MEMOIRS OF THE

CONNECTICUT ACADEMY OF ARTS AND SCIENCES

INCORPORATED A. D. 1799

VOLDME II JULY, 1910

Osteology of Pteranodon

BY

GEORGE F. EATON, Ph. D.

CURATOR OF THE OSTEOLOGICAL COLLECTION, AND ASSOCIATE CURATOR

IN VERTEBRATE PALEONTOLOGY
PEABODY MUSEUM OF YALE UNIVERSITY

' .

PUBLISHED UNDER THE AUSPICES OF

YALE UNIVERSITY

NEW HAVEN, CONNECTICUT

1910

MEMOIRS OF THE

CONNECTICUT ACADEMY OF ARTS AND SCIENCES

INCORPORATED A. D. 1799

VOLUME II JULY, 1910

Osteology of Pteranodon

BY

GEORGE F. EATON, Ph. D.

CURATOR OF THE OSTEOLOGICAL COLLECTION, AND ASSOCIATE CURATOR

IN VERTEBRATE PALEONTOLOGY
PEABODY MUSEUM OF YALE UNIVERSITY

PUBLISHED UNDER THE AUSPICES OF

YALE UNIVERSITY

NEW HAVEN, CONNECTICUT
1910

KCMANGE

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WEIMAR : PRINTED BY R. WAGNER SOHN

OSTEOLOGY OF PTERANODON.

BY GEORGE F. EATON.

(WITH PLATES i— xxxi.)

The collection of North American Cretaceous pterodactyls assembled by Professor
Marsh at the Peabody Museum of Yale University is numerically very large, consisting
of the remains of 465 individuals of Pteranodon as well as seven individuals of the
allied genus Nyctosaurus, these two genera from the Niobrara Cretaceous of western
Kansas being originally placed by Marsh in the order Pteranodontia. For various rea-
sons it has .seemed wise to limit the present memoir to the treatment of Pteranodon,
postponing until a more opportune time the discussion of a few additional facts regard-
ing the structure and affinities of Nyctosaurus. Of the great number of examples referred
to Pteranodon, a few are complete enough to show new generic characters, but the
majority of individuals are so incomplete and fragmentary as to be of comparatively
little value. Owing to this condition of the material, it has been found inadvisable to
treat each species separately, and the present memoir has been accordingly divided into
topics based on the principal skeletal parts. As with one exception the specific names
have remained unchanged, an elaborate synonymy is obviated, the only species here
recognized that has been known under another name being Pteranodon occidentalis, which
was first described by Professor Marsh as Pterodactylus Oweni (Am. Jour. Sci., June, 1871).

As might be expected, in carrying on the work done by Professor Marsh on this
group, considerable difficulty was met with at the outset because of the incomplete and
fragmentary condition of much of the material first obtained, and from which the types
of the species of Pteranodon were necessarily chosen. With this fact in view, it need
occasion no surprise that of the three individual specimens originally referred to Pteran-
odon occidentalis^ only one, No. 1164,1 is complete enough to be of any value in the
present work. This specimen consists of a right humerus peculiarly crushed, three
carpals, and the first and fourth phalanges of the wing finger, together with a few barely
recognizable fragments presumably belonging to the same wing. Later Professor Marsh
observed the form of the jaws of P. occidentalis in a fragmentary skull, No. 1179, and
from his notes it is evident that he considered this specimen also a type of the species.

P. ingens, the second species described by Marsh, was based upon much more satis-
factory material. One of the types, No. 1175, is a magnificent but incomplete skeleton,
which does not include the fifth digij of the hand, the so-called wing finger. Another
valuable type of this species is the large nearly complete skull, No. 2594, to be partic-
ularly described in the following pages. The other types of P. ingens consist only of
a few poor fragments of wing bones, adding nothing to the characters shown by No. 1175
and No. 2594.

When Professor Marsh separated'-?, ingens from P. occidentalis, the skull of neither
species was known to him. With the exception of the carpals, the humerus was the

1 The numbers used in the present memoir refer to the Paleontological Catalogue of the Peabody
Museum of Yale University.

230436

2 OSTEOLOGY OF PTERANODON.

only entire skeletal element common to the two types, and he evidently distinguished
these species by their marked difference in size and by supposedly contrasting charac-
ters ascribed to the humeri and to the proximal ends of the ulnae.

While it might be expected that the great difference in size of P. occidental™ and
P. ingens would be accompanied by some minute but reliable differences in the form of
the wing bones, recent careful work by the preparator has not proved such to be the
case. On the contrary, the slight differences in the form of the humeri and of the
proximal ends of the ulnae, noted by Professor Marsh, now appear to be due entirely to
extraneous causes. To the critical reviewer of Professor Marsh's early work on this
subject, it is evident that the two skulls referred by him to P. ingens and P. occidentalis
were specifically identified by their size alone. There can have been no other reason
for associating them with the skeletal parts belonging to the original types of the two
species.

That such action was arbitrary, can not be disputed, yet it was in accordance with
the established usage of Paleontology, and the ultra-critical course of denying the specific
identity of these two skulls would be equally arbitrary and would involve the subject
in still greater uncertainty. It seems advisable to let this part of Professor Marsh's work
stand unchallenged, and to attempt the separation of the Pteranodon material in the
collection into three species by slight but fundamental differences displayed by the skulls.

P. velox was based upon the distal end of the right metacarpal of the wing finger and
the proximal end of the adjoining first phalanx. It now appears that the form of this
fragmentary metacarpal is considerably altered by an attached concretion of foreign
matter; otherwise it and the proximal end of the first phalanx differ no more in form
from the same portions of the types of the foregoing species than is to be expected in
view of the crushing they have undergone.

P. longiceps is represented by a nearly perfect skull, No. 1177, with atlas and axis,
which offers striking similarities to the skull of P. ingens, but is only about two-thirds
its size. The matrix was not thoroughly removed from the skull of P. ingens until after
Professor Marsh's death, and it appears that the difference in size recorded by him was
the only comparison of these two species possible under the circumstances. Professor
Marsh regarded the skull of P. longiceps as the type of the genus Pteranodon, and it
seems especially desirable that this species be retained. Its distinction from P. ingens
can be accepted without too great difficulty, in view of the marked contrast in size
accompanied by the slight structural differences noted in the following pages. Obviously,
it is impossible to differentiate a species represented by the skull only from another
species represented by wing bones only, but by accepting Professor Marsh's choice of
the fragmentary skull No. 1179 as a type of P. occidentalis, it becomes possible to com-
pare that species with P. longiceps.

P. comptus, which was described in the American Journal of Science, vol. xi, June, 1876,
is untenable. It was based upon portions of three skeletons in the Yale Museum, and
was defined by Professor Marsh as " the smallest Pterodactyle known from American
strata." The types were said to include distal ends of two fifth metacarpals, the distal
end of the ulna, and two sacral vertebrae. Of the three supposed individuals referred
to this species, No. 2287, marked " P. comptus, type in part," consists of two posterior
dorsal centra detached from their neural arches. They are smaller than the correspond-
ing parts of any example of Pteranodon known to the writer, and should perhaps be
referred to Nyctosaurus. No. 2335, also labeled "P. comptus, type in part," comprises

SKULL OF PTERANODON LONGICEPS MARSH. 3

the distal ends of both tibiae, together with the right tarsus. The skeleton to which
they belonged was of about the size of P. occidentalis. No. 1164. Associated with these
types in the collection is No. 2397, which is clearly composed of parts of two individ-
uals, because the distal end of the femur and the distal end of the tibia, with frag-
mentary metatarsals included under this number, are of incompatible size. The tibia
evidently belonged to an individual of about the size of the type of P. occidentalis,
No. 1164, while the femur is that of a slightly smaller animal. It is a matter of con-
siderable surprise to find that the measurements of the distal end of this tibia exactly
equal those given by Professor Marsh for the distal end of the wing metacarpal, in his
specific definition. The peculiarly crushed distal end of the tibia looks wonderfully like
the distal end of the wing metacarpal, and Professor Marsh may have confused the two
at a time when the osteology of pterodactyls was little understood. The only course
open under the circumstances is to regard P. comptus as no longer valid.

P. nanus clearly does not belong in the genus Pteranodon and may be referred to
Nyctosaurus.

The collection also contains many incomplete specimens of doubtful specific identity,
which have proved of considerable value in determining the characters of the genus.

SKULL OF PTERANODON LONGICEPS MARSH.

The nearly complete skull of Pteranodon longiceps Marsh, No. 1177, which was origi-
nally described as the type of the genus *• and later more fully discussed and figured,2
is shown in Plate I, figure 1. The result of further investigation has been to reveal new
structure rather than to discover inaccuracies in Professor Marsh's preliminary work,
which was necessarily somewhat incomplete. The purpose of the present memoir will
therefore be best served by making free use of original definitions as far as they have
proved correct, while new structure may be properly described in detail.

It should be noted that fusion of the elements has resulted in almost complete oblit-
eration of the cranial sutures in this genus. The terminology of the skull is therefore
somewhat lax, and must at times refer to the regions usually occupied by these elements,
their exact limits being indeterminable.

The head was remarkably long in proportion to its width, and in this respect Pterano-
don probably surpassed all other vertebrate animals. The skull is greatly produced in
the axial direction, the attenuated jaws continuing forward into long sharp points, while
the enormous sagittal crest extended far backward over the cervical region. The mar-
gins of the jaws are smooth and thin, though not especially sharp, and no remains of
horn sheaths have been observed.

Under Side of Skull.

The occipital condyle is small, its smooth rounded surface forming more than a hemi-
sphere. It is directed downward and backward at an angle of about 45° with the
palatal axis of the skull, and is separated by a slightly constricted neck from the main
part of the basioccipital bone, which is represented by an irregularly oval plate about

1 Am. Jour. Sci. (3), vol. xi, p. 507, June, 1876.

2 Ibid., vol. xxvii, p. 423, pi. xv, May, 1884.

4 OSTEOLOGY OF PTERANODON.

2 <™ in length. A slight break, probably occurring along the line of the original suture,
separates this from the basisphenoid bone, a long narrow ossification of triangular section
underlying the entire bony interorbital septum and terminating anteriorly in the basi-
pterygoid expansions.

In the crushed specimen, broad and flat paroccipital processes extend outward and a
little downward from the occipital condyle. At their outer extremities they are com-
pletely fused with the hinder ends of the remarkable elongate bars formed by the
united quadrates and squamosals. The foramen magnum appears to have been a round
opening about 4mm }n diameter. Above this and separated from the paroccipital proc-
esses by narrow elliptical vacuities rises the triangular supraoccipital plate, bearing
throughout its entire length a thin but prominent median ridge. At this point the in-
ferior border of the great supraoccipital or sagittal crest originates.

The skulls of the three species recognized in this memoir differ considerably in the
pitch of their supraoccipital plates. To express this more definitely, in P. longiceps
the supraoccipital plate rises less abruptly from the general axis of the basisphenoid
than in P. occidentalis, while in P. ingens the supraoccipital rises so little that its apex
is a trifle below the line made by prolonging the axis of the basisphenoid. The vary-
ing pitch of the supraoccipital plate may be regarded as a valid difference, for as the
three type skulls are crushed laterally the midline ossifications subtending these critical
angles have not been subjected to displacement.

The extreme specialization of the American Cretaceous pterodactyls is well shown by
the form of the articular portion of the quadrate. Professor Marsh's figure of the type
did not sufficiently emphasize this structure, although he stated that the distal end of
the quadrate was one of the most characteristic parts of the skeleton. Dr. Plieninger
was probably the first to illustrate this peculiar bone correctly, but his monograph does
not throw light on its true significance and function. The distal ends of the quadrates,
instead of forming simple ginglymal joints with the mandibles, participate with them in
the formation of one of the most remarkable mechanical devices to be found in the
reptilian class. The articular surface of each quadrate bears a spiral groove, left handed
in the right quadrate and right handed in the left. The articular elements of the man-
dibles have a reciprocal form, their surfaces bearing stout threads exactly corresponding
with the quadratic grooves. The left quadrate of the type of P. longiceps, No. 1177,
with part of the jugal is shown in Plate V, figure 1. As the articular facet of the left
mandibular ramus of this skull is wanting, the same portion of another individual, No. 2578,
equal in size, has been used for illustration (Plate V, figure 2). Any possible difficulty
in the interpretation of these fragments will be removed by comparing them with the
quadrate and articular of No. 2476 (Plate V, figures 4, 5, and 6). So perfect is the
mutual adjustment of these parts that unless dislocation took place, which is not suppos-
able, opening the mouth must have caused considerable widening of the lower jaws
posteriorly. The quadrates being immovably fixed by the supporting bones of the
pterygo-palatine arch, an expansion of the posterior parts of the mandible was the only
way by which lateral motion caused by the spiral articulations could be taken up
mechanically. The fact is of especial interest in its bearing upon the prevailing suppo-
sition that the mandibular rami were joined by an immovable symphysis and their com-
ponent elements firmly anchylosed.

In a preliminary description of this part (Am. Jour. Sci., July, 1903), the writer called
attention to the suspensorium of the Pelican, which is mechanically equivalent. Although

SKULL OF PTERANODON LONGICEPS MARSH. 5

this bird lacks the perfect spiral groove and thread characteristic of the quadrate and
articular of Pteranodon, the modeling of these bones seen in the prepared cranium forms
an effective screw that thrusts apart the mandibular rami when the mouth is opened.
That the spiral articulation is directly concerned in the widening of the mouth of both
Pteranodon and the Pelican, there can be little doubt. In the Pelican, however, this
skeletal modification may have arisen as a result of the peculiar musculature of the
lower jaw referred to by Dr. Coues (Key to N. A. Birds, p. 721). The reference, which
is not original with Dr. Coues but quoted from another author whose name is not given,
is repeated here : " When the bill is opened, the crura of the lower mandible separate
from each other to a considerable extent [in their continuity — not at the symphysis], by
the action of muscles inserted into their base, and the sac is expanded." Possibly the
mechanical similarity between the suspensorium of Pelican and Pteranodon should be
received as evidence of the possession of a gular sac by the pterodactyl also. This
would be in harmony with the views of Mr. F. A. Lucas, who stated (Ann. Rept. Smith-
sonian Inst. for 1901, p. 657): "In the peculiar shape of the lower, back portion of the
beak there is a suggestion of the former presence of a small pouch, like that found in
cormorants, and this would be in accord with the supposed fish-eating habits of Ornitho-
stoma" (Pteranodon Marsh).

Maxillary Arch.

In this skull no demarcation is shown between the premaxillse and maxillae, and here
as well as in the type of P. ingens, to be described later, the maxillo-jugal sutures are
entirely obliterated. A skull of Pteranodon sp. in the Museum of the University of
Kansas shows a long splintlike development of the jugal overlapping the maxilla on its
outer surface and extending forward to a point beneath the anterior end of the narial
vacuity. This is quite in accord with Professor Williston's view as to the position of
the suture in question, expressed in his paper : " On the Skull of Nyctodactylus." Pecu-
liar breaks occur in the types of P. longiceps and P. ingens, nearly beneath the centers
of the antorbital vacuities. At first glance, these seem to indicate the position of the
maxillo-jugal sutures, but it is much more probable that they are merely fractures caused
by pressure, this part of the maxillary arch being subjected to an unequal strain, owing
to the partial support afforded by the transpalatine bone.

Palato-pterygoid Arch.

The extraordinary form of the palatines and pterygoids, together with their associated
elements, is one of the most striking characters of Pteranodon, and still further sepa-
rates the genus from other groups of the Pterosauria.

Although certain important parts are yet wanting in the type skull of P. longiceps,
careful and persistent work on this specimen has resulted in considerable advance in a
knowledge of the palatal region. The complete demonstration of the bony palate will
be found on page 9, where the type skull of P. ingens is described in detail. The pecu-
liar form of the bones of the palato-pterygoid arch here described is based on these
elements as preserved in the type of P. longiceps and also in another skull, No. 2440, of
about the same size.

Stout transverse buttresses of bone about 3 cm in length extend outward and slightly
downward from the anterior extremity of the basisphenoid, fusing at their distal ends
with the quadrates, which they support in the strongest manner. The inner ends of

6 OSTEOLOGY OF PTERANODON.

these buttresses may be termed basipteryc/oids, as they are evidently outgrowths of the
basisphenoid. It is impossible to determine to what extent the pterygoids share in the
formation of these parts, many of the elements being, as previously stated, so completely
fused as to obliterate the original sutures ; but it will be in strict agreement with the
usual interpretation of the reptilian skull to consider the outer portions uniting with the
inner sides of the quadrates as parts of the true pterygoids.

