CHAPTER XVIII. How Pterodactyles May Have Originated

HOW PTERODACTYLES MAY HAVE ORIGINATED

Ornithosauria have many characters inseparably blended together which are otherwise distinctive of Reptiles, Birds, and Mammals, and associated with peculiar structures which are absent from all other animals. They are not quite alone in this incongruous combination of different types of animals in the same skeleton. Dinosaurs, which were contemporary with Ornithosaurs, approximate to them in blending characters of Birds with the structure of a Reptile and something of a Mammal in one animal. If an Ornithosaur is Reptilian in its backbone, in the articular ends of each vertebra having the cup in front and ball behind in the manner of Crocodiles, Serpents, and many Lizards, a Dinosaur like Iguanodon, which had the reversed condition of ball in front and cup behind in its early vertebrae, may be more Mammalian than Avian in a corresponding resemblance of the bones to the neck in hoofed Mammals. But while Pterodactyles are sometimes Mammalian in having the head of the thigh bone moulded as in carnivorous Mammals and Man, the corresponding bone in a Dinosaur is more like that of a Bird. And while the Pterodactyle shoulder-girdle is often absolutely Bird-like, that region in Dinosaurs can only be paralleled among Reptiles.

Such combinations of diverse characters are not limited to animals which are extinct. There were not wanting scientific men who regarded the Platypus of Australia, when first sent to Europe, as an ingenious example of Eastern skill, in which an animal had been compounded artificially by blending the beak of a Bird with the body of a Mammal. Fuller knowledge of that remarkable animal has continuously intensified wonder at its combination of Mammal, Bird, and Reptile in a single animal. It has broken down the theoretical divisions between the higher Vertebrata, demonstrating that a Mammal may lay eggs like a Reptile or Bird, that the skull may include the reptilian characters of the malar arch and pre-frontal and post-frontal bones, otherwise unknown in Mammals and Birds. The groups of Mammals, Birds, and Reptiles now surviving on the earth prove to be less sharply defined from each other when the living and extinct types are considered together. But in Pterodactyles, Mammal Bird and Reptile lose their identity, as three colours would do when unequally mixed together.

This mingling of characteristics of different animals is not to be attributed to interbreeding, but is the converse of the combination of characters found in hybrid animals. It is no exaggeration to say that there is a sense in which Mammal, Bird, Reptile, and the distinctive structures of the Ornithosaur, have simultaneously developed from one egg, in the body of one animal.

The differences between those vertebrate types of animals consist chiefly in the way in which their organisation is modified, by one strain of characters being eliminated so that another becomes predominant, while a distinctive set of structures is elaborated in each class of animals. The earlier geological history of the higher Vertebrata is very imperfectly known, but the evidence tends to the inference that the older representatives of the several classes approximate to each other more closely than do their surviving representatives, so that in still earlier ages of time the distinction between them had not become recognisable. The relation of the great groups of animals to each other, among Vertebrata, is essentially a parallel relation, like the colours of the solar spectrum, or the parallel digits of the hand. It was natural, when only the surviving life on the earth was known, to imagine that animals were connected in a continuous chain by successive descent, but Mammals have given no evidence of approximation to Birds; and Birds discover no evidence that their ancestors were Reptiles, in the sense in which that word is used to define animals which now exist on the earth. When the variation which animals attain in their maturity and exhibit in development from the egg was first realised, it was imagined that Nature, by slow summing up and accumulation of differences which were observed, would so modify one animal type that it would pass into another. There is little evidence to support belief that the changes between the types of life have been wrought in that way. The history of fossil animals has not shown transitions of this kind from the lower to higher Vertebrata, but only intermediate, parallel groups of animals, analogous to those which survive, and distinct from them in the same way as surviving groups are distinct from each other. The circumstance that Mammals, Birds, and Reptiles are all known low down in the Secondary epoch of geological time, is favourable to the idea of their history being parallel rather than successive. Such a conception is supported by the theory of elimination of characters from groups of animals as the basis of their differentiation. This loss appears always to be accompanied by a corresponding gain of characters, which is more remarkable in the soft, vital organs than in the skeleton. The gain in higher Vertebrates in the bones is chiefly in the perfection of joints at their extremities; but the gain in brain, lungs, heart, and other soft parts is an elaboration of those structures and an increase in amount of tissue.

The resemblances of Ornithosaurs to Mammals are the least conspicuous of their characters. Those seen in the upper arm bone and thigh bone are manifestly not derived from Mammals. They cannot be explained as adaptations of the bones to conditions of existence, because there is no community of habit to be inferred between Pterodactyles and Mammals, in which the bones are in any way comparable.

Other fossil animals show that a fundamentally Reptilian structure is capable of developing in the Mammalian direction in the skull, backbone, shoulder-girdle, hip-girdle, and limbs, so as to be uniformly Mammalian in its tendencies. This is proved by tracing the North American Texas fossils named Labyrinthodonts, through the South African Theriodonts, towards the Monotremata and other Mammalia. Just as those animals have obliterated all traces of the Bird from their skeletons, Birds have obliterated the distinctive characters of Mammals. The Ornithosaur has partially obliterated both. With a skull and backbone marked by typical characters of the Reptile, it combines the shoulder-girdle and hip-girdle of a Bird, with characters in the limbs which suggest both those types in combination with Mammals.

