Case.Comp.Tablet.Specimen.Ja21—23
CORACOID.Pl. 2, fig. 1-6.
Commonly the coracoid in the Cambridge Pterodactyles is anchylosed to the scapula: occasionally the bones are separate, though the separation has hitherto only been observed in the largest species. In 1851 Professor Owen, when figuring the anchylosed ends of the scapula and coracoid in Pterodactylus giganteus (Bowerbank), observed that in no part of the skeleton does the Pterodactyle more nearly resemble a bird than in the scapular arch; a view again urged emphatically in 1859 when similar fragments were described from the Cambridge Greensand. Since then perfect examples of the coracoid have occurred, which show the characters given in the following description.
The bone is long, with sub-parallel sides, sub-triangnlar in section, with the proximal end expanded exteriorly and posteriorly, resembling in form the coracoid of a bird. The front surface looks forward and outward; it is flattened, is a little convex transversely, and a little convex in length; it is rugose with muscular attachments, which terminate in a tubercle on the uppermost fourth of the front, usually near to the inner side. The middle third of the slightly concave inside margin of the front aspect, is sharply angular; the parts above and below it have the angularity rounded off. The outside margin, a little more concave than the inside margin, is sharply angular in its distal third, in which the front gradually widens to near the sternal articulation, when it contracts—the whole sternal termination of the bone being directed a little inward towards the manubrium of the sternum. The inside, which faces the opposite coracoid, is convex transversely in the lower half or two-thirds; its distal termination is carried inward. The expanded proximal end of the inside is flattened, or channelled, by the developement inwardly, at the proximal end of the ridge formed with the front side, of a long strong process homologous with that on the inner side of the coracoid in birds. The channel so formed rounds on to the proximal surface of the bone, and extends backward to the limit of the scapula; over it the second pectoral muscle may be presumed to have worked[N]. The third side of thebone is much more concave in length than either of the others; it looks backward, outward, and downward, the proximal end being turned outward and downward more than the distal end; it is a little concave transversely at the expanded proximal end. Near the distal end there are sometimes visible a few faint marks of the insertion of muscular fibres, but they are much less distinct than those made by the coraco-brachialis muscle in the corresponding region of the coracoid in birds. Throughout its length it rounds into the inner side, and the upper third rounds convexly into the front. On the most posterior part of this aspect of the proximal end is a groove terminating in a long pneumatic foramen, partly in the coracoid, partly in the scapula.
[N]The homologous process is more developed in Pterodactylus giganteus. See f. 7. pl.XXXI.Owen, Cret. Rept.
[N]The homologous process is more developed in Pterodactylus giganteus. See f. 7. pl.XXXI.Owen, Cret. Rept.
The muscular attachments on the front aspect of the coracoid appear to be two; one large and long inserted into the inner half of the middle third of the bone, terminating at the proximal end in a tubercle. No specimen shows the distal end of the insertion. This may indicate a subdivision of the first pectoral muscle. The other insertion, if it be distinct, is long and much narrower and at the distal end of the bone. This, according to the analogy of birds, should be the third pectoral muscle; if the insertion should be but part of that to which it is distally adjacent, then the third pectoral muscle must have had an enormous developement unparalleled in birds.
The distal end of the bone terminates in a synovial articulation concave transversely, convex from front to back, in form transversely ovate: the narrow side of the articulation, like the thin edge of the coracoid, being exterior. The articulation is about three fourths of the transverse diameter of the distal end; it is at right angles with the long axis of the bone, and looks downward and a little backward.
The proximal end, massively enlarged outward and backward, presents on the proximal surface three well defined regions. The largest of these is an irregular flattened surface half ovate in form, inclined to the axis of the bone at about 45°, looking backward, and upward also, when the bone is held vertically; the mesial hindermost half of the radius of this area is occupied by a pneumatic cavity: to this surface is applied the scapula. The next largest surface is rectangular and oblong, looking upward, outward, and a little forward. The transverse aspect which looks outwardbeing nearly half as long again as the antero-posterior aspect which looks forward; in the latter direction the area is slightly concave, in the former direction it is slightly convex; its posterior boundary is parallel with the front of the bone: this area forms the anterior moiety of the glenoid cavity, to which the proximal end of the humerus is applied.
The remaining surface of the proximal end is sub-quadrate, adjoins the two other surfaces as well as the front and the inside of the shaft, it is conically concave.
The entire bone when applied to the sternum looked outward, backward and upward.
Professor Owen remarked (1859) that the "coracoid is shorter and straighter in birds than in Pterodactyles, but is commonly broader, and with a longer and stronger anterior process."