From the middle of the anterior edge of each of these pterygoid buttresses, a thin
ribbon of bone about 1 cm Jn width extends forward and slightly outward, widening a
little anteriorly until its outer border becomes confluent with the palatal border or shelf
of the maxilla at a point about 5 cm in front of the quadrate. The inner border of
this palato-pterygoid ribbon, forming the boundary of the great palatal vacuity or pos-
terior nares, can be traced in skull No. 2440 (which is of similar size to the type skull)
to about 10 cm in advance of the quadrate. Other fragmentary skulls of the genus
show that in this region the inner margins of the palato-pterygoids converged, but no
specimen in the collection indicates whether any posteriorly directed style in the midline
separated the posterior nares. From the large palatal vacuity forward to the tip of the
beak, the palate extends as a continuous tract of bone, showing no demarcation between
premaxillae, maxillae, paired vomers, and palatines. In front of the basisphenoid there is
a small smooth and curved natural edge of bone, supposed by Professor Marsh to be
part of the posterior border of the large and simple oval palatal vacuity including the
posterior nares. That the skull of this species bore a most remarkable ossification in
the roof of the oral cavity anterior to the basisphenoid, was made evident by the for-
tunate identification of a fragment of the palato-pterygoid, which had escaped notice when
the type was first described. For want of this piece, Professor Marsh was compelled to
restore by conjecture the middle third of the palato-pterygoid, and was led to overlook
a small but important ossification clearly representing the transpalatine or ectopterygoid
of other Reptilia. In Plate V, figures 7 and 8 of the type show the completed palato-
pterygoid ribbon with its associated bones, from the under side (figure 7), and the same
parts as they would appear from above if the roof of the skull were removed (figure 8).
From these figures it is clear that the pterygo-jugal vacuity is bridged across by a small
transpalatine whose outer end in the type remains as a conical stub on the inner surface
of the posterior end of the maxilla. Not only is the inner end of the transpalatine bone
fused with the palato-pterygoid ribbon after the usual manner, but it is continued as an
oblique rod backward and inward across the upper surface of the palato-pterygoid, its
broken inner extremity actually projecting freely into the posterior part of the large
palatal vacuity. Plate V, figure 9, shows the same portions of the palato-pterygoid and
transpalatine in skull No. 2440, as seen from above. The precise form of this extraor-
dinary oblique rod at its origin near the midline of the skull is not shown in any speci-
men of P. longiceps, but comparison with the almost identical structure seen in the type
of P. ingens, No. 2594 (Plate IV, figure 2), demonstrates beyond all possibility of doubt
that these remarkable ossifications are lateral outgrowths from the base of the para-
sphenoid.

It is difficult to compute the true form of the upper margin or ridge of the skull.
Specimens crushed laterally at first sight seem to indicate a form quite different from
those crushed vertically. Professor Marsh, whose material was mainly of the former
description, stated : " A sharp ridge extends from the end of the premaxillaries along
the median line to the true cranium, and is continued backward by the thin elevated

SKULL OF PTERANODON LONG1CEPS MARSH. 7

crest." An examination of small fragments retaining the natural curvature of this region
leads to the conclusion that the ridge was not so marked over the upper jaw as Pro-
fessor Marsh supposed. On the midline between the orbits, however, the beginning of
the upper border of the great sagittal crest is clearly to be seen.

Side View of Skull.

The side view of the skull is scarcely less instructive than the palatal view, as it
gives an excellent idea of the general proportions of this remarkable type. In front of
the large narial vacuity extends an almost unbroken arch of bone formed by the united
premaxillae, maxillae, and nasals. The outline of the superior border of the upper jaw
or snout is continued in a slightly ascending curved line above the narial vacuities
and orbits into the upper margin of the sagittal crest. In figuring this strange out-
growth from the parietal and supraoccipital bones, Professor Marsh gave an example of
his exceptional shrewdness in working from fragmentary material. As seen in Plate I,
figure 1, there remains only the basal portion of the great crest once borne by the type
skull. From the evidence offered by this, he was able to anticipate later discovery by
figuring and describing an enormous crest that formed about one-third of the entire
length of the skull. The only complete large crest known is that of a specimen identi-
fied with P. ingens, No. 2473 (Plate II, figure 2). Under that species, the form and func-
tion of this remarkable part of the skull will be further discussed.

Beneath the antorbital vacuities, the maxillae are seen extending backward to meet
the supposed jugal elements that continue the cutting edges of the jaw almost to the
quadrates. From the middle of the jugal arises the flat bar of bone separating the ant-
orbital vacuity or nares from the orbit. In the type, the ossifications forming this bar,
supposedly lachrymal, prefrontal, and nasal, can not be distinguished from each other.
The orbit is bounded inferiorly by the jugal alone, which apparently united posteriorly
with the squamosal and postorbital or postfrontal to form the supratemporal arcade, no
demarcation being shown between the two last-named bones in any skull of the genus
in the Marsh Collection.

The exact relations and extent of the squamosal remain a vexed problem. In the
type skull of P. longiceps, as well as in that of P. ingens, an unbroken tract of bone,
which may be the squamosal, arises from the paroccipital region and after participating
with the jugal and postorbital elements in the formation of the supratemporal arcade
extends forward and downward in a long splintlike process overlapping the inferior
border of the quadrate. This interpretation of the squamosal is slightly at variance with
the views of Professor Williston,1 who regards the inferior outer part of the supratempo-
ral bar of Nyctosaurus as a quadrato-jugal articulating with the postorbital, jugal, squa-
mosal, and quadrate. In the types of P. longiceps and P. ingens, suture-like lines show
on the outer sides of the quadrates, and may possibly indicate the position of thin
quadrato-jugal plates. Such a hypothetical arrangement of the lateral temporal elements
has at least the merit of agreeing with the position of the corresponding bones in the
generalized Hatteria skull, and the extreme elongation of basisphenoid, jugal, and
quadrate in Pteranodon removes any possible lack of harmony in a proportionately long
squamosal.

1 On the Skull of Nyctodactylus.
MEMOIRS CONN. ACAD., Vol. II.

8 OSTEOLOGY OF PTERANODON.

The largest opening seen in the side view of the skull was originally termed by
Professor Marsh " the antorbital vacuity." Professor Williston describes l and figures an
oval depression or excavation in front of the orbit in Nyctosaurus, which in his opinion
" clearly corresponds to the antorbital vacuity of the earlier pterodactyls." He con-
cludes : " From this it is evident that the antorbital vacuity is not united with the nares
in this, genus or Ornithostoma'1'' (Pteranodon). This depression does not appear in the
types of P. longiceps and P. ingens, and the term " antorbital vacuity " is here retained.

The orbit as seen in the type is pear-shaped, with the elongation forward and down-
ward, in this respect as well as in its position above the infratemporal vacuity differing
greatly from the orbit of Nyctosaurus, in which genus it is situated much further for-
ward, overlying in fact the anterior end of the quadrate when the line of the jaws is
horizontal.

The supraorbital ridge of the frontal projects boldly outward over the orbit and is one
of the stoutest parts of the skull. The orbits are without floor and open anteriorly into
each other and into the great narial cavity. The interorbital septum as seen in the
type rests upon the entire length of the basisphenoid, its anterior edge leading back-
ward and upward until on the level with the center of the orbit, when it curves sharply
forward and upward to merge with the under surface of the frontals. The sclerotic
circle has been lost in the skull of P. longiceps, but is excellently preserved in the type
of P. ingens (Plate III, figure 1, and Plate V, figure 3).

Lower Jaws.

The articular part of the mandible has been already described in connection with the
remarkable form of the quadrates. As seen in the lateral view of the type skull of
P. longiceps (Plate I, figure 1), the lower jaws fit closely against the cutting edges of
the maxillary arch, which they simulate in general form. In the type, the points of both
the upper and lower jaws are wanting, and no specimen in the Marsh Collection is
complete in this respect. By fairly carrying out the lines of the remaining portions of
the jaws, extremely slender terminal points are indicated. That this was the true form
of these parts in the smaller allied genus Nyctosaurus, is clearly shown by abundant
material, and the wonderful delicacy of other portions of the skeleton of Pteranodon
renders such a hypothesis tenable.

For a little over two-thirds of their total length, the mandibular rami meet in a firm
symphysis. Behind this, the separated rami quickly diminish in depth and increase
slightly in transverse diameter, their form becoming oval in section immediately in front
of the quadratic articulations. Posterior to the articular facets there are small angular
projections.

Professor Williston has given an excellent restored figure of the posterior half of the
mandible, seen from above (Note on the Mandible of Ornithostoma, Kansas Univ. Quart.,
vol. iv, July 1, 1895). The Marsh Collection contains a fragment of this part, No. 2478,
which is here figured from the right and left sides (Plate I, figures 2 and 3), so as to
show the posterior part of the mandibular symphysis and the bony floor of the oral
cavity, which united the parapets of the jaw nearly as far back as the termination of
the symphysis. The front end of the fragment can not well be figured, but it demon-
strates the presence of a long cavity of triangular section, enclosed between the floor

1 Ibid.

SKULL OF PTERANODON INGENS MARSH. 9

and side walls. Other specimens indicate that this cavity extended nearly or quite to
the point of the mandible.

The principal measurements of the type skull of P. longiceps, No. 1177, are as fol-
lows : —

Length from extremity of sagittal crest to end of premaxillary . . . 720. mm

Length from occipital condyle to end of premaxillary 630.

Transverse diameter of occipital condyle 8.4

Distance from occipital condyle to distal end of quadrate .... 105.

Length of mandible 570.

Maximum depth of mandible 70.

Depth of mandible immediately in front of articulation 26.

It should be noted that the measurements given by Professor Marsh included the
calculated missing portions of the crest and the tip of the jaws. The foregoing meas-
urements are taken directly from the skull as preserved.

SKULL OF PTERANODON INGENS MARSH.

The type skull of this species, No. 2594, a preliminary notice of which was published
by Professor Marsh in the American Journal of Science and Arts, vol. xi, June, 1876, is
shown in Plate II, figure 1, Plate III, figure 1, and Plate IV, figure 2. Not only is it of
much larger size than the types of P. longiceps and P. occidentalis, but it differs materially
in the slope or pitch of the supraoccipital. In the side view of this skull (Plate II,
figure 1), it will be seen that a line carried out in extension of the basisphenoid passes
through the apex of the supraoccipital plate, which rises less abruptly in P. ingens than
in the type skulls of the other species. The basal portion of the crest is accordingly
deeper than in P. longiceps.

Another slight difference between the skulls of P. ingens and P. longiceps is seen in
the arrangement of the open network of slender rods of bone forming the lower section
of the interorbital septum, where it rests upon the basisphenoid. In P. ingens, the solid
upper portion of the septum merges into the open fabric of the lower part. In P. lon-
giceps, this transition is more abrupt, and there is a stout and well-defined inferior border
to the solid upper portion. It is of course impossible to determine whether this minor
difference, drawn from the two skulls only, is of taxonomic importance. Additional
material may prove it to be merely an individual variation. The anterior border of the
septum divides, right and left, into two branches whose upper ends abut against the
under side of the frontal or prefrontal region. This structure is apparently similar to that
admirably figured and described by Dr. Plieninger, from a fragmentary skull of Pteran-
odon sp., in his memoir entitled : " Beitrage zur Kenntniss der Flugsaurier," but the
complete condition of the overlying elements in the roof of the skull here prevents a
thorough examination.

The greatest value of the type skull of P. ingens lies in the excellent preservation of
the palatal region. The lower aspect of the skull is similar to that of P. longiceps, as
far as the latter is preserved, so that it is necessary to describe in detail only those
structures of P. ingens that are lacking in other skulls of the genus.

To demonstrate the palatal region more clearly, a drawing (Plate IV, figure 2) has
been prepared from this unique type skull, and every effort has been made to restore the

10 OSTEOLOGY OF PTERANODON.

associated elements to their original form. The anterior border of the large palatal vacuity
is the only part of the drawing which is conjectural.

The small curved and natural edge of bone in front of the basisphenoid, which in P.
longiceps Professor Marsh supposed to be the posterior limit of a large and simple palatal
vacuity, is here shown to be merely the rear border of a small oval foramen occupying
in part the position of the small median vacuity of Nyctosaurus, described and figured
by Professor Williston (Jour. Geol., 1902) as the interpterygoid vacuity. In front of this
extends a remarkable trident-shaped ossification, the slender and pointed median spindle
of "which is here identified as the parasphenoid. At the base of this element arises on
each side a round and tapering rod, which projects diagonally forward and outward
across the palatal vacuity, as shown in the figure. After fusing with the palato-pterygoid
ribbon, which it overlies, it becomes continuous with the delicate transpalatine. In the
fossil skull, the diagonal of the right side is broken close to its origin at the base of
the parasphenoid, and the distal portion has been lost ; the diagonal of the left side was
broken midway of its length, and owing to the lateral crushing of the specimen the
posterior part slightly overlaps its own forward extremity. The pneumatic canals
pervading nearly every part of the skull are visible even at the fractures of these
slender rods.

Dr. J. Versluys, Jr., of the University of Giessen, who has examined the type skulls of
Pteranodon, has kindly expressed his satisfaction with the plate showing the form of the
palatal region of P. ingens, although his views as to the homology of some parts of the
skull differ from those of the present writer. Thus Dr. Versluys identifies as " basiptery-
goid processes of the basisphenoid" the oblique rods arising at the base of the para-
sphenoid ; and accordingly he would apply the name of basioccipital to the ossification
in the base of the skull supposed by the writer to represent the united basioccipital and
basisphenoid.

There is perhaps no more convenient test for the interpretation of any reptilian cranium
than the ease with which its homologies may be traced in the extremely generalized
skull of Hatteria. The writer is confident, therefore, that when submitted to this test
the homologies of Pteranodon as understood by Marsh and Williston will prove generally
correct.

The sclerotic circle is composed of twelve thin plates of bone arranged with over-
lapping edges. In Plate III, figure 1, the left orbit of the type is shown as actually
preserved. By removing the matrix from the orbit, the circle was exposed, pressed
inward against the interorbital septum, the component plates being apparently little dis-
placed from their normal position. As these parts are somewhat indistinctly rendered
in the photographic plate, they are again shown in Plate V, figure 3.

Supraoccipital Crest.

The supraoccipital crest is better preserved than that of the type of P. longiceps, but
here also an indefinite part has been lost. The form of the complete crest is known
only from the fragmentary skull No. 2473, represented in Plate II, figure 2. Enough of
the base of this cranium remains to show that it is of almost exactly the same size as
the type skull No. 2594, and fragments of the wing bones also prove that the skeleton
of which it was a part nearly equaled in size the type skeleton of P. ingens, No. 1175.
The crest may have been flexible, for in all examples known it is found to be ex-
tremely thin, in the type its transverse measurement posterior to the supraoccipital plate

SKULL OF PTERANODON INGENS MARSH. H

being only 3mm. To give a better conception of the complete skull, a composite
restoration, based upon the type and No. 2473 jointly, is shown in Plate IV, figure 1.

Since the great supraoccipital crest is one of the most striking characters of the
genus, it is of the highest importance to learn what its true function may have been.
Professor Seeley in " Dragons of the Air," p. 70, has aptly compared the Pteranodon
crest with those borne by the Cormorant and the Chamaeleon, stating by way of ex-
planation th£t the separate and movable crest of the Cormorant (Phalacrocorax) is not
strictly the equivalent of the fixed crest of the pterodactyl. Although the Pteranodon
crest is now known to have been much longer than it was supposed to be when first
described, the recent animals referred to by Professor Seeley help greatly toward a
satisfactory understanding of its function, especially when they are considered as stages
in a developmental series including Plotus (the Darter), Phalacrocorax, Chamseleo, and
Chelydra. A brief review of the comparative anatomy of these types of vertebrate
crania may throw light upon the present discussion.

In Chelydra serpentine/, the Snapping Tortoise (Y. U. Osteol. Coll., No. 5454), the
united supraoccipital and parietals form a strong crest of considerable length (Plate V,
figure 10). Dissection of the head shows that the main function of this crest is to furnish
the origin of the divisions of the enormous musculus temporalis, which gives this tor-
toise its dreaded power to seize and lacerate its prey. Another noteworthy reptilian
example of this structure is offered by the Chamaeleon. Plate V, figure 11, of Chamceleo
vulgaris, shows the remarkable extension of the parietals and supraoccipital, strengthened
on each side by the elongated squamosals. The definition of the temporalis muscle
given by Mivart (On the Myology of Chamceleon parsonii, Proc. Zool. Soc. London, p. 850,
1870), is quoted here:-

" Temporalis. This muscle is of prodigious size ; and it would be interesting to know
what is the use to the Chameleon of so singularly voluminous a temporal. It springs
from the whole surface of the temporal fossa, and from the occipital crest, where it
appears on the back of the head, having the most anterior part of the longissimus
dorsi on its inner side, and the complexus on its outer side. It is inserted into the
upper border of the mandible, between the coronoid process and the articular surface."

Since the origin of the temporalis extends so widely over the lateral surface of the
Chamaeleon's crest, the inference may be drawn that the principal direct function of the
crest is to serve for the attachment of this remarkably powerful muscle. The fact that
the animal's feeding habits, as far as known, do not require any such development of
the muscles for closing the jaws in no way invalidates this conclusion. As in Chelydra
so here in Chamaeleo. the insertions of the longissimus dorsi and of the complexus
are situated so low down on the occipital arch that the crest is not to be considered
as a lever to facilitate the elevation of the head. This is equally true of the insertions
of the neck muscles in the genera of recent birds to which reference is now made.