The bones have been compared in the skeleton of each order of existing Reptiles, and found to show side by side with their peculiar characters not only resemblances to the other Reptilia, but an appreciable number of Mammalian and Avian characters in their skeletons. The term "crocodile," for example, indicates an animal in which the skeleton is dominated by one set of peculiar characters. Crocodiles retain enough of the characteristics of several other orders of reptiles to show that an animal sprung from the old Crocodile stock might diverge widely from existing Crocodiles by intensifying what might be termed its dormant characters in the Crocodile skeleton. Comparing animals together bone by bone it is possible to value the modifications of form which they put on, and the resemblances between them, so as to separate the inherited wealth of an animal's affinities with ancestors or collateral groups, from the peculiar characters which have been acquired as an increase based upon its typical bony possessions or osteological capital. There is no part of the Pterodactyle skeleton which is more distinctly modified than the head of the upper arm bone, which fits into the socket between the coracoid bone and the shoulder-blade. The head of the humerus, as the articular part is named, is somewhat crescent-shaped, convex on its inner border, and a little concave on its outer border, and therefore unlike the ball-shaped head of the upper arm bone in Man and the higher Mammals. It is much more nearly paralleled in the little group of Monotremata allied to the living Ornithorhynchus. In that sense the head of the humerus in a Pterodactyle has some affinity with the lowest Mammalia, which approach nearest to Reptiles. The character might pass unregarded if it were not found in more striking development in fossil Reptiles from Cape Colony, which from having teeth like Mammals are named Theriodontia. In several of those South African reptiles the upper arm bone approaches closer to the humerus in Ornithosaurs than to Ornithorhynchus. Such coincidences of structure are sometimes dismissed from consideration and placed beyond investigation by being termed adaptive modifications; but there can be no hope of finding community of habit between the burrowing Monotreme, the short-limbed Theriodont, and the flying Pterodactyle which might have caused this articular part of the upper arm bone to acquire a form so similar in animals constructed so differently. If the resemblance in the humerus to Monotremes in this respect is not to be attributed to burrowing, neither can the crescent form of its upper articulation be attributed to flight; for in Birds the head of the bone is compressed, but always convex, and Bats fly without any approach to the Pterodactyle form in the head of the humerus. This apparently trivial character may from such comparisons be inferred to be something which the way of life of the animal does not sufficiently account for. These deepest-seated parts of the limbs are slow to adapt themselves to changing circumstances of existence, and retain their characters with moderate variation of the bones in each of the orders or classes of animals. It therefore is safer to regard Mammalian characters, as well as the resemblances which Pterodactyles show to other kinds of animals, as due to inheritance from a time when there was a common stock from which none of these animals which have been considered had been distinctly elaborated.

A few characters of Ornithosaurs are regarded as having been acquired, because they are not found in any other animals, or have been developed only in a portion of the group. The most obvious of these is the elongated wing finger; but in some genera, like Dimorphodon, there is also a less elongation of the fifth digit of the foot, and perhaps in all genera there is a backward development of the first digit of the hand, which is without a claw, and therefore unlike the clawed digit of a Bat. An acquired character of another kind, which is limited to the Cretaceous genera, is seen in the shoulder-blade being directed transversely outward, so that its truncated end articulates by a true joint with the early vertebrae of the back, and defended the cavity inclosed by the ribs by a strong bony external arch. And finally, as the animals later in time acquire short tails, and relatively longer limbs, the bones of the back of the hand, termed metacarpals, acquire greater and distinctive length, which is not seen in the long-tailed types like Rhamphorhynchus.

These and such-like acquired characters distinguish the class of animals from all groups with which it may be compared, and mark the possible limits of variation of the skeleton within the boundary of the order. But no further variation of these parts of the skeleton could make a transition to another order of animals, or explain how the Pterodactyles came into existence, because the characters which separate orders and classes of animals from each other differ in kind from those which separate smaller groups, named genera and species, of which the order is made up. The accumulation of the characters of genera will not sum up into the characters of an order or class.

In making the division of Vertebrate animals into classes the skeleton is often almost ignored. Its value is entirely empirical and based upon the observed association of the various forms of bones with the more important characters of the brain and other vital organs. What is understood as a Mammalian or Avian character in the skeleton is the form of bone which is found in association with the soft vital organs which constitute an animal a Mammal or a Bird.

The characters which theoretically define a Mammal appear to be the enormous overgrowth of the cerebral hemispheres of the brain by which the cerebrum comes into contact with the cerebellum, as among Birds. This character distinguishes both groups of animals from all Reptiles, recent and fossil. But in examining the mould of the interior of the brain case it is rare to have the bones fitting so closely to the brain as to prove that the lateral expansion below the cerebrum and cerebellum is formed by the optic lobes of the brain. Otherwise the brain of a Pterodactyle might be as like to the brain of Ornithorhynchus as it is like that of a Bird (Fig. 19). But it is precisely in this condition of arrangement of the parts of the brain that the specimens appear to be most clear. The lateral mass of brain in specimens of Ornithosaurs from the Lower Secondary rocks appears to be transversely divided into back and front parts, which may be thought to correspond to the structures in a Mammal brain named corpora quadrigemina, but to be placed as the optic lobes are placed in Birds, and to have relatively greater dimensions than in Mammals. No evidence has been observed of this transverse division of the optic lobes of the brain in Pterodactyles from the Chalk and Cretaceous rocks, and so far as the evidence goes this part of the brain was shaped as in birds, but rather smaller.

