The History of Creation Volume II Part 13

Tortoises, Chelonia.

Flying Reptiles, Pterosauria.

Dragons, Dinosauria.

Billed Reptiles, Anomodontia.

Birds, Aves.

Suckling animals, Mammalia.

Billed Animals, Monotrema.

Pouched Animals, Marsupialia.

Placental Animals, Placentalia.

[Vertical axis:]

Cenolithic or Tertiary Epoch.

Pliocene Age.

Miocene Age.

Eocene Age.

Mesolithic or Secondary Epoch.

Chalk Period.

Jura.s.sic Period.

Tria.s.sic Period.

Palaeolithic or Primary Epoch.

Permian Period.

Coal Period.

Devonian Period.

Archilithic or Primordial Epoch.

Silurian Period.

Cambrian Period.

Laurentian Period.

[Legend:]

Single or MONOPHYLETIC PEDIGREE of the Stem of the BACK-BONED ANIMALS Based on Palaeontology.

Relative lengths of the 5 Epochs in per centages.

Quarternary Epoch 0.5 Tertiary Epoch 2.3 Secondary Epoch 11.5 Primary Epoch 32.1 Primordial Epoch 53.6 ------ _Total_ 100.0]

In the first order, that of _Primary Reptiles_, or _Primary Creepers_ (Tocosauria), we cla.s.s the extinct _Thecodontia_ of the Trias, together with those Reptiles which we may look upon as the common primary form of the whole cla.s.s. To the latter, which we may call _Primaeval Reptiles_ (Proreptilia), the Proterosaurus of the Permian system very probably belongs. The seven remaining orders must be considered as diverging branches, which have developed in different directions out of that common primary form. The Thecodontia of the Trias, the only positively known fossil forms of Tocosauria, were Lizards which seem to have been like the still living monitor lizards (Monitor, Vara.n.u.s).

SYSTEMATIC SURVEY

_Of the 8 Orders and 27 Sub-orders of Reptiles._

(Those groups marked with * became extinct even during the Secondary Period.)

----------------------------------------------------------------------------------- | _Sub-orders_ | _Systematic Name_ | _A Generic Name_ _Orders_ | _of_ | _of the_ | _as_ _of Reptiles._ | _Reptiles._ | _Sub-orders._ | _an example._ ----------------------------------------------------------------------------------- I. =Primary= { 1. Primaeval reptiles 1. Proreptilia * (Proterosaurus?) =Reptiles= { +Tocosauria+ { 2. 2. Thecodontia * Palaeosaurus

{ 3. Cleft-tongued 3. Fissilingues Monitor { 4. Thick-tongued 4. Cra.s.silingues Iguana II. =Lizards= { 5. Short-tongued 5. Brevilingues Anguis +Lacertilia+ { 6. Ringed lizards 6. Glyptodermata Amphisbaena { 7. Chameleons 7. Vermilingues Chamaeleo

{ 8. Adders 8. Aglyphodonta Coluber { 9. Tree serpents 9. Opisthoglypha Dipsas III. =Serpents= { 10. 10. Proteroglypha Hydrophis +Ophidia+ { 11. Vipers 11. Solenoglypha Vipera { 12. Worm serpents 12. Opoterodonta Typhlops

{ 13. Amphicla 13. Teleosauria * Teleosaurus IV. =Crocodiles= { 14. Opisthocla 14. Steneosauria * Steneosaurus +Crocodilia+ { 15. Prosthocla 15. Alligatores Alligator

{ 16. Sea tortoises 16. Thala.s.sita Chelone V. =Tortoises= { 17. River tortoises 17. Potamita Trionyx +Chelonia+ { 18. Marsh tortoises 18. Elodita Emys { 19. Land tortoises 19. Chersita Testudo

{ 20. Long-tailed 20. Rhamphorhynchi * Rhamphorhynchus VI. =Flying= { Flying lizards =Reptiles= { 21. Short-tailed 21. Pterodactyli * Pterodactylus +Pterosauria+* { Flying lizards

{ 22. Giant dragons 22. Harpagosauria * Megalosaurus VII. =Dragons= { 23. Elephantine 23. Therosauria * Iguanodon +Dinosauria+* { dragons

{ 24. Dog-toothed 24. Cynodontia * Dicynodon VIII. =Beaked= { 25. Toothless 25. Cryptodontia * Udenodon =Reptiles= { 26. Kangaroo reptiles 26. Hypsosauria * Compsognathus +Anomodontia+* { { 27. Bird reptiles 27. Tocornithes * (Tocornis)

Of the four orders of reptiles now existing, and which, moreover, have alone represented the cla.s.s since the beginning of the tertiary epoch, that of _Lizards_ (Lacertilia) is probably most closely allied to the extinct Primary Reptiles, and especially through the monitors already named. The cla.s.s of _Serpents_ (Ophidia) developed out of a branch of the order of lizards, and this probably not until the beginning of the tertiary epoch. At least we at present only know of fossil remains of serpents from the tertiary strata. _Crocodiles_ (Crocodilia) existed much earlier; the Teleosauria and Steneosauria belonging to the cla.s.s are found fossil in large quant.i.ties even in the Jura; but the still living alligators are first met with in a fossil state in the chalk and tertiary strata. The most isolated of the four existing orders of reptiles consists of the remarkable group of _Tortoises_ (Chelonia); fossils of these strange animals are first met with in the Jura. In some characteristics they are allied to Amphibia, in others, to Crocodiles, and by certain peculiarities even to Birds, so that their true position in the pedigree of Reptiles is probably far down at the root. The extraordinary resemblance of their embryos to Birds, manifested even at later stages of the ontogenesis, is exceedingly striking.