The occipital styles seen in two genera of Totipalmate birds, Phalacrocorax and
Plotus, have been the cause of considerable difference of opinion among zootomists,
and many thrusts have been given and parried on the subject of the u xiphoid bone "
so aptly named by an early writer, William Yarrell, Esq., F. L. S., etc., whose instructive
paper: "On the use of the xiphoid bone and its muscles in the Corvorant" (Sowerby's
Zool. Jour., vol. iv, 1828) contains two excellent engravings of the skull of Phalacro-
corax carbo. Owing to the difficulty of reproducing these engravings, figures (Plate V,
figures 13 and 14) have been made from a skull of P. dilophus (Y. U. Osteol. Coll.,

12 OSTEOLOGY OF PTERANODON.

No. 538), to show the form and position of the occipital style and the attachment of
the temporal muscles, the arrangement of these muscles being adapted from Yarrell's
figure. As Yarrell's description of this structure can not be improved upon, it is quoted
here : —

"This additional bone (occipital style] is about one inch in length, triangular in shape,
somewhat grooved on its surfaces, and from its articulation with the occiput tapers
gradually to a point. The mode by which this bone is articulated to the occiput is
similar to that observed in the ribs of serpents, in which the condyle is situated upon
each vertebra, and the cavity is at the end of the rib ; so in the Corvorant, the con-
dyle is upon the occipital bone, the cavity at the triangular end of the xiphoid bone :
the joint is therefore hemispherical : admitting great extent of motion, the advantages
of which will be hereafter pointed out.

" From the upper edge of this bone to its lateral angle throughout its whole length
from the extreme point to the occiput, there arises on each side a triangular-shaped
long muscle, the fibres of which are directed forwards, downwards and outwards to be
inserted by a strong tendon upon the upper edge of the lower mandible, immediately
behind the insertion of the tendon of the temporal muscle. The muscles of the upper
part of the neck, giving motion to the head, are inserted upon the occipital bone and
its elevated crest, over which these additional muscles slide with every movement of
the head, the particular articulation of the xiphoid bone only permitting it to become
a fixed point of support to its own particular muscles, when both act simultaneously
as additional elevators of the lower mandible, thus assisting in prehension, and materi-
ally increasing the power of the bird in securing a slippery prey."

The literature on the anatomy of Plotus, the Darter, is equally complete. Professor
A. H. Garrod states in his paper : " Notes on the Anatomy of Plotus anhinga " (Proc. Zool.
Soc. London, 1876):-

" In the Society's female specimen there is a fibro-cartilaginous similarly situated
process, not more than one sixth of an inch long, which is ossified in the evidently
older male. In .his notes on the anatomy of the Cormorant, Hunter tells us that ' a
small bone, about an inch long, passes back from the os occipitis and gives origin to
the temporal muscle, which is very strong.' The same bone in the Darter, although
comparatively not so long, performs the same function, the superficial temporal muscles
meeting behind the skull along the median raphe, which becomes ossified to form the
above-mentioned bony style in the adult bird." Professor Garrod's drawing is exactly
reproduced in Plate V, figure 12, although the length of the occipital style as it appears
in the figure does not accord with the length given in the text.

In a later paper (Proc. Zool. Society, London, 1878), Professor Garrod records that in
P. levaillanti, the African Darter, the temporal muscles run back beyond the skull, being
separated by a median fibrous raphe, which is not ossified into a separate bony style.

In the five recent animals here referred to are seen four different stages in the de-
velopment of an occipital crest, Chelydra and Chamseleo representing the same stage as
far as the present discussion is concerned.

The first and lowest stage is that ascribed to Plotus levaillanti and to the female of
P. anhinga, in which the enlarged temporal muscles meet behind the cranium and their
line of contact has been occupied by a minute " fibro-cartilaginous process." In the
older male of P. anhinga, the second stage, the fibro-cartilage has become ossified and
the process converted into a true bony style. In the third stage, represented by Phala-

SKULL OF PTERANODON INGENS MARSH. 13

crocorax, the occipital style or " xiphoid bone " has attained such size that it can no
longer be overlooked in a hasty examination of the skull. Finally, in Chelydra and
Chamaeleo, the crest occupies about one-third the entire length of the cranium, and the
muscles that are attached to it are the most prominent in the anatomy of the head. With
the exception of Chamaeleo, these animals are all noted for their skill in capturing fish.

To quote from a letter in which Dr. R. W. Shufeldt has kindly expressed his views,
there is at present no doubt on the matter of the physiology of the occipital style :
' Owing to the character of the food (living, struggling fish) and the mode of feeding of
such birds as Cormorants, Plotus, etc., it is undoubtedly a structure that has been devel-
oped in time, to afford an increased surface for the origin of the temporal muscles upon
either side. The seizing and prehensile power of the jaws is thus manifestly increased."

This statement applies equally well to the development of the crest in Chelydra and
other chelonians, e. </., the quasi-marine Toxochelys from the Upper Cretaceous of
Kansas, whose skull in this respect is similar to that of Chelydra.

In all these examples, the relation of the crest to the temporal muscles is regarded
as simple, and the function of the crest is supposedly limited to satisfying the need of
increased muscular origin ; the earlier stages of the development which culminated in the
crest of Pteranodon may well have been similar to the developmental stages through which
the ancestors of Phalacrocorax among birds and of Chelydra among reptiles have passed.

In Pteranodon, the temporal muscles must have extended from their mandibular inser-
tions through the pterygo-jugal vacuities and so upward and backward to the large
supratemporal fossae. How far their, origins spread posteriorly is not shown by the fossil
remains ; but in the absence of large bladelike pterygoids, such as are present in the
Crocodilia, it is evident that the temporal muscles wer.e the principal elevators of the
lower jaws, just as in the genera of recent birds and reptiles referred to above. And.
as in these recent animals, the size and power of the temporal muscles could best be
increased by extending their origins posteriorly along the sides of a median crest. Such
a modification would have been strictly in accord with the general change of form which
the skull of Pteranodon had undergone during its specialization.

The occurrence of Pteranodon remains in the chalk deposited in a shallow sea and
at a distance of not less than one hundred miles from the probable shore line, also the
shape and proportionate size of the jaws, have given rise to the supposition that this
pterodactyl lived principally upon small fish taken at the surface in a manner somewhat
similar to that adopted by the Skimmer, Rhynchops, which is said to feed as it skims
low over the water with the fore parts inclined downward, the under mandible grazing
or cutting the surface. If this were true, it would add greatly to the probability that
Pteranodon originally developed a crest in the same way that certain piscatorial birds
have developed theirs. It is scarcely imaginable, however, that the temporal muscles ofL^
the pterodactyl extended backward along the entire length of the fully developed crest,
as in Phalacrocorax, Chelydra, and Chameeleo ; and in order to account for the complete
development of this part it seems necessary to fall back upon the general theory that
growth along certain lines may be initiated through the exercise of one function, while
further development is dependent upon another totally distinct function. Of what use
the posterior part of the crest was to Pteranodon remains largely conjectural. The high
crest carried by the head of the male Basilicus, to which in regard to form and direction
Professor Marsh compared the Pteranodon crest, is strictly exoskeletal, and therefore
is of little assistance in the present case. The weight of the crest would appear not to

mm

14 OSTEOLOGY OF PTERANODON.

be required as a counterpoise to the long jaws of Pteranodon, for the form of the
cervical vertebrae indicates a strong musculature of the upper part of the neck ; neither
the weight of the crest nor its effect as a vertical aeroplane, however, can be entirely
disregarded.

The principal measurements of the type skull of P. ingens, No. 2594, are as follows : -

Total length of specimen . 840

Length from occipital condyle to distal end of quadrate 153

Transverse diameter of occipital condyle (approximate) . . .13

Depth of mandible immediately in front of articulation 34

Length of occipital condyle to posterior end of imperfect crest . . 515

The length of the complete crest of No. 2473, from the center of the occipital condyle
to the tip of the crest, is 784 mm.

SKULL OF PTERANODON OCCIDENTALS MARSH.

The imperfect skull No. 1179 (Plate III, figure 2) is evidently the one referred to as
P. occidentalis in the definition of P. longiceps (Am. Jour. Sci., June, 1876. p. 508), where
Professor Marsh stated that the skull of the latter " is somewhat larger than P. occidentalis
Marsh, which apparently has more slender jaws." His notes also furnish collateral evi-
dence on this point, yet for some reason this specimen was never fully described. No. 1179
may therefore be regarded as one of the types of P. occidentalis. Not only is this skull
of about the same relative size as the smallest individual of the genus, which fact pre-
sumably had much to do with its original reference to P. occidentalis, but it differs
materially in form from the type skulls of the two other species. The figure shows that
the posteriorly directed face of the supraoccipital rises more sharply in this species than
in the type of P. longiceps, in this regard the difference between P. occidentalis and
P. ingens being even more striking. The supraoccipital crest is smaller than in the type
skulls of other known species, and the curved and regular form of its superior margin
favors the supposition that it is here practically complete, while in P. ingens, No. 2594. and
P. longiceps more or less of the crest has been lost.

The apparent slenderness of the jaws alluded to by Professor Marsh is not an alto-
gether satisfactory character. While it is true that in its present condition the left man-
dibular ramus is not so deep immediately behind the symphysis as are the same parts of
P. longiceps and P. ingens, there is some doubt whether the inferior margin of the mandible
may not have been broken away at this point. If the rami were no deeper immediately
behind the symphysis than this fragment indicates, it would appear impossible for the
transverse diameter of the mandible to approximate the corresponding measurement of
the maxillary arch. The angular part of the mandible posterior to the articulation is
missing, and the connection between the maxillary arch and the basal portion of the
skull has been destroyed. With the exception of the points of difference already men-
tioned, the skull in its general form is similar to those of the other species.

Measurements of Skull No. 1179.

Distance from occipital condyle to distal end of quadrate . . . . 75. mm

Distance from occipital condyle to apex of supraoccipital surface . . . 46.

Diameter of occipital condyle . . , . 7.5

CERVICAL VERTEBRAE OF PTERANODON. 15

CERVICAL VERTEBRAE OF PTERANODON.

The cervical vertebrae are nine in number, counting the elementary atlas and axis as
the first two units of the column. This is proved beyond all doubt by comparing the
cervical series in the type of P. ingens, No. 1175 (Plate VI, figures 1-6), which consists
of the seven anterior vertebrae, with the parts preserved of the cervical series of a
smaller example of Pteranodon sp., No. 2692 (Plate VI, figures 7-9), in which the com-
plete seventh, eighth, and ninth vertebrae remain in their natural sequence. Both these
series have been slightly restored by the artist. In all examples of the genus found in
the collection, the atlas and axis are coossified, and neither in the small type of P. longi-
ceps, No. 1177 (Plate VI, figure 11), nor in the much larger P. ingens, No. 1175 (Plate VI,
figures 1 and 12), is it possible to trace readily the limits of the elements theoretically
composing these united vertebrae. As the atlas and axis of P. longiceps have been
crushed transversely, while the same parts of P. ingens have been subjected to pressure in
the axial direction only, the true form of these bones may be more easily understood
by a comparison of the two figures mentioned. Viewed laterally, these vertebrae have
much the same appearance as the corresponding parts of Nyctosaurus, figured by Pro-
fessor Williston (On the Osteology of Nyctosaurus). Above the neural arch, which is pro-
portionately smaller than in Nyctosaurus, the thin spine extends upward and backward
in an easy curve. At its mid-height, the wide-spreading postzygapophyses are given off.
The sides of the axial centrum are excavated deeply, thus materially lessening the
weight. In the types of P. ingens* Nos. 2594 and 1175, pneumatic foramina may be seen
leading forward and backward from the lateral excavations. In the posterior view, the
convex oval termination of the centrum appears more produced transversely than that
of Nyctosaurus, and the supplementary articulating processes, termed by Professor Willis-
ton the exapophyses, are not confluent, but remain separate and distinct as in the
other cervicals. That these vertebrae, in spite of their apparently massive form, were
extremely light, is also indicated by the paired fenestrae seen on the posterior wall of
the arch, a little above the level of the neural canal. The delicate cancellous structure
disclosed within may have been occupied by the pneumatic cells that seem to have
pervaded nearly all parts of the skeleton in this genus.

The third, fourth, fifth, sixth, and seventh cervicals are alike in general form, and the
slight differences which they offer lie in their comparative lengths. There can be no
serious doubt as to the natural sequence of these vertebrae, for in P. ingens, No. 1175,
they were preserved in so close juxtaposition as to lead to the conclusion that they
had been but little disturbed before being covered by the chalk matrix. The measured
lengths of the cervical centra of this example are as follows : Third, 61 mm ; fourth,
67mm; fifth, 83mm; sixth, 76 mm ; seventh, 65mm. From this it would appear that of
these five vertebrae, the third cervical was the shortest, the fourth and fifth successively
increasing in length, and the sixth and seventh again becoming shorter, the length of
the seventh being reduced nearly to that of the fourth. This sequence is substantiated
in part by P. ingens, No. 2594, where the length of the third cervical is but little greater
than that of the united atlas and axis to which it remains attached. The fourth ver-
tebra of No. 1175, anterior and posterior views of which are shown in Plate VI, figures
13 and 14, is very similar to the other long cervicals, and has been already described
by Professor Williston (Restoration of Ornithostoma) as follows : -
MEMOIRS CONN. ACAD., Vol. II

16 OSTEOLOGY OF PTERANODON.

"The centrum is elongated. The ball is much broader than high, and strongly con-
vex in both directions ; its upper border is convex, but the inferior margin is emargi-
nate on each side. . . . there is a stout process, jutting downwards and backwards
from the side of the centrum on each side, having on the posterior surface a concave
articular facet, oval in shape and touching or slightly separated from the articular sur-
face of the ball. The facet looks downwards, backwards, and outwards. . . . The
corresponding articular facets on the anterior end of the centrum are somewhat smaller,
are convex and distinctly separated from the concavity of the centrum. The artic-
ulation of the centra with each other thus depends upon three distinct, or nearly
distinct surfaces, the lateral inferior ones convex on the cup end, concave on the
ball end. Such a mode of articulation would seem to limit the motion to one in
a vertical, antero-posterior plane, while greatly strengthening the joints. I know of no
similar arrangement in any other vertebrate animal, and will, for convenience, call the
articulations exapophyses. The anterior zygapophyses project distinctly beyond the
plane of the cup and are widely separated from each other. From the tip of the proc-
esses a ridge runs downward and inward to the outer part of the pre-exapophyses.
The post-zygapophyses are concave and oblique. Above them there is a stout met-
apophysis.1 The spine is elongate and thin, and apparently only a ridge.''

The elongated cervicals all possess distinct tubercular hypapophyses, which project
from the anterior ends of the centra beneath the oval articular cups. The vertebrae are
lightened by pneumatic canals, which enter the centra midway of the sides, and
also by paired canals that under favorable conditions of preservation may be seen at
both ends a little above the level of the neural canal. The first seven cervicals are
without ribs.

The eighth and ninth vertebrae resemble each other closely, but differ greatly from
those preceding them. Their form is well preserved in Pteranodon sp., No. 2692 (Plate VI,
figures 8 and 9, figure 10 portraying diagrammatically the anterior view of the eighth
cervical). The centra are short, their length and breadth being nearly equal. The artic-
ular facets of the prezygapophyses and preexapophyses remain much the same as in the
elongated cervicals, but their basal portions are produced laterally to form transverse
and capitular processes bearing ribs. The ribs of the eighth cervical somewhat resemble
the hatchet ribs characteristic of these vertebra? in certain other groups of Reptilia, but
they are little produced anteriorly and posteriorly. They are firmly coossified with the
supporting processes. The right rib of the ninth cervical is of the usual double-headed
form (Plate VI, figure 16). Its diameter is comparatively small and its length is only
about one-half that of the first dorsal ribs. Evidently it did not reach and connect with the
sternum. A pair of short double-headed ribs found with P. ingens, No. 1175, the right
member of which is shown in Plate VI, figure 15. probably belonged to the missing
ninth cervical. From the inferior margin of the articular cup of the eighth cervical pro-
jects a small hypapophysis. It is slightly bifid in two examples in the collection ; in
others, both large and small, the hypapophysis is simple, but because of the incomplete-
ness of the types, it is impossible to make use of these differences as specific charac-

•

1 In this instance, Professor Williston evidently uses the term metapophysis in a general sense,
just as he does in his paper on the Osteology of Nyctosaurus. Another authority informs us that
we must apply this term only to the "apophysis developed on the prezygapophysis or anterior
articulating process of a vertebra."

DORSAL VERTEBRA. 17

ters. The centrum of the ninth cervical bears no hypapophysis. The articular facets
of the postexapophyses of the eighth and ninth cervicals remain much the same as in
the vertebrae preceding them, but there are no posteriorly directed processes below these
facets. Instead of curving backward in the bladelike form characteristic of the third to
the seventh cervicals, the neural spines rise straight upward and are abruptly truncated
at their full height. When these vertebrae have been crushed in the axial direction and
the thin neural spines have been destroyed, the stout processes, termed by Williston
metapophyses, assume the appearance of bifid spines.

