ORNITHOSAURS FROM THE UPPER SECONDARY ROCKS
When staying at Swanage, in Dorsetshire, many years ago, I had the rare
good fortune to obtain from the Purbeck Beds the jaw of a Pterodactyle,
which had much in common in plan with the _Cycnorhamphus Fraasii_ from
the Lithographic Slate, which is preserved at Stuttgart. The
tooth-bearing part of this lower jaw is 8 inches long as preserved,
extending back 3 inches beyond the symphysis portion in which the two
sides are blended together. It is different from Professor Fraas's
specimen in having the teeth carried much further back, and in the
animal being nearly twice as large. This fragment of the jaw is little
more than 1 foot long, which is probably less than half its original
length. A vertebra nearly 5 inches long, which is more than twice the
length of the longest neck bones in the Stuttgart fossil, is the only
indication of the vertebral column. Professor Owen described a wing
finger bone from these Purbeck Beds, which is nearly 1 foot long. He
terms it the second of the finger. It may be the third, and on the
hypothesis that the animal had the proportions of the Solenhofen fossil
just referred to, the first wing finger bone of the English Purbeck
Pterodactyle would have exceeded 2 feet in length, and would give a
length for the wing finger of about 5 feet 3 inches. For this animal the
name Doratorhynchus was suggested, but at present I am unable to
distinguish it satisfactorily from Cycnorhamphus, which it resembles in
the forms both of the neck bones and of the jaw. Very small
Pterodactyles are also found in the English Purbeck strata, but the
remains are few, and scattered, like these larger bones.
[Illustration: FIG. 65. THE LONGEST KNOWN NECK VERTEBRA
From the Purbeck Beds of Swanage. (Half natural size)]
ORNITHODESMUS LATIDENS
[Illustration: FIG. 66. CERVICAL VERTEBRA OF ORNITHODESMUS
From the Wealden Beds of the Isle of Wight]
The Wealden strata being shallow, fresh-water deposits might have been
expected to supply better knowledge of Pterodactyles than has hitherto
been available. Jaws of Ornithocheirus sagittirostris have been found
in the beds at Hastings, and in other parts of Sussex. Some fragments
are as large as anything known. The best-preserved remains have come
from the Isle of Wight, and were rewards to the enthusiastic search of
the Rev. W. Fox, of Brixton. In the principal specimen the teeth were
short and wide, the head large and deep with large vacuities, but the
small brain case of that skull is bird-like. The neck bones are 2-1/2
inches long. In the upper part of the back the bones are united together
by anchylosis, so that they form a structure in the back like a sacrum,
which does not give attachment to the scapula, as in some Pterodactyles
from the Chalk, but the bones are simply blended, as in the
frigate-bird, allied to Pelicans and Cormorants. And then after a few
free vertebrae in the lower part of the back, succeeds the long sacrum,
formed in the usual way, of many vertebrae. I described a sacrum of this
type from the Wealden Beds, under the name _Ornithodesmus_, referable to
another species, which in many respects was so like the sacrum of a Bird
that I could not at the time separate it from the bird type. This genus
has a sternum with a strong deep keel, and the articulation for the
coracoid bones placed at the back of the keel in the usual way, but with
a relation to each other seen in no genus hitherto known, for the
articular surfaces are wedge-shaped instead of being ovate; and instead
of being side by side, they obliquely overlap, practically as in wading
birds like the Heron. I have never seen any Pterodactyle teeth so
flattened and shaped like the end of a lancet; and from this character
the form was known between Mr. Fox and his friends as "latidens." The
name Ornithodesmus is as descriptive of the sternum as of the vertebral
column. The wing bones, as far as they are preserved, have the
relatively great strength in the fore limb which is found in many of the
Pterodactyles of the Cretaceous period, and are quite as large as the
largest from the Cambridge Greensand. In the Sussex species named _P.
sagittirostris_ the lower jaw articulation was inches wide.
[Illustration: FIG. 67. STERNUM OF _ORNITHODESMUS_
Showing the overlapping facets for the coracoid bones (shaded) behind
the median keel]
[Illustration: FIG. 68. FRONT OF THE KEEL OF THE STERNUM OF
_ORNITHODESMUS LATIDENS_
Showing also the articulation for the coracoid bone]
A few Pterodactyles' bones have been discovered in the Neocomian sands
of England and Germany, and other larger bones occur in the Gault of
Folkestone and the north of France; but never in such association as to
throw light on the aspect of the skeleton.
