ON DINOSAURIAN REPTILES FROM THE TWO
MEDICINE FORMATION OF MONTANA
By Charles W. Gilmore
Curator of Vertebrate Paleontology, United States National

MuseumINTRODUCTION
The Blackfeet Indian Reservation in northern Montana has been
the object of two expeditions by the Smithsonian Institution.

It

was here in deposits of the Two Medicine (Upper Cretaceous) formation that, in 1913, I discovered the type specimen of Brachyceratops inontanensis}

Thecollectionsof thisfirst

expedition were

was deemed highly desirable that the region
should be visited a second time. This desire was realized in 1928,
and the specimens described in the following pages are a part ofso promising that it

adds considerably to ourknowledge of this meagerly known fauna and places it on a basis
where comprehensive comparisons with Upper Cretaceous faunas

this latter collection, which, as a whole,of adjacent regions are now possible.

The bulk of the collection will be described in a later paper, but
I have thought it advisable to record as soon as possible the discoveryof three genera new to the fauna, which include two new species.
1.

A NEW SPECIES OF PALAEOSCINCUS

Among vertebrate fossils collected from the Two Medicine formation(Upper Cretaceous) of Montana, by a Smithsonian paleonto-

logical expedition in 1928, is a disarticulated skeleton of an armoreddinosaur displaying characters which indicate it to be an undescribed
species of the long established but little known genus Palaeoscincus.

Palaeoscincus co8tatus{ founded by Dr. Joseph Leidy in 1856 on
fig. 3) was the first named North American
armored dinosaur. For more than half a century this remained agenus of doubtful affinities, but with the acquisition by the Americana single tooth (pi. 4,1 Gilmore, C. W., Prof. Paper 103, IT. S. Geol. Surv., 1917.
2Proc. Phila. Acad. Sciences, vol. 8, 1856, p. 72.

No. 2839.— Proceedings U.

2601—30S.

National Museum, Vol. 77. Art.

16.

1
1

Z

PROCEEDIISrGS OF

THE jSTATIONAL MUSEUM

vol.77

Museum of Natural History of an unusually well preserved anterior
portion of a skeleton(pi. 8)with the armor in place, a real concep-

tion of the extraordinary characteristics of this animal was first disclosed.

A few teeth found in the cavities of the skull are said by

Matthew ^ to be identical in character with the type of Palaeoscincus
costatus thus establishing its identity.

Keference of the present specimen to the genus Palaeoscincus isbased on similarity of dermal armor and skull resemblances to theAmerican Museum specimen. Although much of the anterior portion of that skeleton is present, it has not yet been described, and forcomparative purposes one must rely almost entirely upon the excellent
illustrations published by Matthew.
The specimen from the Two Medicine formation, considered here,
contributes so much to our knowledge of the skeletal anatomy of theanimal that it is described in considerable detail. The teeth, however, although having the general cut of the Palaeoscincus costatus
tooth, differ sufficiently in their details to indicate a distinct species.

The new genus and species Edmontonia longiceps recently described by C. M. Sternberg,* displays such striking likeness in its skull
structure to the Palaeoscincus cranium noAv before me as to raise aquestion as to the validity of this new genus.

In the arrangement
and number of skull plates, and structure of the palate, the two skulls

are almost identical, differing pricipally in proportions.

The teeth
At thisalso are not greatly unlike the typical Palaeoscincus tooth.

time I am not fully satisfied that there are good generic distinctions
for separating these two genera but shall withhold final judgment
until other parts of the Edmontonia type have been studied.

The occurrence of Edmontonia in the geologically higher Edmonton formation, may lend some weight to the possiblity of its genericdistinctness, for few dinosaurian genera are known to pass over fromone formation to another.

PALAEOSCINCUS KUGOSIDENS, new species
Plates 1, 2, 3, 4, Figure 1;

Plates 5,

6,

and 7

Type.—^o. 11868, U.S.N.M., consists of a complete skull; rightramus; coossified atlas and axis; the third and two other cervicalvertebrae; ten dorsal and eleven caudal vertebrae; sacrum; twoischia; portion of right ilium; right pubis; seventeen ribs half ofwhich are complete; chevrons; numerous parts of bones; and fifty
dermal ossifications of various kinds. The specimen was found hj
George F. Sternberg, June 3, 1928.
'Natural History, vol. 22, No. 4, 1922, p. 334.
* Trans. Roy. Soc. Canada, vol. 22,
1928, pp. 93-106.

FOSSIL KEPTILES

AET. 16

FROM MONTANAGILMOEE

3

Tyfe locality.— '&QC. 16, T. 37 N., R. 8 W., Milk Eiver, Blackfeet
Indian Eeservation, Glacier County, Montana.
Horizon. Two Medicine formation. Upper Cretaceous.
The specimen on which the present description is based was foundon the north side of Milk River about one-half mile west and southfrom the locality where the type of Brax^hyceratops montanensis
was discovered by the writer in 1914. All the bones were disarticulated and widely scattered, but it was quite apparent they pertained
to a single individual as there was no duplication of parts.
Shull. The skull, aside from slight flattening due to postmortem

—

''

—

crushing, is in an almost perfect state of preservation. Normallydepressed, it diminishes in both height and breadth toward the muzWidest immediately posterior to thezle, which is squarely truncate.

breadth abruptly contracts behind the eyes, forming a
distinct notch on either side as contrasted with those of much lesser
degree in both Panoplosamms mirus and Edmontonia longiceps.
The orbits are of moderate size and set far back. The narial openings are large and open outward and upward. The lateral temporalfenestra look outward and slightly backward.
The whole of the exposed skull surface, top, front, and sides, iscovered by a few ossified dermal plates. These are coossified withthe underlying skull bones, concealing them from view. The plates
are defined by shallow circumscribing sulci, which in this specimen
can not be traced out in their entirety, as is shown in Plate 2.
In so far as the number, form, and proportions of these headplates can be determined, they most nearly resemble those of Edmontonia longiceps. The observed difference in form and proportions
between the plates of Palaeoscincus 7'ugosidens and those of E.
longiceps and Panoplosaurus mirus, in all probability are of but
little anatomical significance, for in dermal bones there seems to beorbits, theamong individuals of the same species.
Viewed from the side the superior outline of the skull is moderately
convex from front to back and likewise from side to side. Behindconsiderable variation

the line of the orbits on either side of the midline are large shallow

The withdrawal
inward of the dentigerous border of the maxillary, brings about adepressions as in the cranium of E. longiceps.

depressed buccal area of considerable extent, well illustrated in Figure 2.