The brain is the only soft organ in which a Mammalian character could be evidenced. The uniformity in character of the brain throughout the group in Mammals is remarkable, in reference to the circumstance that the reproduction varies in type; the lowest, or Monotreme division, being oviparous. If there is no necessary connexion between the Mammalian brain and the prevalent condition under which the young are produced alive, it may be affirmed also that there is no necessary connexion between the form of the brain and the form of the bones, since the brain cavity in Theriodont reptiles shows no resemblance to that of a Mammal, while the bones are in so many respects only paralleled among Monotremata and Mammalia. The variety of forms which the existing Mammalian orders of animals assume, shows the astonishing range of structure of the skeleton which may coexist with the Mammalian brain. And therefore we are led to the conclusion that any other fundamental modification of brain--such as distinguishes the class of Birds--might also be associated with forms and structures of the skeleton which would vary in similar ways. In other words, if for convenience we define a Mammal by its form of brain, structure of the heart and lungs, and provision for nutrition of the young, without regard to the covering of the skin, which varies between the scales of a pangolin and the practically naked skin of the whale--a bird might be also defined by its peculiar conditions of brain and lungs, without reference to the feathered condition of the skin, though the feathered condition extends backward in time to the Upper Secondary rocks, as seen in the Archaeopteryx.

The Avian characters of Pterodactyles are the predominant parts of their organisation, for the conditions of the brain and lungs shown by the moulds of the brain case and the thin hollow bones with conspicuous pneumatic foramina, give evidence of a community of vital structures with Birds, which is supported by characters of the skeleton. If any classificational value can be associated with the distribution of the pneumatic foramina as tending to establish membership of the same class for animals fashioned on the same plan of soft organs, the evidence is not weakened when a community of structures is found to extend among the bones to such distinctive parts of the skeleton as the sternum, shoulder-girdle, bones of the fore-arm and fore-leg; for in all these regions the Pterodactyle bones are practically indistinguishable from those of Birds. This is the more remarkable because other parts of the skeleton, such as the humerus and pelvis, show a partial resemblance to Birds, while the parts which are least Avian, like the neck bones, have no tendency to vary the number of the vertebrae, in the way which is common among Birds, following more closely the formula of the seven cervical vertebrae of Mammals.

It would therefore appear from the vital community of structures with Birds, that Pterodactyles and Birds are two parallel groups, which may be regarded as ancient divergent forks of the same branch of animal life, which became distinguished from each other by acquiring the different condition of the skin, and the structures which were developed in consequence of the bony skeleton ministering to flight in different ways; and with different habit of terrestrial progression, this extinct group of animals acquired some modifications of the skeleton which Birds have not shown. There is nothing to suggest that Pterodactyles are a branch from Birds, but their relation to Birds is much closer, so far as the skeleton goes, than is their relation with the flightless Dinosaurs, with which Birds and Pterodactyles have many characters in common.

On the theory of elimination of character which I have used to account for the disappearance of some Mammalian characters from the Pterodactyle, that loss is seen chiefly in the removal of the parts which have left a Reptilian articulation of the lower jaw with the skull, and the articulation of the vertebrae throughout the vertebral column by a modified cup-and-ball form of joint. The furculum of the Bird is always absent from the Pterodactyle. No specimen has shown recognisable clavicles or collar-bones. Judged by the standard of existing life, Pterodactyles belong to the same group as Birds, on the evidence of brain and lungs, but they belong to a different group on account of the dissimilar modifications of the skeleton and apparent absence of feathers from the skin.

The most impressive facts in the Pterodactyle skeleton, in view of these affinities, are the structures which it has in common with Reptiles. Some structures are fundamental, like the cup-and-ball articulation of the vertebrae, which is never found in birds or mammals. Although not quite identical with the condition in any Reptile, this structure is approximately Lizard-like or Crocodile-like in the cup-and-ball character. It shows that the deepest-seated part of the skeleton is Reptile-like, though it may not be more Reptilian than is the vertebral column of a Mammal, if comparison is made between Mammals and extinct groups of animals known as Reptiles, such as Dinosaurs and Theriodontia.

The orders of animals which have been included under the name Reptilia comprise such different structural conditions of the parts of the skeleton which may be termed reptilian in Ornithosaurs, that there is good reason for regarding the cup-and-ball articulation as quite a distinctive Reptilian specialisation, in the same sense that the saddle-shaped articulation between the bodies of adjacent vertebrae in a bird is an Avian specialisation. From the theoretical point of view the Ornithosaur acquired its Reptilian characters simultaneously with its Avian and Mammalian characters.

There is nothing in the structure of the skeleton of the Dinosauria, to which Ornithosaurs approximate in several parts of the body, which would help to explain the cup-and-ball articulation of the backbone, if the Flying Reptile were supposed to be an offshoot from the carnivorous Dinosaurs.

The elimination of Reptile characters from so much of the skeleton, and the substitution for them of the characters of Birds and Mammals, would be of exceptional interest if there had been any ground for regarding the flying animal as more nearly related to a Reptile than to a Bird. But if the evidence from the form of the brain and nature of the pneumatic organs seen in the limb bones accounts for the Avian features of the skeleton, the Reptilian condition of the vertebral column helps to show a capacity for variation, and that the fixity of type and structure, which the skeleton of the modern Bird has attained, is not necessarily limited to or associated with the vital organs of Birds.

The variation of the cup-and-ball articulation in the neck of a Chelonian, which makes the third vertebra cupped behind, the fourth bi-convex, the fifth cupped in front, and the sixth flattened behind, shows that too much importance may be attached to the mode of union of these bones in Serpents, Crocodiles, and those Lizards which have the cup in front; for while in Lizards the anterior cup, oblique and depressed, is found in most of its groups, the Geckos show no trace of the cup-and-ball structure, and in that respect resemble the Hatteria of New Zealand.

If, therefore, the cup-and-ball articulation of vertebrae in Ornithosauria has any significance as a mark of affinity to Reptiles, it could only be in approximation to those living Reptiles which possess the same character, and would have it on the hypothesis that both have preserved the structure by descent from an earlier type of animal. This hypothesis is negatived by the fact that the cup-and-ball articulation is unknown in the older fossil Reptiles.