The points in which the Pterodactyle coracoid resembles that of birds (e. g. Gallinaceæ) are the long slender triangular shaft; the concavo-convex articulation to the sternum; the convexity of the distal end in front, and its concavity behind; the posterior aspect of its scapular surface, and the pneumatic foramen.
The points in which it is distinct from birds are that the bone is not produced proximally beyond the glenoid cavity for the humerus, which, instead of being lateral as in birds, and looking outward, in Pterodactyles forms the proximal-termination of the bone. The sternal articulation is proportionally much shorter transversely in Pterodactyles, terminating in a convex margin which rounds up into the thin outer margin, as in the immature coracoid of the common Cock. It is bow-shaped in front instead of being straight, and is commonly longer than in birds. The usual ossified connection with the scapula is not entirely unparalleled in birds, the whole pectoral girdle being sometimes anchylosed into a bony mass as in the frigate bird.
In the monotremata, the only mammals in which the coracoids are separate bones, they rather recall those of Ichthyosaurus than those of any other animals, and have no connection with the sternum. The bone which represents it functionally in placental mammals is the clavicle.
In no reptile is there any structure resembling the Ornithosaurian coracoid. The nearest approximation is made by the Crocodile, in which as in the Chameleon the pectoral girdle isformed as in pterodactyles and struthious birds by scapula, coracoid and sternum. But in the Crocodile the coracoid is compressed, and expanded from side to side both proximally and distally. Distally it has no synovial articulation with the sternum; and proximally a wide process of the bone extends beyond the articulation for the humerus as in birds, only the scapula unites with the prolonged part, and the glenoid cavity looks forward and inward.
The coracoid is essentially avian in its affinities, though with peculiar characters of its own. In the German genera it closely resembles specimens from the Cambridge Greensand.
23 specimens are exhibited. Nos. 4, 10, 12, are the middle parts of shafts of left coracoids. Nos. 3-12, 22, are the middle parts of shafts of right coracoids. Nos. 2, 5, 14, are proximal ends of left coracoids. Nos. 1, 6, 8, 9, 23, are proximal ends of right coracoids. Nos. 15, 16, 17, 18, 19, 20, 21, are distal ends of left coracoids. No. 13 is a nearly perfect left coracoid, and No. 7 is the glenoid cavity for the humerus formed by a right coracoid with the anchylosed scapula.
Case.Comp.Tablet.Specimen.Ja31—1741— 651— 4
SCAPULA.Pl. 1, figs. 2-12.
Professor Owen described the scapula of Pterodactylus giganteus in 1851, and added further particulars regarding the Species from the Cambridge Greensand, in 1859; but, as with the coracoid, only the humeral end has hitherto been figured. The only example sufficiently perfect to give the length and proportions of the bone is preserved in the collection of Mr Reed, of York. This left scapula is a stout strong bone, short in proportion to its strength, of flattened ovate form in section, expanding at the humeral end into an irregular sub-rhomboid mass. It is smaller in the middle, contracting both from side to side and from back to front till the back to front measurement is7/16of an inch, and the side to side measurement is11/16of an inch, and it expands a little at the free end, which terminates in a smooth heart-shaped surface, convex in the long diameter, which measures7/8of an inch, and flat in the shortone, which measures nearly5/8of an inch; it is at right angles with the inside of the bone. The sharp superior lateral outline is concave, but less so than the inferior lateral outline; into that inferior aspect of the bone the sides are more fully rounded. The flattened inner surface applied to the ribs is concave in the length of the bone, which measures 31/2inches; the posterior half of which is convex transversely, the anterior humeral half is concave transversely so as to be cup-shaped, and measures in extreme width 111/16inch; the outline of the transversely convex outer side in length is nearly straight, but the exterior part and glenoid cavity of the proximal end is broken away, and there only remains a small median proximal surface broken at both ends, a little concave in length, measuring5/8of an inch, and convex in breadth measuring1/4of an inch.
As there is no specimen in the Woodwardian Museum showing clearly the connection of the proximal with the distal end, the specimens are arranged on separate tablets.
Humeral End of Scapula.
The humeral end of the scapula exhibits in the different species much diversity of form, spreading laterally from the shaft, and terminating in an elongated articular surface truncating the bone nearly at right angles. On its inferior border it throws out a large convex tuberosity, separated from the humeral articular surface by a deep emargination. From the tuberosity usually arises a crescentic row of muscular insertions, which is continued inward and forward over the most compressed part of the scapula towards the middle of the humeral articulation. From the superior margin, interior to the coracoid, arises a prominent ridge, the spine of the scapula, which is directed diagonally backward and downward, terminating in the middle of the outer surface, where it is bordered on the anterior aspect by a long narrow muscular attachment. Between this spine and the elevated margin of the glenoid cavity the bone is much compressed and concave.
