The Ornithosauria

H. G. Seeley

The Ornithosauria

Published by Good Press, 2019

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EAN 4064066168629

Table of Contents

OSTEOLOGICAL COLLECTION

THE BONES OF THE HEAD.

NATURAL MOULD OF THE BRAIN CAVITY OF A CAMBRIDGE ORNITHOSAURIAN [U] . (Cast.)

A SUMMING UP.

CLASSIFICATION.

APPENDIX.

INDEX.

Osteological collection illustrative of modifications of Ornithosauria in the Cambridge Greensand, pp. 28–94.

ERRATA.

For epipubic bone read prepubic bone, pp. 61, 102, 109, 110, 111, and pl. 8.

INTRODUCTION

TO THE

OSTEOLOGY OF THE ORNITHOSAURIA FROM THE CAMBRIDGE UPPER GREENSAND.

Materials.

The Cambridge Upper Greensand has yielded to collectors bones which illustrate nearly every part of the skeleton of the animals that are commonly named Pterodactyles. Large collections have been acquired for the Woodwardian Museum. A series of more than 500 bones have been arranged to exemplify the osteology and organization of the Ornithosauria in the area when the Cambridge Greensand was deposited. And this memoir is written to explain briefly some of the structures of the soft and hard parts of those animals which are exhibited or demonstrated by these relics. Another collection of nearly 400 bones has been arranged, which displays in association, as they were found entombed in the old Greensand sea-bed, the remains of the skeletons of thirty-three animals of the Pterodactyle kind. The whole of the remains from this formation hitherto gathered cannot be computed to have pertained to fewer than 150 individuals, which indicate a new sub-class of animals, two new genera and at least twenty-five new species.

The bones were mostly of a paper or card-like thinness, and were originally hollow like the thin bones of birds. In the jaws of other animals, and in the sea, they were easily fractured, so that proximal ends and distal ends and shafts and split bones abound, while perfect bones are almost unknown. Even those bones like the carpals, which almost retain their entirety, invariably show indications of having been rolled on the sea-shore among the nodules of phosphate of lime with which they now occur, in their angular margins being rounded, and in the removal of slender processes. The rock in which these fossils are found is a thin bed of chalky marl which is heavily charged with dark-green grains of Glauconite, and is quarried largely, and entirely dug away to be deprived of the dark-brown nodules of phosphate of lime with which it is stored. In digging and in the subsequent washing, the workmen, stimulated by an ample reward, pick out the fossils as they are discovered. They are separated easily from the matrix of investing marl, so that every aspect of each bone is seen, except for the occasionally adherent oysters and the masses of phosphate of lime, with which material the bones are also filled. Hence these remains afford facilities for the study of the joints such as no other specimens have presented; and from their large size and comparatively great numbers, render easy the labour of the student who seeks to contrast them with the bones of other animals.

The osteological collection has been formed without regard to species or genera, and arranged to exhibit the structure and organization of the tribe of animals. So far as possible each bone, as humerus, femur, &c., has its variations of structures and form contrasted on a single tablet. The series comprises the following bones:

Fore-part of sternum.

Coracoid (perfect).

Scapula (nearly perfect).

Humerus (perfect).

?Radius (proximal end).

Radius (distal end).

?Ulna (proximal end).

Ulna (distal end).

Proximal carpal.

Distal carpal.

Lateral carpal.

Wing-metacarpal (proximal and distal ends).

First phalange (proximal and distal ends).

Second phalange (proximal end).

Metacarpal or metatarsal (distal end).

Claw phalange.

Os innominatum (parts of ilium, ischium, and pubis).

Femur (perfect).

?Tibia (proximal end).

Atlas and axis.

Cervical vertebræ.

Dorsal vertebræ.

Sacrum and sacral vertebræ.

Caudal vertebræ.

Lower jaw (dentary and articular ends).

Premaxillary bones, &c.

Teeth.

Quadrate bone (distal end with quadrato-jugal).

Ethmoid with basi-sphenoid.

Occipital and parietal segments of skulls.

Basi-occipital and basi-temporal.

Cast of brain-cavity.

They are exhibited in Compartments a, b, c of the Table-case of Cabinet J. The letter F in a circle is placed against figured specimens.

History.