Dermal ossifications cover the entire side of the skull, thus

obliterating all sutures between the individual bones.

In the posterior view (fig. 1) the skull bones are free from dermal
covering and although the individual elements can be determined, allof the sutures are coalesced thus rendering it impossible to determine
their precise limits.
sGilmore, C. W., Prof. Paper, 103, U.

S. Geol. Surv.,

1917.

PROCEEDINGS OF THE NATIONAL MUSEUM

TOL. 77

The occipital condyle is relatively large and directed obliquely
downward in relation to the longer axis of the skull, indicating thenormal pose of the head to form an obtuse angle with the neck.

The condyle is subspherical, the greatest diameter being transverse.
It has a greatest width of 58 mm., and a greatest vertical diameterof 52.5 mm.

The exoccipitals extend outward and backward, their outer ends
projecting backward beyond the occipital condyle. The outer orform the two small horn-like projections
shown in the superior view of the skull (pi. 2). These bones areparaoccipital processes

indistinguishably fused with the exoccipitals.

LTJ^.

Figure 1. Skull op Palaeoscincus bugosidens. Txpe. No. 11868, U.S.N.M.
POSTERIOH VIEW. OnE-THIRD NATURAL SIZE. Bs. pt. ProC, BASIPTERTGOID
process, of THE BASISPHENOID EtC^ ECTOPTERYGOID Ex. OC, ExOCCIPITAL
L. T. F., LATERAL TEMPORAL FENESTRA Oc, OCCIPITAL CONDYLE P. OC, PARAOCCIPITAL PROCESS Pt., Pterygoids Qu., Quadrate S. oc, Supraoccipital
;

;

;

;

;

;

;

The supraoccipital strongly overhangs the foramen magnum.
latter is suboval in outline,Theand has a greatest transverse diameterof 33 mm. and a vertical diameter of 28 mm.

The quadrates are wide transversely, and of moderate thickness.

A wide process that projects forward and inward is firmly coalescedwith the pterygoids. The upper end is fully enveloped by the overlying squamosal and posteriorly these ends are coalesced with theparaoccipitals. Viewed from below the distal articular end of thequadrate is triangular in outline (fig. 2). The main articular face
for the ramus has its greatest diameter fore and aft. Toward theoutside it slopes upward. From an external view only the thin edgeof the quadrate is seen and it is covered by a roughtened dermal

growth of bone.

The palate side of the skull is in an excellent state of preservation.
Slight crushing and loss of a few minor pieces

is

all

that mars

FOSSIL KEPTILES

ART. 16

PROM MONTAE"AGILMOEE

5

Unfortunately most of the sutures are obliterated,making it quite impossible to determine the extent of many of theitsperfection.

elements.

Except for differences in proportion, the palate structures

seems to be identical with Edmontonia longiceps as described by
Sternberg.*^

The outstanding peculiarities of structure observed in the palateof this specimen are the ladle-shaped form of the premaxillary region; the division of the mouth longitudinally by a vertical plateof bone that extends backward from the median junction of thepremaxillaries the great shortening of the pterygoids, the inward;

curvature of the tooth rows, and the wide overhanging buccal area
along the outer sides of the maxillary bones.

The edentulous premaxillary bones form the greater part of the
As mentioned above, their combined
inner surfaces are hollowed out, in form suggesting a ladle. The
outer anterior borders curve strongly downward, forming a sharp
cutting edge that in life was doubtless covered by a chitinous sheath.
large rectangular muzzle.

On either side external to this sharp ridge of bone the premaxillaries
are widened by dermal bones that are firmly coossified to it.

Alow,subacute median ridge rising on the anterior third extends backward
to the junction with the prevomers.
On either side of the midline
the premaxillaries are pierced by small rounded foramina that lead

upward and forward through the floor of the anterior nares.

The

sutures between premaxillaries, maxillaries, and prevomers are clearly

determinable as shown in Figure 2.

On the right side the border ofthe premaxillary shows deformation in the form of a notch, evidently

due to an injury received in life, since the edges of the bone had
healed as indicated by their rounded borders.
The maxillae have the greater portion of their outer surfaces
hidden by the covering of dermal bone. Anteriorly they meet thepremaxillae, internally the prevomers, and toward the posterior end

The striking characteristic of these bones is thecurved nature of the dentigerous border. The teeth are borne ona downwardly descending plate that gradually recedes in height
toward the front. The tooth rows are wide apart posteriorly (144mm.), but curve in rapidly to a point forward of their mid-length
where they become parallel. In front the teeth of opposite sides are
only 77 mm. apart, exactly half the space of the posterior ones.
There are sixteen alveoli in each maxillary bone, and these occupy
the ectopterygoids.

a space of 120 mm. measured in a straight line.

Judging from thefrom backrelative sizes of the alveoli, the teeth decrease in size
to front.
« Trans.

Roy. Soc. Canada, vol. 22, 1928, pp. 98-100, pi.

2.

6

is

PEOCEEDINGS OP THE NATIONAL MUSEUM

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The spear-shaped bone filling the interspace between the maxillae
here regarded as the combined prevomers. The pointed end isinterposed between the coalesced premaxillae, while the hinder ends

L.T.E

Bs.Pl.Pi'oc.

Figure 2. Skull of Palaeoscincus eugosidens. Ttpe. No. 11868, U.S.N.M.
One-thikd natural size. Bs. Pt. Proc, Basiptertgoid
Intekioh view.
PROCESSES Ect., ECTOPTEEYGoiD Ex oc, ExocciPiTAL L. T. p.. Lateral
temporal FENESTRA Max., Maxillary T^ar. Vac, Narial vacuity 0,
Orbit; Oc, Occipital condyle; Pmx., Pre maxillary Prv., Prevomer Pt.,
Pterygoids; Qu., Quadrate; Qiij., Quadratojugal Sq., Squamosal; IX,
XI, XII, Exits for cranial nerves
;

;

;

;

;

;

;

;

;

form the anterior borders of the internal nares, and on the midline
Sternberg was certainly mistaken inarticulate with the palatines.
regarding this portion of the palate in Edmontonia longiceps as

ART. 16

FOSSIL REPTILES FROMMONTANAGILMOKE

7

being a posterior extension of the premaxillae. The most striking
feature of these bones is the development of a vertical plate that
extends downward and divides the mouth longitudinally. This plateanteriorly extends below the level of the tooth rows. In the specimen under consideration the greater part of this plate is missing,but is completely preserved in the type of Edmontonia longiceps andhas been described in detail by Sternberg/ who says " This plate
seems to be a development of the fused premaxillae." In this, however, I think he is mistaken; for in specimen No. 11868 this ridged:

shown in Figure 2.
The purpose of this longitudinal plate is as yet unexplained, but
plate certainly develops on the prevomers asthat it had a function there can be no doubt.