On the inside surface of the bone there appear to be small muscular attachments in front of and behind the great tuberosity. The area between the spine and the inner surface is sometimes flattened, sometimes gently convex.
With well-marked distinctive characters in the inferior tuberosity,the pre-tuberous emargination and the thick rounded form of the bone, the Pterodactyle scapula is intermediate in character between that of a mole, a bird, and the crocodile; wanting the sabre shape of the bird's scapula, it also wants the wide expanded form of the scapula of the Crocodile, but resembles the latter in the direction and degree of developement of the spine. This modification is probably due to the outward direction and clavicular function of the coracoid, as well as to the raptorial habit of the organism.
In no living Reptile is there a scapula to be compared with that of the Pterodactyle, for besides the free end being expanded, in the crocodile, it is also thin and squamous and the bone makes a continuous curve with the coracoid as in struthious birds, and not a sharp angle as in Pterodactyles. The "spine" in crocodiles is on the anterior border of the bone and directed upward and backward, while in Pterodactyles it is on the posterior border and directed upward and forward. In the Chameleon the scapula is more elongated and narrow, narrower in proportion to its length than in Pterodactyle, but becomes rapidly wide at its union with the coracoid. It is curved in length so as to fit on to convex ribs. A scapula presenting some resemblance to Pterodactyle is found in certain Liassic Ichthyosaurs.
Among mammals a straight elongated narrow scapula is rare. The mole however has a scapula of this kind somewhat cylindrical in its proximal half and not much expanded at the free end, on which there is a small spine. The anterior emargination above the glenoid cavity in Pterodactyle is entirely mammalian, as is the anterior tuberosity above the emargination, for it entirely corresponds with what in ruminants, pachyderms and many mammals would be named the coracoid process. If that process is accurately determined it is difficult to say what this is.
In birds there is often a prolonged process on the inner side of the coracoid, which however extends interior to other parts of the scapula, and to this the furculum is attached. Such traces of a spine as are to be detected in the swan conform to the Pterodactyle.
No bird has the scapula cylindrical, even struthious birds only making an approximation to such a condition; and no birds have the scapula so straight. The bone is more avian and mammalianthan reptilian; and more avian than mammalian but with strong distinctive characters of its own.
17 specimens of the humeral ends of scapulæ are exhibited. Nos. 1, 4, 6, 7, 8, 9, 11, 13, 14, 15, 17 are left scapulæ. Nos. 2, 3, 5, 10, 12, 16 are right scapulæ.
The tablet of the distal ends of scapulæ comprises 6 specimens.
Case.Comp.Tablet.Specimen.Ja61—4671— 381
Fore-Limb.HUMERUS.Pl. 4.
There are among the fossils of the Cambridge Greensand at least two well-markedtypesof Pterodactyle humerus, readily recognised by the forms of the proximal and of the distal ends, and by the positions of the pneumatic foramina. In the group having the ulnar ridge developed the pneumatic foramen is on the posterior aspect of the bone[O]under the ulnar ridge, as in birds; but in some of the small Pterodactyles the foramen is on the anterior surface, and on its radial side. This latter kind of humerus has the distal end more or less divided into three convex surfaces, while the radial crest is enormously developed and terminates in a smooth oblong flattened surface nearly as large as the proximal articular surface, and looking anteriorly. The distal articular surfaces are not as in birds parallel to that of the proximal end, though they agree with those of birds in being at right angles to the radial crest; this ridge in Pterodactyles being directed much further outward and backward than in birds.
[O]Professor Owen states (p. 16, 3d Supt.) that the foramen is palmar. Fig. 15. T.III.2d Supt. shows it to be anconal.
[O]Professor Owen states (p. 16, 3d Supt.) that the foramen is palmar. Fig. 15. T.III.2d Supt. shows it to be anconal.
The largest forms of Pterodactyle all have the distal articular surface flatter, and the proximal articulation less bent back so as to look more upwards. No specimen of this kind of humerus has occurred with the radial crest preserved; but it is apparently carried farther down the shaft and not so far forward as in the other group. This latter kind of bone is shown by Prof. Owen in T.III.figs. 1, 2, 3rd Sup. Cret. Reptiles; the former kind has been illustrated in figure 5 of the same plate.