DORSAL VERTEBRAE.

In a short paper entitled : " Note on American Pterodactyls " (Am. Jour. Sci., vol. xxi,
April, 1881), Professor Marsh wrote: "To aid the powerful wings [of Pteranodon] in
flight, the pectoral arch is strengthened, (1), by the ankylosis of several vertebrae; (2), by
the robust scapulae articulating on opposite sides of the common neural spine of these
vertebrae." This brief description was accompanied by a foot-note calling attention to
a similar structure in some of the English Cretaceous pterodactyls also. Following this
suggestion, Professor Seeley published an instructive paper: "On the Shoulder-girdle
in Cretaceous Ornithosauria " (Ann. Mag. Nat. Hist., May, 1891), in which he described
the structure in Ornithocheirus Seeley, and figured a composite restoration of three dorsal
vertebrae united by a " supra-neural ossification," with lateral facets for the scapulae.
The Marsh Collection contains several more or less perfect examples of the anterior
dorsal or notarial vertebrae of Pteranodon. These have been carefully prepared in order
to ascertain, if possible, the exact number of anchylosed vertebrae and their form. The
best preserved notarium is that of Pteranodon sp., No. 2692. Photographic views show-
ing the actual condition of the left and right sides may be seen in Plate VII, figures 1
and 2. Attention should be called to the fact that the last cervical is still in contact
with the notarium. The slight dislocation it has suffered is apparent only in the view
from the right side. Obviously, to separate this ninth cervical from the notarium would
necessitate destroying its delicate rib. While this specimen is by no means complete,
it is possible, by supplying the missing portions of one side from those preserved on the
other, to reconstruct accurately the original form. Figures 1, 2, 3, and 4, of Plate VIII,
have been made in this way to show the notarial vertebrae as seen from the left side,
from the front obliquely, from above, and from below, respectively. These diagrams are
slightly at fault in that they represent the ribs as issuing nearly at right angles to the
vertebral column ; the ribs were probably directed a little posteriorly. The most impor-
tant characters of this series of vertebrae in No. 2692 are as follows :—

The centra of the eight anterior dorsal vertebrae are firmly coossified. The dorsal
spines are bound together and surmounted by a thin median ossification, the supraneural
plate, which is fused with their upper extremities. The vertical depth of this median
ossification is greatest above the interval between the third and fourth dorsal spines,
where on each side it presents an oval facet for the lodgment of the upper ends of the
scapulae. These eight vertebrae are also bound together by paired ossifications that
extend the length of the notarium, fusing with the ends of the transverse processes in
the same manner that the supraneural ossification unites with the dorsal spines. The
centrum of the first dorsal is the largest of the series. Its length and breadth are about

18 OSTEOLOGY OF PTERANODON.

equal and the oval articular cup and anterior articulating facets resemble those of the
last cervical. The transverse and capitular processes are remarkably large, and are com-
pletely fused with the stout ribs which they support. Posteriorly, the centrum of the
first dorsal vertebra is so perfectly coossified with that of the second dorsal as to be
inseparable and almost indistinguishable from it. The postexapophyses of the first
dorsal and the preexapophyses of the second are only vestigial. The centrum of the
second dorsal vertebra is narrower than the first centrum. The transverse and capitular
processes are much lighter, as are also the anchylosed ribs which they support. Since
the sutures are effaced, it has become impossible to determine accurately where the
capitula proper of the ribs begin and the corresponding processes end. This is also true
of the preceding vertebra and its ribs. In the second dorsal, however, the capitular
processes are given off from the centrum at a slightly higher level. The third centrum
is united to the second without the aid of exapophyses. The slender anchylosed rib
which it supports is still of the double-headed form, but the capitulum is situated so
high up on the centrum that the foramen enclosed by the two branches of the rib is
greatly reduced in size. The centra of the five succeeding vertebrae, the fourth, fifth,
sixth, seventh, and eighth of the notarium, progressively diminish in breadth until they
become nearly circular in section, being constricted in the middle and expanded at the
ends. Toward the end of the series, the fusion of the centra is possibly a little less
complete, and in one specimen, No. 2699, the fifth and sixth vertebras were found slightly
displaced, the exposed ends showing anteriorly a cup and posteriorly a reciprocal convex
articular surface. The zygapophyses, too, which are completely fused anteriorly, appear
less thoroughly united toward the rear end of the notarium. In the posterior vertebrae
of the series, the transverse processes are a little longer and are given oft* higher up on
the neural arches ; in fact, they originate considerably above the level of the neural
canal. Both the transverse processes and the neural spines are slighter than those of
the anterior dorsals. No ribs are in place behind the third pair, but the indications are
that all the posterior dorsal vertebrae carried slender single-headed ribs. With the no-
tarium of No. 2692, one free dorsal vertebra was found which is similar in form and size
to the last notarial, and may be accordingly regarded as the ninth of the dorsal series.
In another and larger example of Pteranodon sp., No. 2616 ; four dorsals similar to the
free dorsal of No. 2692 were found in close contact with each other, though not in
perfect articulation (Plate XIII, figure 1 ; also Plate VI, figures 17-20). Like all the
separate precaudal vertebrae, these four free dorsals are proccelous. Judging from the
character of the articulating surfaces, both central and zygapophysial, of the three an-
terior vertebrae of this series, and from the condition of the distal end of their trans-
verse processes and neural spines, which ^are not modified for attachment with either
notarium or pelvis, they are evidently free vertebrae. Front and rear views of the first
vertebra of this series are shown in Plate VI, figures 21 and 22. These same figures
would equally well portray the characters of the free dorsal found with No. 2692. The
fourth vertebra differs from the three preceding in having some further osseous develop-
ment at the extremity of its neural spine. This may be the vestige of a median longi-
tudinal band uniting the neural spines of the sacral vertebrae. Unfortunately, the anterior
portion of the sacrum of No. 2616 is not preserved, so that it is impossible to determine
to what extent the vertebra in question may have been connected with the sacral series.
Other examples of the genus offer clearer evidence upon the number of free dorsals and
are briefly described.

DORSAL VERTEBRA. 19

In Pteranodon sp.. No. 2451, which is a little smaller than No. 2692, there are preserved
the last two notarial vertebrae so completely fused that they are as one bone ; next,
three separate dorsal centra, and following these the four anterior centra of the sacral
series inseparably fused together (Plate XII, figure 1). While this sacrum is manifestly
incomplete, enough remains to show that ten vertebrae enter into its composition, three
of them anterior to that vertebra whose transverse processes share in the formation of
the anterior pelvic brim. Without anticipating further the discussion of the sacrum, it
seems best to designate in this way one of the sacral vertebrae which will serve as a
fixed point in calculating the number of dorsal vertebrae.

Again, in the type of P. ingens, No. 1175, there are preserved three dorsal vertebrae.
In these, the articular surfaces of the centra and of the zygapophyses indicate a little
movement, which of course argues in favor of their supposed location between notarium
and sacrum. The sacrum of this type, to be described later, is composed of a thoroughly
fused column of ten vertebrae, the fourth member of the series bearing the transverse
processes that partly define the anterior pelvic brim. No. 2451 and No. 1175 thus appear
to differ from No. 2616 in having only three free dorsals. There is, however, not the
slightest evidence that the total number of vertebrae is variable. The possible existence
of a fourth free dorsal in No. 2616 is best explained by referring to the fragmentary
pelvis of Pteranodon sp., No. 2489 (Plate XIII, figure 3), in which the sacral vertebrae
number but nine, the third member of the series giving rise to the transverse processes
which enter into the formation of the anterior pelvic brim. This matter will appear
more clear after the pelvis has been described in detail.

The series of notarial vertebrae finds its counterpart in the consolidated dorsal verte-
brae of many recent birds ; and as the musculature of birds and reptiles is also much
the same, a study of the avian dorsal region will help toward a better understanding
of the notarium of Pteranodon. The subject can be best introduced by quoting from
Newton's "Dictionary of Birds," p. 854: "In many birds the thoracic vertebrae shew a
tendency to more rigid junction, which is often effected in old individuals by the ossi-
fication of the various ligaments connecting the processes of adjoining vertebrae, or even
by the ossification of the attached tendons of the spinal muscles. In other cases con-
solidation is carried further by the co-ossification not only of the centra but also of the
spinous, transverse and zygapophysial processes of adjoining vertebrae, so that in ex-
treme cases the whole dorsal region may become one continuous mass of bone."

If the eminent writer of the foregoing quotation had been describing the notarium of
Pteranodon, his words could hardly have been better chosen, so nearly does the ptero-
dactyl resemble the extreme case cited. This coalescence of dorsal vertebrae in the
avian sk'eleton is generally regarded as directly correlated with increased power of
flight. Such was clearly the view of Sir Richard Owen when he wrote (Comparative
Anatomy and Physiology of Vertebrates, Vol. II. p. 17): "The neural spine is a compressed
quadrate plate, its truncate summit is often thickened, sometimes produced forward and
backward to fix the vertebrae from their highest points ; ossified tendons of spinal mus-
cles, also, aid the coalesced spinous and transverse processes in fixing part of the dorsal
region, but only in birds of powerful flight, and not in all such. The partial anchy-
losis of the dorsal region is associated in Falcons with their 'hovering1 action." The
exception to the rule is happily stated, for in the Frigate-bird, of extremely wide wing-
spread and noted for its powers of flight, the vertebral column anterior to the pelvis
retains its flexibility to advanced age, if not throughout life, the vertebrae remaining

20 OSTEOLOGY OF PTERANODON.

unfettered by ossified tendons and ligaments. On the other hand, the Gallinaceous
birds, a group incapable of long-sustained flight, have the anterior dorsal vertebrae rigidly
connected by the coossification of the dorsal spines and of the transverse processes,
the hypapophyses also being more or less united in the same manner.

Drawings have been made of the dorsal and sacral vertebrae of three representative
adult birds, and the writer has attempted to identify the points of attachment of the
muscles of the trunk by comparison with the excellent figures and definitions given by
Dr. Shufeldt in "The Myology of the Raven." Figure 1, Plate IX, is taken from a
skeleton of the Burgomaster Gull, Larus glaucus (Y. U. Osteol. Coll., No. 2290). The
squarely truncate summits of the dorsal spines are made to appear bifurcated behind
by the tendons of origin of the longissimus dorsi, which lie close against the spines
of the succeeding vertebras. Underneath these and hidden by them are other paired
tendons, which are directed forward from the summits of the dorsal spines and which
presumably afford insertion for the same muscle. Extending forward and backward from
the ends of the transverse processes are tendons serving as further points of attachment
for the longissimus dorsi and for the sacro-lumbalis. Plate IX, figure 2, shows the
dorsum of the Coot or Scoter, Oidemia nigra (Y. U. Osteol. Coll., No. 429), in which
the tendons arising from the dorsal spines are less developed than those of the previous
example, while the tendons of muscles attached to the transverse processes have ex-
panded into broad sheets binding the dorsal vertebrae firmly together in an almost in-
flexible column. In the dorsum of the Wild Turkey, Meleagris gallipavo (Y. U. Osteol.
Coll., No. 360), the vertebral coalescence has reached its highest development (Plate IX,
figure 3). The centra of four vertebrse are fused into one continuous mass, and their
dorsal spines with the attached tendons are represented by a thin median plate of bone.
Lateral flexion of this region is rendered equally impossible by the paired ossifications
resulting from the fusion of tendons attached to the transverse processes. Since this
consolidation of the dorsal vertebrae in birds, though usually associated with increased
power of flight, is not brought about by ossification of the tendons of any muscles
of the fore limb, but rather by the ossification of the tendinous origins and insertions
of muscles of trunk and neck, it seems possible that the extent to which such
development is carried may depend in some slight degree upon the physiology of
the cervical region. Should this prove to be the case, there will be less difficulty
in accounting for the marked variations of this structure in closely related groups of
birds.

Comparing the figures of the notarium of Pteranodon with that of Meleagris just
described, it will be seen that, with the exception of the presence in the pterodactyl of
a supraneural plate with oval facets for the scapulae, these two animals have developed
similar and equivalent structures ; and, considering the general similarity of avian and
reptilian musculature, there can remain little doubt that Pteranodon acquired its remark-
able notarium by the same developmental process that may be traced in birds.

It is interesting to note that while in most birds the coalesced anterior dorsals
are more or less rigidly connected with the posterior dorsals underlying the blades of
the ilia, in Meleagris a free dorsal intervenes between the sacral or pelvic series and
the anterior group, indicating slight flexibility in the same part of the vertebral column
where in Pteranodon the writer supposes three or four free vertebrae to have persisted.

SACRUM AND PELVIS. 21

SACRUM AND PELVIS.

The preservation of the sacrum and pelvis of the type of P. inc/ens Marsh, No. 1175,
is remarkable, displaying to advantage the principal characters of these important skeletal
parts. Plate X exhibits the slightly distorted form of this specimen, while restored
diagrams have also been prepared to show the side, top, and bottom views, respectively
(Plate XI, figures 1, 2, and 3).

Ten vertebras firmly anchylosed together constitute the sacral series, using this term
in its broader sense — the " synsacrum " of Professor T. J. Parker. The entire length
of the inflexible column so formed is 184 mm. The extremities of the neural spines of
all these vertebrae are united by a continuous median longitudinal band about 9 mm
wide and about 6 mm in vertical depth. In general form, the three anterior members
of this series are similar to the free dorsals which precede them. Their transverse
processes arise from the sides of the neural arch above the level of the centra and are
fused distally with the anterior blades of the ilia. The first of these vertebras bears
anterior zygapophyses for articulation with the last free dorsal, and the transverse
processes of these three anterior vertebrae have on their lower surfaces small facets for
the support of ribs, as is frequently the condition in the avian sacrum. These facets are
most distally situated on the transverse processes of the first vertebra, least so on those
of the third. What appears to be the proximal portion of one of these ribs still lies
upon the third vertebra with little displacement • from its original position. The distal
ends of the transverse processes of vertebra 4 extend downward and backward as stout
buttresses, which support the ilia more broadly than do the transverse processes of the
preceding and of the following vertebrae. The transverse processes of vertebrae 5, 6,
and 7 are separated by much smaller foramina, and they unite distally to form a con-
tinuous support for the ilia, as in some herbivorous Dinosaurs. The three remaining
vertebrae, numbers 8, 9, and 10 of this series, bear shorter transverse processes arising
more nearly at the level of their centra; they are separate at their distal ends, which
connect with the ilia. Their neural spines also aid in supporting the pelvis.

The ilia extend forward as broad thin plates resting against the transverse processes
of the anterior sacral vertebrae. Posteriorly, they unite with the transverse processes of
vertebrae 8, 9, and 10. They also converge medially on the dorsum and fuse with the
median longitudinal band over the neural spines of vertebrae 8, 9, and 10. So complete
is the anchylosis of these parts that they can not be differentiated with any degree of
certainty.

The united pubes and ischia are directed downward and backward, and meet below
in a median symphysis. The obturator foramina lie just beneath the imperforate ace-
tabula. They are circular in form, of about half the diameter of the acetabula, and may
be considered as marking the theoretical line of fusion between the true pubic and
ischial elements. On the anterior border of these ischio-pubic expansions are small
facets, which undoubtedly served for the attachment of the prepubes. The prepubes of
this example have not been preserved, and in no specimen in the Marsh Collection
have they been found in place. Plate XVI, figure 3, shows the prepubis belonging to
Pteranodon sp., No. 2472, which is about the size of No. 1175.

The remarkable similarity of Pteranodon's sacrum to those of many recent birds is
distinctly brought out by comparing it with the sacrum of the Wild Turkey, Meleagris

22 OSTEOLOGY OF PTERANODON.

gallipavo1 (Y. U. Osteol. Coll., No. 2112), shown in Plate IX, figure 4. Morphologically
considered, the fourth synsacral vertebra of P. ingens, No. 1175, is clearly the homologue
of that vertebra in the avian sacrum here figured, whose transverse processes aid in
the formation of the incomplete anterior pelvic brim, and also bound anteriorly the fovea
containing the kidneys. The three following vertebrae of P. ingens, numbers 5, 6, and 7,
occupy precisely the same position as those avian vertebrae which Huxley identified as
true sacrals, on the ground that the nerves issuing from their intervertebral foramina
form the sacral plexus. It has been already pointed out that vertebras 8, 9, and 10 of
the synsacrum of P. ingens support the posterior extensions of the ilia both by their
transverse processes and also by their neural spines, in this regard differing from ver-
tebrae 5, 6, and 7, and resembling the " posterior parapophysial vertebrae '' of the avian
sacrum, to adopt the phrase used by Messrs. Mivart and Clarke, in their treatise : " On
the Sacral Plexus and Sacral Vertebrae of Lizards and other Vertebrata" (Linn. Soc.
Trans., 2nd series (Zool.), vol. i, p. 513). The following quotation from the scholarly
work of these gentlemen is of especial interest in this connection : —

" The determination of the homological relations of the different parts of the post-
dorsal part of the spinal column of Birds is a matter of much difficulty. It might be
anticipated, however, from the close relations and probable genetic affinity between Birds
and Reptiles, that the true sacral vertebrae of the former class might be readily deter-
mined by the aid of reptilian characters. But however close may be the morphological
affinities, they are so strangely disguised by great physiological differences, that the
results of comparison are much too unsatisfactory to justify the anticipation above re-
ferred to. The enormous forward prolongation of the iliac bones and the great power
and activity of the erect and vigorous legs of birds, compared with the backwardly ex-
tending ilia and the sprawling and feebly pushing legs of Saurians, combine to produce
in Birds a redundancy of both osseous and nervous structures compared with those of
the existing Reptilia. Could we dissect the different forms of Pterosauria and Dinosauria.
these difficulties and obscurities would no doubt disappear; but the hiatus is too great
between the most Sauroid of existing Birds and any form of Lizard for the homological
relations, in this respect, to be readily and easily solved."

