The flying Reptiles, which belong
to this group, and are commonly known as Pterodactyls, are,
and long have been, extinct, their remains occurring only in
Mesozoic rooks, from the Lias to the Chalk inclusively.
They are all remarkable for their proportionally long heads
and necks, and for the great size of the anterior limb, the
ulnar finger of which, enormously elongated and devoid of a
claw, appears to have supported the outer edge of an expansion
of the integument, like the patagium of a Bat (Fig. 79).
The vertebral column is distinctly divided into cervical,
dorsal, sacral, and caudal regions, the cervical vertebrae being,
as in Birds, the stoutest of all. The atlas and axis are anchylosed
together, at least in the eretaceous species. The other
cervical vertebrae, apparently not more than six or seven in
number, have low, or obsolete, spinous processes; and, like
the vertebrae of the rest of the spine, are procoelous, and
have the neuro-central suture obliterated. The existence of
cervical ribs is doubtful. From fourteen to sixteen vertebrae
intervene between the cervical and the sacral regions; and
not more than one or two of the hindermost of them, if any
are devoid of ribs. The number of vertebrae auchylosed
together to form the sacrum, is not fewer than three, nor more
The tail is very short in Pterodactylus
, and, in this genus,
all the vertebrae are movable upon one another; but in Rhamphorhynchus
it is extremely long, and the vertebrae are
immovably fixed by what appear to be ossified ligamentous
The vertebral ribs are slender, and the anterior ones, at
any rate, have distinct capitula and tubercula. There are ossified sternal ribs, and splint-like abdominal ribs.
The sternum is broad, and, unlike that of other Reptilia
, is very
completely ossified, and bears a strong median crest on the
anterior part of its ventral surface. No median posterior prolongation
has been observed in connection with it.
The brain-case is more rounded and bird-like than in the
, and, in many other respects, the skull approaches
that of birds. Thus, the occipital condyle is on the
base of the skull, not on its posterior face; the cranial bones
anchylosed very early; the orbits are very large, and the external
nares are situated close to them. The premaxillae are
very large, the maxillae slender, and the dentary pieces of the
mandible are fused together into one bony mass, without any
trace of a symphysial suture.
The resemblance to birds is still further increased, in some
species, by the presence of wide lachrymo-nasal fossae between
the orbits and the nasal cavities, and by the prolongation of
the extremities of the premaxillae and of the symphysial part
of the mandible into sharp, beak-like processes, which appear
to have been covered with horny sheaths. But the reptilian
type is kept up by the presence of a distinct post-frontal, which
unites with the squamosal and thus gives rise to a supratemporal
fossa. The post-frontal and the jugal unite behind
the orbit, in Lacertilan fashion; and both the upper and the
lower jaws contain teeth. The sclerotic is supported by a ring
of bones, as in many other Sauropsida
The scapula and the coracoid are wholly unlike these
structures in any other Sauropsida,
but are extremely similar
to the same parts in birds, and indeed to the shoulder-girdle
of the less reptilian Carinatae
. The scapula is slender and
blade-like, and its long axis is inclined, at less than a right
angle, to that of the coracoid. The glenoidal surface is cylindroidal,
concave from above downward, convex from side to
side. The coracoid, elongated and comparatively narrow, is
devoid of fontanelle, epicoracoid, or procoracoid.
|Fig. 79. - The nearly entire skeleton of Pterodactylus spectabilis (Von Meyer), as shown
by the two halves of a split block of lithographic slate, a, the left pre-pubic bone
on the right side this bone is not shown, and the ilium is exposed.
No trace of any clavicle has been discovered.
The humerus has a great deltoid ridge or process. The
radius and ulna are equal in size and separate. There are
four distinct metacarpal bones, that on the ulnar side being
very much stronger, though not longer, than the others. Another
styliform bone attached to the carpus does not appear
to have belonged to the metacarpal series. The radial metacarpal
bears two phalanges; the second, three; the third, four,
so that these represent the pollex and the succeeding digits
of the Lizard's manus. The terminal phalanx of each of these
digits is strong and curved, and was doubtless ensheathed in
a horny claw. The fourth, like the corresponding digit in the
Crocodile, has four phalanges, the last of which is straight and
bears no nail. But these phalanges are enormously elongated
and of great relative strength. A strong process projects from
the dorsal side of the proximal end of the first phalanx, and
doubtless gave attachment to the tendon of a correspondingly
powerful extensor muscle. The articular surface below and
behind it is concave, and plays over the convex distal pulley
of the fourth metacarpal.
The pelvis is remarkably small. The ilia are elongated
bones, produced both anteriorly and posteriorly, as in Birds;
but the rest of the pelvis is not at all ornithic. The flat and
broad ischia appear to be united with the pubes into wide
bony plates, which pass, at right angles with the ilia, to their
median ventral symphysis. A large spatulate bone articulates
with each pubis near the symphysis, and seems to be an exaggeration
of the pre-pubic process of Lacertilia
Or it may be (though I do not think this very probable) that
the broad flat plates correspond almost altogether to the ischia,
and that the spatulate ossifications are the pubes; in which
case the structure of the pelvis would be a sort of extreme exaggeration
of that observed in the Crocodilia.
The hind-limb is small compared with the fore-limb. The
fibula is imperfect, and appears to coalesce with the tibia at
its distal end. The structure of the tarsus requires further
elucidation. In some Pterosauria
there seem to be only four
digits, with, perhaps, a rudiment of a fifth, in the pes; but
others, such as Rhamphorhynchus Gemmingi
, have five digits
in the foot. Where there are only four, each digit is terminated
by a curved and pointed ungual phalanx, and the number
of the phalanges from the tibial to the fibular side is 2, 3,
4, 5. These digits, therefore, are the hallux, and the three which
immediately follow it; and the rudimentary digit is the
The long bones of the Pterosauria
have thin walls, enclosing
a large cavity, which appears to have contained air, as in
many birds; and pneumatic foramina are visible on the sides
of the vertebrae.
The remains of more than twenty species of Pterosauria
have been discovered. Some of them are exquisitely preserved
in the fine matrix of the lithographic stone of Solenhofen.
They are thus grouped into genera:
- With two joints in the ulnar digit of the manus.
- With four joints in the ulnar digit.
- The jaws strong, pointed, and toothed to their anterior extremities.
The tail very short. The metacarpus usually
longer than half the length of the antebrachium.
- The extremities of the jaws produced into toothless beaks,
probably ensheathed in horn. The tail very long. The metacarpus
shorter than half the length of the antebrachium.
- All the mandibular teeth similar.
- The posterior teeth for the most part very short. The anterior long.
I am much inclined to suspect that the fossil upon which
the genus Ornithopterus
has been founded, appertains to a true