Some of the most gigantic Pterodactyles appear to have hadthe limb-bones as solid as those of crocodiles, and unpermeated by air; and there is no evidence that the high Avian characteristics of most of these Greensand fossils also pertained to all the previously known types from the lower secondary rocks.
The osteological series comprises 46 specimens. No. 30 is a nearly perfect right humerus. Nos. 1, 2, 5, 6, 7, 8, 9, 11, 18, 22, 23, 25, 39 are examples of the proximal ends of left humeri. Nos. 3, 4, 10, 12, 13, 14, 15, 16, 17, 19, 24, 26, 27, 28, 38, 40, 41 are examples of the proximal ends of right humeri. Nos. 20, 21, 32, 33, 34, 35, 37, 42, 44, 45, are examples of the distal ends of left humeri. Nos. 29, 31, 36, 43 and 46 are distal ends of right humeri.
No. 30 shows the entire length of the humerus to be 21/2inches. It has a nearly circular shaft with a diameter of a little more than a quarter of an inch, being more slender than the corresponding bone of Pt. suevicus, which has the same length. Theproximalarticular surface is crescentic, the anterior concavity corresponding with the concave anterior aspect of the proximal end, while the convex border corresponds to the convex posterior side of the bone, which it overhangs: it is worn, but appears to measure half an inch from the radial to the ulnar side. The ulnar ridge (which is worn) has not extended more than a quarter of an inch beyond the articular surface. The thin bird-like radial crest, arising rather more distally than the ulnar ridge, is flat on its posterior surface, and extends anteriorly for a distance nearly half as far again as the length of the proximal articular surface of the humerus. On the proximal third of the posterior face are two contiguous long narrow oblique muscular insertions. The proximal ends Nos. 22, 23, 24, 25 are examples of this kind of bone, having the pneumatic foramen radially situated on the anterior aspect near to the articular surface, as may be seen in No. 24. No. 25 shows the termination of the radial crest in an oblique oblong smooth surface, slightly convex in length and breadth, directed distally towards the ulnar side.
No. 6, 7, 13, 27, are examples of another kind of proximal end, where the pneumatic foramen is an oval hole on the ulnar side of the posterior surface. The radial crest arises more distally, and the ulnar ridge more proximally, than in the small species, like No. 30.
Nos. 4, 11, 14, 16 are examples of other species with the foramen placed as in the last group, only less near to the proximal end, while it enters obliquely, being directed distally from the broad concave area proximal to it. The largest proximal ends known, such as No. 2, which though very imperfect measures 23/4inches over what remains of the articular surface, appear to conform to this latter type.
Distallythe humerus No. 30 enlarges, widening rapidly on the radial side, which is bordered near the distal end by a sharp ridge showing a muscular attachment, while the ulnar side is rounded and rather inflated. The articular surface looks downward and in the direction of the radial process. There is a mesial concavity on the radial side which is bordered on the right and on the left by a prominent rounded condyle, and behind by a condyloid convexity. On that side which in conformity with the nomenclature applied to birds' bones, has here been named the ulnar side, the ulnar and mesial condyles are impressed with a flattened slightly concave sub-rhomboid area, which looks downward, backward, and towards the ulnar side. These characters are not well seen in No. 30, but may be effectively studied in their specific variations in Nos. 36, 37, 42, 43, 44, 45, and 46.
Nos. 20, 21, 29, 31, 32, 33, 34, 35, are examples of the distal ends of humeri of a different type. They are mostly larger than the preceding group, and correspond in characters with the large proximal ends, but appear to be separable into two groups, namely those with a pneumatic foramen on the anterior radial side near to the articular surface, and those where no pneumatic foramen is seen. Unlike the previously considered type, the ulnar side is sometimes more inflated than the radial side.
The mesial condyle in this group appears in every case to be an epiphysis, which is wanting. The radial condyle becomes a large flattened slightly convex surface looking downwards, which in some of the species, as Nos. 21 and 32 (in other respects remarkable species), shows an approach to a trochlear character on its anterior side. In Nos. 33, 34 and 35 the mesial anterior concavity becomes flattened and abuts at an angle against the flattened radial condyle. No. 20 shows the rhomboid impression on the ulnar side to be more concave and more ovate. The ulnar condyle remains a smaller but prominent tubercle directed distally. Nos. 21, 22 and 34 show aridge developed on the ulnar side of the shaft like that on the radial side in the other group, while the radial ridge is not so near to the articular surface. The largest and smallest distal ends of humeri known, both show the characters here enumerated. The great distal end of a left humerus, figured by Prof. Owen, Pl.IV.f. 1, 2, 3 of the 1st Supplement to the Cretaceous Pterosauria, is of this kind, and though imperfect measures more than three inches over what remains of the articular surface. In the small humerus, No. 30, the width over the distal articular surface is5/8ths of an inch. If it is assumed that the large bone was no more than 5 times the length of the small one, the entire length of the humerus would have been about twelve inches. The smallest humerus, No. 29, measures over the shaft rather more than one eighth of an inch.