Returning to Pteranodon, certainly no form of reptilian sacrum could be desired by
Paleontologists, which should approach more closely the common type of avian sacrum.
The difficulty lies not in comparing Pteranodon's sacrum with that of Birds, but in reconcil-
ing its peculiar specialized development with the simpler forms known in other Reptilia.
Since the eighth and ninth vertebrae of the synsacrum of P. ingens so closely resemble
the two " posterior parapophysial vertebrae " of the avian sacrum, it will be instructive
to compare the sacrum of P. ingens with that of an older and more primitive pterosaur.
Quenstedt's plate of Pt.erodactylus (Cycnorhamphus) suevicus, published in 1855 (Ueber
Pterodactylus suevicus), shows two anchylosed vertebra? whose transverse processes unite
distally to support the ilia. Immediately in front of these two sacrals is a somewhat
longer vertebra, described by that author in the following words : —

" Nicht minder interessant als das Kreuzbein ist der starke Wirbel Nro. 22, man konnte
ihn den Kreuzbeintrager nennen, denn seine iiberaus kraftigen Querfortsatze gehen plotz-
lich unter einem Winkel von 60° gegen die Medianlinie nach hinten, ragen die Halfte

1 In this case, the sacrum of a young bird has been chosen for illustration. The transverse
processes of the avian vertebra referred to appear to be ossified from separate centers.

CAUDAL VERTEBRA. 23

ihrer Lange iiber den Wirbelkorper hinaus, um mit ihrer fast vierseitigen Endigung dem
Knochenwulste des Kreuzbeins so nahe zu treten, dass dadurch eine besonders feste Ver-
bindung moglich wurde."

That vertebra of Pteranodon's synsacrum whose long backwardly directed transverse
processes mark the anterior limits of the renal depressions bears the same relation to
the three following vertebrae as does the twenty-second vertebra of Quenstedt's specimen
to the two vertebrae which follow it. Obviously, the two united vertebrae of Pterodactylus
sueoicus supporting the iliac bones are true sacrals, for the following vertebrae have no
pelvic connection. Applying the terminology of the simpler case to the more complex,
it is evident that the fifth, sixth, and seventh vertebrae of Pteranodon's synsacrum are
to be considered true sacrals rather than the two following, whose place in the series
so closely resembles that of the two " posterior parapophysial vertebrae " regarded by
many recent authors as the true avian sacrals. The definition of the sacral vertebrae
used by such authors can not then be applied to the extremely birdlike Pteranodon,
and it seems best to retain for this highly specialized pterosaur the simpler definition
used by Professor Huxley.

Four other fragmentary sacra preserved in the Marsh Collection are figured here.
Three of these, Nos. 2451, 2570, and 2616 (Plate XII, figures 1, 2, and Plate XIII, figure 2)
closely resemble the sacrum of P. ingens. No. 1175, except in their dimensions, which
are much smaller. As they are unaccompanied by other skeletal parts of taxonomic
value, they may belong to any of the three species of Pteranodon, and no useful ends
would be attained by arbitrarily giving them specific names. Two of these specimens
have been already alluded to in the discussion of the dorsal vertebras. Plate XIII,
figure 3, shows the sacrum of Pteranodon sp., No. 2489, to which reference has also been
made in the preceding pages. Great interest attaches to this specimen because of the
reduced number of its vertebral parts. The synsacrum is here composed of only nine
vertebrae, and as stated above it is not the fourth vertebra, but the third of the series,
which sends out the stout transverse processes forming the anterior bounds of the renal
depressions. So little is preserved of the rest of the skeleton of No. 2489 that it is
quite impossible to determine the taxonomic value of this marked variation. This con-
dition is of course more primitive than that seen in the other sacra, and indicates how
near the sacrum of Pteranodon may approach that of the allied genus Nyctosaurus,
figured by Professor Williston (On the Osteology of Nyctosaurus'), where the second syn-
sacral vertebra bears the stout transverse processes.

It is important to note that the anterior synsacral vertebra is in every case firmly
anchylosed to the following member, whether there are ten vertebrae in the series or
only nine; the first vertebra included in the synsacra of Nos. 1175, 2451, and 2570 can
not then be considered as an insecurely attached unit, which may or may not retain
its connection with its fellows according as the local conditions at the time of interment
were quiet or disturbed. The coalescence of the synsacrals must have taken place early
in the development of the individual.

CAUDAL VERTEBRAE.

The number of caudal vertebrae in Pteranodon is not definitely known, but the opinion
of Professor Marsh and Professor Williston expressed in various papers, that the tail
MEMOIRS CONN. ACAD., Vol. II.

24 OSTEOLOGY OF PTERANODON.

was short, is well supported by the material preserved in the Marsh Collection. In
Pteranodon sp., No. 2489, five free caudal vertebrae have been preserved, and are shown
from above, obliquely, in Plate XIII, figure 4. These apparently followed the three
primitive caudals or urosacrals forming the posterior division of the synsacrum. They
dwindle rapidly in size, and although badly crushed, are supposed to indicate a length
of tail of from 12 to 16 mm in an animal about nine-tenths the size of P. ingens. No. 1175.
So short a caudal member could have been of little service as a rudder, and the animal
must have depended largely or wholly upon other means of guiding its flight. It will
be remembered in this connection that other practically tailless forms of flying animals
have no apparent difficulty in directing their movements. Plate VI, figure 23, shows
the lower surface of four caudal vertebrae of another example of this genus, No. 2546,
about the same size as No. 2489. These vertebrae are still contained in the matrix and
presumably represent the middle third of the caudal series.

The caudal vertebrae have been described by Professor Williston as amphiplatyan
(Kansas Univ. Quart., vol. vi, No. 1, Jan., 1897), while Professor Gadow (Amphibia and
Reptiles) regards the caudal vertebrae of all Pterosauria as amphiccelous. Some of the
larger caudals of Pteranodon in the Marsh Collection appear slightly concave at both
ends, but their original condition is uncertain, their form having been greatly altered
by pressure. It is to be expected that the character of the central articulations would
be somewhat obscure in the degenerate tail ascribed to this genus.

SHOULDER GIRDLE.

The shoulder girdle, consisting of the scapula, coracoid, and the sternum, has been
so fully described by Professor Williston that little further remains to be recorded about
the osteology of these parts. Characterizing the sternum of one of the "smaller species"
of Pteranodon (Restoration of Ornithostoma, Kansas Univ. Quart., vol. vi, No. 1, Jan., 1897),
Professor Williston writes : " It is extremely thin and [is] pentagonal in outline. Pro-
jecting in front of the articulations for the coracoids is a stout process, obtusely pointed,
and evidently directed somewhat ventrally in life. The articular facets [for the
coracoids] look dorsad and laterad and are gently convex from side to side and concave
antero-posteriorly. Just back of the articulations the moderately thickened borders slope
obliquely backward to the full width of the bone. The first articular facet for the ribs
begins at the angles and runs backward a half inch. It is of considerable thickness,
and may be for the attachment of the stout co-ossified rib attached to the first of the
consolidated dorsal vertebrae. The lateral margins of the sternum, back of the angle,
are thin, and have three emarginations, separating four articular projections. The three
posterior ones are small and pointed, and could have given attachment to only slender
ribs. The lateral borders are parallel with the longitudinal axis of the bone. The
posterior border is not preserved, but from the general resemblance to the bone in
Nyctodactylus, I believe that it is nearly straight, although it may have been gently
concave or convex. The bone was in all probability concave above in life."

No perfect sternum is known to the writer, and indeed such is the tenuity of the
posterior border of the bone that none is likely to be found. Three more or less com-
plete examples have been selected from which a fairly accurate idea of the entire bone
may be obtained. Plate XIV, figure 1, shows the lower surface of the vertically crushed

SHOULDER GIRDLE. 25

sternum of a large animal, Pteranodon sp., No. 2546. Through comparison of other
skeletal parts, this individual is known to be about nine-tenths the size of the type of
P. ingens, No. 1175. Its specific identity, however^ remains doubtful, as no skeletal parts
of taxonomic value have been preserved. The inner or upper surface of the anterior
portion of another sternum of slightly smaller size, No. 2616, is shown in Plate XIV,
figure 2, while figures 1 and 2 of Plate XV are taken from the right and left sides,
respectively, of a laterally crushed sternum, No. 2692. This last example is especially
useful in giving an idea of the natural shape of the bone, which must presumably have
been intermediate between the forms of those crushed vertically and those crushed laterally.

The nearly complete restoration of the sternum, No. 2546, shown in Plate XVI, figure 5,
has been obtained mainly by replacing missing portions of one side by the correspond-
ing portions preserved on the other side. The form of the manubrium has been
determined partly from the impression left upon the matrix by the portion lost by the
collector, and partly by recourse to the sternum of No. 2692. The four lateral articular
projections described and figured by Professor Williston, and supposed by the present
writer to be for the attachment of sternal ribs, are well shown both in this drawing and
in the photographic view (Plate XIV, figure 1). There is also a fifth pair of projections
that appear to be for articulation with a fifth pair of sternal ribs. A small round vacuity
is seen in the midline close to the posterior border of the sternum. (This has been
also observed in another specimen in the Marsh Collection.) Immediately in the rear
of this vacuity is a pair of closely approximated articular projections, which probably
served to connect with the abdominal ribs. There seems to have been another pair of
articulations separated from the median pair by shallow emarginations, as shown in the
restored figure, but the frail and imperfect margin of the bone here permits of no definite
conclusions. On the right side of the sternum (the left in the figure) a small oblong
ossicle lies in each of the first two shallow emarginations. Only one of these ossicles
remains on the left side. Their significance is not understood by the writer.

The manubrium is evidently much deeper in the vertical direction than wide, and its
sharp inferior edge is continued backward to the middle of the broad part of the sternum
as a rudimentary keel. This is also the condition in the laterally crushed sternum of
No. 2692, but in another example that has been subjected to great vertical pressure, as
evidenced by the almost total obliteration of the coracoidal facets, no trace of the keel
is to be seen. While it is not desired to convey the idea that Pteranodon's sternum
bore a prominent keel for the attachment of the pectoral muscles, it would be equally
erroneous to describe it as strictly of the ratite type.

The lateral halves of the broad and thin body of the sternum appear to have been of
rounded form, so that this part of the bone may have resembled a shallow dish or trough,
with the addition of the low keel-like process on the anterior portion. In the restored
figure, the transverse measurement is of course somewhat reduced through foreshortening.

A posterior view of the right scapula and coracoid of P. ingens (type), No. 1175, is
shown in Plate XVII, figure 1. The two united bones are defective behind and below
the glenoid, and in order to assemble the fragments it has been necessary to replace
the missing portions with plaster of Paris. The general outline will be found fairly
correct, but no attempt has been made to restore the bone in detail. In size, this speci-
men exceeds all other examples preserved in the Marsh Collection. In the left scapula
and coracoid of Pteranodon sp., No. 2512, a posterior view of which is shown in Plate
XVII, figure 2, the general proportions are admirably preserved, although the bones are

26 OSTEOLOGY OF PTERANODON.

slightly incomplete. Across the middle of the glenoid surface can be seen the suture
between the component elements. Two views, front and rear, are shown of the left
scapula and coracoid belonging to the smaller Pteranodon sp., No. 2616 (Plate XVIII,
figures 1 and 2). The articular coracoidal facets of the sternum of this individual have
been shown in Plate XIV, figure 2. Upon examination, these figures will be found to
agree in the main with Professor Williston's admirable description of this part of the
shoulder girdle in his paper entitled : " Restoration of Ornithostoma." In the right scap-
ula and coracoid of Pteranodon sp.. No. 1181 (Plate XXIII, figure 1), a deep and narrow
depression lies immediately behind the glenoid surface. It is presumably the coracoidal
foramen mentioned by Professor Williston. While no other specimen in the collection
shows unmistakable evidence of this foramen, there is no reason for supposing that it
was wanting in some of the species.

The following quotation is from Professor Williston's description of the u Coraco-
scapula " : —

" This bone is stout, U-shaped, with the coracoid arm distinctly longer than the
scapular. The distal extremity of the scapula has a large oval facet placed obliquely to
the long axis, and evidently also obliquely to the transverse axis of the body, indicating
that the bone was directed not only outward and downward, but also more or less for-
ward. The shaft in all the known specimens below the articulation is trihedral or flat-
tened, but in life it was evidently round or oval in cross-section. On the lower part
the width is greater, due to a projection of the dorsal side before the glenoid articulation,
for the attachment of muscles. The glenoid articulation is deeply concave from above
downward, convex from side to side and bounded both above and below by a prominent
ridge, that on the inferior border being much stronger than the upper one. The surface
is markedly oblique to the plane of the bone, doubtless in life directed outwardly and
posteriorly in the oblique position of the bone that I have described. The surface is
considerably narrower from side to side below than above, and in this direction [side to
side] it is convex throughout. A rugose line, indicating the junction of the two bones,
passes directly backward near the middle of the articular surface. At the bottom of the
U, formed by the conjoined bone, there is a process arising from the scapula and reach-
ing to the anterior surface of the coracoid, to which it is joined ; it incloses a small,
oval foramen just back of the middle of the glenoid surface. The diameter of the
foramen is about twelve millimeters.

" The shaft of the coracoid is flattened antero-posteriorly in all the specimens, though
probably in life oval. On its proximal half there is a prominent process on the inferior
border for muscular attachment. From beyond the middle the sides of the bone are
parallel. The sternal articulation is gently concave in one direction and slightly convex
in the other, to agree with that of the sternum, forming a reciprocal joint, which must
have had considerable mobility. A little above the sternal end, on the posterior side,
there is a narrow rugosity, more than an inch in length, for muscular attachment."

The different skeletal parts comprising the thorax have been described separately and
may now be considered in their joint relationship to the act of respiration. The only
considerable and essential portion of the thoracic frame remaining in any doubt is the
series of sternal ribs. As the writer is not aware that these have ever been positively
identified in Pteranodon, it may be well to call attention to a small but seemingly com-
plete bone (Plate XVI, figure 4) found with the skeleton of P. ingens (type), No. 1175.
While this bone is only 41 mm in length, its form closely resembles that of some of

SHOULDER GIRDLE. 27

the sterno-costalia of Campylognathus zitteli, figured by Dr. Plieninger in : " Die Ptero-
sauria der Juraformation Schwabens," p. 222.

The quotation from Professor Williston's " Restoration of Ornithostoma," in regard to
the sternum, conveys the idea that one or more " coossified " vertebral ribs issuing from
the anterior dorsal vertebrae were connected directly with the sternum ; and the same
eminent paleontologist has written concerning the more or less closely allied genus
Nyctosaurus (Osteology of Nyctosaurus, p. 136) : " There are apparently four pairs of stout
ribs arising from the first four dorsal vertebrae, the first three of which, at least, are
anchylosed to the centrum in the adult animal. They were doubtless all attached to
the four tubercles on each side of the sternum." And again in the same work, p. 139 :
"It has been suspected that there are sternal ribs intervening between the vertebral ribs
and the sternum, but there is no evidence of such in the present specimen."

The notarium of Pteranodon sp., No. 2692, already figured, proves beyond all doubt
that the vertebral sections of the first three dorsal ribs are anchylosed to their vertebrae.
If the lower ends of these vertebral ribs articulated directly with the lateral sternal pro-
jections, the sternum would be immovably fixed in its position ; and, no account being
taken of diaphragmatic breathing, which is at the most but rudimentary and negligible in
Aves and Reptilia, this pterodactyl could have filled its lungs only by gulping air into
them as do the Chelonians with fixed plastron. On general grounds, such limited res-
piratory action would seem inadequate in a flying reptile, the pneumaticity of whose
skeleton almost or quite equaled that of the most lightly-framed existing bird.

More direct evidence on the question of the fixity or mobility of the sternum is offered
by the peculiar saddle-shaped facets at the base of the manubrium sterni, for the artic-
ulation of the lower ends of the coracoids, a joint which Professor Williston himself
stated " must have had considerable mobility " (see p. 26). There is no doubt whatever
that Professor Williston is correct in his statement that the sternum moved upon the
coracoids, although such a conclusion appears at variance with his ideas on the struc-
ture and connections of the dorsal ribs. The mechanical principle involved is simple,
and from the diagram of the thorax (Plate XXXI), it will be readily seen that not only
must well-developed sternal ribs have intervened between the anterior vertebral ribs and
the sternum, but also that there must have been a slight rotation of the scapulae upon
the supra-neural facets of the notarium ; otherwise there could have been no movement
of the sternum. Even then the mechanical action of respiration woujd not be exactly
equivalent to that prevailing in many reptiles and in birds, where both the vertebral ribs
and the corresponding sternal ribs are free to move when drawn forward by the inspira-
tory muscles, the main action of these muscles being to straighten the angles between
the vertebral and sternal sections of the ribs, and thus by the well-known principle of
the "toggle-joint" to force the sternum away from the vertebral column.