A suggested similarity

found in the palate of Troodon validus, but in that genus it consists only of a pointed pendant ^ process.
is

The palatines as distinct bones can not be differentiated in this
It is presumed, however, that they form the median barof bone which separates the internal nares. That they probably
form the posterior boundary of the nares is indicated in the type ofskull.

Edfnontonia longiceps, where Sternberg was able to trace out a partof the palatine-pterygoid suture. In the present skull all trace of
this suture has been obliterated.
If correct in the determination ofthese bones, the palatines form a considerable portion of the vertical plate which divides the mouth cavity.

prevomers,

apparently

intercalated

Anteriorly they join the

betweenslenderposteriorly

directed processes of those bones.

The pterygoid bones, as in nearly all of the armored Dinosauria,
antero-posteriorly. Each element may besaid to consist of three plates of bone, a rather narrow wing thatare greatly shortened

extends backward and outward and joins the quadrate, further infront a nearly vertical lamina that extends forward to articulate

with the ectopterygoids^ and at the junction of the two processes
mentioned above a heavier vertical plate extends transversely tomeet its counterpart of the opposite side on the median line. At
their junction the bone swells out into a truncated triangular processthat projects downward considerably below the rest of the bone.
median septa continues forward and upward from this process tomeet the palatines. On either side of this septa the pterygoids arehollowed out. The sutural contact with the ectopterygoids seem tobe as indicated in Figure 2, but I have some misgivings as to whetherA

they are fractures or true sutures.
^ Trans.
8Roy. Soc. Canada, Art. 3, Vol. 22, 1928, pp. 99-100.
Gilmore, C. W., Univ. of Alberta, Bull. No. 1, 1924, pi. 5.

PROCEEDINGS OF THE NATIONAL MUSEUM

VOL. 77

Table of comparative measurements
Type of
Palaeonscincus
rugosidens

Mm.
Greatest length of skull, in straight line
Greatest breadth iust back of orbits
Breadth of beak, anterior end__ _ _Greatest breadth of beak._

_
_

_

_

Breadth of paroccipital processes-_
Length of quadrate___
Distance between distal ends of quadrates .
Greatest length of orbit
Vertical diameter of orbit

_

_

_

_

_

_

Greatest diameter of foramen magnum
Transverse diameter of occipital condyle
1

470
340
145
187
240
1 150
185
64
40
57

Type of
Edmontonia
longiceps

Mm.

Type of
Panoplosaurus
mirus

Mm.

490
290

355
294

110
150

121

210
118
165
70
50
32
50

66
47
58
58

Estimated.

—

The right ramus is preserved almost in its entirety
shown in Figure 3. Its outstanding peculiarities of structure

Lowe?' jaw.
as

are the great depth of the posterior third;

the brevity of the post-

the curved dental row;

and the short, inwardly

coronoidal portion;

curved sj^mphysial end.

It probably includes all of the elements

common to the ramus of the predentate dinosauria but in thisspecimen most of the sutures are fully fused so that the separate
elements of the jaw can not be differentiated.
Much of the outer and lower surface of the ramus, except at theposterior end, is covered by a thick dermal bone which effectuallyconceals most of the underlying elements. The keeled nature ofthis dermal bone is well shown in Plate 3.
The dermal plate is
everywhere fully fused to the underlying bones. The armor does
not cover the posterior end of the ramus and here the posterior
mandibular elements can be seen. The angular-surangular sutureremains distinct from the posterior border to the point where it
passes beneath the overlying armor. It shows the angular to havea greatest posterior depth of 42 millimeters, but this rapidly diminishes as the bone passes forward.
All of the sutures of the in-'ternal side of the ramus are obliterated through fusion. The
dentary, which constitutes fully two-thirds of the entire ramus, isroughly rectangular with a much narrowed portion that turns
strongly inward to form the symphysis. The alveolar border showssockets for 21 teeth, the same as in Euoplocephalus tutus, but three
more than in the ramus of Edmontonia longiceps. These occupy
a space 140 millimeters in extent, indicating the teeth to be slightly
smaller than in E. lo7igiceps where 18 teeth occupy a space 155 millimeters in length. The tooth row forms a sinuous curve that con-

FOSSIL KEPTILES FROM

ART. 16MONTANAGILMOEE

9forms to the curved maxillary row (fig. 3B). Posterior to the last
alveolus the superior border curves gently upward as a pointed
process that is enveloped by the coronoid which appears to be
astride it. On the internal side the splenial completely covers
Meckel's groove. On this side a horizontal ridge is developed
which becomes more prominent anteriorly where it finally forms theposterior boundary of the symphysial part of the dentary. Herethe main body of the bone changes from a vertical to a horizontal
position.
The union of the dentary with the posterior elements
can not be determined.

Right ramus of Palboscincus edgosidens. Type. No. 11868,
Both one-third natural
A, Inner view
B, Supeeior view.
Art., ArticularC, Coronoid 8., Symphtsical border

FiGUEB 3.
U.S.N.M.
SIZE.

;

;

;

The coronoid sends forward an anterior portion that laps along
shown in Figure 3.
It forms much of the anterior border of the mandibular fossa, which
the supero-posterior portion of the dentary asAsecond process is sent forward on the outside of thedentary but its full extent can not be determined. Posteriorly, however, it is so fully fused that its limits can not be recognized.
The articular is prominently developed extending inward as ashelf-like platform that, viewed from above, is subtriangular inshape. The cotylus is shallowly concave antero-posteriorly, being
divided into two parts by a low, rounded, longtiudinal ridge. The
prearticular is probably present but is thoroughly coossified.
is extensive,PROCEEDINGS OP THE NATIONAL MUSEUM

10VOL. 77

Measurements of ramus

Mm.
Greatest length of ramus
Greatest depth through coronoid
Greatest depth of dentary at center
Greatest depth of dentary at symphys s

360
121
87
17
140

Length of dentigerous border

Teeth.