The Ornithosaurian humerus has but little in common with that of any mammal. Most mammals have the proximal head of the bone hemispherical, and a pit at the distal end for the olecranon process of the ulna, while there is usually little indication of a radial crest, and the proximal and distal ends are in the same plane. In the Bat however the bone is twisted a little so that the slight radial crest looks in the same direction as the distal end, here also there is no pit for the olecranon; but the bone is sigmoid and proportionally much longer than in Pterodactyles. In the horse, hippopotamus, &c., the radial process becomes more developed but never resembles that of a Pterodactyle.
Among reptiles, the bone may be compared with lizards and crocodiles. In crocodiles the proximal and distal ends are nearly in the same plane, the distal end has two condyles, the head is convex from side to side, and the radial crest is moderately developed and never extends so far outward or so far proximally as in Pterodactyle. In the Chameleon the bone is more twisted than in Crocodile, and as in Pterodactyle the distal end is compressed on the radial side to a sharp margin. In Iguana, Scink, and Monitor both proximal and distal ends are much expanded, and the radial process makes no approximation to that of a Pterodactyle.
The bird humerus does not approximate more closely in form to that of the Pterodactyle than does the Chameleon humerus, though it has the cardinal distinction of pneumatic foramina, and these sometimes corresponding in position in the two groups.
The bird humerus is commonly longer, though in the parrots the proportions and straightness are not unlike Pterodactyle. In some respects a nearer resemblance is seen in the raptorial birdGypogeranus serpentarius, in which the radial process is rather more developed than in the Crocodile, and extends further proximally though still much smaller than in Pterodactyle; here too the superior surface is concave from side to side, and the distal articulation is not unlike that of some Pterodactyles. But no Pterodactyle has the head of the humerus convex from the radial to the ulnar sides, and the bird is distinctive in having the ulnar crest developed on the inferior side of the head: a faint approximation to a similar development is seen in Crocodile, but there is no trace of such a process in Pterodactyle. The distal end is more Bird-like than Lacertian in form, but is twisted to a greater angle with the proximal end than in birds.
Altogether the bone is distinctive. The points in which it is unlike birds and reptiles are those in which Birds and Lizards resemble each other; it would not be easy to say that in form it resembles one group more than the other. But it is linked with birds by the pneumatic foramina.
Case.Comp.Tablet.Specimen.Ja95— 6101—10111— 7121— 4135— 6
RADIUS AND ULNA.
Of neither of these bones has a perfect specimen been found. While fragments of humeri are met with frequently, fragments of these bones are rare. In accordance with the analogy with birds the Ulna might be presumed to be the larger bone of the two. But from a study of German specimens the larger bone is found to be the Radius, which according to the mammalian plan is placed in front of the ulna. As a whole, the fore-arm of Ornithosaurians is only to be compared with the insectivorous mammalChrysochloris Capensis, in which there are also three bones in the fore-arm,—the third bone like thePteroid bonein Ornithosaurians, extending about half-way from the carpus to the humerus, and holding, relatively, a similar position and development to the fibula in bats.
The pteroid bone articulated with a separate carpal, and was placed on the side of the arm, adjacent to the radius, which at the distal end extended in German specimens more inward than the ulna. In Chrysochloris the third bone appears to be behind the other bones, and adjacent to the ulna[P].
[P]See D'Alton and PanderChiropteren und Insectivoren, Bonn, 1831, pl. 5, Chrysochloris.
[P]See D'Alton and PanderChiropteren und Insectivoren, Bonn, 1831, pl. 5, Chrysochloris.
Among neither birds nor reptiles is any comparable modification of the fore-arm to be found. Then by examining the proximal surface of the proximal carpal, the characters of the distal end of the Radius are readily discovered. The proximal carpal shows on the same surface another articular facets with which however only one fragmentary distal end of a bone corresponds. That accordingly is identified as the ulna. Besides these, three other articular ends of bones occur, one of which fits on to the distal end of the femur. The remaining two are both large bones, with epiphyses which formed portions of the articular surfaces, and are usually wanting. One of these bones corresponds in form with the ulna of a bird, and would fit the facet on the ulnar side of the distal end of the Pterodactyle humerus. The other bone is massive with a sub-quadrate articular end, and might well be the proximal end of the radius. Some specimens are among the largest fragments of Pterodactyle bone known. The only other bone that either of these could be is the distal end of the tibia, a bone not yet known, but probably not unlike that of a bird.
