pinions, like those of the bird, but with a membrane like that of the bat, and this, instead of being stretched over four enormously lengthened fingers, as in that quadruped, was supported on a single elongated finger, corresponding, singularly enough, to the little finger, which usually inconspicuous member constituted in some of these strange creatures a limb longer than the whole body (Figs. 146, 147.) The other fingers of the hand were left free for walking or grasping. They are thus believed to have been able to walk as well as to fly, and even in case ofneed, to swim; while they could probably perch like birds on rocks and trees. Their heads, though very lightly framed, were large and reptilian in aspect, and furnished with sharp teeth, and sometimes probably with a beak as well. Few creatures of the old world are of more hideous and sinister aspect. Yet some of them must have been as light and graceful on the wing as swallows or sea-gulls. There are many species, most of them small, but some of those in the later Mesozoic attained to so great a size that the expanse of their wings must have exceeded twenty feet, making them veritable flying dragons, probably formidable to all the smaller animals of their time. Though these animals were strictly reptiles, they combined in their structures contrivances for aërial locomotion now distributed between the bats and the birds. They had bat-like wings and bird-like chests. Some had horny beaks. All had hollow limb bones, and air cavities to give lightness to the skull. Their brains approach to those of birds, and, as already stated, their respiration and circulation must have been of a high order. These facts are very suggestive, and perhaps in no point is the imagination or the faith of the devout evolutionist more severelytested than in realising the spontaneous assumption of these characters by reptiles, and their subsequent distribution between the very dissimilar types in which they are now continued.