Although the articulation for the lower jaw with the skull in Ornithosaurs is only to be paralleled among Reptiles, the structure is adapted to a brain case which is practically indistinguishable from that of a Bird, except for the postorbital arch.

The hypothesis of descent, therefore, becomes impossible, in any intelligible form, in explanation of distinctive character of the skeleton. The hypothesis of elimination may also seem to be insufficient, unless the potential capacity for new development be recognised as concurrent, and as capable of modifying each region of the skeleton, or hard parts of the animal, in the same way that the soft organs may be modified. From which we infer that all structures, which distinguish the several grades of organisation in modern classifications, soft parts and hard parts alike, may come into existence together, in so far as they are compatible with each other, in any class or ordinal division of animals.

Although the young Mammal passes through a stage of growth in which the brain may be said to be Reptilian, there is no good ground for inferring that Mammal or Bird type of skeleton was developed later in time than that of Reptiles. The various types of Fishes have the brains in general so similar to those of Reptiles that it is more intelligible for all the vertebrate forms of brain to have differentiated at the same time, under the law of elimination of characters, than that there should be any other bond of union between the classes of animals.

If we ask what started the Ornithosauria into existence, and created the plan of construction of that animal type, I think science is justified in boldly affirming that the initial cause can only be sought under the development of patagial membranes, such as have been seen in various animals ministering to flight. Such membranes, in an animal which was potentially a Bird in its vital organs, have owed development to the absence of quill feathers. Thus the wing membrane may be the cause for the chief differences of the skeleton by which Ornithosaurs are separated from Birds, for the stretch of wing in one case is made by the skin attached to the bones, and in the other case by feathers on the skin so attached as to necessitate that the wing bones have different proportions from Ornithosaurs.

It is a well-known observation that each great epoch of geological time has had its dominant forms of animal life, which, so far as the earth's history is known now, came into existence, lived their time, and were seen no more. In the same way the smaller groups of species and genera included in an ordinal group of animals or class have abounded, giving a tone to the life of each geological formation, until the vitality of the animal is exhausted, and the species becomes extinct or ceases to preponderate. This process is seen to be still modifying the life on the earth, when some kinds of animals and plants are introduced to new conditions. Plants appear to wage successful war more easily than animals. The introduction of the Cactus in some parts of Cape Colony has locally modified both the fauna and flora, just as the Anacharis introduced into England spread from Cambridge over the whole country, and became for many years the predominant form of plant life in the streams. The Rabbit in Australia is a historic pest. Something similar to this physical fertility and increase appears to take place under new circumstances in certain organs within the bodies of animals, by the development of structures previously unknown. A familiar example is seen in the internal anatomy of the Trout introduced into New Zealand, where the number of pyloric appendages about the stomach has become rapidly augmented, while the size and the form of the animal have changed. The rapidity with which some of these changes have been brought about would appear to show that Nature is capable of transforming animals more rapidly than might have been inferred from their uniform life under ordinary circumstances. Growth of the vital organs in this way may modify the distinctive form of any vital organ, brain or lungs, and thus as a consequence of modification of the internal structures due to changes of food and habit, bring a new group of animals into existence. And just as the group of animals ceases to predominate after a time, so there comes a limit to the continued internal development of vital structures as their energy fails, for each organ behaves to some extent like an independent organism.

Under such explanations of the mutual relations of the parts of animals, and groups of animals, time ceases to be a factor of primary importance in their construction or elaboration. The supposed necessity for practically unlimited time to produce changes in the vital organs which separate animals into great orders or classes is a nightmare, born of hypothesis, and may be profitably dismissed. The geological evidence is too imperfect for dogmatism on speculative questions; but the nature of the affinities of Ornithosaurs to other animals has been established on a basis of comparison which has no need of theory to justify the facts. It is not improbable that the primary epoch of time, even as known at present, may be sufficiently long to contain the parent races from which Ornithosaurs and all their allies have arisen.

In thus stating the relation of Ornithosaurs to other animals the Flying Reptile has been traced home to kindred, though not to its actual parents or birthplace. There is no geological history of the rapid or gradual development of the wing finger, and although the wing membrane may be accepted as its cause of existence, the wing finger is powerfully developed in the oldest known Pterodactyles as in their latest representatives.

Pterodactyles show singularly little variation in structure in their geological history. We chronicle the loss of the tail and loss of teeth. There is also the loss of the outermost wing digit from the hind foot as a supporter of the wing membrane. But the other variations are in the length of the metacarpus, or of the neck, or head. One of the fundamental laws of life necessitates that when an animal type ceases to adapt its organisation and modify its structures to suit the altered circumstances forced upon it by revolutions of the earth's surface its life's history becomes broken. It must bend or break.

The final disappearance of these animals from the earth's history in the Chalk may yet be modified by future discoveries, but the Flying Reptiles have vanished, in the same way as so many other groups of animals which were contemporary with them in the Secondary period of time. Such extinctions have been attributed to catastrophes, like the submergence of land, so that the habitations of animals became an area gradually decreasing in size, which at last disappeared. It appears also to be a law of life, illustrated by many extinct groups of animals, that they endure for geological ages, and having fought their battle in life's history, grow old and unable to continue the fight, and then disappear from the earth, giving place to more vigorous types adapted to live under new conditions.

The extinct Pterodactyles hold a relation to Birds in the scheme of life not unlike that which Monotremata hold to other Mammals. Both are remarkable for the variety of their affinities and resemblances to Reptiles. The Ornithosauria have long passed away; the Monotremes are nearing extinction. Both appear to be supplanted by parallel groups which were their contemporaries. Birds now fill the earth in a way that Flying Reptiles never surpassed; but their flight is made in a different manner, and the wing is extended to support the animal in the air, chiefly by appendages to the skin.