I. Distal End of Ulna.
Four specimens which show articular ends such as the ulna should have, are mounted together. They are compressed bones with the section of the fracture elongately oval; and the shaft widens from the fracture to the articulation without increasing in thickness. The outer surface is gently convex, becoming concave mesially near the articulation; the inner surface has the same characters, only the concavity at the extreme distal end reaches from side to side of the bone. The two short sides both look outward as well as laterally; one of them flattened so as to thicken the bone, is concave in vertical outline owing to the extreme distal end turning suddenly outward; the other side a little convex, compresses the bone and inflects its inner margin. The longestspecimen measures 15/8inch;5/8inch wide at the fracture, and 11/8inch wide at the distal end. The greatest thickness at the distal end is half an inch, the thickness of the fractured shaft is5/8of an inch.
The articular surface appears to have an elongated sub-reniform shape, the part at the compressed side of the bone being narrower than the broad ovate part on the thick side of the bone, to the lateral limit of which it extends, while the narrow part does not extend laterally nearly so far as the inflected border, which appears to give attachment to powerful muscles. There is also a strong muscular attachment at the corresponding diagonal corner of the bone where the outer surface on its right meets the side of the bone in an elevated ridge.
In its long diameter the articulation is a little convex; transversely it is very convex in the ovate part, but more flattened in its narrower continuation. Where widest it measures about4/10ths of an inch.
Nos. 5 and 6 on another tablet appear to be distal ends of ulna of another kind of Pterodactyle. They are less compressed, more quadrate in section, and have the sides more nearly parallel The flattened side similarly has a concave border, but instead of having its distal termination developed laterally, has it thickened behind. The opposite side of the bone which in the other specimens was compressed is here thick and well rounded, and not at all inflected. There is an absence of the concavity noticed on the outer surface of the bone in the compressed specimens. The articular surface is much flatter, and a little concave in length instead of being convex; as in the other examples it looks downward. The largest fragment. No. 5, measures 13/8inch long; it is6/8inch wide at the fracture, and4/8inch thick. The sub-quadrate distal end is more than an inch long, more than4/8ths inch thick on the thick side, and nearly4/8ths inch thick on the compressed side.
II. Distal End of Radius.
The best preserved of the 10 specimens here exhibited is 3 inches long, No. 2. The shaft is oval, flattened on one side; measuring at an inch from the fractured end7/10ths of an inch in the least diameter, and one inch in the wide diameter. It widensdistally at first slowly, then rapidly, till at the articular end its greatest width is two inches. But while expanding laterally it contracts from side to side, the more convex side of the two at about an inch from the articular end, beginning to approximate to the flatter side till the articular end has a short diameter of less than half an inch.
On the left-hand corner of the convex inner side of the bone is an elevated flattened disc for muscular attachments, fully half an inch in diameter, there is a slight muscular attachment interior to this, nearer the middle of the bone. The left-hand corner of the flattened outer side of the distal end of the radius is marked by a vertical ridge bordering a similarly elevated oval muscular attachment. Parallel to this nearer the middle of the side is a much stronger and acutely elevated ridge.
The articulation is made up of three distinct parts, all in a straight line. The portion of bone adjacent to the large muscular disc is compressed and rounded on the distal end; then first there is a rather deep circular cup3/8ths of an inch wide, nearer to the more convex than to the flatter side of the bone; adjacent to this cup is a convex ball of about the same size; while the remainder of the articulation is concave in length, convex from side to side, and looks downward and a little towards the inner convex side of the bone. The specimens are arranged so as to display these characters.—The example described is of nearly the same size as that figured for the humerus in fig. 1, T.XXIV.of the Cretaceous Reptilia. The less well preserved bone in that figure exhibits the Ulna in its true position behind the Radius.
III. Proximal End of Ulna.
This bone has much the proportions of the Ulna in birds, the smaller specimens nearly resembling the ulna of the Heron. The specimen (No. 1) with the shaft best preserved is 21/4inches long, cylindrical at the fracture, where it measures in diameter3/16ths of an inch. It gradually enlarges proximally widening to about7/10ths of an inch; near the proximal end it is a little curved, the side which is concave in length being a little flattened, while there is a lateral elevation on the opposite side, apparently corresponding to the quill-ridge on the convex side of the bird-ulna. There is a separate ossification for the olecranon, which is an irregular sub-oblongbone forming the outer part of the articulation; it is only preserved in No. 1. Nos. 4, 5 and 6 show the concave transverse groove from which it has come away.
