Part 11

Thus, if with an avian basis some parts of the skeleton present points of agreement with reptiles, in other points there are resemblances with mammals not less characteristic. These phænomena do not show that in so far the animal is a mammal or a reptile, but only that mammals, ornithosaurians, and reptiles have had a common origin, and that while they have been differentiated so as to form separate classes they have severally retained characters which formerly were united in one class. It is a skeleton intermediate between reptiles and mammals, and well distinguished by mammalian, reptilian, and peculiar characters, from birds. It therefore forms a parallel group with birds, displaying the ornithic organization in a differently modified skeleton. Yet it differs more from existing birds than they differ among themselves, for the discrepancies are in points of structure in which all existing birds agree: they are in having teeth, in the procœlous centrum, in the separate condition of the carpal and metacarpal (and of the tarsal and metatarsal) bones; in having more than two bones in the fore-arm, in the sacrum formed of few vertebræ, in the expanded pubic (and prepubic) bones, in a long neck to the femur, and in the modification of the wing by the great development of the phalanges of one finger.

I therefore regard the Pterodactyles as forming a group of equal value with birds, for which group the name Ornithosauria is here used. It cannot form a separate class, because they have a fundamental organization in common; and it cannot form an order of birds, because its differences from birds are greater than those of an order. It is a group which itself probably includes several orders, and must constitute a sub-class, which finds its place in nature side by side with birds and between mammals and reptiles, thus:--

Mammalia. \ | | Ornithosauria. Aves | Reptilia. /

Restoration.

Of the form and size[W] of the animals from the Cambridge Greensand, an idea will best be given by a few measurements.

[Footnote W: There are Ornithosaurians hereafter to be described compared with which the largest at present known will seem diminutive. A vertebra of one such, from the Wealden, is contained in the British Museum (numbered 28632). The centrum alone is between 9 and 10 inches long and 8 inches deep. It is named Streptospondylus, but constitutes a new group of Ornithosaurians. Nothing so gigantic exists in the Woodwardian Museum. Another vertebra of the same or an allied genus has been figured by Prof. Owen as the tympanic bone of ?Iguonodon (Fossil Reptilia of the Wealden, Part 2, pl. 10).]

In the species Ornithocheirus nasutus (Seeley), =J=._c_.2.11.1:

The premaxillary extends for 6 inches without reaching the nares.

The lower jaw is 3/4 of an inch deep at the articulation.

The four cervical vertebræ are each 1-1/2 inch long.

The sternum measures 1-1/2 inch over the facets for the coracoids.

The humerus is 2-1/16 inches over the proximal end, the radial crest not being preserved.

The coracoid is 1-1/4 inch over the proximal end.

The scapula is about 3-1/2 inches long.

The proximal carpal (imperfect) is 1-5/8 inch wide.

The distal carpal is 1-1/2 inch wide.

The lateral carpal is 1-1/4 inch long.

The wing-metacarpal is 1-1/4 inch wide at the proximal end, and 7/8 inch wide at the distal end.

The proximal end of the first phalange is about 1-5/8 inch wide.

The proximal end of the second phalange is less than an inch wide.

The claw-phalange (imperfect) is about 1-1/4 inch long.

The femur is 4 inches long.

Putting the animal together, the bones give this size :

Head 1 ft. 3 in. long. Neck 9 " (_Back and sacrum_) ? 8 " (_Tail_) ? 10 "

With the hypothetical parts, this would give a length of about 3 ft. 6 in. from the tip of the snout to the tip of the tail. Then

Humerus 8 in. long. (_Fore-arm_) ?1 ft. 0 " Carpus 2 " Metacarpus 10 "

Which, if the fore-limbs were kept together as in ordinary quadrupeds, would give a height to the body of about 2 ft. 6 in., but as the limbs probably spread in walking as among the bats, the hind-limb would give a better idea of the height of the animal.

(Flesh, sacrum, os innominatum). 2 in. Femur 4 " (_Tibia_) 6 " (Metatarsus, &c.) 1 "

Which would give a height of about 13 inches; and, standing in the position of a bird, the height to the crown of the head would be about 2 feet. The majority of the Ornithosaurians of the Cambridge Greensand are of this size.