—Four teeth are preserved, three in theleftmaxillary and

The tooth illustrated (fig. 4) is the fifth
enumerated from the posterior end of the maxillary, while the germ
tooth shown in Figure 5 is the twelfth of thisone in the right dentary.

same

AV/</W^TIirifll
illlilt

ijjff'VlfvA

internal surfaces are visible and for that reason

'

1

'

l^w

fs

^^^j^^tiMlmij\

can not be completely compared with the teethof other described forms.

'

The functional toothconsists of a laterally compressed crown"^''ilji_
Figure 4.

These teeth are retained in theirrespective alveoli in such a manner that only theirI'//

series.

I'

dently a long cylindrical root.
*^

i

TOOTH

OF palaeosciNCDs KUGosiDENs.
Type.
No.
11868,
INTERNAL
u.s.N.M.

VIEW.

TWO AND ONE-

HALF

NAT-

and evi-

The crown isswolleu at the base with a roughened cmgulum as„
Maxillae'?

gj^^^j^ ^^iFigurc
4.
=

It

Is

to thisroughening of.

the lowcr part of the crown that the specificrefers. The anterior and posteTuoosidens^^
margins of the crown are denticulate, there
being three denticles posterior and four anterior to the apical denThe three central denticles, which in thisticle, making eight in all.
tooth are missing, appear to have been united as they are in the
TIMES
URAL SIZE

jjg^j^g

^

^

_

rior

typical PalaeoscincMS costatus tooth(fig. 3, pi.

4).

The other denti-

sharp pointed and continue down the inner face of thecrown as low, well-defined ridges. The germ tooth hascles areseven denticles, all displaying distinct points, as shownin Figure5.

The apical denticle is slightly posterior
The anterior teeth, judg-

to the central vertical line.

ing
O from the relative sizes of the alveoli, are smaller'

than the posterior.
In relative size, the one functional tooth 'present
agrees almost precisely with the type tooth of Palaeosdncus costatus. 'They also agree in having a similar
number of denticles with the median ones closely'_

united.

On the other hand their successive arrange-

figure 5.—?^^,\^°J
MAXILGERM
lary tooth
palaeos°^
CINCUS RUGOsidens.typb.

^ g^^ m'^^internalview.

JiTe^hIlp

nattimes
ment differs, and whereas P. rugosidens has the lower^^^^ ^^™
part of the crown ornamented with a rugose crinklingof the surface, the crown surface in P. costatus is always smooth.
In the paleontological collections of the United States National
Museum there are between 50 and 60 teeth from the Judith River
beds of Montana, that with a few exceptions are of similar pattern

FOSSIL REPTILES FEOM

ART. 16MONTANAGILMOEB1and can be identified as P, costatus. None of these, however, shows
sculpturing of the crown surface. From this brief review it isquite apparent that the teeth are near enough alike to indicate congeneric relationships, but are sufficiently unlike, in the light of ourpresent knowledge, to show them to pertain to distinct species.
Three other species of this genus have been proposed at various
times, Palaeoscincus asyer Lambe,® P. lotus Marsh," and P. tnagoder

The last is said by Hay ^^ to be a nomen nudum and may,therefore, be dismissed from further consideration. The type of
P. latus^ from the Lance formation, is a stegosauroid style of tooththat can at once be distinguished from the teeth of P. rugosidens
Hennig.^^by its low crown and the regularity of its denticles. (See pi. 4, fig.
P. as'per may likewise be distinguished by the more numerous
4. )denticles, sides of crown more conspicuously ridged, and a double
row of denticles at one end of the cutting edge. (See pi. 4, fig. 2.)
Atlas and axis. The atlas and axis are fused together by theircentra, nueral arches, and spines, a condition previouslj^^ observed by—

Sternberg ^^ in Panoplosaurus mirus. The English Scelidosaurus ^*likewise has a fusion of the atlas and axis. In Stegosaurus thesebones remain distinct.
The cup on the anterior extremity of the atlas for the receptionof the occipital condyle is deep and subcircular in shape. It has adepth of 31 millimeters and a greatest estimated transverse diameterof 57 millimeters. The atlas is long, broad, relatively low and without ventral keel. It bears strong, coosified, single-headed cervicalribs that project downward and strongly backward, as shown in
Figure 6A. It is estimated that the atlas centrum had a length ofabout 88 millimeters.
The pedicals of the neuropophyses set well back from the anterior
margin of the centrum. (See fig. 6A.) On the posterior borders they
develop a thin process that extends upward, backward, and inward.
These converge and unite medially with the neural spine of the axis
arching over the anterior border of the neural canal, as well as thevertebral arterial canals.
Above and posterior to the vertebral
arterial canal, these processes are completely fused with the axis,
leaving hardly a trace of the anterior zygapophyses of the axis or
the posterior zygapophyses of the atlas.
A broad anterior processof the neurapophyses extends inward above the neural canal but does
»Lambe, L. M., Geol. Surv. Canada, Cont. Can. Pal., vol. 3, pt. 2, 1902, p.
fig.

54, pi. 17,

5.

" Marsh, O. C, Amer. Jour. Sci., ser. 3, vol. 44, 1892, p. 173, pi. 8, flg. 3.
11

Honnig, Edwin, Naturw. Wochenschr., new

ser.,

vol.

18,

no.

51,

1919, p. 771.

"Hay, O. P., Second Bibliography of the Fossil Vertebrata of North America, vol. 2,
1919,

p.

237.

13 Trans.

Roy. Soc. Canada, vol. 15, 1921, pp. 93, 94, pi. 1, flg.

1.

" A monograph of the Fossil Keptilia of the Liassic formation, pt. 2, PaleontographicalSoc, 1863.

PROCEEDINGS OF THE NATIONAL MUSEUM

12VOL. 77

not meet its fellow of the opposite side, thus leaving the spinal cord
exposed for a considerable space, a condition also found in Scelidosaurus as well as in the ceratopsian dinosaurs.
The axis centrum is heavier than that of the atlas but apparently
subequal in lengtli.
The posterior articular face is deeply cupped,

6.
Atlas and axis of Palaeoscincus rugosidens. Type.
No. 11868, U.S.N.M.
A, Lateral view
B, Posterior view of
AXIS, ABOUT ONB-THIED NATURAL SIZE. At., ATLAS .la;., AXIS 1st C.
R.J First cervical rib

FiGORE;:as shown in Figure 6B.