The articular surface looks upward and forward, in which aspect it has a trapezoidal form. Sometimes, as in No. 2, the great sigmoid area is divided into two parts by a vertical ridge, the more elevated part of the articulation on the radial side of the bone being concave, while the outer part, as in the heron, besides being concave, has its border on the concave side of the bone produced and rounded. There is a small triangular elevation on the radial aspect of the proximal end like that on the corresponding part of the ulna of the heron. On this aspect the bone is flattened, on the opposite and outward aspect it is compressed and produced as in the bird. No. 2 measures 11/8inch over the articular end. The series includes 6 specimens.
IV. Proximal End of Radius.
This bone terminated in an epiphysis which formed part of the articular surface, and has disappeared from all the 7 specimens mounted. So much of the articulation as remains does not oppose the idea of its having been attached to the humerus, while the large size of the example No. 7, which could not have measured less than 21/2inches from side to side over the articulation, is more in accordance with what is at present known of the dimensions attained by the distal end of the humerus than with the size that would be expected in the distal end of the tibia, which is the only other unknown bone to which these specimens could be referred.
The longest specimen, No. 3, is 3 inches long; broadly ovate at the fracture, measuring in the long diameter 1 inch, and in the short diameter more than3/4ths of an inch. Nearer the articular end the bone becomes in section sub-quadrate or rather sub-rhomboid. No. 1 shows these terminal characters extremely well. On the posterior aspect of the specimen the surface is divided into two flattened slightly convex parts by a median vertical well-rounded angular bend. In front the side is similarly divided into two parts, both of them a little concave proximally, by a sharp median vertical ridge, which does not reach to the articulation by a varying distance, never so long as the bone is wide. The ridgeterminates in, and is pierced by, a vertical groove apparently for a nutritive vessel. Where the anterior and posterior aspects of the bone converge laterally the sides are well rounded.
Only a small part of the articular surface is preserved, looking upward and a little forward; it terminates the wider of the halves of the bone laterally and in front. The remainder of the articular surface, from which the epiphysis has come away, may be divided principally in the majority of specimens into a posterior flattened median rhomboid space and an oblong cup-shaped anterior space divided from it by an elevated ridge. The extreme lateral termination appears to have been a ball-shaped convexity.
The great length of the fore-arm relatively to the humerus, characteristic of German Ornithosaurians, from the fragmentary condition of Cambridge specimens is not seen.
Although the fore-arm resembles Chrysochloris inplanthe resemblance is not close in the details of form. In many Mammals it is characteristic for the radius to be the principal bone of the fore-arm, and among Ruminants in which this is especially the case the radius is altogether in front and the ulna behind as is the position with Birds and Crocodiles. And among mammals with claws, as in the Lion, Bear, &c., and in the Chameleon, it is characteristic, for the radius also to be on the inside of the limb at the distal end, as in Ornithosaurians. In form, ridges, and muscular attachments (see pl. 3) the distal end of the radius approximates closely to the Bear and the Lion, and may also be compared with the Bats and Birds, though with Birds it is a small bone. From the epiphysis of the proximal end apparently being wanting it would be difficult to compare closely. But though not like any particular mammal, it might have pertained to a mammal since it has the large perforation for the nutritive vessel near to the proximal end as in the Camel and many of the mammalia.
The ulna of the Pterodactyles is at the proximal end altogether distinguished from mammals by the slight development of the olecranon, nor can the distal end, especially in its relation to the carpus, be paralleled.
Among birds and reptiles the ulna is the large bone, and here a general resemblance in form to the ulna of Pterodactyles is seen at the proximal end. It is not compressed from side to side as in the Crocodile, Iguana, Monitor, &c., but from back to fronts in thisrather resembling Birds than the Chameleon. It however at the distal end is more crocodilian.
The fore-arm in plan is mammalian. The Pteroid bone is mammalian, the Radius is mammalian and avian; the Ulna is avian, and crocodilian in form, but mammalian in proportion. The pneumatic foramen of the ulna is peculiarly avian.
Case.Comp.Tablet.Specimen.Jb11—1321—1831— 441— 8
CARPUS.Pl. 5.
The pterodactyle wrist is made up of three bones, arranged as a proximal carpal, a distal carpal, and a lateral carpal. Two of them are figured by Professor Owen, who regarded the distal carpal of this description as the scapho-cuneiform; while A very imperfect example of the proximal carpal is named the unciform: neither of these determinations, the reverse of those which follow, were given as more than probable guesses.