In Pteranodon, on the other hand, the action of the thoracic mechanism was greatly
lessened by the immobility of the anterior vertebral ribs, as well as by the complete
anchylosis of the coraco-scapular union, an articulation which permits of considerable
movement in almost all carinate birds ; and the movement of the sternum was accom-
plished by swinging it bodily downward and backward about the distal ends of the
vertebral ribs, to which points it was united by sternal ribs. Clearly, in this animal,
the anterior vertebral ribs being fixed, the levatores costarum and the external inter-
costals would cease to function as contractile muscles, and in the adult pterodactyl they
would probably degenerate into aponeurotic tissue, serving only to close the intercostal

28 OSTEOLOGY OF PTERANODON.

^

spaces. Similar changes would probably take place in the expiratory muscles attached
to the anterior vertebral ribs. On the other hand, those muscles of the thorax and
abdomen controlling the movement of the sternum and sternal ribs would be developed
in proportion to the respiratory needs of the animal.

WING BONES.

Of all the skeletal parts of Pteranodon, the wing bones perhaps offer the least in-
ducement to further investigation. Obtained more abundantly at the outset by collec-
tors, and usually in better preservation than the axial skeleton, they naturally form the
subject of much of the earlier contributions to the osteology of this genus, with the
result that their study has been carried nearly to completion. It is proposed in this
memoir to figure the entire skeleton as far as it is possible to do so from specimens in
the Marsh Collection, and some brief comment upon the wing bones may properly
accompany their illustration without attempting to paraphrase descriptions, the excellent
definitions recorded by Marsh, Williston, and Plieninger being easily accessible.

In the introductory pages of the present memoir, Professor Marsh's separation of the
two species P. occidentalis and P. ingens is shown to have been based partly upon the
relative size of the types and partly upon differences in the form of their humeri and
of the proximal ends of their ulnae. It is also stated that further work upon the collec-
tion has led the writer to the conclusion that these differences are of no taxonomic
value, as they appear to be merely the variant results of unequal pressure in the matrix.
It is impossible to record anything more satisfactory in regard to the proximal articula-
tions of the ulnae in question than the statement that these bones having been so
greatly distorted, the wonder is, not that the original investigator gave undue impor-
tance to their differences, but rather that he so promptly recognized in them the same
skeletal element.

In regard to the supposed specific difference of the two humeri, it is now possible
to write more explicitly. When the humerus of P. occidentalis (type), No. 1164, was
described by Professor Marsh, the " anconal " side alone was entirely exposed to view
(Plate XIX, figure 9). He was therefore deceived by the appearance of the radial crest,
which then seemed much smaller than the corresponding process of the humerus of
P. ingens. Upon removing the matrix from the opposite side of P. occidentalis (Plate XIX,
figure 10), it became evident that the radial crest had been crushed and shortened by
pressure, and that no specific difference could be pointed out in these processes of the
two types. The humerus of P. ingens (type), No. 1175, is somewhat better preserved
than that of P. occidentalis, which it resembles closely except in size, and although the
radial crest is by no means perfect, the generic characters of the bone are well dis-
played. Two views of this humerus are given, Plate XIX, figure 1, showing the
" anconal " or dorsal surface, and figure 2, the palmar or inferior surface.

The vagaries of form assumed by the humerus under pressure in the matrix are
surprising, the first result of this perplexing situation being that almost every humerus
in the collection seems to represent a distinct species. From an examination of four-
teen practically complete humeri of Pteranodon, variously distorted, it appears that
pressure in the vertical direction (the vertebral axis of the pterodactyl being supposed
to lie in the horizontal plane, with the wings outstretched laterally) usually crushes
and shortens the radial crest, while pressure in the horizontal plane not only leaves the

WING BONES. 29

radial crest extended at its full length, but also alters the head of the humerus in such
a way that the radial crest appears to originate further from the proximal condyle.

A practical test of this theory has been obtained by performing the following simple
experiments, adapted from Professor Daubree's admirable method of artificial mountain-
making : Two models of the humerus were made from soft clay, simulating the original
form of the bone as closely as possible. These models were crushed between two flat
surfaces, the direction of pressure in one instance being normal to the upper or anconal
side, and in the other instance being normal to the radial side of the bone. The result
of the first experiment was that the crushed model assumed the form of the humerus
of P. occidentalis (type), while the result of the second experiment was that the model
assumed the form of the humerus of Pteranodon sp., No. 2302, shown in Plate XX,
figures 4 and 5. While these simple ossifragous experiments obviously failed to comply
with the exact conditions prevailing in nature, they add considerable weight to the
writer's opinion that the different forms of humeri shown in Plate XX are due solely
to the varying conditions of pressure to which the bones were subjected. All doubt
upon this matter would be removed if the humeri belonging to one individual were
found differently crushed ; unfortunately, in not one of the 465 examples of Pteranodon
in the collection are the proximal portions of both humeri preserved.

In Plate XIX, figures 3, 4 a, and 4b, the left ulna and the ends of the left radius of
P. ingens, No. 1175, are shown, the palmar or inferior surface of the ulna being toward
the observer. The proximal ends of the radius and ulna and the distal end of the
radius, all three fragments belonging to the right wing of No. 1164, type of P. occiden-
talis, are shown in Plate XIX, figures 11, 12 a, and 12 b. Some of the bones of the
left wing of Pteranodon sp., No. 2425, are figured in Plate XXI, just as they are pre-
served in the matrix. The radius and ulna are here practically entire, and appear to
have retained their natural positions relative to each other, although their articulations
with the humerus and carpus are dislocated. This specimen is also valuable for the
excellent state of preservation of the two larger carpals, usually distinguished by the
terms "proximal" and "distal." A view of the inferior or palmar surface of these
bones, on a larger scale, is shown in Plate XXII, figure 1. A small slender bone of
doubtful identity occupies the place of the third or lateral carpal in this specimen, but
the process for the support of that carpal, arising from the radial side of the distal
carpal, is admirably preserved. The reverse side of the slab containing this specimen
has been excavated so as to permit Plate XXII, figure 2, to be made, which shows the
dorsal side of the carpus. Three views of the left carpus of P. ingens. No. 1175, are
given in Plate XIX, figures 6, 7, and 8. In figure 6, showing the proximal surface of
the carpus, the distal carpal is nearly concealed, but the greater part of the lateral
carpal is visible. Figure 7 is taken from the dorsal view of the carpus, all three bones
being compressed in the direction of the axis of the wing. In figure 8, the distal view
of the carpus, the outlines of the distal and lateral carpals are clearly seen, the latter
borne by a process extending from the radio-palmar angle of the distal carpal. In
assembling the carpus for illustration, it was found impossible to maintain a perfect
contact between the distal and lateral carpals without rotating the lateral carpal slightly
from that position in which it would best support the first metacarpal or " pteroid
bone." The carpus of P. occidentalis No. 1164, shown in Plate XIX, figures 13 and 14,
appears to be precisely similar to that of P. ingens just described, except that the lateral
carpal of P. occidental^ is differently crushed and makes a better contact with the distal

30 OSTEOLOGY OF PTERANODON.

carpal, when in the supposed natural position. The lateral carpal of this example has
two foramina on opposite sides of the bone.

In another example of Pteranodon sp.. No. 2683, the two larger carpals of the right
wing are preserved with but little distortion, and the lateral carpal, although found in
two separated fragments, has been restored well enough to be photographed in its
supposed natural position relative to the main body of the carpus. The writer is not
aware that the three carpals have yet been found in true contact in any example of the
genus, and until either this is done or the lateral carpal is found in contact with the
pteroid bone, it will remain an open question which end of the lateral carpal is rightly
supported by the process arising from the radio-palmar angle of the distal carpal. Com-
parison with the European pterodactyls offers little aid toward the solution of this prob-
lem. In support of the position of the lateral carpal in the accompanying figures, it
may be said that the articular sockets characterizing the ends of the bone are of une-
qual size, and the end of the bone bearing the larger socket may be reasonably sup-
posed to be turned toward the distal carpal, inasmuch as the articular process of the
distal carpal is considerably larger than the proximal head of the pteroid. In Plate XXII,
figure 4, the main body of the carpus of No. 2683 is seen from the palmar side, as
found in contact with the proximal end of the large fifth metacarpal. In figure 5, the
carpus has been removed from the matrix so as to exhibit the dorsal side.

The form of the great metacarpal, recognized by most paleontologists as the fifth, is
shown in Plate XXI, taken from the wing bones of Pteranodon sp., No. 2425. The
dorso-radial surface of the bone is here presented to view. It will appear at a glance
that all the sections of this wing are more or less dislocated. The characteristic forms
of metacarpals II, III, and IV may be learned from such parts of these bones as are
preserved, all three appearing to consist of extremely slender rods of bone closely
pressed to the great metacarpal and expanding distally into rounded condyles for the
articulation of the phalanges of the short clawed fingers. The greater part of the
pteroid bone remains with its proximal head almost in contact with the carpus. Its
shaft, however, has been turned from its normal position. In most specimens, the pteroid
is directed nearly toward the head of the humerus. A complete pteroid may be seen
in Plate XXIII, figures 1 and 2, showing the wing bones of Pteranodon sp., No. 1181.
The bone bears a slight resemblance to the distal parts of the lateral metacarpals, next
to which it lies in the matrix. It is, however, easily distinguished by its greater cur-
vature at the articular end and by its stouter shaft. The question whether or not the
so-called pteroid should be properly identified as the metacarpal of the first digit of
the manus need not be entered into here, as there is no new evidence to be offered in
support of either view.

Previous attempts to assemble the phalanges of the three clawed fingers of the hand,
viz., digits II, III, and IV, have not been entirely successful. The best diagrammatic
reconstruction of these parts was given by Professor Williston in his paper : " On the
Osteology of Nyctosaurus," p. 145. In explanation of the figure, he states : " I give
herewith a diagrammatic figure of these parts in Pteranodon, based on a specimen in
which nearly all the bones were present and in position, some of the terminal phalanges
only being misplaced, and one or two of the fourth finger missing. In a former paper
I stated that the phalanges of the hand were of two kinds, long and short. Possibly
this is the case in some of the smaller species, but I think not. I doubt not that the
small phalanges there described were from the foot, and had become misplaced and

WING BONES. 31

associated with the hand phalanges in the specimen described." In an article entitled :
" The Fingers of Pterodactyls " (Geol. Mag., February, 1904), Professor Williston gives
the number of phalanges of the three clawed digits in the hand of Pteranodon, as two,
three, four, respectively, but he does not discuss further the occurrence of the very
short phalanx which he had previously noted.

No complete manus of Pteranodon with the parts in their natural position is found in
the Marsh Collection, yet the specimens preserved afford conclusive evidence as to the
number and arrangement of the phalanges. Figure 2, Plate XXIII, has been prepared
to show to better advantage the phalanges of the right manus of Pteranodon sp., No. 1181.
Although the bones are disarticulated, it is clear that there are here preserved five
phalanges of moderate length, one very short phalanx, and three terminal claws. One
of the longer phalanges has a deep process at the proximal end on the lower side.
Judging from other material, this process appears to be characteristic of the first phalanx
of the fourth digit.

In another specimen of Pteranodon sp., No. 2428, the greater part of the right manus
is preserved ; in fact, the claw-shaped distal phalanges only are wanting. In this manus,
as well as in that of No. 1181, there is one very short intermediate phalanx whose length
is but a trifle greater that its diameter. Plate XVI, figure 2, based upon No. 2428, pre-
sents the writer's mature views of the phalanges of the manus, which, it will be seen,
are in accordance with the recognized general formula for the digits of the reptilian
hand. The forms of the bones actually preserved are shaded, while the missing claws
and the distal end of metacarpal II are represented in outline. The short phalanx already
mentioned has been identified as the second phalanx of the fourth digit, thus agreeing
perfectly with the condition generally prevailing in the older pterodactyls, where the
second phalanx is considerably shorter than its proximal and distal neighbors. Professor
Williston's doubt as to whether the short phalanges which he found associated with the
manus might not have been interpolated from the foot is removed by comparing the
diameter of the phalanges of the manus with those of the podials. The digits of the
foot are so much more slender than those of the hand that they may be readily distin-
guished by their size alone. Three nearly complete digits of the right manus of Pteran-
odon sp , No. 2493, are shown in Plate XXII, figure 3. The arrangement of the phal-
anges is evidently unnatural, although these parts are said to occupy the same order as
when discovered by the collector. The short phalanx of digit IV, which lies near the
distal end of the metacarpal, has clearly been dislodged from its true position, and one
of the long phalanges of digit III is wanting. The same forces that moved backward
the short phalanx of digit IV may have removed one of the phalanges of the adjacent
digit, and closed the gap so formed.

Reverting again to the large metacarpal V (that of the wing finger), six figures are
especially introduced to show its distal articulation with the first phalanx. The adjacent
ends of these two bones belonging to the left wing of a large example of Pteranodon
sp., No. 2628, are shown in Plate XXIV, figures 1 and 2, taken from the ulnar and
radial sides, respectively. Figures 3 and 4 portray the corresponding portions of the left
wing of a smaller example of P. occidentalis (Marsh's own identification), No. 1165, at
the angle of extreme flexure, though there is some reason to suppose that slight dis-
location has here been effected.

The articulation of metacarpal V with the first phalanx of digit V has been figured,
in the examples cited, from bones crushed transversely. To demonstrate better the form
MEMOIRS CONN. ACAD., Vol. II. 5

32 OSTEOLOGY OF PTERANODON.

of this joint viewed from the palmar side, figure 5 has been made from the conjoined frag-
ments of the left metacarpal and the first phalanx of Pteranodon sp., No. 2660, which
are crushed vertically. The bones are here represented in actual contact, with the joint
extended just as preserved in the matrix. Figure 6 shows these same parts when separated.

The distal end of the first phalanx of the wing finger, as described by Marsh, "presents
an elliptical, convex, articular face, which does not entirely cover the distal surface. The
second phalanx has its proximal extremity adapted to this articular face by a shallow
elliptical cup, which does not extend over the most proximal portion of the extremity.
The distal end resembles in everything but size the corresponding part of the first
phalanx. The next or third phalanx is quite similar to that which precedes it, except that
it is more attenuated. The slender terminal .phalanx appears to have been more nearly
circular at its proximal end, although apparently compressed toward its other extremity.
The articular surfaces of all the bones preserved are smooth and well defined, like those
of mammals and birds. All the bones of the wing, moreover, even the carpals, appear to
have been pneumatic." The shafts of the wing bones generally are of extreme tenuity,
fragments from some of the larger specimens having only a thickness of one millimeter.

From the form of the articulation, it is evident that the flexion of these phalanges
upon each other was limited to an angle of about 45°. When the wing was fully ex-
tended, it is probable that the flexion of these bones upon each other was very slight.
In Plate XXV, figures 1-7, the wing bones preserved in Pteranodon sp., No. 2452, have
been arranged so that the relative lengths of the phalanges may be seen. The wing
bones preserved in another individual, No. 2774, are displayed in Plate XXVI, figures 1,
2, and 3. The fourth or terminal phalanx is missing in this example, but is preserved
in No. 2470 (Plate XXVI, figures 4-7) and No. 2591 (Plate XXVI, figures 8 and 9). The
curvature of the fourth phalanx of the wing finger, which is clawless, varies slightly in
different individuals, and indeed is not precisely the same in the right and left wings of
one of the few examples in which both members are preserved. In no specimen in the
Marsh Collection is this bone straight. The pteroid bone, lacking its proximal articula-
tion, might easily be mistaken for a terminal phalanx. In face of this evidence, it would
appear unwise to attempt to separate species on slight differences of curvature in the
terminal phalanx of digit V.

From twenty-five examples of Pteranodon in the collection, linear measurements of
various wing bones have been taken, and are presented in Table A. In Table B, each
of the first five sections of the wing has been taken in turn as the unit of length, the
lengths of the other bones being expressed as percentages. The original purpose of
these tables — to aid in separating the species — is in large measure foiled by the imper-
fection of the material. Perhaps their greatest value lies in the indications they afford
as to the size attained by the genus.

For convenience, the measurements of the femur and tibia have been included in these
tables ; and at the bottom of Table B, the comparative measurements of the wing bones
of P. ingens given by Professor Williston in his paper : " On the Osteology of Nycto-
saurus " have been entered. These measurements, as stated in a letter from Professor
Williston, were " taken from a life-sized drawing made of the mounted specimen in the
Kansas Museum." It now seems impossible to prove positively that the wing bones
referred to belonged to a single individual ; for the Curator having charge of the col-
lection writes : " I find that in some cases the bones have been mounted on wires, etc.,
and that the catalogue number must have been either erased or is underneath." On

TABLE A.