If these fossils have taught that Ornithosaurs have a community of soft vital organs with Dinosaurs and Birds, they have also gone some way towards proving that causes similar to those which determined the structural peculiarities of their bony framework, originated the special forms of respiratory organs and brain which lifted them out of association with existing Reptiles.

These old flying animals sleep through geological ages, not without honour, for the study of their story has illuminated the mode of origin of animals which survive them, and in cleaving the rocks to display their bones we have opened a new page of the book of life.

APPENDIX

The best public collections of Ornithosaurian remains in England are in the British Museum (Natural History); Museum of Practical Geology, Royal College of Surgeons; the University Museum, Oxford; Geological Museum, Cambridge; and the Museum of the Philosophical Society at York.

Detailed descriptions and original figures of the principal specimens mentioned or referred to may be found in the following writings:--

H. v. Meyer, Reptilien aus dem Lithograph. Schiefer. 1859. Folio. v. Quenstedt, Pterodactylus suevicus. 1855. 4to. Goldfuss, Nova Acta Leopold. XV. v. Munster, Nova Acta Leopold. XV. A. Wagner, Abhandl. Bayerischen Akad., vi., viii. Cuvier, Annales du Museum, xiii. 1809. " Ossemens fossiles, v. 1824. Buckland, Geol. Trans., ser. 2, iii. R. Owen, Palaeontographical Society. 1851, 1859, 1860, 1870, 1874. K. v. Zittel, Palaeontographica, xxix. 1882. T. C. Winkler, Mus. Teyler Archives. 1874, 1883. Oscar Fraas, Palaeontographica, xxv. 1878. Anton Fritsch, Boehm. Gesell. Sitzber. 1881. R. Lydekker, Catalogue of Fossil Reptilia in British Museum I. 1888. O. C. Marsh, Amer. Jour. Science. 1882, 1884. S. W. Williston, Kansas University Quarterly. 1893, 1896. E. T. Newton, Phil. Trans. Royal Soc. 1888, 1894. H. G. Seeley, Ornithosauria. 8vo. 1870. " Annals and Mag. Natural Hist. 1870, 1871, 1890, 1891. " Linn. Society. 1874, 1875. " Geol. Mag. 1881. Felix Pleininger, Palaeontographica. 1894, 1901.

INDEX

Abdominal ribs, 85, 154

Accumulation of characters, 220

Acetabulum, 95

Acquired characters, 219

Adjacent land, 136

Air cells, 10, 48

Albatross, 23, 36, 176

Alligator, brain, 53; pelvis, 98

American Greensand, 185

-- ornithosaurs, 87, 126

Amphibia, 4, 191

Anabas, 17

Anacharis, 227

Anchisaurus, 199

Angle of lower jaw, 75

Ankle bones, 103, 195, 207

Anomodonts, 192

Ant-eater of Africa, 142; India, 40; South America, 40, 185

Apteryx, lungs, 48; pelvis, 95

Aquatic mammals, 141

Aramis, scapular arch, 113

Archaeopteryx, 58, 76, 104, 130, 197, 211

Aristosuchus, 129, 190, 205, 209

Armadillo, 40, 141

Articulation of the jaw, 12, 75

Ashwell, 177

Atlantosaurus, 202

Atlas and axis, 80, 81

Aves, 190

Avian characters, 220, 222

Backbone, 78, 84

Banz, 148

Barbastelle, 25

Barrington, 177

Barton, 177

Bat, 38, 110, 197; sternum of, 107; metacarpus, 128

Bavaria, 156, 185

Beak, horny, 74, 178

Bear, skull of, 12; femur, 100

Bel and the Dragon, 15

Belodon, 202

Bird, 80, 110, 120

-- resemblances, 63, 65, 71, 95, 102, 108, 113, 119, 120, 211

Bird-reptile, 188

Bird wing, 128, 130

Birds in flight, 22; with teeth, 76

Black-headed bunting, 47

Blainville, D. de, 30, 193

Blood, temperature of, 56

Bohemia, 34

Bonaparte, Prince Charles, 30

Bones of birds, variation in, 41

-- of reptiles, variation in, 42

-- about the brain, 69

-- in the back, 84

Bone texture, 59, 209

Bonn Museum, 32, 85, 156

Brain and breathing organs, 55

Brain cavity, in birds and reptiles, 52; in mammals, 221, 226; in Solenhofen pterodactyles, 54, 220

Brazil, 34

Breathing organs, 8

Bridgewater Treatise, 143

British Museum, 133, 183

Brixton, Isle of Wight, 55, 174

Buckland, Dean, 143, 148, 231

Burrowing limb, 38

Cactus, 227

Calamospondylus, 203

Cambridge Greensand, 33, 89, 176

-- Museum, 177

Camel, 83

Campylognathus, 68, 71, 135; size of, 149

Canary, 47

Carnivorous dinosaurs, 129

Carpus, 122

Caudal fin, 91, 161

-- vertebrae, 89, 92, 203

Ceratodus, 4, 5, 9, 17

Ceratosaurus, 203, 204

Cervical rib, 81

Cetacea, 40

Cetiosaurus, 198, 203

Chalinolobus, 25

Chalk, pterodactyles in, 136; of Kansas, 103, 132

Chameleon, 17, 51, 70; scapula, 112; sternum, 107

Chameleonoidea, 191

Cheek bones, 178

Chelonia, 86, 112, 193

Chesterton, 177

Chlamydosaurus, 21

Chrysochloris capensis, 121

Classification, 192; on pelvis characters, 195; of dinosaurs, 198

Clavicles, 111, 112

Claw, 105, 116, 183, 208

Coelurus, 203, 209

Coldham Common, 177

Collar bone, 111

Collini, 27

Comparison with dinosaurs, 198; of pelvis, 204, 206; of skulls, 192, 199, 201

Cope, Professor, 31, 34

Coracoid, 109, 112, 113

Cordylomorpha, 191

Cormorant, 70, 174; sternum, 108

Corpora quadrigemina, 221

Crisp, Dr., on pneumatic skeleton, 47

Crocodile, characters of, 217; heart, 56; lung, 9; shoulder-girdle, 111; skull, 46; vertebrae, 79