I. Proximal Carpal.
No. 10 shows the proximal surface well; portions of it are seen in Nos. 4, 5, 6, 8, 9, 11, and 12. The distal surface is best exhibited in No. 1; portions of it are shown in Nos. 2, 3, 5, 7, 8. No. 13 is an impression taken from the proximal surface of a distal carpal to show its correspondence with distal surface of the proximal carpal. The bone is proximally of an irregular oblong form, being five sided, and much broader towards the inner end than towards the outer end. The two ends are sub-parallel, and rather obliquely connected on one side by a nearly straight border more than twice as long as the shorter end. The other limits of the sub-parallel ends are connected by two concave borders meeting in a well rounded convexity, which is near to the broader inner end.
The proximal surface of the bone is flattened, and may be divided into a sub-rhomboid space, adjacent to the shorter of the sub-parallel ends, which is moderately concave in the long axis of the bone and slightly convex transversely, and an oblong space adjacent to the longer of the two ends. This is separated from the sub-rhomboidspace, toward the straight side of the bone, by an elevated ridge sub-parallel with the ends. It is directed towards the convexity on the opposite side, in which the long and short concave parts meet, but after half crossing the bone it becomes forked in a U shape, and less elevated; the smooth unarticular included space shows an oval pneumatic foramen, which varies in size with the different species. The region between this Y-shaped ridge and the longer of the two ends, is sub-reniform, slightly concave in its long diameter, and deeply concave in the short diameter, exactly corresponding in form with the articular surface already described as the distal end of the ulna. Also parallel with the long end of the bone are marks of an articular surface exactly corresponding with those described as the distal end of the radius; that is, at the convex angle of the angulated side is placed a hemispherical boss,' interior to which is a hemispherical concavity, and extending toward the straight side is the oblique smooth border of the sub-rhomboid area described. There still remains a space to be accounted for. This consists of a sub-quadrate area forming the corner of the bone made by the concave side and the shorter outer end; it is made up of an inner concave part separated from the radial articulation by a ridge, and an outer convex part constituting the shorter end of the bone.
This carpal is moderately compressed from the proximal to the distal side, except towards the shorter end of the bone, being there prolonged distally into a wedge-shaped process, showing at its termination marks of a powerful muscular attachment.
The outer lateral surface is of variable antero-posterior extent.
The distal articular surface is placed entirely toward the narrow end of the bone, leaving at the proximal end a large smooth rhomboid unarticular area, of which every side is a little concave: it connects obliquely the proximal with the distal articular surfaces. The distal articular area is divided by a diagonal ridge into a long oblong area of which the inner and outer sides are sub-parallel and the ends rounded: it is slightly concave in length as well as transversely, and is slightly twisted like the flukes of a screw. Adjacent to this region laterally is the other and sub-triangular part of the articulation. The broad end of the triangle is toward the broad end of the bone; it is concave in length and flattened transversely. The two parts of the articulationare inclined to each other at a large angle, both looking downward and outward, but on opposite sides of the bone.
II. Distal Carpal.
The tablets of this bone comprise 22 specimens. Nos. 2, 3, 4, 5, 6, 8, 9, 10, 15, 16, 19 and 22 are so mounted as to exhibit the proximal surface. Nos. 7, 11, 12, 13, 14, 15, 16, 20 and 21 show the distal surface of the bone. No. 17 is a cast from the distal surface of a proximal carpal for comparison with the proximal surface of the distal carpal. No. 16 is a cast from the proximal end of the wing-metacarpal for comparison with the distal surface of the distal carpal. No. 20 is a distal carpal of unusual type, 19 is a cast from its proximal surface, and 21 is a cast from the distal surface of the same specimen.
The proximal aspect of this bone is rather narrower than the distal aspect; each is sub-triangular in outline, the sides being convexly curved. In the long axis from the apex on the inside to the short outer[Q]side the bone is convex proximally with an oblique transverse depression; in the short axis, that is, between the two longer sides, the middle of the bone is hollow, but the oblique transverse depression makes both sides of the hollow convex,—so that excepting the smooth unarticular triangular area adjacent to the apex, the sub-quadrate articular surface is shaped somewhat like two cones put side by side in such manner that the apex of each touches the base of the other: the apex of that cone which should touch the short side or base of the triangle formed by the bone, is truncated by a depression which exhibits an oval pneumatic foramen. Towards the apex, on the same side as the pneumatic foramen, the margin of the bone is rounded for a small terminal oval articulation which looks outward and upward.