33

the supposition that they are taken from a single individual, it is instructive to note
that the ratio of the ulna to the humerus is 136, which is only a trifle greater than the
ratio of the corresponding bones of Professor Marsh's type of P. ingens, No. 1175. In
all other examples of Pteranodon in the Yale Collection, the length of the ulna is still
greater in comparison with that of the humerus.

TABLE A.
Lengths of long bones of the wing and leg in millimeters.

Cat. No.

Hum.

Ra.

Ul.

Me. V.

1st Phal.

2d Phal.

3d Phal.

4th Phal.

Femur

Tibia

1164

167

430

2616

180

260

510

. . .

. . .

190

• • •

1175

290

. . .

384

. . .

270

...

2425

155

217

223

360

. . .

. . .

t . .

2692

170

. . .

. . .

. . .

453

358

125+

. . *

> • •

2767

. . .

. . .

, . .

400

240

...

175

. . .

2493

202

284

296

454

550

474

• • •

192

290

1181

144

205

210

. . .

. . .

. . .

. . .

2348

, . .

283

290

455

470

322

165+

2591

. . .

. . .

. . .

323

193

. . .

2738

. . .

. . .

670

500

260

353

2499

. . .

338

. . .

480

330

. . .

. . .

. . .

2662

. . .

. . .

, . .

325

185

. . .

2452

315

550?

623

460

301

160+

. . .

. . .

2680

242

250

. . .

. . *

370?

260

. . .

. . .

2451

173

382

452

. . .

. . .

. . .

248

2730

230

325

445+

2689

. . .

. . ,

. , .

705

. . .

358

2470

. . .

495

380

260

152

. . .

2414

355

572

. . .

. . .

. . .

2774

. . .

454

372

263

. . .

. . .

2708

476

, . .

255

. . .

. . .

2403

490

315

170

. . .

2473

. . .

600

. . .

. . .

. . .

2496

206

34

OSTEOLOGY OF PTERANODON.

TABLE B.
Proportional lengths of long bones of the wing and leg.

Cat. No.

Hum.

Ra.

Ul.

Me. V.

1st Phal

2d Phal.

3d Phal.

4th Phal.

Femur

Tibia

1175

100

132

...

93

2730

100

141

193+

. . .

2425

100

140

144

232

. . .

. . .

. . .

. . .

2493

100

141

147

225

272

235

95

144

1181

100

142

146

. . .

. . .

. . .

2616

100

144

148 l

. , ,

283

106

1164

100

. . .

257

. . .

. . .

. . .

. . .

2451

100

. . .

221

261

143

2692

100

. . .

266

212

74+

2493

100

153

186

160

... ...

65

94

2348

. . .

100

157

162

Ill 57+

2414

. . .

. . .

100

161

. . .

. . .

. . .

. . .

2452

. . .

. . .

100

174

194

147

95

51+

2730

...

100

137+

, ,

. . .

2499

. . .

100

, . .

142

98

. . .

. . .

2680

. . .

100

. . .

148?

104

1175

100

• • i

. , .

70

2452

. . .

100?

113

84

55

29+

. . .

2451

. . .

. . .

100

118

. . ,

. . .

. . .

63

2493

. . .

100

121

104

. , .

42

63

2348

. . .

. . .

100

103

71

36+

. . .

2767

100

. . .

. . ,

60

44

2452

. . .

, . ,

. , .

. . .

100

74

48

26+

. . .

2738

. . .

... ...

100

75

• . .

. . .

40

53

2470

. . .

100

77

53

31

. . .

. . .

2692

. . .

100

79

. . .

28+

. . .

2774

. . .

...

100

81

57

2493

. . .

100

86

• . .

35

53

2689

. . .

. . .

100

51

. . .

. . .

2708

. . .

. . .

100

54

2451

. . .

. . .

100

. . .

, . ,

55

2403

. . .

. . .

100

64

35+

2452

. . .

. . .

100

65

35+

. . .

2470

. . .

• • •

100

68

40

2348

. . .

... ...

100

69

35+

. . .

2499

. . .

. . .

100

69

. . .

. . .

2680

. . .

, , .

. . .

...

100

70

• • >

. . .

. . .

2774

100

71

Average

100

142

143

226

268

ji

100

79

53

31

. . .

2

100

136

210

268

172

106

150

i)

100

154

197

126

...

1 Calculated.

! Taken by S. W. Williston, from a specimen in the Museum of the University of Kansas.

LEG BONES. 35

LEG BONES.

The femur of Pteranodon ingens has been amply described by Professor Williston
in the following paragraph (On the Osteology of Nyctosaurus. p. 150), which will be
found to agree well with the form of the bone as shown in Plates XXVII, XXVIII,
and XXIX:-

"The convexity of the head is regular, covering nearly half of a circle transversely,
probably a little less in the conjugate diameter, the surface thus forming an oval or
ovate figure, the plane of whose base is nearly at right angles to the long diameter of
the bone. The convex surface is sharply limited from the neck. The neck is cylindrical,
rather stout, and is directed nearly vertically downward. The rounded and moderately
prominent trochanter is placed over the middle of the shaft, descending into the con-
cavity at the side of the neck, and externally separated from the margin of the bone.
The shaft is nearly of equal width throughout ; doubtless in life it was nearly cylindrical,
with a strong anterior curvature, and a flattening in the popliteal region. The sharp
margin of the inner condyle encompasses nearly half a circle. The outer condyle,
though extending further, is much less in extent. The inner distal articular surface is
the larger, and is separated from the inner surface by a distinct ridge, especially
posteriorly."

Professor Williston's description of a tibia of Nyctosaurus immediately following the
above quotation applies equally well to the tibia of Pteranodon, showing how closely
the leg bones of these two genera resemble each other. His words are as follows : —

" The tibia is a slender, straight bone, moderately expanded at the upper extremity.
The margin of the articular surface above is nearly transverse to the longitudinal axis.
The width contracts chiefly at the expense of the posterior margin to the lower part
of the upper fourth of the bone, the shaft below being of nearly uniform width. The
trochlear surface at the distal extremity is pulley-shaped, covering about half of a circle,
perhaps more, and has a moderately deep groove." Professor Williston adds : " There
is no trace of any fibula, either in the preserved remains or in any tibial articulation."
This is also true of the Pteranodon material contained in the Marsh Collection.

Of the leg bones of P. ingens (type), No. 1175, only the right femur (entire), the
proximal end of the left femur, and the proximal and distal ends of the right tibia are
preserved; the bones of the right leg are shown in Plate XXVII, figures 4, 5 a, and 5b.
The two femora and their tibiae of a slightly smaller individual of Pteranodon sp.,
No. 2738 (Plate XXVIII), will be found similar to those of P. ingens (type), as are also
the leg bones of Pteranodon sp., No. 2489, which are figured on Plate XXVII, figures 1,
2, and 3, together with the partially complete set of podials found with them. The leg
bones of a still smaller individual of Pteranodon sp., No. 2493, are shown in Plate XXIX,
with the nearly perfect right tarsus and metatarsus. The state of preservation of the
two tarsals is such that it is now impossible to fit these bones accurately together in
contact with the tibia and metatarsus. In this plate, they are shown as found in the
matrix, a little removed from their natural position. The stout claw-shaped bone asso-
ciated with them is supposed to be the rudimentary fifth metatarsal. In the illustration
of the right foot of No. 2502 (Plate XVI, figure 1), the tarsals are figured from the
proximal surface. The claw-shaped fifth metatarsal is preserved, and distinctly shows
the articular facet on its proximal end. Unfortunately, these three bones are so badly

36 OSTEOLOGY OF PTERANODON.

distorted that they can not be accurately assembled.1 The metatarsals and phalanges of this
example, although fractured and separated, are yet capable of being fitted together so
as to form a nearly complete member, perhaps the most complete foot that has been
observed in material of this genus. In addition to the four long metatarsals, Nos. I-IV,
and the claw-shaped rudimentary metatarsal V, there are preserved six long phalanges,
the proximal end of a long phalanx, three extremely short phalanges, and four small
claw-shaped terminal phalanges. In the figure, these parts have been arranged in what
seems to the writer to be their natural order, --assuming that metatarsal II is the longest
and metatarsal IV the shortest. The number of phalanges forming each digit is thus
calculated to be : Digit I, 2 phalanges : digit II, 3 phalanges ; digit III, 4 phalanges :
digit IV, 5 phalanges. It will be seen that this foot agrees closely with that described
by Professor Williston in " Osteology of Nyctosaurus," p. 152. The number and order
of the long and extremely short intermediate phalanges are the same as stated by
Professor Williston, and the only departure from the arrangement of podials proposed
by that author is that four terminal claw-shaped phalanges, instead of two, are called
for by the present scheme. That the four small claw-shaped phalanges found together
belong to the same foot, is sufficiently proved by the fact that the four long slender
penultimate phalanges of the foot terminate in small but distinct trochlear articulations.
In No. 2489 (Plate XXVII, figure 3) and also in No. 2554, which is not figured here,,
the distal termination of the penultimate phalanx of digit I is known to be of the
same form.

RESTORATIONS OF PTERANODON.

Only a very imperfect conception of the entire skeleton of Pteranodon can be ob-
tained from the detailed description of its component parts, and a restoration with the
wings outspread as in flight (Plate XXX) is here introduced in the attempt to show to
better advantage the general proportions of this most highly specialized and grotesque
animal. The drawing is virtually a composite restoration, the cranial characters being
based mainly on the type skull of P. longiceps, No. 1177, while the pelvis and the greater
part of the vertebral column are copied from the type of P. ingens, No. 2594. As the
utmost care has been taken to reduce all the skeletal parts of the examples consulted
to the same relative size, the figure should have considerable value in its portrayal of
the generic characters.

Hardly less instructive is the lateral view of the skeleton shown in Plate XXXI. In
making this diagram, it was found advisable to figure the bones of the left wing and
leg only, as it seemed impossible to represent the limbs of both sides in true perspec-
tive in the lateral view without giving an erroneous idea of their length. In these two
plates, sternal ribs are figured, also short curved ribs borne by the free posterior dorsal
vertebrae. As stated in the foregoing pages, the form of these ribs is not known from
any example in the Marsh Collection ; neither is it possible to represent with certainty
the gastralia and the cartilaginous structure which doubtless connected the prepubes
with the sternum.

The bizarre aspect of the great supraoccipital crest of the skull, extending backward

1 The anterior surface of the distal end of the tibia is also figured in order to show the relative
size of the foot.

RESTORATIONS OF PTERANODON. 37

over the dorsal region, is most striking. And the appearance of the hind limbs in the
complete restoration well sustains the truth of Professor Seeley's contention that the
" slender toes of many bird?, and even the two toes of the ostrich, may be thought to
give less adequate support for those animals than the metatarsals and digits of Ptero-
dactyles." The small size of the pelvis compared with the rest of the skeleton will at
once arrest the attention of a biologist in whose mind the question arises how the
females of this genus could have produced their young. Were it not for the greatly
elongated wings and the supraoccipital crest, the pelvic diameters would not seem so
disproportionate ; for compared with the size of the thorax of the adult animal, the
channel enclosed by the ischio-pubes is not relatively much smaller than that observed
in some of the Crocodilia and Chelonia. That this character is perhaps a little more
pronounced in Pteranodon than in the earlier pterosaurs, need cause no surprise, inas-
much as Pteranodon is in nearly every respect more specialized than the other genera.
The seemingly immoderate proportions of the head and wings were probably due en-
tirely to postnatal growth ; and while difficulty of parturition might ultimately have
become a factor in exterminating the genus, it should be remembered that the pro-
portions of the axial skeleton and limb girdles figured in the restorations are taken from
well-preserved specimens and therefore can not be regarded absurd. There is as yet
no definite evidence to show whether the animals were viviparous or produced soft-
shelled eggs.

Like many another extinct group of American vertebrates described as being of " gi-
gantic size," Pteranodon seems in this respect to have surpassed its Old- World congeners.
The wing-spread of any example — a dimension that perhaps conveys a more definite idea
of size than do other measurements - - may be calculated by assuming that the wing
bones missing in any individual were of average proportions, and by computing their
lengths from the averages given in Table B ; but it is obvious that the resultant calcu-
lation is approximate only. Allowance must also be made for the diameter of the thorax
and for the carpus. Contrary to precedent, the wing-spread is here estimated as the
distance from the tip of one terminal phalanx to that of the opposite limb, with all the
joints slightly flexed, especially the elbow and the carpus, this position of the wings
affording a more natural measurement than the total length of the same bones stretched
in a straight line from shoulder to wing-tip, although by the latter method the size would
be made to appear about five per-cent. greater.

The wing-spread of several of the examples referred to in the foregoing pages may
be approximately stated, as follows : -

m. ft. in.

No. 1164, type of P. occidentals 3.855 = 12 8

No. 1175, type of P. ingens 6.803 = 22 3

No. 2493, Pteranodon sp 4.902 = 16 0

No. 1181, Pteranodon sp 3.390 = 11 1

The wing-spread of the type of P. longiceps, No. 1177, was probably nearly equal to
that of No. 2493; the type skull of P. occidentalis, No. 1179, belonged to an individual
of about the same size as No. 1164, while the two types of P. inyens, Nos. 1175 and
2594, apparently had about the same wing-spread. Perhaps the largest example of Pteran-
odon sp. in the Marsh Collection is No. 2514, represented by the right quadrate and
the proximal ends of the radius and ulna. The quadrate exceeds in size that of P. ingens,
No. 2594, by one-fifth. If this proportion remained constant throughout the entire skeleton,

38 OSTEOLOGY OF PTERANODON.

the wing-spread of No. 2514 would be about 8.163 m5 Or 26 feet, 9 inches. The proximal
ends of the radius and ulna, however, do not appear so robust as those of P. ingens
(type), No. 1175, supposed to be of the same size as No. 2594, a comparison that argues
against the extreme size computed above. It would seem quite as reasonable to con-
clude that the proportionate size of the skull and limbs may have varied considerably
in Pteranodon, just as in other genera of recent and fossil vertebrates.

Important data concerning the types and other valuable examples of Pteranodon are
given below. As previously stated, all the material in the Marsh Collection referred to
this genus was obtained from the Niobrara Cretaceous beds of western Kansas. The
color of the matrix seems to be affected to some extent by exposure to the elements,
and can not at present be relied upon as a criterion of age.

Pteranodon occidentalis (type), No. 1164, was collected by Professor O. C. Marsh, July,
1871, from the "Gray Shale" of the Niobrara Cretaceous, on the north side of the
Smoky River in western Kansas. It comprises the following bones of the right wing:
The humerus ; the proximal end of the ulna ; the proximal and distal ends of the radius ;
the carpus ; the greater part of the fifth metacarpal, including both ends ; the first phalanx,
both ends of the second phalanx, both ends of the third phalanx, and the greater part
of the fourth phalanx, of the fifth digit.

Pteranodon ingens (type), No. 1175, was collected by E. W. Guild, alias E. S. Field,
May 17, 1876, from the "Yellow Chalk" of the Niobrara Cretaceous, in Wallace County,
Kansas. It comprises the following bones : The basioccipital, the left quadrate, the ar-
ticular portions of the mandibular rami ; cervical vertebrae 1, 2, 3, 4, 5, 6, and 7; three
dorsal vertebrae ; the pelvis, with series of ten vertebras ; the right scapula and coracoid ;
the right humerus, ulna, proximal and distal ends of the radius ; the carpus, proximal and
distal ends of the fifth metacarpal ; the right femur, and the proximal and distal ends of
the right tibia; the proximal part of the left femur.

Pteranodon longiceps (type), No. 1177, was collected by Professor S. W. Williston, May 2,

1876, from the "Yellow Chalk" of the Niobrara Cretaceous, near the Smoky River in
western Kansas. The type consists of the skull, together with the atlas and axis.

Pteranodon occidentalis (type skull), No. 1179, was collected by E. S. Field, alias E. W.
Guild, 1875, from the "Yellow Chalk" of the Niobrara Cretaceous, near Castle Rock in
Trego County, Kansas. The specimen is imperfect.

Pteranodon ingens (type), No. 2594, was collected by Professor S. W. Williston, July 20,

1877, from the "Yellow Chalk" of the Niobrara Cretaceous, in Wallace County, Kansas.
The skull, with atlas and axis, is preserved.

Pteranodon sp., No. 1181, was collected by Professor B. F. Mudge, April 24, 1875,
from the "Yellow Chalk" of the Niobrara Cretaceous, in Trego County, Kansas. It
comprises : The right scapula and coracoid ; the right humerus, radius, and ulna ; lateral
carpal and pteroid ; fragments of the fifth metacarpal ; fragments of the second, third, and
fourth metacarpals, and most of the phalanges of the manus.

Pteranodon sp., No. 2493, was collected by E. S. Field, alias E. W. Guild, September 4,
1876, from the " Yellow Chalk " of the Niobrara Cretaceous, in Trego County, Kansas.
It comprises the following bones : The anterior part of the sternum, the right scapula
and coracoid, and fragments of the left scapula and coracoid ; the right humerus, radius,
and ulna ; two carpals ; the right fifth metacarpal and portions of the lateral metacarpals ;
the first, second, and third phalanges of the fifth digit ; two femora ; two tibiae, and most
of the right podials.