The spread of the wings, if there were 4 phalanges, would be

Body 10 in. wide. Two arms 5 ft. 2 " Two wing fingers 7 0 "

Giving a total expanse of about 13 feet. But, from the indications of the wing-finger, I should incline to think an expanse of 10 feet a truer estimate. The largest species attained to twice this size, and the smallest was a fourth as large. Another memoir will present descriptions and restorations of the Greensand species.

Habits.

The varying organization of different Ornithosaurians probably depends on the different habits of the tribes. That they could all fly is probable from the enormous radial crest to the humerus and the great development of the wing-bones, to which a wing-membrane was stretched, comparable to that of a Bat in texture, but more comparable to a Bird in its extent. The groups with long hind-legs probably had the membrane limited to the bones of the arm, while in the species with small hind-legs it may have attained even as great a development as in Bats, though there is no reason for suspecting that it extended to the tail. A Pterodactyle cannot be supposed to have hung itself up by the hind-legs as does a Bat, because the hind-claws appear invariably to be directed forward. A Bat walks upon four legs with considerable elegance and speed; the wing is folded in, close to the side, so as to be scarcely noticed; and the outer claw is free to climb with. There can be little doubt but that Pterodactyles walked in a similar way. The thickened mammilate knob at the proximal end of the first phalange is well calculated for contact with the ground. And if it were supposed that the large wing-metacarpal bone were only used to support the wing, and the small metacarpals only used to support the claws by which the creature has sometimes been pictured suspending itself, it would be difficult to believe that the forces of pressure and tension in flying so exactly corresponded to the forces manifested in suspension as to cause the large and the small metacarpals invariably to attain the same length. A correspondence of this kind may be presumed to indicate a correspondence in function; and since the animal did not fly by means of its claws, the inference is that it walked by means of the metacarpal bones. In no other way could the bones have been used equally. The avian ilium would suggest a probability that they also at times stood erect like birds, from which position they could with more ease expand their wings; nor is such an idea opposed by the resemblance of some bones of the hind-limb to what obtains in birds, and of the neck of the femur to what is seen in mammals of great power in the hind-legs.

That they lived exclusively upon land and in air is improbable, considering the circumstances under which their remains are found. It is likely that they haunted the sea-shores, and, while sometimes rowing themselves over the water with their powerful wings, used the wing-membrane as does the Bat to enclose their prey and bring it to the mouth. But the superior development of the pneumatic foramina suggest that their activity was greater than in ordinary sea-birds.

The large Cambridge Pterodactyles probably pursued a more substantial prey than dragon-flies. Their teeth are well suited for fish, but probably fowl and small mammal, and even fruits, made a variety in their food. As the lord of the cliff, it may be presumed to have taken toll of all animals that could be conquered with tooth and nail. From its brain it might be regarded as an intelligent animal. The jaws present indications of having been sheathed with a horny covering, and some of the species show a rugose anterior termination of the snout suggestive of fleshy lips like those of the Bat, and which may have been similarly used to stretch and clean the wing-membrane.

The high temperature, coupled with the sub-aerial life, are opposed to the idea of the animal having been naked. The undisturbed condition of the skeleton and some points of structure are opposed to the idea of their having had large feathers. The absence of such remains does not favour the hypothesis of their having been covered with scales, though in the legs of birds a scaly covering is met with. I should anticipate for them a filamentous downy feather, or hair, like a Bat's. The Bat combs its hair with its claws, and the Ornithosaurians may have used their claws in a similar way.

They cannot be supposed to have been gregarious, from the large number of species relatively to specimens. The reproduction may have been much the same as in birds; and the young were probably reared with affectionate care[X].

[Footnote X: Mr Carruthers has shown me crushed Turtle-like eggs from the Stonesfield slate, which in the external pitting of the egg-shell are not so different from some birds as to preclude a suspicion that they might possibly be Ornithosaurian.]

* * * * *

_The following notes indicate structures in perfect specimens from the Lithographic slate which supplement the fragmentary remains from the Cambridge Greensand_[Y].