The four extinct orders of Reptiles show among one another, and, with the four existing orders just mentioned, such various and complicated relations.h.i.+ps, that in the present state of our knowledge we are obliged to give up the attempt at establis.h.i.+ng their pedigree. The most deviating and most curious forms are the _Flying Reptiles_ (Pterosauria); flying lizards, in which the extremely elongated fifth finger of the hand served to support an enormous flying membrane. They probably flew about, in the secondary period, much in the same way as the bats of the present day. The smallest flying lizards were about the size of a sparrow; the largest, however, with a breadth of wing of more than sixteen feet, exceeded the largest of our living flying birds in stretch of wing (condor and albatross). Numerous fossil remains of them, of the long-tailed Rhamphorhynchia and of the short-tailed Pterodactylae are found in all the strata of the Jura and Chalk periods, but in these only.

Not less remarkable and characteristic of the Mesolithic epoch was the group of _Dragons_ (Dinosauria, or Pachypoda). These colossal reptiles, which attained a length of more than fifty feet, are the largest inhabitants of the land which have ever existed on our globe; they lived exclusively in the secondary epoch. Most of their remains are found in the lower cretaceous system, more especially in the Wealden formations of England. The majority of them were fearful beasts of prey (the Megalosaurus from twenty to thirty, the Pelorosaurus from forty to fifty feet in length). The Iguanodon, however, and some others lived on vegetable food, and probably played a part in the forests of the chalk period similar to that of the unwieldy but smaller elephants, hippopotami, and rhinoceroses of the present day.

The _Beaked Reptiles_ (Anomodontia), likewise also long since extinct, but of which very many remarkable remains are found in the Trias and Jura, were perhaps closely related to the Dragons. Their jaws, like those of most Flying Reptiles and Tortoises, had become changed into a beak, which either possessed only degenerated rudimentary teeth, or no teeth at all. In this order, if not in the preceding one, we must look for the primary parents of the bird cla.s.s, which we may call Bird Reptiles (Tocornithes). Probably very closely related to them was the curious, kangaroo-like Compsognathus from the Jura, which in very important characteristics already shows an approximation to the structure of birds.

The cla.s.s of _Birds_ (Aves), as already remarked, is so closely allied to Reptiles in internal structure and by embryonal development, that they undoubtedly originated out of a branch of this cla.s.s. Even a glance at Plates II. and III. will show that the embryos of birds at a time when they already essentially differ from the embryos of Mammals, are still scarcely distinguishable from those of Tortoises and other Reptiles. The cleavage of the yolk is partial in the case of Birds and Reptiles, in Mammals it is total. The red blood-cells of the former possess a kernel, those of the latter do not. The hair of Mammals develops in closed follicles in the skin, but the feathers of birds and also the scales of reptiles develop in hillocks on the skin. The lower jaw of the latter is much more complicated than that of Mammals; the latter do not possess the quadrate bone of the former. Whereas in Mammals (as in the case of Amphibia) the connection between the skull and the first neck vertebra is formed by two k.n.o.bbed joints, or condyles, in Birds and Reptiles those have become united into a single condyle. The two last cla.s.ses may therefore justly be united into one group as Monocondylia, and contrasted to Mammals, or Dicondylia.

The deviation of Birds from Reptiles, in any case, first took place in the mesolithic epoch, and this moreover probably during the Trias. The oldest fossil remains of birds are found in the upper Jura (Archaeopteryx). But there existed, even in the Trias period, different Saurians (Anomodonta) which in many respects seem to form the transition from the Tocosauria to the primary ancestors of Birds, the hypothetical Tocornithes. Probably these Tocornithes were scarcely distinguishable from other beaked lizards in the system, and were closely related to the kangaroo-like Compsognathus from the Jura of Solenhofen. Huxley cla.s.ses the latter with the Dinosauria, and believes them to be the nearest relations to the Tocornithes.

The great majority of Birds-in spite of all the variety in the colouring of their beautiful feathery dress, and in the formation of their beaks and feet-are of an exceedingly uniform organization, in much the same way as are the cla.s.s of insects. The bird form has adapted itself on all sides to the external conditions of existence, without having thereby in any way essentially deviated from the strict hereditary type of its characteristic structure. There are only two small groups, the feather-tailed birds (Saururae) and those of the ostrich kind, which differ considerably from the usual type of bird, namely, from those with keel-shaped b.r.e.a.s.t.s (Carinatae), and hence the whole cla.s.s may be divided into three sub-cla.s.ses.

The first sub-cla.s.s, the _Reptile-tailed_, or _Feather-tailed Birds_ (Saururae), are as yet known only through a single, and that an imperfect, fossil impression, which, however, in being the oldest and also a very peculiar fossil bird, is of great importance. This fossil is the Primaeval Griffin, or Archaeopteryx lithographica, of which as yet only one specimen has been found in the lithographic slate at Solenhofen, in the Upper Jura system of Bavaria. This remarkable bird seems on the whole to have been of the size and form of a large raven, especially as regards the legs, which are in a good state of preservation; head and breast unfortunately are wanting. The formation of the wings deviates somewhat from that of other birds, but that of the tail still more so. In all other birds the tail is very short and composed of but few short vertebrae; the last of these have grown together into a thin, bony plate standing perpendicularly, upon which the rudder-feathers of the tail are attached in the form of a fan. The Archaeopteryx, however, has a long tail like a lizard, composed of numerous (20) long thin vertebrae, and on every vertebra are attached the strong rudder-feathers in twos, so that the whole tail appears regularly feathered. This same formation of the tail part of the vertebral column occurs transiently in the embryos of other birds, so that the tail of the Archaeopteryx evidently represents the original form of bird-tail inherited from reptiles. Large numbers of similar birds with lizard-tails probably lived during the middle of the secondary period; accident has as yet, however, only revealed this one fossil.