The Cambridge Pterodactyles first attain prominence in scientific literature in the year 1859. Professor Owen had figured (plate 32, fig. 6–8) fragments of bones in the Palæontographical Society's Monograph for 1851; the distal end of a large ulna (fig. 6); the shaft of a phalange of the wing-finger, probably the first (fig. 7); and the upper portion of the shaft of a small humerus showing part of the radial crest (fig. 8). Inadvertently the last specimen was referred to the Lower Greensand. But although fragments of humerus of Pterodactyle and vertebræ of Pterodactyloid animals have in the last few years been gathered from the Potton Sands, those deposits were believed to be barren of fossils when Prof. Owen wrote; and all the Pterodactyles yet made known from near Cambridge were collected from the Cambridge Upper Greensand.

Among the earliest successful collectors were Mr. James Carter, the Rev. H. G. Day, St. John's Coll.; Prof. G. D. Liveing, St. John's Coll.; the Rev. T. G. Bonney, St. John's Coll.; and Mr. Lucas Barrett, Trin. Coll.; and the Rev. Prof. Sedgwick, Trin. Coll., on behalf of the Woodwardian Museum. Mr. Day and Mr. Bonney both presented every specimen from their cabinets which could enrich the University collection. And in the last ten years the Woodwardian Museum has acquired, through the skillful collecting of the Messrs Farren, the present materials. The associated sets of bones were formed by William and Robert Farren, who, obtaining the specimens from day to day as they were discovered, were enabled to put together such parts of the skeleton as remained together on the sea-bottom. These collections will hereafter be used for the elucidation of species. They are the only materials which can give the proportions of the Cambridge Ornithosaurians, and the contrast of aspect which distinguished the living animals from those from other rocks.

The other collections of these fossils are those of Mr. William Reed and Mr. J. F. Walker at York, the Museum of Practical Geology, and the British Museum.

The Woodwardian specimens as collected were placed in the hands of Prof. Owen, and were first made known in the Professor's lectures on reptiles and birds delivered at the Museum of Practical Geology in 1858. In that year Prof. Owen communicated to the British Association for the Advancement of Science, and printed in their Report, the matter of the memoir which was published with plates by the Palæontographical Society in 1859. In this latter year Prof. Owen communicated to the Royal Society an account of the vertebral column of Pterodactyles. In 1859 Prof. Owen also produced a classification of recent and fossil reptiles at the meeting of the British Association, in which the order Pterosauria appears with new characters—such as the pneumatic structure of most of the bones—drawn from Cambridge specimens. In 1860 Prof. Owen produced another memoir on Pterodactyles, which was published by the Palæontographical Society. A brief account of the tribe appeared about the same time in the Professor's Palæontology.

In these writings are descriptions of the various parts of the vertebral column. Their procœlian centra are described, and the pneumatic foramina are noticed and supposed to have communicated with air-cells. They are compared with birds, and distinguished from birds; but although the order is classed with reptiles no contrast with reptiles is made. Other bones described are a basi-occipital, and a doubtful bone, then thought to be a frontal, but which is more like the neural region of the sacrum.

The sternum is compared with the sternum of the birds Apteryx and Aptenodytes, is stated to be formed, in the main, on the Ornithic type, and to possess distinct synovial articular cavities for the coracoids such as only occur in birds. The inter-coracoid process of the sternum is compared with that of Bats, Birds, and Crocodiles.

The mechanism of the framework of the wings is said to be much more bird-like than bat-like, the anchylosed scapula and coracoid being remarkably similar to those of a bird of flight. The coracoid is shorter and straighter in birds than in Pterodactyles, but no comparisons are made with reptiles.

The humerus is known only by the proximal end. It is said to conform at its proximal end more with the Crocodilian than with the Avian type, but to have the radial crest much more developed than in either Crocodile or Bird. The bone is, however, chiefly compared with birds, and is figured between corresponding bones of a Vulture and a Crocodile. The pneumatic texture is said to be as well marked as in any bird of flight.

Of the carpus it is said, the Pterodactyle, in the complete separation of the metacarpus from the antibrachium by two successive carpals answering to the two rows, adheres more closely to the reptilian type than to that of birds. But the row which was regarded as proximal is the distal row, while the supposed distal row is proximal.