[Footnote Y: The German animals form different family groups. And it cannot be inferred that the structures seen in them pertained to Cambridge specimens.]

In the head, Cambridge specimens show no trace of the parts which are between the brain-cavity and the fore-part of the jaw. The form and condition of the orbits, nares, and of the space between them, vary in German specimens. Some Birds and certain Ruminants, such as deer, the giraffe, &c., have an interspace between the orbits and nares corresponding to that in some Pterodactyles, but no such perforation is found in living reptiles. In mammals it appears to be surrounded by the frontal, nasal, lachrymal, and often by the maxillary bone. In birds the bones appear to be the lachrymal, nasal, maxillary and premaxillary, as is the case with Pterodactyles, except that the nasal bones would seem sometimes to be excluded. The chief peculiarity of the Pterodactyle skull in this region is made by the malar bone (and, according to some authors, the maxillary also) sending up a process to meet the lachrymal. This is not seen in birds, but is characteristic of many mammals and reptiles.

The premaxillary bone is single, as in birds and Iguana; but it appears to attain as great a development as in birds, and to occupy the portion of the jaw which among reptiles and mammals is made by the maxillary bone. Owing to the great development of the premaxillary bones, the exterior nares are placed far back toward the middle of the skull as in birds, and not near the tip of the snout as in living reptiles and most mammals.

The orbits in Pterodactyles are surrounded with bone, as is commonly the case with mammals and reptiles. Among birds a complete orbit is seen among the parrots, in which it is completed below by a prolongation of the outer posterior corner of the frontal, which would correspond to the post-frontal bone, and by the lachrymal bone. Thus the malar bone, which in most mammals and reptiles forms an important part of the lower margin of the orbit, is in birds entirely excluded. In Pterodactyles the malar bone is placed between the lachrymal and the post-frontal process of the frontal bone.

The quadrate bone in German Pterodactyles, instead of being vertical as in birds, stretches obliquely forward below the malar bone, so that the articulation for the lower jaw is brought forward to be under the middle of the orbit. In _Pterodactylus Kochi_ and in other species there appears to be a process, or small separate triradiate bone, comparable to a diminished lacertian post-frontal, and homologous with the post-frontal process of the parrots. Its upper branch meets the frontal. In some genera the front appears to meet the malar. The lower branch goes to the front of the quadrate bone, and the backward branch goes to the squamosal immediately above the articulation for the quadrate bone. Thus it is a post-frontal bone resembling that of the Iguana, but modified and adapted to a cranium like that of a bird. Its form and size in the different genera are very variable. No similar development is seen among mammals, where the post-frontals have probably ceased to exist. It is a carious point of resemblance, but from the other resemblances to Iguana being so few it is robbed of much of its force as a mark of affinity, and becomes of interest chiefly as an evidence of independent persistence of structures.

The pterygoid and palatine bones approximate to those of bird and lizard in Pterodactylus crassirostris. And the bones in Pterodactylus suevicus, which Quenstedt names vomera, should rather have been named palatines. There is a bone in Goldfuss' specimen, between the malar and palatine, which he identifies with the transverse bone, but it is not seen in any other specimen.

The ribs sometimes appear to articulate by single heads, but in P. crassirostris they are apparently articulated as in the Crocodile. Some species show abdominal ribs like those of some reptiles; but the segments of the mammalian sternum and abdominal ribs are to be regarded as homologous structures. The vertebræ offer considerable variety in size and shape, but the greatest variation in number is seen in the tail, which is sometimes stiff and long, and sometimes short. The pelvic bones show a large amount of variation in different genera, often appearing to be crocodilian, sometimes lacertian, sometimes mammalian. In the aim the humerus is variable in the length of the radial crest, and the metacarpus also varies in length.

When the external similarity of the skeletons of birds is borne in mind, it is impossible, without disregard of classification altogether, to place animals differing so widely as do the different Ornithosaurians in the few genera in which they are at present packed.

CLASSIFICATION.

The orders of Ornithosaurians may be established hereafter. Under the name Pterosauria, Prof. Owen founded one order which has for its type the Pterodactylus longirostris.

