Part 10 (2/2)

The Pterodactylia are less variable; and the variation among the species is chiefly confined to relative length of the head, length of the neck, and the height of the body above the ground. The tail is always so short as to be inappreciable. Many of the specimens are fragmentary, and the characters of the group are not easily determined without careful comparisons and measurements. The bones of the fore limb and wing finger are less stout than in the Rhamphorhynchus type, while the femur is generally a little longer than the humerus, and the wing finger is short in comparison with its condition in Rhamphorhynchus. These short-tailed Pterodactyles give the impression of being active little animals, having very much the aspect of birds, upon four legs or two.

The neck is about as long as the lower jaw, the antorbital vacuity in the head is imperfectly separated from the much larger nasal opening, the orbit of the eye is large and far back, the teeth are entirely in front of the nasal aperture, and the post-orbital vacuity is minute and inconspicuous. The sternum is much wider than long, and no specimens give evidence of a manubrium. The finger bones progressively decrease in length. The prepubic bones have a partially expanded fan-like form, and never show the triradiate shape, and are never anchylosed. About fifteen different kinds of Pterodactyles have been described from the Solenhofen Slate, mostly referred to the genus Pterodactylus, which comprises forms with a large head and long snout. Some have been placed in a genus (Ornithocephalus, or Ptenodracon) in which the head is relatively short.

The majority of the species are relatively small. The skull in _Ornithocephalus brevirostris_ is only 1 inch long, and the animal could not have stood more than 1-1/2 inches to its back standing on all fours, and but little over 2-1/2 inches standing as a biped, on the hind limbs.

A restoration of the species called _Pterodactylus scolopaciceps_, published in 1875 in the _Ill.u.s.trated London News_ in the position of a quadruped, shows an animal a little larger, with a body 2-1/2 inches high and 6 to 7 inches long, with the wing finger 4-1/2 inches long.

Larger animals occur in the same deposit, and in one named _Pterodactylus grandis_ the leg bones are a foot long; and such an animal may have been nearly a foot in height to its back, standing as a quadruped, though most of these animals had the neck flexible and capable of being raised like the neck of a Goose or a Deer (p. 30), and bent down like a Duck's when feeding.

[Ill.u.s.tration: FIG. 59. RESTORATION OF THE SKELETON OF _PTENODRACON BREVIROSTRIS_

From the Solenhofen Slate. The fourth joint of the wing finger appears to be lost and has not been restored in the figure. (Natural size)]

The type of the genus Pterodactylus is the form originally described by Cuvier as_ Pterodactylus longirostris_ (p. 28). It is also known as _P.

antiquus_, that name having been given by a German naturalist after Cuvier had invented the genus, and before he had named the species.

There are some remarkable features in which Cuvier's animal is distinct from others which have been referred to the same genus. Thus the head is 4-1/2 inches long, while the entire length of the backbone to the extremity of the tail is only 6-1/2 inches, and one vertebra in the neck is at least as long as six in the back, so that the animal has the greater part of its length in the head and neck, although the neck includes so few vertebrae. Nearly all the teeth--which are few in number, short and broad, not exceeding a dozen in either jaw--are limited to the front part of the beak, and do not extend anywhere near the nasal vacuity. This is not the case with all.

In the species named _P. Kochi_, which I have regarded as the type of a distinct genus, there are large teeth in the front of the jaw corresponding to those of Pterodactylus, and behind these a smaller series of teeth extending back under the nostril, which approaches close to the orbit of the eye, without any indication of a separate antorbital vacuity. On those characters the genus Diopecephalus was defined. It is closely allied to Pterodactylus; both agree in having the ilium prolonged forward more than twice as far as it is carried backward, the anterior process covering about half a dozen vertebrae, as in _Pterodactylus longirostris_. A great many different types have been referred to _Pterodactylus Kochi_, and it is probable that they may eventually be distinguished from each other. The species in which the upper borders of the orbits approximate could be separated from those in which the frontal inters.p.a.ce is wider.