ORNITHOCHEIRUS
Within my own memory Pterodactyle remains were equally rare from the
Cambridge Greensand. The late Professor Owen in one of his public
lectures produced the first few fragments received from Cambridge, and
with a knowledge which in its scientific method seemed to border on the
power of creation, produced again the missing parts, so that the bones
told their story, which the work of waves and mineral changes in the
rock had partly obliterated. Subsequently good fortune gave me the
opportunity during ten years to help my University in the acquisition
and arrangement of the finest collection of remains of these animals in
Europe. Out of an area of a few acres, during a year or two, came the
thousand bones of Ornithosaurs, mostly associated sets of remains, each
a part of a separate skeleton, described in my published catalogues, as
well as the best of those at York and in the British Museum and other
collections in London.
The deposit which yields them, named Cambridge Greensand, may or may not
represent a long period of time in its single foot of thickness; but the
abundance of fossils, obtained whenever the workmen were adequately
remunerated for preserving them, would suggest that the Pterodactyles
might have lived like sea-birds or in colonies like the Penguins, if it
were not that the number of examples of each species found is always
small, and the many variations of structure suggested rather that the
individuals represent the life of many lands. The collections of remains
are mostly from villages in the immediate vicinity of Cambridge, such as
Chesterton, Huntingdon Road, Coldham Common, Haslingfield, Barton,
Shillington, Ditton, Granchester, Harston, Barrington, stretching south
to Ashwell in Bedfordshire on the one hand, as well as further north by
Horningsea into the fens. Each appears to be the associated bones of a
single individual. The remains mostly belong to comparatively large
animals. Some were small, though none have been found so diminutive as
the smallest from the Solenhofen Slate. The largest specimens with long
jaws appear to have had the head measuring not more than eighteen inches
in length, which is less than half the size of the great toothless
Pterodactyles from Kansas.
[Illustration: FIG. 69. RESTORATION OF THE SKULL OF ORNITHOCHEIRUS
The parts left white are in the Geological Museum at Cambridge. The
shaded parts have not been found. The two holes are the eye and the
nostril (From the Cambridge Greensand)]
The Cambridge specimens manifestly belong to at least three genera.
Something may be said of the characters of the large animals which are
included in the genus Ornithocheirus. These fossils have many points of
structure in common with the great American toothless forms which are of
similar geological age. The skull is remarkable for having the back of
the head prolonged in a compressed median crest, which rose above the
brain case, and extended upward and over the neck vertebrae, so as to
indicate a muscular power not otherwise shown in the group. For about
three inches behind the brain this wedge of bone rested on the vertebrae,
and probably overlapped the first three neural arches in the neck.
Another feature of some interest is the expansion of the bone which
comes below the eye. In Birds this malar or cheek bone is a slender rod,
but in these Pterodactyles it is a vertical plate, which is blended with
the bone named the quadrate bone, which makes the articulation with the
lower jaw in all oviparous animals.
The beak varies greatly in length and in form, though it is never quite
so pointed as in the American genus, for there is always a little
truncation in front, when teeth are seen projecting forward from a
position somewhat above the palate; the snout is often massive and
sometimes club-shaped. Except for these variations of shape in the
compressed snout, which is characterised by a ridge in the middle of the
palate, and a corresponding groove in the lower jaw, and the teeth,
there is little to distinguish what is known of the skull in its largest
English Greensand fossils from the skull remains which abound in the
Chalk of Kansas.
This English genus Ornithocheirus, represented by a great number of
species, had the neural arch of the neck bones expanded transversely
over the body of the vertebra in a way that characterises many birds
with powerful necks, and is seen in a few Pterodactyles from Solenhofen.
It is difficult to resist the conclusion that the neck vertebrae were
not usually more than twice to three times as long as those of the back,
and it would appear that the caudal vertebrae in the English Cretaceous
types were comparatively large, and about twice as long as the dorsal
vertebrae. Unless there has been a singular succession of accidents in
the association of these vertebrae with the other remains, Ornithocheirus
had a tail of moderate length, formed of a few vertebrae as long as those
of the neck, though more slender, quite unlike the tail in either the
long-tailed or short-tailed groups of Solenhofen Pterodactyles, and
longer than in the toothless Pterodactyles of America.