;

The lateral surfaces are concave and there

is a heavy median keel, on either side of which, on theanterior half,
are well developed parapophysial facets.
The neural arch is low
and massive. The postzj^gapophyses strongly overhang the posteTheir articular faces are flat and esrior border of the centrum.

FOSSIL REPTILES FROM

ART. 16MONTANA— GILMORE

13

The diapophyses are short and stout, extending
outward at nearly right angles from the extreme lower side of thearch.
They have ovate, slightly cupped articular ends that lookdownward and backward.
peciaily expanded.

Measurements

of atlasand axis

Mm.
Greatest length of combined centra^

Greatest length of atlas centrum (estimated)
Greatest length of axis
Greatest height of axis centrum
Greatest height of atlas centrum
Greatest length of first crevical rib

165
88
77
68
58
126

—

Gervicals posterior to the axis. In addition to the atlas and axis
there are three cervical vertebrae, one of which can be positively
identified as the third and the remaining two are provisionally regarded as the fifth and seventh respectively. The third, except foritsslightly increased size, has the proportions of the axis, as shownin Figure 7.

The cupped parapophysial facet has moved upward on

FiGDEE 7. Third cervical vertebra OF Palaeoscincus rugosidens. Type. No. 11868,
U.S.N.M. Lateral view. One-

third NATURAL SIZE

Figure 8. Fifth? cervical
VERTEBRA OF PaLABOSCINCUS
RUGOSIDENS.
TYPE.
No. 11868, U.S.N.M.
Lateral
VIEW. One-third

NATURAL SIZE

the median anterior border of the centrum and the diapophyses
have increased in length and general robustness. The top of the low
stout spine is somewhat expanded transversely.
The centra of all
the cervicals are deeply amphicoelous. In the center of these cupped
ends, both front and back, are transversely elongated notochordal
projections that stand out prominently from the surrounding surface.

PROCEEDINGS OF THE NATIONAL MUSEUM

14VOL. 77

The vertebra regarded as the fifth of the cervical series is illustrated in Figure 8.

It differs considerably from those both anterior

and posterior to it in having a much shorter centrum, and narrower(antero-posteriorly) neural arch, and in having the anterior articularface at a higher level than the posterior articular, as may be seenin the figure. In an articulated series, this would give the neck a
decided upward inflection. This feature is little if at all developedin the other cervicals. The neutral spine also shows the peculiarityof being very thin antero-posteriorly, whereas the spines of the othercervicals both front and back are of the usual stout form.

The sides of all the cervicals are deeply concave and there is no
The vertebrae increase in general robust-evidence of a ventral keel.
ness posteriorly;

the di apophyses become slightly longer and heavier,

Seventh? cervical vertebra of Palaeoscincus rugosidens. Type.
Both figures
No. 11868, U.S.N.M. A, Lateral view B, Anterior view.
ONE-THIRD NATURAL SIZE

Figure 9.

;

the neural canal increases somewhat in size, and the pleuropophyses
gradually rise on the side of the centra as is shown in Figure 9A.

The spines, however, do not increase in height posteriorly.
The complete cervical series is as yet unknown in any of thearmored dinosaurs from the Upper Cretaceous. Nopsca recognized
six as cervical in the articulated skeleton of Scolosaurus in the
British Museum, and the atlas and axis and perhaps more were

missing from the anterior end of the articulated column. Thus
there were at least eight. Gilmore regarded Stegosaumis as having
twelve in the complete cervical series.

FOSSIL REPTILES FROM

ART. 16MONTANAGILMORE

15

Measurements
Cervicals

Greatest length of centrum.- __Greatest width of centrum
Greatest height over all
Width of neural canal>

Estimated.

_

_

__

Fifth

Seventh

Mm.

Mm.

Mm.

55
120
172
53

82. 5
1

107
150
39

66
123
187

48

'^

Dorsal vertebrae.
resenting

.

Third

all

—There are 10 vertebrae of the dorsal region rep-parts of the column.

About half of these are permuch distorted byfectly preserved, while the other half are either

crushing or important parts are missing.

The centra are relatively short and amphicoelous throughout theseries;lOA).

expanded and sides deeply excavated (fig.
In the dorsals the transverse diameter of the centra always

articular faces

FigureDENS.
VIEW.

Anterior dorsal vertebra of Palaeoscincds rdgosiNo. 11868, U.S.N.M. A, lateral view B, Anterior
Both figures one-third natural size

10.

Type.

exceeds the vertical.

;

The centra of greatest length are near the

middle of the thoracic region. In the anterior half of the column
the centra have a well developed median keel bordered on either side
Posteriorly, however, the distinct keelby shallow depressions.
disappears and the bottom of the centra is obtusely rounded.
Theneural arch is low and massive throughout (fig. lOB). The transverse processes are massive, of moderate length, and project obliquely

upward but not so sharply

as in Stegosaurus.

They

are deeply

PROCEEDINGS OF THE NATIONAL MUSEUM

16VOL. 77

cupped on their outer ends for close union with the ribs. In theposterior part of the series, these processes become so fully fusedthat the line of demarcation between the two elements can be distinguished with great difficulty, as shown in Figure 11.
In describing Ankylosaurus^ Brown ^^ points out that " in the fourposterior dorsals preserved the ribs are firmly coossified to the vertebra."

Three such vertebrae are present in this specimen, but thiscondition probably continues in those dorsals ankylosed with thesacrals.

In Panoplosaurus mirus all of the ribs are said to be free.

The pleuropophyses gradually rise from the top of the mid partof the centrum to a point well up on the side of the arch.
In themid-dorsal region this facet is large and cupped.
The neural canalis large and vertically oval but diminishes slightly in size posteriorly.

The anterior zygapophyses are much enlarged, trough-like, andThe posterior zygapophyses have flattened articular faces,

united.

Figure 11. Posterior dorsal vertebra with coossified rib of Palaeoscincus
RUGosiDENS.
TYPE.
Posterior view. About one-fifth
No. 11868, U.S.N.M.
natural size

not rounded as in Ankylosawus, and are distinct one from the other.
The spines are relatively short, thin plates with transversely enlarged extremities, this enlargement being mainly on the posteriorhalf.

The last free dorsal is peculiar in having the posterior articularface of the centrum smaller than the anterior, and also in having it

raised to a higher level, which gives the vertebra an inclined appear-

ance when viewed laterally.

In the articulated backbone this would

serve to accentuate the curve of the sacro-lumbar region.