Von Meyer proposed to separate this order into two groups, one with two phalanges in the wing-finger, of which Ornithopterus is the only example, forming his Diathri; while the other group, Tetrathri, or those "with four fingers, comprised all other Pterosaurians. The Tetrathri he again subdivided, following out, as he states, the suggestion of Munster and Goldfuss, into _Dentirostres_ or such Pterodactyles as have the jaws furnished with teeth to their anterior termination; and the _Subulirostres_, or such as want teeth at the extremities of the jaws. To the former group he left the name Pterodactylus, and to the latter was given the name Rhamphorhynchus. Von Meyer says that he might easily have made a few more species, as will be evident to those who inspect his plates, but he "believes that the students of living animals go too far in their tendency to subdivide:" a fancy that, if indulged in by Palæontologists, would have the effect of restoring the old Linnæan groups; and a complaint which, although often heard, has usually come from those who do not readily discern and appraise classificational characters. In Palæontology genera are sometimes co-extensive with orders, while species often mean genera. It may be wearisome to the collector to be lured on to follow the devious ways of a science, but Palæontology, the source whence the mysteries of existing nature must unravel their meaning, is the handmaid of all nature's truths which have been buried in evolving the existing creation; and a duty devolves upon Palæontologists to make the past an inseparable part of the present, by applying to the two the same scientific method.

A year previous to the formation of Owen's Pterosauria, Bonaparte named the Order Ornithosaurii, and divided it into a family--Pterodactylæ, and a sub-family Pterodactylinæ.

Fitzinger (_Systema Reptilium_, 1843) also used the same ordinal name, and recognized three genera--

_Pachyrhamphus_, of which the type is Pterodactylus crassirostris (Gold.).

_Pterodactylus_, with the type P. longirostris (Cuv.).

And _Ornithocephalus_, with the type O. brevirostris (Sömm.).

These and other attempts at classification all endeavour to subdivide Ornithosaurians by the head or by the tail. Other characters for primary divisions may be obtained from the pelvis.

In the majority of German Pterodactyles the ilium extends for a long distance in front of the os pubis, and only for a very short distance behind the large ischium; and the small pubis from its anterior margin gives attachment to a large prepubic bone, which resembles in form the os pubis of the Crocodile[Z], and is unlike that of the Monotreme. These appear to include the long-legged animals with short tails, at present called Pterodactyles, and form a well-marked family or order.

[Footnote Z: Prof. Haughton, from a study of the bones and muscles, came to the conclusion that the pubic bones of Crocodiles are the marsupial bones.]

Another kind of pelvis is that in which the ilium extends a short way in front of the acetabulum, in which the pelvic bones inclose a much larger space. These include the Cambridge Ornithosaurians, the Rhamphorhynchus, and the Dimorphodon, and form another well-marked family.

These long-tailed Pterodactyles subdivide into three sub-families--Rhamphorhynchæ, Dimorphodontæ, and Ornithocheiræ. The four families may then be defined thus:

_Pterodactylæ_. Tail short. Hind-legs long. Ilium narrow, extending far anterior to the acetabulum; ischium extending behind the acetabulum. Epipubic bones ficiform. Head with the middle holes large, often confluent with the exterior nares. Jaws toothed to the anterior extremity.

_Rhamphorhynchæ_. Tail long and stiff. Hind-legs short. Pubis and ischium small, oblique to ilium, which extends less far anteriorly than in Pterodactylæ. Epipubic bones narrow and bent; they unite mesially and form a three-sided bow in front of the pelvis. Head with the middle holes and nares both small. Jaws never toothed to the anterior extremity.

_Dimorphodontæ_. Tail long and stiff. Hind-legs long. Pubis and ischium forming an expanded sheet of bone at right angles with the narrow ilium, which extends as far behind as in front [prepubic bones triangular (?) attached by the apex of the triangle]. Head with the nares and middle holes large. Quadrate bone large. Jaws with large teeth at the extremities, and small teeth behind. No sacrum.