The claw-phalange and distal end of the wing-metacarpal, the mandible, teeth, and jaw are the other bones described, but their comparative osteology is not discussed. In the Professor's account of a fragment of a jaw it is said, The evidence of the large and obviously pneumatic vacuities now filled with matrix, and the demonstrable thin layer of compact bone forming their outer wall, permit no reasonable doubt as to the Pterosaurian nature of this fossil. All other parts of the flying reptile being in proportion, it must have appeared with outstretched pinions like the soaring Roc of Arabian romance, but with the demoniacal features of the leathern wings with crooked claws, and of the gaping mouth with threatening teeth, superinduced.

When the specimens on which Prof. Owen had founded the foregoing views of the osteology and classification of these animals were at length returned to the Woodwardian Museum, it became a duty of the present writer to arrange and name them. And in a Memoir on Pterodactyles which was communicated to the Cambridge Philosophical Society and read March 7 and May 2 and 16, 1864, a position was claimed for them, distinct from reptiles, as a separate sub-class of Sauropsida, nearly related to birds.

In September of the same year a communication was made to the British Association On the Pterodactyle as evidence of a new sub-class of vertebrata (Sauromia), with enlarged drawings of the skull and some of the other bones, in which the conclusions arrived at were that, excepting the teeth, there is little in such parts of the head as are preserved to distinguish the Cambridge Pterodactyles from birds; and that the remainder of the skeleton gives a general support to the inference from the skull.

Papers were communicated to the Cambridge Philosophical Society on February 17, 1868, on indications of Mammalian affinities in Pterodactyles in the pelvis and femur, and February 22, 1869, on the bird-like characters of the brain and metatarsus in the Pterodactyls from the Cambridge Greensand. The other references to Cambridge specimens are in a paper On the literature of English Pterodactyles in the Annals and Magazine of Natural History for Feb. 1865, and in An epitome of the evidence that Pterodactyles are not reptiles, but a new sub-class of vertebrate animals allied to birds, in the same magazine for May, 1866.

In the meantime Prof. Owen's views have somewhat changed. In the first volume of the Comparative Anatomy and Physiology of the Vertebrata (1866), the Pterosauria are classed as the highest group of reptiles, and take rank above the Dinosauria. In the second volume of that work (1866), occurs the following passage:

Derivatively the class of birds is most closely connected with the Pterosaurian order of cold-blooded air-breathers. In equivalency it is comparable rather with such a group than with the Reptilia in totality, or with the Mammalia.

Organization.

Nearly every writer on Pterodactyles, who has expressed any opinion at all, has formed an estimate of his own of their organization. They have been assigned to almost all possible positions in the vertebrate province, by great anatomists who all had before them very similar materials. An account of these views is given by von Meyer in his monograph of the Pterodactyles of the Lithographic Slate. It will not be necessary to discuss these conclusions here, for the materials from the Lithographic Slate and those from the Cambridge Greensand are so different that no light would be thrown on the organization of the animals by an exposition of any fallacious inferences from German specimens. In England they are classed with Reptilia, chiefly through the influence of the discourse upon them given by Baron Cuvier in his Ossemens Fossiles[A]. It therefore may conduce to a clear view of the subject to quote in Cuvier's words the passages in that memoir which have been supposed to establish their position among reptiles. He says—"Ayant encore porté mon attention sur le petit os cylindrique marqué g (i.e. os quadratum) qui va du crâne à l'articulation des mâchoires, je me crus muni de tout ce qui étoit nécessaire pour classer ostéologiquement notre animal parmi les reptiles." The exact relations of the quadrate bone are not seen in either Cuvier's or Goldfuss' or von Meyer's figures of this Pterodactyle, the P. longirostris; but in von Meyer's figures of P. crassirostris, P. longicollum, and P. Kochi it appears to be a free bone articulated to the squamosal and petrosal region of the skull and with the lower jaw. This is not the case with either Chelonians or Crocodiles, which have the quadrate bone firmly packed in the skull; nor is it paralleled even among those lizards and serpents which have the bone as free; while, on the contrary, it is characteristic of the whole class of birds. The form of the bone is not more Lacertian than Avian, while its direct attachment to the bone of the brain-case finds no parallel among lizards, but is exactly paralleled in all birds.

[A] Tome

V.

Part a, pp. 358, 383. Edition, 1814.

Cuvier then goes on to say, "Ce n'étoit pas non plus un oiseau, quoiqu'il eût été rapporté aux oiseaux palmipèdes par