The noto-

chordal projections, if they may be so designated, described in thethroughout the dorsal series, gradually increasing
On the most posterior vertebra they occupy
fully one-half of the entire articular face of the centrum,

cervicals, persist

in size posteriorly.

IB Bull.

Amer. Mus. Nat. Hist., vol. 24, 1908. p. 193.

FOSSIL EEPTILES FROM MOISTTANA

AET. 16

The transverse processes of the posterior

GILMORE17

dorsals appear,whenviewed from the end, to originate far down on the side of the arch,
but this is brought about by the fusion of the rib heads with theparapophyses, as shown in Figure 11, whereas in reality these procThe posterior dorsals of Ankyesses originate some distance above.
losaurus are even more deceptive in this respect.
Measurements of dorsal t'ertehrae

Greatest length of centrum
Greatest height of centrum, posterior end
Greatest height over all
Greatest expanse of transverse process1

Anterior

MiddlePosterior

Mm.

Mm.

Mm.

65
97
235
248

68

83
95
1

100. 5

258
200

180

Estimated.

Sacrum.

—The sacrum of Palaeoscincus rugosidens consists of threesacral vertebrae in the

primary sacrum, four presacrals(sacro-lumbars), and two sacro-caudals, all coalesced into a synsacrum complex of nine vertebrae in all. This is the same number and arrangement as in Nodosaurus textilus as described by Lull.^^ In P. rugosidens only the ventral surface of the sacrum

ispreserved, as

shown in Plate 4. The upper side was eroded away before the final
entombment of the skeleton. Viewed laterally the sacrum complex
The centra areis bowed from end to end, especially posteriorly.
so firmly coossified that the line of demarcation between successive

vertebrae has practically been obliterated.

The usual dilaaon of
fromthe ends of the centra is missing, hence no clue is to be had

Ventrally the sacrum is characterized by a longitudinalgroove that traverses all except the first two sacro-dorsals and thethat feature.

last sacro-caudal.

The anterior coosified centra are relatively long and slender, broadening into a wide plate in the true sacral region, narrowing again in
the sacro-caudal region. The three sacrals bear long, relatively slender ribs which are coossified to their respective centra, their lower
margins being on the same level as that of the centra. The expanded
distal ends are coossified, especially one and two, together forming
the sacricostal yoke which abuts against the inner side of the ilium.
Dorsally these ribs appear to have been continuous with the cliapophysial lamina.
The transverse processes are lacking in the first sacro-caudal, but
in the second they are preserved as long, slender processes origi"Amer. Journ. Sci., vol. 1, 1921, p. 102.

2601—30

2

PEOCEEDINGS OF THE NATIONAL MUSEUM

18

VOL. 77

nating on the posterior half of the centrum extending outward,
strongly backward, and slightly upward. These processes are
T-shaped in cross section. The first pair may have abutted against
odosaurus.
the posterior border of the ilium as inN

Measurements

Mm.
725
540

Greatest len^itb of sacral series
Greatest width across sacral ribs

Caudal vertebrae. There are 11 free caudal vertebrae present
but these do not form a continuous series, at least five being necessary to fill the gaps in addition to an unknown number missing fromthe distal end. In the complete caudal series of Dyoplosaurus^
Parks ^^ recognized no less than 23 vertebrae, and it seems quite probable that the animal here described may have had an equal number.

Figure 12. Third caudal vertebra oi Palaeoscincus rugosidens.
Type. No. 11868, U.S.N.M. A, Lailr^l vie\\ B, Anterior view.
Both figures about one-third natural size,

The caudal centra are short, articular faces wider than high, amphicoelous, and having the notochordal protuberances at the center asin the presacrals.

The sides of the centra are deeply excavated inthose vertebrae having transverse processes, but more moderately soposteriorly.

A single vertebra from the region posterior to the mid-dle of the tail is considerably longer than

any that precede it.

The transverse processes are long, horizontal, and, excepting theanterior three which articulate in part with the side of the arch,
all spring from the superior side of the centrum; posteriorly theirlength decreases regularly. The transverse processes of the first

three have slightly expanded ends

(fig. 12).
Those of the second
caudal are directly slightly forward and are in contact with thoseof the first on the outer border where there is a rugose roughening.

Similarly,

number one was in contact with the last sacro-caudal.

"Univ. Toronto Studies, Geol. ser., 1924, pp. 14-16.

MONTANAFOSSIL REPTILES PROM

AKT. 16

GILMORE

19

Whether these combined outer ends gave support to the ilium cannot be determined from this specimen. The wedge shape of the anterior centra, especially the third (fig. 12A), indicates a rapidly
dropping tail, a feature also found in the Jurassic Stegosaurus.
In all of the anterior caudals the arch is massive and the shortspines are heavy, angularly rounded in cross-section with expanded
extremities. In the mid-caudal region, however, the spines are flat-

tenedwith slight trans-verse

dilation

^

their

of

upper ends (fig. 13.) Allof the spines on the anterior two-thirds of the tailstrongly
centra.

overhang the
In the smallest

vertebra present the spine

no longer stands uprightbut

persists

roundedasridge

a low,
without

expansion, terminating posteriorly in abluntlyrounded point
projecting directly back-lateralward beyond the posterior
zygapophyses which arefast becoming sessile.

No

indication" tail-club "ofaFigure 13. Median caudal vertebra of PalaeoscinCUS RUGOSIDENS. TYPE. No. 11868, U.S.N.M. A,
Lateral view B, Anterior view Ch., Chevron.
Both figures about one-third natural size

was foundand but two vertebrae
from the anterior half of the tail showed indication of ankylosis.
These have their centra fully coossified, a condition, as indicated by
the deformed nature of the bones, brought about by an injury.
;;

Measurements of caudal vertebrae

No. of vertebra in series

Greatest
length ofcentra

Mm.
1

2
3
5(?)
7(?)
8(?)
9(?)
11(?) or 12(?)
14(?)
15(?)
(?)

67
52
49
44
57
58
44
56
52
56
66

Greatest

Greatest

width ofwidth ofcentra(post, end)transverse
processes

Mm.

Mm.

Greatestheightover all

Mm.

107
107
103
100

404
367
310
216
194

211
208
200
190

85
88
85
86

183

172

90

107

81

66

Remarks

Coossified.

Centrum only.
135
87

PROCEEDINGS OF THE NATIONAL MUSEUM

20

—The

first

chevronin Dyoplosaurus

and

all

Chevron.

isVOL. 77

carried on the fourth caudal as

are coosified with the vertebral centra.