Crocodilia, 190

Curlew, 68

Cuvier, 1, 27, 28, 54, 76, 77, 130, 231

Cycnorhamphus, 70, 94, 171, 173, 204

Cycnorhamphus Fraasii, 80, 96, 169

-- suevicus, 169, 170

Cypselus, 42

Dacelo gigantea, 63

Darwin, 3

Davy, Dr. John, 142

Deuterosaurus, 97

Dicynodon, 200

Dicynodon lacerticeps, 71

Digits, of ostrich, 23; of pterodactyle, 128

Digits with claws, 130; foot bones in, 105

Dimorphodon, 63, 64, 66, 67, 73, 74, 83, 90, 102, 113, 143, 192, 194, 199, 201, 206

Dinosauria, 6, 77, 84, 87, 95, 129, 144, 198, 209

Dinosaurs from Lias, 135, 192; from Elgin, 201, 207; Stuttgart, 202; Trias dinosaurs, 199, 200

Diopecephalus, 168

Diving birds, 23, 83, 102

Dolichosauria, 191

Dolphin, 107

Doratorhynchus, 173

Dorygnathus, 74, 148

Dragons, 3, 15, 17

Drumstick bone, 103, 195

Duck, 22, 83

Echidna, 75, 76, 95, 100

Edentata, 185

Edentulous beak, 153

Eichstaedt, 32

Elephant, head of, 46

Enumeration of characters, 223, 225

Ephesus, winged figure, 16

Epiphysis to first phalange, 123

Exocoetus, 18

Extinctions, 129

Eye hole, 144; sclerotic bones in, 65

Farren, William, 34

Femur, 100

Fibula, 102, 183, 206

Fifth outer digit, 132; in foot, 145

Figure from temple at Ephesus, 16

First phalange, 151

Fish-eating crocodile, 137

Flight, organs of, 17; in bats, 25

Flying limb, 38

Flying fishes, 18, 57; foxes, 26; frogs, 19, 197; gecko, 21, 24; lizards, 20; reptiles, 37, 46; squirrel, 24

Foot, 104; digits in, 105, 146

Fore leg, 102, 206

-- limb, 38, 107, 116, 120

Four claws, 147

Fox, Rev. W., 55, 174

Fraas, Professor Oscar, 172, 231

Frigate bird, vertebrae of, 86, 174

Frog, lungs of, 8

Furculum, 114

Gaudry, Professor A., 31

Gavial, 136

Gecko, 21, 23

Genera, comparison of, 192

Geological distribution, 186

Gills, 4

Giraffe, 38, 39

Glossy starling, 47

Golden eagle, 120

-- mole, 121

Goldfuss, 30, 231

Granchester, 177

Great ant-eater, 40, 185

Guillemot, 102

Gull, 22

Haarlem, Teyler Museum at, 32

Habits, probable, 134, 176, 198

Hairless skins, 141

Hand in mammals, 38

Harston, 177

Haslingfield, 177

Hastings, 174

Hatteria lung, 9, 27; brain, 53; skull, 70, 77; ribs, 86; a reptile type, 13

Head, characters of, 76

Heidelberg Museum, 32, 54, 159

Herpetomorpha, 191

Heron, 65, 174

Hesperornis, 76

Hind foot, 104, 135

-- limb, 93, 99, 159, 206

Hip-girdle in whale tribe, 39, 159

Homoeosauria, 191

Horningsea, 177

Horse, metacarpus of, 127; vertebrae of, 79

Humerus, 46, 117, 217

Huxley, Professor, 31, 89, 154, 188

Hyo-mandibular arch, 13

Hypothesis of descent, 226

Hyrax, 101

Ichthyornis, 76

Ichthyosaurus, 6, 191

Iguanodon, 209; pelvis, 206

Ilium, 93, 95, 96, 98, 204

Instep, 105, 207

Inherited characters, 217

Interclavicle, 111

Ischium, 93, 96, 203, 204

Isle of Wight, 174

Jaw, in birds, 12; in fishes, 13; in mammals, 12; in reptiles, 13; in pterodactyles, 63; suspension of, 11, 74, 76

-- lower, 75

Kansas, Chalk of, 72, 103, 115; University Museum of, 181

Kelheim, 32

Keuper, 33

Kimeridge Clay, 132

Kingfisher, 63

Kiwi, 23

Labyrinthodontia, 191

Lachrymal bones, 67

Laramie rocks, 34

Largest ornithosaur, 133

Lateral vacuities in skull, 147

Lawrence in Kansas, 181

Lengths of bones, 146

Lepidosiren, 17

Lias, 33

Lithographic Slate, 35, 156

Lizards, 20, 21, 27, 123

Llama, neck of, 79, 83

Loach, swim bladder of, 52

Lower jaw, 12, 74, 76, 149

Lumbar vertebrae, 89

Lungs, 47; in apteryx, 48; in chameleon, 51; in ostrich, 49; in reptiles, 8, 9, 51