[Illustration: FIG. 70. CERVICAL VERTEBRA, ORNITHOCHEIRUS
Under side, half natural size. (Cambridge Greensand)]
The singular articulation for the humerus at the truncated extremity of
the coracoid bone is a character of this group, as is the articulation
of the scapulae with the neural arches of the dorsal vertebrae, at right
angles to them (p. 115), instead of running over the ribs as in Birds
and as in other Pterodactyles.
The smaller Pterodactyles have their jaws less compressed from side to
side. The upper arm bone, the humerus, instead of being truncated at its
lower end as in Ornithocheirus, is divided into two or three rounded
articular surfaces. That for the radius, the bone which carries the
wrist, is a distinct and oblique rounded facet, while the ulna has a
rounded and pulley-like articulation on which the hand may rotate. These
differences are probably associated with an absence of the remarkable
mode of union of the scapulae with the dorsal vertebrae. But I have
hesitated to give different names to these smaller genera because no
example of scapula has come under my notice which is not truncated at
the free end. I do not think this European type can be the Nyctodactylus
of Professor Marsh, in which sutures appear to be persistent between the
bodies of the vertebrae and their arches, because no examples have been
found at Cambridge with the neural arches separated, although the
scapula is frequently separated from the coracoid in large animals.
[Illustration: FIG. 71. UPPER AND LOWER JAWS OF AN ENGLISH
PTERODACTYLE FROM THE CHALK, AS PRESERVED]
ORNITHOSTOMA
[Illustration: FIG. 72. THE PALATE OF THE ENGLISH TOOTHLESS
PTERODACTYLE, ORNITHOSTOMA]
[Illustration: FIG. 73. TYPES OF THE AMERICAN TOOTHLESS PTERODACTYLE,
ORNITHOSTOMA
Named by Marsh, Pteranodon]
The most interesting of all the English Pterodactyle remains is the
small fragment of jaw figured by Sir Richard Owen in 1859, which is a
little more than two inches long and an inch wide, distinguished by a
concave palate with smooth rounded margins to the jaws and a rounded
ridge to the beak. It is the only satisfactory fragment of the animal
which has been figured, and indicates a genus of toothless
Pterodactyles, for which the name Ornithostoma was first used in 1871.
After some years Professor Marsh found toothless Pterodactyles in
Kansas, and indicated several species. There are remains to the number
of six hundred specimens of these American animals in the Yale Museum
alone; but very little was known of them till Professor Williston, of
Lawrence, in Kansas, described the specimens from the Kansas University
Museum, when it became evident that the bones of the skeleton are mostly
formed on the same plan as those of the Cambridge Greensand genus,
Ornithocheirus. They are not quite identical. Professor Williston adopts
for them the name Ornithostoma, in preference to Pteranodon which Marsh
had suggested. Both animals have the dagger-shaped form of jaw, with
corresponding height and breadth of the palate. The same flattened sides
to the snout, converging upwards to a rounded ridge, the same compressed
rounded margin to the jaw, which represents the border in which teeth
are usually implanted, and in both the palate has the same smooth
character forming a single wide concave channel. Years previously I had
the pleasure of showing to Professor Marsh the remarkable characters of
the jaw, shoulder-girdle bones, and scapulae in the Greensand
Pterodactyles while the American fossils were still undiscovered. I
subsequently made the restoration of the shoulder-girdle (p. 115).
Professor Williston states to me that the shoulder-girdle bones in
American examples of Ornithostoma have a close resemblance to those of
Ornithocheirus figured in 1891, as is evident from remains now shown in
the British Museum. It appears that the Kansas bones are almost
invariably crushed flat, so that their articular ends are distorted. The
neck vertebrae are relatively stout as in Ornithocheirus. The hip-girdle
of the American Ornithostoma can be closely paralleled in some English
specimens of Ornithocheirus, though each prepubic bone is triangular in
the American fossils as in _P. rhamphastinus_. They are united into a
transverse bar as in Rhamphorhynchus, unknown in the English fossils.
The femur has the same shape as in Ornithocheirus; and the long tibia
terminates in a pulley. There is no fibula. The sternum in both has a
manubrium, or thick keel mass, prolonged in front of its articular
facets for the coracoid bones, which are well separated from each other.
Four ribs articulate with its straight sides. The animal has four toes
and the fifth is rudimentary; there are no claws to the first and
second.