The anterior chevrons are intervertebral but posteriorly articulate
entirely with their respective vertebrae.

These bones of the anterior
half of the tail have the proximal articular ends bridged across withbone but more posteriorly these ends are distinct. The anteriorchevrons are long and bladelike with slightly expanded ends, but
as the shaft shortens posteriorly their distal ends become correspondingly enlarged as shown in Figure 13.

The haemal canal is large anteriorly but becomes very small in
the posterior part of the series.

—

Ribs. There are parts of no less than 28 ribs present, half ofwhich are complete. These pertain to both right and left sides^

representing all sections of the body.

The outstanding features of the ribs
are their generalwide

spread.

massiveness andThe

thoracicribs,

when articulated, rise as high as the
top of the spines, thus forming an
exceedingly broad back and great
girth.

Of the above-mentioned ribs six
are regarded as cervical, the firstpair being firmly coossified with thecoalesced atlas and axis, as shown in
Figure14.
Second? left cervical
OF PALAEOSCINCUS RUGOSIDENS.
Type. No. 11868. U.S.N. M. A, Lateral VIEW B, ventral view. BothFIGURES one-third NATURAL SIZE

KIB;

Figure 6. They are single headed,with widely expanded ends which
not only articulate with the centrumof the atlas but are in contact withthe anterior end of the axis as well.

The shaft is stout, sub-ovate
The rib ofin cross-section, with a bluntly pointed distal extremity.

the right side is 130 millimeters long.

The cervical rib illustrated in Figure 14 is tentatively identified
It was found widely separated fromas the second of the left side.

the axis, but the spread of the tubercular and capitular processesisin agreement with the dia- and parapophysial facets on the axis.

Its slightly increased length over the first cervical rib corroborates

this assignment.

On the other hand, when compared with the second

cervical rib of Panoplosaurus mirus as describedby Sternberg,^^such differences are found, especially in the proximal end, as to raise
a question as to its really being the second of the series.
a greatest length over all of 143 millimeters.

This rib has

The tubercular andcapitular processes are of about equal length, the former as usual'Trans. Roy. Soc. Canada, vol. 15, 1921,

pi.

1, figs.

3.

FOSSIL EEPTILES PROM

AET. 16

being

much the stouter.

MONTANAGILMOEE

21

The shaft is flattened, the distal fourth

curved slightly inward and terminated with a bluntly rounded end.
The external surface is angularly convex transversely. On theexternal surface there is a longitudinal ridge-like roughening of thebone which occupies its distal two-thirds, as shown in Figure 14B.
The proximal half of a larger rib, probably the fourth or fifth ofthe left side, records the following changes: The capitular process
has become much longer than the tubercular, the shaft is morerounded, and the posterior side deeply concave. On the externalsurface the roughened longitudinal area has assumed a somewhat
lower position on the shaft the distal end is missing. The proximal
has a spread of 101 millimeters as compared with 70 millimeters in;the second.

The proximal end of a right rib farther back in the series displays
a decided lengthening of the capitular process which is slender andAnearly circular in cross section.
right rib from the posterior partof the cervical series much curved from end to end is illustrated in

Figure 15C. The distal extremity is missing, but from the taperingcharacter of the bone above the break it is quite evident that it waspointed. On the upper half the posterior margin extends backwardfrom the heavier shaft, forming a deep longitudinal concavity on theposterior side. This rib, measured over the curve from the top of
the tuberculum, is estimated to have a length of 375 millimeters and awidth at the center of 40 millimeters the broken distal end measures;

11 millimeters antero-posteriorly.

A complete anterior rib of the left side which may possibly represent the first throracic rib is illustrated in Figure 15B.

That it may

have been joined to the sternum is indicated by its slightly enlarged
distal end.
In cross section below the tuberculum, the shaft has apeculiar shape in so much as the usual elliptical rib has its outersurface developed posteriorly into a thin flange that forms a deep
longitudinal concavity on the posterior side. The tuberculum ismerged into and extends inward on the upper edge of the capitular
process, which is nearly as wide and heavy as the shaft itself.
Thisbone, measured over the curve from the tuberculum, has a length of
510 millimeters.

The longest rib of the entire series is shown in Figure 15A. It
measures 890 millimeters in length and is heavy and massive throughout.
The upper portion is T-shaped in cross section. At a point
midway between the middle and the distal end is an enlarged roughened area which morphologically appears to correspond to the position of an uncinate process. Whether these processes existed as distinct elements in the armored Dinosauria has not yet been determined.
Nopsca ^° attributed the flangelike overhang of the anterior thoracic" Geologica Hungarica, Budapest, vol. 1, 1928, p. 56.

22

PEOCEEDIJSTGS OF

THE ISTATIOFAL MUSEUM

VOL. 77

Figure 15. Ribs of Palaeoscincds rdgosidbns.
Type.
No. 11868, U.S.N.M.
A
Thoracic rib; B, First? thoracic rib; O, Posterior cervical rib
Z)/ Rib op
UNDETERMINED POSITION. ALL FIGURES ABOUT ONE-FOURTH NATURAL SIZE;'FOSSIL KEPTILES FROM MONTAN^A

ART. 16

GILMORE

23

ribs as representing the processus uncinatus, but I believe he was mis-A

more logical explanation, it seems to me, is the one
taken in this.
given by Brown that this enlarged area on the anterior ribs may have
served for attachment of the heavy shoulder muscles in Ankylosaurus.
Posteriorly the ribs become progressively more slender with pointed
There is evidence that at least three of the posterior dorsals had the ribs fully coossified with the neural arch as
shown in Figure 11. So complete is this coalescence that the line ofdemarcation between the two bones can scarcely be detected. Thesemost posterior ribs are exceptionally wide and thin below the T-shaped
section of their upper portion.
In addition to the above-described ribs there are three singleheaded ribs of the type of the one illustrated in Figure 15D. They
have a roughened rugose articular proximal end slightly bowed fromend to end, shaft of moderate width, tapering to a pointed end. I
am unable to determine their proper position in the skeleton. That
they do not pertain to the sacro-dorsals seems to be indicated by theflat, wide ends found attached to the blade of the ilium (fig. 3,
The most perfect one
pi. 7) whereas these have narrow pointed ends.
of the three which lacks the extreme distal end measures 350 millidistal extremities.