[Ill.u.s.tration: FIG. 60. CYCNORHAMPHUS SUEVICUS FROM THE SOLENHOFEN SLATE SHOWING THE SCATTERED POSITION OF THE BONES

_Original in the Museum at Tubingen_]

[Ill.u.s.tration: FIG. 61. CYCNORHAMPHUS SUEVICUS RESTORATION SHOWING THE FORM OF THE BODY AND THE WING MEMBRANES]

It is a remarkable feature in these animals that the middle bones of the foot, termed instep bones or metatarsals, are usually close together, so that the toes diverge from a narrow breadth, as in _P. longirostris_, _P. Kochi_, and other forms; but there also appear to be splay-footed groups of Pterodactyles like the species which have been named _P.

elegans_ and _P. micronyx_, in which the metatarsus widens out so that the bones of the toes do not diverge, and that condition characterises the Ptenodracon (_Pterodactylus brevirostris_), to which genus these species may possibly be referred. Nearly all who have studied these animals regard the singularly short-nosed species _P. brevirostris_ as forming a separate genus. For that genus Sommerring's descriptive name Ornithocephalus, which he used for Pterodactyles generally, might perhaps have been retained. But the name Ptenodracon, suggested by Mr.

Lydekker, has been used for these types.

[Ill.u.s.tration: FIG. 62. _CYCNORHAMPHUS SUEVICUS_

Skeleton restored from the bones in Fig. 60]

[Ill.u.s.tration: FIG. 63. RESTORATION OF SKELETON CYCNORHAMPHUS FRAASI SHOWING THE LIMBS ON THE RIGHT SIDE

_From a specimen in the Museum at Stuttgart_]

[Ill.u.s.tration: FIG. 64. CYCNORHAMPHUS FRAASI RESTORATION OF THE FORM OF THE BODY]

Some of the largest specimens preserved at Stuttgart and Tubingen have been named _Pterodactylus suevicus_ and _P. Fraasii_. They do not approach the species _P. grandis_ in size, so far as can be judged from the fragmentary remains figured by Von Meyer; for what appears to be the third phalange of the wing finger is 7-1/2 inches long, while in these species it is less than half that length, indicating an enormous development of wing, relatively to the length of the hind limb, which would probably refer the species to another genus. _Pterodactylus suevicus_ differs from the typical Pterodactyles in having a rounded, flattened under surface to the lower jaw, instead of the common condition of a sharp keel in the region of the symphysis. The beak also seems flattened and swan-like, and the teeth are limited to the front of the jaw. There appear to be some indications of small nostrils, which look upward like the nostrils of Rhamphorhynchus, but this may be a deceptive appearance, and the nostrils are large lateral vacuities, which are in the position of antorbital vacuities, so that there would appear to be only two vacuities in the side of the head in these animals. The distinctive character of the skeleton in this genus is found in the extraordinary length of the metacarpus and in the complete ossification of the smaller metacarpal bones throughout their length.

The metacarpal bones are much longer than the bones of the fore-arm, and about twice the length of the humerus. The first wing phalange is much longer than the others, which successively and rapidly diminish in length, so that the third is half the length of the first. There are differences in the pelvis; for the anterior process of the ilium is very short, in comparison with its length in the genus Pterodactylus. And the long stalk of the prepubic bone with its great hammer-headed expansion transversely in front gives those bones a character unlike other genera, so that Cycnorhamphus ranks as a good genus, easily distinguished from Cuvier's type, in which the four bones of the wing are more equal in length, and the last is more than half the length of the first; while the metacarpus in that genus is only a little longer than the humerus, and much shorter than the ulna. The _Pterodactylus suevicus_ has the neck vertebrae flat on the under side, and relatively short as compared with the more slender and narrower vertebrae of _P. Fraasii_.

CHAPTER XV

ORNITHOSAURS FROM THE UPPER SECONDARY ROCKS

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