[Illustration: FIG. 74. RESTORATION OF THE SKELETON OF _ORNITHOSTOMA
INGENS_ (MARSH)
From the Niobrara Cretaceous of Western Kansas. Made by Professor
Williston. The original has a spread of wing of about 19 feet 4
inches. Fragments of larger individuals are preserved at Munich]
In the restoration which Professor Williston has made the wing
metacarpal is long, and in the shortest specimen measures 1 foot 7
inches, and in the longest 1 foot 8 inches. This is exactly equal to the
length of the first phalange of the wing finger. The second wing finger
bone is 3 inches shorter, the third is little more than half the length
of the first, while the fourth is only 6-3/4 inches long, showing a
rapid shortening of the bones, a condition which may have characterised
all the Cretaceous Pterodactyles. The short humerus, about 1 foot long,
and the fore-arm, which is scarcely longer, are also characteristic
proportions of Ornithostoma or Pteranodon, as known from the American
specimens. Professor Williston gives no details of the remarkable tail,
beyond saying that the tail is small and short, and that the vertebrae
are flat at the ends, without transverse processes. In the restoration
the tail is shorter than in the short-tailed species from the
Lithographic Slate, and unlike the tail in Ornithocheirus.
This is the succession of Pterodactyles in geological time. Their
history is like that of the human race. In the most ancient nations
man's life comes upon us already fully organised. The Pterodactyles
begin, so far as isolated bones are concerned, in the Rhaetic strata;
perhaps in the Muschelkalk or middle division of the Trias. And from the
beginning of the Secondary time they live on with but little diversity
in important and characteristic structures, and so far as habit goes,
the great Pterodactyles of the Upper Chalk of England cannot be said to
be more highly organised than the earlier stiff-tailed genera of the
Lias or the Oolites. There is nothing like evolution. No modification
such as that which derives the one-toed horse or the two-toed ox from
ancestors with a larger number of digits. On the other hand, there is
little, if any, evidence of degeneration. The later Pterodactyles do not
appear to have lost much, although the tail in some of the Solenhofen
genera may be degenerate when compared with the long tail of
Dimorphodon; but the short-tailed types are found side by side with the
long-tailed Rhamphorhynchus. The absence of teeth may be regarded as
degeneration, for they have presumably become lost, in the same way that
Birds now existing have lost the teeth which characterised the fossil
birds--Ichthyornis of the American Greensand, and Archaeopteryx of the
Upper Oolites of Bavaria. But just as some of the earlier Pterodactyles
have no teeth at the extremity of the jaw, such as Dorygnathus and
Rhamphorhynchus, so the loss of teeth may have extended backward till
the jaws became toothless. The specimens hitherto known give no evidence
of such a change being in progress. But just as the division of Mammals
termed Edentata usually wants only the teeth which characterise the
front of the jaw, yet others, like the Great Ant-eater of South America
named Myrmecophaga, have the jaws as free from teeth as the toothless
Pterodactyles or living Birds, and show that in that order the teeth
have no value in separating these animals into subordinate groups any
more than they have among the Monotremata, where one type has teeth and
the other is toothless.
The following table gives a summary of the Geological History and
succession in the Secondary Rocks of the principal genera of Flying
Reptiles.
-----------------------+----------------------------------------------
| NAMES OF THE GENERA.
GEOLOGICAL FORMATIONS. +-----------------------+----------------------
| British and European. | North American.
-----------------------+-----------------------+----------------------
Upper Chalk | |} Ornithostoma
| |} (_Pteranodon_)
Lower Chalk |} Ornithocheirus |} Nyctodactylus
Upper Greensand |} | Ornithostoma |
Gault | | |
-----------------------+ | |
Lower Greensand | | |
Wealden | Ornithodesmus |
Purbeck | Doratorhynchus |
-----------------------+ |
Portland |{ Pterodactylus |
|{ Ptenodracon |
Kimeridge Clay and |{ Cycnorhamphus |
Solenhofen Slate |{ Diopecephalus |
|{ Rhamphorhynchus |
Coralline Oolite |{ Scaphognathus |
| |
Oxford Clay | |
-----------------------+ |
Great Oolite and | |
Stonesfield Slate | Rhamphocephalus |
| |
Inferior Oolite | |
-----------------------+ |
Upper Lias |{ Campylognathus |
|{ Dorygnathus |
Lower Lias | Dimorphodon |
-----------------------+ |
Rhaetic | bones |
| |
Muschelkalk | ? bones |
-----------------------+-----------------------+----------------------