Plate I.

Figure 1. — Skull of the type of P. longiceps Marsh, No. 1177: seen from the left side.
x 0.34

Figure 2. — Fragmentary mandible of Pteranodon sp., No. 2478 ; seen from the right side,
x 0.64

Figure 3. — The same specimen ; seen from the left side, x 0.64

MEM. CONN. ACAD., VOL. II.

PLATE I.

Plate II.

Figure 1.— Skull of the type of P. ingens Marsh, No. 2594, with the anterior cervical
vertebrae ; seen from the right side, x 0.28

Figure 2. — Complete supraoccipital crest of the fragmentary skull of Pteranodon sp.,
No. 2473 ; seen from the right side, x 0.29

MEM. CONN. ACAD., VOL. II.

PLATE II.

Plate III.

Figure 1. — Skull of the type of P. ingens Marsh, No. 2594; middle section; seen from
the left side, x 0.42

Figure 2. — Skull of the type of P. occidentalis Marsh, No. 1179; seen from the right side.
x 0.58

MEM. CONN. ACAD., VOL. II.

PLATE III,

Plate IV.

Figure 1. — Composite restoration of the skull of Pteranodon. based on the type of P.
ing ens Marsh, No. 2594, and on Pteranodon sp.. No. 2473 ; seen from the left
side, x 0.14

Figure 2. — Restoration of the skull of the type of P. ingens Marsh, No. 2594; palatal
view, x 0.50

Plate V.

Figure 1. — Left quadrate of the type of P. longiceps Marsh, No. 1177, with part of the
jugal; seen from below, x 1.0

Figure 2.— Articular facet of the left mandibular ramus of Pteranodon sp., No. 2578;
seen from above, x 1.0

Figure 3.— Left orbit of the skull of the type of P. ingens Marsh, No. 2594, as actually
preserved, x 0.50

Figure 4. — Left quadrate and articular of Pteranodon sp., No. 2476; seen from the left
side, x 0.75

Figure 5. — Left quadrate of the same specimen; seen from below, x 1.0
Figure 6. — Left articular of the same specimen ; seen from above, x 1.0

Figure 7. — Diagram of the palato-pterygoid ribbon in the type of P. longiceps Marsh,
No. 1177, with the associated bones of the right side; seen from below.

Figure 8. — The same elements ; seen from above.

Figure 9. — Restored palato-pterygoid and transpalatine of the right side in Pteranodon
sp., No. 2440 ; seen from above.

•

Figure 10. — Skull of Chelydra serpentina (Snapping Tortoise ; Y. U. Osteol. Coll., No. 5454) ;
left side, x 0.66

Figure 11. — Skull of Chamceleo vulgaris; left side; to show the temporal muscles. (After
Dollo.)

Figure 12. — Skull of Plotus anhinga ; superior view ; showing the occipital style and the
origin of the temporal muscles. (After Garrod.)

Figure 13.— Skull of Phalacrocorax dilophus (Y. U. Osteol. Coll., No. 538); left side;
showing the occipital style, x 0.50

Figure 14. — Skull of the same ; showing the mandibular musculature. (After Yarrell.)
x 0.50

MEM. CONN. ACAD., VOL. II.

PLATE V.

Mat

12

10

11

13

14

Plate VI.

Figures 1-6. — Seven anterior cervical vertebrae of the type of P. ingens Marsh, No. 1175;
seen from the left side ; slightly restored, x 0.50

Figure 1. — Atlas and axis.
Figure 2. — Third cervical.
Figure 3. — Fourth cervical.
Figure 4. — Fifth cervical.
Figure 5. — Sixth cervical.
Figure 6. — Seventh cervical.

Figure 7. — Seventh cervical vertebra of Pteranodon sp., No. 2692 ; seen trom the left side.
x 0.66

Figure 8. — Eighth cervical vertebra of the same individual ; seen from the left side ;
showing rib. x 0.66

Figure 9. — Ninth cervical vertebra of the same individual ; seen from the left side.
x 0.66

Figure 10. — Eighth cervical vertebra of the same individual ; anterior view, x 0.66

Figure 11. — Atlas and axis of the type of P. longiceps Marsh, No. 1177; seen from the
left side. < 1.0

Figure 12. — Atlas and axis of the type of P. ingens Marsh, No. 1175; seen from the rear.
x 0.66

Figure 13. — Fourth cervical vertebra of the type of P. ingens Marsh, No. 1175: anterior
view, x 0.50

Figure 14. — The same specimen ; posterior view, x 0.50

Figure 15. — Right rib of the ninth cervical vertebra of the type of P. ingens Marsh,
No. 1175; posterior view, x 0.50

Figure 16. -Right rib of the ninth cervical vertebra of Pteranodon sp., No. 2692 ; anterior
view, x 0.66

Figures 17-20. — Four free dorsal vertebrae of Pteranodon sp.. No. 2616; seen from the
left side ; slightly restored, x 0.66

Figure 21. — First free dorsal vertebra of the foregoing series; anterior view, x 0.66

Figure 22. — The same vertebra ; posterior view, x 0.66

Figure 23. — Four caudal vertebrae of Pteranodon sp., No. 2546; seen from below, x 0.66

oo IBH

Plate VII.

Figure 1.— Notarium of Pteranodon sp., No. 2692, with the ninth cervical vertebra
attached ; seen from the left side, x 1.04

Figure 2. — The same specimen ; seen from the right side, x 0.98

MEM. CONN. ACAD., VOL. II.

PLATE VII.

Plate VIII.

Figure 1.— Restoration of the notarium of Pteranodon sp., No. 2692; seen from the left
side, x 0.75

Figure 2. — The same specimen ; seen from in front, obliquely, x 0.75
Figure 3. — The same specimen ; superior view, x 0.75
Figure 4. — The same specimen ; inferior view, x 0.75

Plate IX.

Figure 1. — Dorsum of Larus glaucus (Y. U. Osteol. Coll., No. 2290); seen from above.
xO.62

Figure 2.— Dorsum of Oidemia nigra (Y. U. Osteol. Coll., No. 429) : seen from above.
x 0.67

Figure 3. — Dorsum of Meleagris gattipavo (Y. U. Osteol. Coll., No. 360) ; mature individual ;
seen from above, x 0.50

Figure 4. — Sacrum of Meleagris gallipavo (Y. U. Osteol. Coll., No. 2112) ; young individual ;
seen from below, x 0.50

Plate X.

Sacrum and pelvis of the type of P. ingens Marsh, No. 1175; seen from below, x 0.96

MEM. CONN. ACAD., VOL. II.

PLATE X.

I

Plate XL

Figure 1. — Sacrum and pelvis of the type of P. ingens Marsh, No. 1175; seen from the
left side, x 0.75

Figure 2. — The same specimen ; seen from above, x 0.75
Figure 3. — The same specimen ; seen from below, x 0.75

MEM. CONN. ACAD., VOL. II.

PLATE XI.

V

Plate XII.

Figure 1. — Two notarial vertebrae, three free dorsal vertebras, and the anterior sacral

vertebrae of Pteranodon sp., No. 2451 ; seen from below, x 0.85

Figure 2.— Sacrum of Pteranodon sp., No. 2570; seen from below, x 1.0

MEM. CONN. ACAD., VOL. II.

PLATE XII,

Plate XIII.

Figure 1.— Four free dorsal vertebrae of Pteranodon sp., No. 2616; seen from below.
x 1.0

i

Figure 2.— Fragmentary sacrum of Pteranodon sp., No. 2616; seen from below. x 1.0
Figure 3. — Sacrum of Pteranodon sp., No. 2489; seen from below, x 1.0

Figure 4. — Five caudal vertebras of the same individual ; seen from above, obliquely.
x 1.0

MEM. CONN. ACAD., VOL. II.

PLATE XIII.

Plate XIV.

Figure 1.— Sternum of Pteranodon sp., No. 2546; seen from below, x 0.60

Figure 2.— Anterior portion of the sternum of Pteranodon sp., No. 2616; inner or upper
surface, x 1.0

X

UJ

i-l

o

u
<

2

z

o

Plate XV.

Figure 1.— Sternum of Pteranodon sp., No. 2692; right side, x 1.0
Figure 2. — The same specimen ; left side, x 1.03

MEM. CONN. ACAD., VOL. II.

PLATE XV,

Plate XVI.

Figure 1. — Distal end of the right tibia, and the podial bones of Pteranodon sp.,
No. 2502 ; dorsal view, x 0.66

Figure 2. — Digits II, III, and IV of the right manus of Pteranodon sp., No. 2428; missing
parts are represented in outline, x 0.66

Figure 3. — Prepubis of Pteranodon sp., No. 2472. x 1.0

Figure 4. — Supposed sternal rib of the type of P. ingens Marsh, No. 1175. x 1.0

Figure 5. — Nearly complete restoration of the sternum of Pteranodon sp.. No. 2546; seen
from below, x 0.66

*p-!*; • •
UN'lvtv, i !

Plate XVII.

Figure 1.— Right scapula and coracoid of the type of P. ingens Marsh, No. 1175; pos-
terior view, x 0.75

Figure 2.— Left scapula and coracoid of Pteranodon sp., No. 2512; posterior view.
x 0.75

MEM. CONN. ACAD., VOL. II,

PLATE XVII.

Plate XVIII.

Figure 1. — Left scapula and coracoid of Pteranodon sp., No. 2616; seen from in front.
x 0.88

Figure 2. —The same specimen ; seen from the rear, x 0.89

MEM. CONN. ACAD., VOL. II.

PLATE XVIII.

Plate XIX.

Figures 1-8. — Bones of the left wing preserved in the type of P. ingens Marsh, No. 1175.
xO.30

Figure 1. — Humerus ; superior or anconal surface.

Figure 2. — The same bone ; inferior surface.

Figure 3. — Ulna; inferior surface.

Figures 4a, 4b. — Proximal and distal ends of the radius ; inferior surface.

Figures 5 a, 5b. — Proximal and distal ends of metacarpal V.

Figure 6. — Carpus ; proximal surface.

Figure 7. — Carpus ; dorsal view.

Figure 8. — Carpus ; distal view.

Figures 9-19.— Bones of the right wing preserved in the type of P. occidentalis Marsh,
No. 1164. x 0.30

Figure 9. — Humerus ; superior or anconal surface.

Figure 10. — The same bone ; inferior surface.

Figure 11. — Ulna; proximal end; superior surface.

Figures 12a, 12b. — Proximal and distal ends of the radius; superior surface.

Figure 13. — Carpalia : proximal surface.

Figure 14. — Carpalia ; distal surface.

Figures 15a, 15b. — Fragmentary metacarpal V.

Figure 16. — First phalanx of digit V (wing finger) ; radial side.

Figures 17a, 17b. — Proximal and distal ends of the second phalanx of digit V;

radial side.
Figures 18a, 18b. — Proximal and distal ends of the third phalanx of digit V:

radial side.
Figure 19. — Fourth phalanx of digit V ; radial side.

MEM. CONN. ACAD., VOL. II.

PLATE XIX.
6

4a

11 12a

13

12b

14

15a

15b

4b

16

5a

m

5b

y

18a

17a

ISb

19

- '-'-'Mi

Plate XX.

Figure 1.— Left humerus of Pteranodon sp., No. 2709; inferior view, x 0.39

Figure 2. — Left humerus of Pteranodon sp., No. 2831 ; superior view, x 0.39

Figure 3. — Left humerus of Pteranodon sp., No. 2589 ; inferior view, x 0.39

Figure 4. — Left humerus of Pteranodon sp., No. 2302 ; anterior view, x 0.39
Figure 5.— The same bone ; posterior view, x 0.39
Figure 6. — Right humerus of Pteranodon sp., No. 2730 ; superior view, x 0.39

MEM. CONN. ACAD., VOL. II.

PLATE XX.

m1

Plate XXI.

Bones of the left wing of Pteranodon sp., No. 2425, as preserved in the matrix ; namely,
the humerus, radius and ulna, the proximal and distal carpals, the metacarpals,
pteroid bone, and the fragmentary proximal phalanges, x 0.43

MEM. CONN. ACAD., VOL. II.

PLATE XXI.

Plate XXII.

Figure 1.— Left carpus of Pteranodon sp., No. 2425; palmar surface, x 0.64
Figure 2. — The same specimen; dorsal surface, x 0.58

Figure 3. — Distal ends of metacarpals II, III, and IV, of Pteranodon sp., No. 2493, with
three nearly complete digits of the right manus, the number and order of the
phalanges in two of these digits being incorrectly preserved, x 0.78

Figure 4. — Right carpus of Pteranodon sp., No. 2683. with the proximal end of meta-
carpal V ; palmar view, x 0.82

Figure 5. — The same carpus removed from the matrix ; dorsal view, x 0.82

MEM. CONN. ACAD., VOL. II.
1

PLATE XXII.

Plate XXIII.

Figure 1. — Right scapula and coracoid and bones of the right wing of Pteranodon sp.,
No. 1181, preserved in the matrix, x 0.45

Figure 2.— Pteroid bone, metacarpals II, III, and IV, and phalanges of the same specimen.
x 1.11

MEM. CONN. ACAD., VOL. II.

PLATE XXIII.

Plate XXIV.

Figure 1. — Adjacent ends of metacarpal V and the first phalanx of the left wing of
Pteranodon sp., No. 2628 ; ulnar side, x 0.50

Figure 2. — The same specimen ; radial side, x 0.50

Figure 3. — Adjacent ends of metacarpal V and the first phalanx of the left wing of
P. occidentalis Marsh, No. 1165 (identification of O. C. M.). at the angle of ex-
treme flexure ; ulnar side, x 0.50

Figure 4. — The same specimen ; radial side, x 0.50

Figure 5. — Conjoined fragments of the left metacarpal V and the first phalanx of Pteran-
odon sp., No. 2660 ; palmar surface, x 0.67

Figure 6. — The same fragments separated ; palmar surface, x 0.67

MEM. CONN. ACAD., VOL. II.

PLATE XXIV.

Plate XXV.

Figures 1-7. — Wing bones preserved in Pteranodon sp., No. 2452. x 0.35

Figure 1. — Right ulna; palmar view.

Figure 2. — Right radius ; palmar view.

Figure 3. — Left metacarpal V.

Figure 4. — First phalanx of the left digit V (wing finger) : radial side.

Figure 5. — Second phalanx of the left digit V ; radial side.

Figure 6. — Third phalanx of the left digit V ; radial side.

Figure 7. — Fourth or terminal phalanx of the left digit V ; radial side.

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Plate XXVI.

Figures 1-3. — Bones of the left wing preserved in Pteranodon sp., No. 2774; radial side.
x 0.35

Figure 1. — Distal end of the metacarpal and first phalanx of digit V.
Figure 2. — Second phalanx of digit V.
Figure 3. — Third phalanx of digit V.

Figures 4-7.— Bones of the right fifth digit of Pteranodon sp., No. 2470; radial side.
xO.35

Figure 4. — First phalanx.
Figure 5. — Second phalanx.
Figure 6. — Third phalanx.
Figure 7. — Fourth phalanx.

Figures 8, 9. — Third and fourth phalanges of the fifth digit of the wing of Pteranodon
sp., No. 2591. x 0.35

Plate XXVII.

Figures 1-3.— Bones of the right leg and foot of Pteranodon sp., No. 2489. x 0.57

Figure 1. — Femur; inner and posterior view.
Figure 2. — Tibia ; inner and posterior view.
Figure 3. — Nearly complete pes.

Figures 4, 5 a, 5b.— Bones of the right leg of the type of P. ingens Marsh, No. 1175:
posterior view, x 0.57

Figure 4. — Femur.

Figure 5 a. — Proximal end of the tibia.

Figure 5b. — Distal end of the tibia.

Plate XXVIII.

Figures 1-4. — Leg bones of Pteranodon sp.. No. 2738. x 0.64

Figure 1. — Left femur; anterior view.

Figure 2. — Left tibia ; anterior view.

Figure 3. — Right femur; inner and posterior view.

Figure 4. — Right tibia ; posterior view.

MEM. CONN, ACAD., VOL. II.

PLATE XXVIII.

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Plate XXIX.

Figures 1-4. — Bones of the hind limbs preserved in Pteranodon sp., No. 2493. x 0.65

Figure 1. — Right femur; from the right side.

Figure 2. — Right tibia (from the right side), tarsus, and metatarsus.

Figure 3. — Left femur ; posterior view.

Figure 4. — Left tibia; posterior view.

MEM. CONN. ACAD., VOL. II.

PLATE XXIX.

Plate XXX.

Restoration of Pteranodon Marsh, based on various individuals of the genus, including
the types of P. longiceps, No. 1177, and of /'. ingens, No. 2594.

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Plate XXXI.

Restoration of Pteranodon Marsh ; from the left side ; based upon various individuals of
the genus. For convenience of representation, the right limbs are omitted and
the left wing is more sharply flexed than would be the case in actual flight.

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