_Ornithocheiræ_. Tail long and flexible. Hind-legs short. Pelvis as in Dimorphodontæ. [Epipubic bones with a small attachment, form unknown.] Head with the quadrate bone small. Sacrum of not fewer than three vertebræ.

In the Pterodactylæ the genera are--

_Pterodactylus_ (Cuvier), in which the exterior nares are at the sides of the face, very large, and only partially, if at all, separated by bone from the small middle hole of the head. The head is elongated. The neck is long. Among others, it includes the species P. longirostris, P. Kochi, P. scolopaciceps, P. longicollum.

_Ornithocephalus_ (Sömmerring), in which the anterior nares are entirely separated from the middle holes of the head, both being small, and the latter exceedingly small. The head is short The neck is short. The large ischium appears to be excluded from the acetabulum, and the ilium appears to extend less far forward than in Pterodactylus[AA].

[Footnote AA: So far as can be judged from figures, it appears to have but three bones in the wing-finger: what Cuvier regarded as a terminal and fourth joint, the bone _n_, Pl. XXIII. fig. 7, _Oss. Foss._, appearing to me to be the fibula of the tibia marked _e_. _s_ in the same figure would be the terminal phalange, and _r_ the first phalange, as may be proved by measuring them with those of the other hand, so that a phalange is missing from between them. Both the terminal phalanges appear to be hooked at the termination. Goldfuss figures the phalanges so as to make the bone which appears to be fibula in Sömmerring and Cuvier look like a fourth phalange.]

_Pachyrhamphus_ (Fitzinger). The nares are entirely separated from the middle holes of the head; both are large. The head is thick and massive. The prepubic bones meet mesially. No evidence of the number of phalanges in the wing-finger. The quadrate bone is massive, but has small attachment to the skull. Two sacral vertebræ. Wing-metacarpal very short. The type is P. crassirostris (Goldfuss).

_Cycnorhamphus_ (Seeley). Nares very small, looking upward from a swan-like beak. The middle hole of the skull very large and elongated and lateral. Neck long. Wing-metacarpal long. Four joints in the wing-finger. Ilium widening in front. Epipubic bones meeting mesially. The type is Pterodactylus suevicus (Quenstedt).

In the Rhamphorhynchæ at present there appears to be but one genus known:

Rhamphorhynchus (von Meyer). The nares and middle holes are both small, ovate, of nearly equal size, and close together at the side of the head in front of the orbit.

In the Dimorphodontæ the only genus is

_Dimorphodon_ (Owen). It has the nares enormously large. The middle holes are also large.

In the Ornithocheiræ the genus is

_Ornithocheirus_ (Seeley), in which teeth are prolonged anterior to the muzzle, and the palate has a longitudinal ridge.

With the osteological illustrations of the Ornithosauria are arranged some premaxillary bones, which show varieties of form of the snout. These variations of shape serve easily to indicate different species. And the following memoranda from those specimens and other specimens in the drawers form a synopsis of the species of the Cambridge genera, which may hereafter be fully elucidated from the copious materials in the series of associated remains.

I.

Ornithocheirus Sedgwicki (Owen).

Case. Comp. Tablet. Specimen. =J= _c_ 13 2

The fragment is 2-7/8ths inches long, with the elliptical teeth opposite to each other, 6 on a side on the palate, and one pair in front. The first three teeth are large; behind these the teeth are about half the size. The palate is gently convex, with a faint median ridge, and measures from side to side over the fourth and subsequent sockets 13/16ths of an inch. The height of the jaw at the fourth socket 1-1/4 inch. The sides converge to an acute rounded rostral keel. The jaws appear to have been long. The anterior termination is vascular.

The rostral keel figured by Owen Pl. I, fig. 1 _d_, in the 1st Supt. _Cret. Reptiles_, is not square as represented there, but rounded; the sides converge more acutely, and at the ridge the keel is not half so wide as the figure makes it. The enormous size of the third tooth-socket is partly due to the cracked bone having absorbed more phosphate of lime than it could hold, and extended the cracks to fissures. The type specimen shows that there was another pair of sockets in front of, but quite close to, those which appear to terminate the lower jaw.

II.