Lydekker, R., 160, 169, 231

Lyme Regis, 33

Macrocercus, palate of, 71

Malar bone, 67

Mallard, 22

Mammal, 8, 12, 24, 79, 53, 95

Mammalia, 38, 141

Mammalian characters, 12, 220

Mammoth, 141

Manis, 40, 57, 142

Manubrium of sternum, 108, 109, 183

Marrow bones in a bird, 134

Marsh, Professor O. C., 31, 72, 90, 115, 121, 131, 140, 160, 165, 180, 181, 210, 231

Marsupial, 70, 94, 99

Megalosaurus, 129, 198

Merganser, 108

Merry-thought, 114

Metacarpus, 116, 124, 126, 128, 130

Metatarsal bones, 104, 207, 208

Meyer, Hermann von, 31, 45, 46, 85, 105, 108, 121, 160, 192, 231

Moa of New Zealand, 35

Mole, humerus, 38; sternum, 107

Monotremes, 70, 94, 111, 121, 185, 218

Mososaurus, 77

Movement of the leg, 101

Mugger, 137

Munich Museum, 32, 159

Munster, von, 231

Muschelkalk, 184

Museum, 32, 156, 231, 159; Natural History, 133, 231

Myrmecophaga, 185

Names of genera, 183

Natural History Museum, 38, 231

Neck, 79; in Dimorphodon, 145; in Giraffe, 39; in Llama, 79; in Pterodactyles, 80; in Whales, 39

Newton, E. T., 55, 70, 158, 160, 201, 232

New Zealand Bat, 25

-- -- Hatteria, 68

Niobrara rock, 183

Nostril, bones round the, 62; small, 147

Notarium, 87, 115

Nothosauria, 192

Nusplingen, 32

Nyctodactylus, 115, 180

Obliteration of characters, 216

Opercular bones, 13

Ophidia, 52, 191

Optic lobes, 53, 221

Organs of flight, 17

Ornithischia, 190, 198

Ornithocephalus, 166

Ornithocheirus, atlas and axis, 81; brain, 55, 69; carpus, 124; cervical vertebra, 83, 179; claw phalange, 129; coracoid, 109; femur, 100; pelvis, 98; pubic bones, 194; sternum, 109; shoulder-girdle, 115; remains, 176; teeth, 74, 76; absence of teeth, 138

Ornithocheirus machaerorhynchus, 139; microdon, 139

Ornithocheiroidea, 193

Ornithodesmus, neck bones, 173, 175; coracoid, 109, 116; dorsal vertebrae, 86; remains of O. latidens, 173; O. sagittirostris, 175

Ornithomorpha, 189

Ornithorhynchus, 40, 53, 95, 117

Ornithosauria, 30, 31, 50, 52, 58, 72, 89, 95, 104, 108, 125, 132, 133, 143, 187, 190, 192, 216

Ornithostoma, 66, 69, 72, 180; lower jaw, 75, 76; pelvis, 98; sternum, 110; phalange, 122; size, 133; skull, 181, 182

Ornithosuchus, 201

Orycteropus, 96

Ossa innominata, 93

Ossified ligaments, 150

Ostrich, 23, 45, 49, 113, 129

Owen, Sir R., 31, 36, 46, 48, 110, 117, 143, 172, 176, 180, 231

Owl, 46, 53

Oxford Clay, 33, 156

-- University Museum, 154

Ox, vertebra of, 79; metacarpus, 127

Palate, bones of, 71

Pangolin, 142

Pappenheim, 32

Parallel groups, 215

Parrot, 71

Patagial membranes, 227

Pelican, 174

Pelvis, 88, 94-98, 151, 195, 202, 204, 206

Penguin, 41, 42, 104, 176

Periophthalmus, 17

Peterborough, bones from, 113, 156

Phalanges, 129, 132; wing finger, 155

Phillips, Professor John, 155

Pigeon, 119

Platydactylus, 21

Platypus, 214

Plesiosaurus, 6, 73, 75, 93, 189

Pleininger, 149, 232

Pneumatic foramina, 45, 83, 88, 132, 209

Pond, Mr., 34

Porcupine, 40

Porpoise, 38, 73, 141, 200

Premaxillary bones, 77, 200, 205

Prepubic bones, 94, 96-98, 194, 204, 205

Protorosauria, 192

Ptenodracon brevirostris, 64, 99, 167, 169, 192

Pterodactyle aspects, 35; avian characters, 222; beak, 200; brain, 53; coracoid, 113; discovery, 27, 33; foot, 104; fore limb, 117; history in Germany, 31, 148; hand, 130; hind limb, 100; long tails, 156; palate, 71; sacrum, 89; short tails, 165; size, 35, 133; sacrum, 89; skull, 192; teeth, 73; vertebrae, 80

Pterodactyles from Kansas Chalk, 177, 181

-- from Lias Clay, 135, 147, 152

-- from Neocomian Sand, 176

-- from Oxford Clay, 155

-- from Purbeck beds, 173

-- from Solenhofen Slate, 156, 158

-- from Stonesfield Slate, 153, 158

Pterodactylia, 30, 165, 193, 199

Pterodactylus antiquus, 167; brevirostris, 99, 167, 169; crassirostris, 156; dubius, 87, 96, 97, 203; elegans, 169; Fraasii, 169; grandipelvis, 87, 90; grandis, 102, 167, 169; Kochi, 12, 61, 87, 90, 168, 169; longirostris, 28, 90, 96, 101, 103, 105, 167, 169; micronyx, 105, 169; rhamphastinus, 183; scolopaciceps, 105, 166; spectabilis, 83; suevicus, 169

Pterodermata, 194, 199

Pteroid bone of first digit, 121

Pteromys, 24

Pterosauria, 187, 193

Pterygoid bones, 72, 147

Pythonomorpha, 191

Quadrate bone, 12, 68, 77

Quenstedt, 231

Rabbit, 227

Radius, 119, 120

Redshanks, 22

Relation between head and tail, 157, 193

Reptile, 6, 79, 80

Resin, 136

Restorations-- Campylognathus, palate of, 71 Dimorphodon, 143, 147, 164 Ornithocheirus, 164 Ornithostoma, 164, 183 Ptenodracon, 167 Pterodactylus, 29, 30 Rhamphocephalus, 164 Rhamphorhynchus, 161, 164 Scaphognathus, 163

Rhacophorus, 19

Rhaetic beds, 184

Rhamphocephalus, 113, 136, 153

Rhamphorhynchus, 118, 192; foot, 104; hind limb, 99; pelvis, 95; sacrum, 88; skull, 54, 63-6, 69; sternum, 108; tail, 91; teeth, 73; tibia and fibula, 103; web-footed, 105

Rhamphorhynchus curtimanus, 163; hirundinaceus, 163; longimanus, 164; phyllurus, 91, 165

Rhinoceros, 40, 141

Rhopoladon, 97

Rhynchocephala, 192

Roc, 36

Rochester, 136

Running limb, 38

Ryle, Bishop, 17

Sacrum, 87, 88

St. George, 15

St. Ives, 156

Sarcorhamphus, 102

Saurians, 27

Saurischia, 190, 195, 198, 199

Sauromorpha, 191, 192

Sauropsida, 188

Sauropterygia, 192

Scaphognathus, 64, 85, 140, 152, 192, 212

Scaphognathus crassirostris, 73-5, 83

Scapular arch, 111, 113

Scelidosaurus, 135

Sclerotic circle, 65

Seals, 41

Sedgwick, Professor Adam, v, 46

Shillington, 77

Shoebill, 67

Shoe-shaped prepubic bones, 204, 205

Short-tailed pterodactyles, 165, 193

Shoulder-girdle, 107, 111, 114, 115, 183

Siberia, 141

Simultaneous origin of characters, 214, 224

Skin covering, 40, 41, 58, 139, 140

Skulls, 68

Sloth, 112

Snipe, 47, 68

Solenhofen Slate, 28, 32, 88, 153, 156

Soemmerring, 29

South African reptiles, 188, 208, 216

Spotted fly-catcher, 47

Squamosal bone, 12, 13

Sternal ribs, 110

Sternum, 107, 158

Stonesfield Slate, 33, 88, 153

Structures common to reptiles, 224

Stuttgart Museum, 32, 172, 203

Swanage, 172

Swan, neck of, 80, 113

Swift, 50

Swimming limb, 38

Synotus, 25

Syrinx, 48

Tail, description of, 90; in Cretaceous Pterodactyles, 193 -- long, 156; short, 166; in Dimorphodon, 145; in Ornithocheirus, 179

Tanystrophoeus, long vertebrae in, 79

Tarsal bones, 102, 207

Tarso-metatarsus, 128

Teeth, 73, 137, 138; in porpoise, 40

Temperature of blood, 56

Temporal arches, 68

-- bone, 12

-- fossa, 67

Teredo, 137

Texas fossils, 216

Thecospondylus, 209

Theriodont pelvis, 97

-- reptiles, 75; of Russia, 96, 97; of South Africa, 96, 117

Theropsida, 188

Thigh bone, 100, 206, 211

Three claws, 146, 197

Tibia, 102, 195; in Iguanodon, 207

Toothless mammals, 40

-- pterodactyles, 138, 181; beak of pterodactyles, 150

Transition from reptiles to birds, 211

Tree frogs, 21

Trias dinosaurs, 199

Triceratops, pelvis of, 204

Trout, 139; of New Zealand, 228

Tuatera, 13

Tuebingen Museum, 32

Tundras, 141

Tunny, 57

Turtles, neck bones, 79

Ulna, description of, 119

Uncinate process of ribs, 85

Unlimited time, 228

Upper arm bone, 117

-- Greensand, remains in, 136

-- Lias of Whitby, 147

-- Oolites, 185, 195

Variation of bones in mammals, 38

-- in Pterodactyles, 229

Variation of bones in vertebrae, 225

Vertebrae, caudal, 89, 92, 203

-- cervical, 173, 179, 203

-- dorsal, 86

Vertebral articulation, 82, 224

-- column, 78

Vulture, neck vertebrae of, 80; tibia and fibula of, 102

Vomer, 147

Vomerine bones, 72

Wagler, 29

Wagner, Andreas, 30, 148, 231

Walker, J. F., 54

Wealden beds, Pterodactyles in, 55, 84; bones in, 135, 136, 173

Weight of Pterodactyle, 106

Whinchat, 47

Whitby, 33, 135

Williston, Professor W. S., 75, 82, 92, 98, 105, 110

Willow-wren, 47

Wing finger, 116, 130, 133, 151, 178, 197

-- membrane, 32, 121, 140, and frontispiece

-- metacarpal, 123; in Dimorphodon, 151; in Ornithostoma, 184; in bats, 131

Wings of Dragons, 16

Winkler, T. C., 231

Woodwardian Museum, 34

Wood-wren, 47

Wrist bones, 122

Wuertemberg, 33

Yale College Museum, 32

York Museum, 34, 176

Zittel, Karl von, 31, 157, 165, 231

Zygomatic arch, 67

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