,

meters in length.
Ilium. The preacetabular portion of the right ilium and a few
scattered, much-worn fragments are all that was preserved of the—This anterior blade is platelike, thickened, nearly straighton the inner border, gradually thinning toward the anterior andouter margins, the latter presenting a sharp edge. The anterior
end is obtusely pointed, its most anterior projection being welltoward the inner side of the bone; externally the border rounds off
toward the laternal margin as shown in Plate 7, Figure 3. The
upper surface of this portion is smooth, slightly convex from side
to side; the under surface is concave both transversely and anteroilia.

posteriorly.

There is no indication of dermal plates having been united to thesuperior surfaces of the ilium as in Stegopelta^ although on the outerhalf of the mid part of this section of the ilium there are shallow
transverse grooves, probably for blood vessels suggesting a cutaneous

investment that was closely applied to this surface of the ilium.
Lull ^° has noted a similar condition on the ilia of Nodosaurus.
On the ventral side the distal ends of three posterior ribs remain
securely coalesced with this surface of the ilium as shown in Plate
7,

Figure 3.

The end of the anterior rib projects slightly beyond

the margin of the ilium, the remaining two terminating an inch or

more inside its border.
=0 Lull

R.

S.,

Amer. Journ. Sci., vol. 1, 1921, p. 105.

PROCEEDINGS OF THE NATIONAL MUSEUM

24
Pubis.

—The small bone illustrated in Figure 16

right pubis.

isVOL. 77

regarded as thean animal,

It is a remarkably small bone for so large

the whole prepubic portion measuring only 140 millimeters in length,
less than one-half the length of the Stegopelta pubis.^^portionis

The anteriora thin vertical blade of bone terminated anteriorly by aslightly thickened rugose end that is rounded off from above downward. On the internal surface at about its mid length the postpubis
branches off, continuing backward and downward. The postpubic
branch terminates in a vertically expanded end that in this specimen
is perfectly preserved (fig. 16).
On the outer side much of thesurface has been eaten away, leaving one at a loss to understand where

and how this bone articulated with the ilium, as
there

an

is

no indication ofenlarged

articulararea.

The small size of thepubis in these Upper
Cretaceous armored dinosaurs has been indicated by Nopcsa in ScoFigure 16. Right pubis of Palaeoscincus rugosiDENS. Type. No. 11868, U.S.N.M. Lateral view.
JosaurtLS, but it was soA., Anterior end
Pp., Postp.. Posterior end
poorlypreserved that hepubis.
One-third natural size
could not determine its
shape. Ankylosaurus also has a very much reduced pubis ^- apparently coossified to the ischium and Nopcsa remarks that "it neither;;

seems very large in Polacanthusy
roughened.
Ischia.

The outer surface—Both ischia are present, theright lacking its distal fourth.

left

is

much

one being complete, theThe ischium is a moderately long

curved bone having a widely expanded proximal and a bluntly
pointed distal extremity. On the outer surface the proximal end isconcave fore and aft and forms a part of the acetabulum. The
acetabular margin is unusually straight. Below this end the shaft is
flattened transversely and gradually decreases in width toward the
distal end, the taper becoming more pronounced a little below the
mid-length where the bone also bends downward, as shown in Figure
17.

A flat roughened area on the external surface at this bend in-

On theinner side the surface of the bone gives no indication that it wasin contact on the midline with its fellow of the opposite side though
doubtless there was a cartilaginous union of the two.
dicates the point of attachment of an important ligament.

^ Moodie, R. L., Kans. Univ. Sci. Bull., vol. 5, No. 14, 1910, p. 265, pi. 58, fig. 1.
=2

Romer, A. S., Acta Zoologiea, vol. 8, 1927, fig. 8. p. 243.

MONTANAFOSSIL REPTILES FROM

ART. 16

GILMORE

25

Measurements

^^
570
275
23

Greatest length in a straight line
Greatest width of proximal end
Greatest width of distal end

Dermal armor.

—Inter-mingled with the scatteredparts of the skeleton some
fifty dermal bones of thisone individual were colThese present alected.
variety ofspines,kinds,

large and small; coossified

rounded scutes,
and without keels;and numerous granular osAlthough thissifications.
plates;with

specimen will contributebut little to our knowledgeof the arrangement of thedermal armor, it does givea considerable insight intothecharacterofthe os-seous dermal covering.

Comparisonof^thesescattered plates and spines

with those of Palaeoscincm
in theAmerican Museumof Natural History,New

York, where the armor has
been preserved in situ enables

me to recognize themanyproper location ofof these scatteredbones.

Furthermore the close similarity in shape, size, andassociation makes it at once
apparent that we are dealing here with two animals
that are generically alike.

—Left ischium of Palaeoscincus rugosiNo. 11868, U.S.N. M. Lateral view.
Articulating surface for ilium P., ArticuII.
lating SURFACE FOR THE PUBIS. ABOUT ONE-FOURTH
natural size

Figure 17.
DENS.

Type.

Neck plates. The dermal armature covering theneck is represented bythree plates each composed of either two or three coossified bony
These are illustrated in Plate 5. The smallest of thesescutes.
plates, a complex of three scutes (fig. 3, pi. 5) is tentatively regarded
J;

PROCEEDINGS OP THE NATIONAL MUSEUM

26

as the right half of the first transverse ring.

vor.. 77

The largest plate, acomposite of two paired scutes, is identified as the median part of thesecond ring (fig. 1, pi. 5) the third plate consisting of two scutes isprovisionally regarded as completing the right half of the secondring (fig. 2, pi. 5).
The articulated Palaeoscincus skeleton illustrated by Matthew -^;(pi. 8, fig. 1)

shows the rings over the neck to consist of six scutes

each, the narrowest ring lying in front, and it is largely on the evi-

dence of this specimen that the provisional identification of theseelements is made.

The upper surfaces of these plates are roughened by irregular,
shallow vascular pits and grooves that are so distinctive of all dermal elements.

The under surfaces are fairly smooth and show no

traces of the coalescence of the individual scutes further than a slightswelling of the bone following the course of the sutural union, buton the dorsal surfaces-straight grooves.

their line of junction is marked by deep
Each scute has a low longitudinal keel that origi-

nates on the front border, rising posteriorly whereitterminates inan obtusely pointed overhanging, spine-like projection.

These keels

are asymmetrically placed.

The first ring in its entirety evidently consists of six scutes divided
in this individual at the center intotwoplates.

It appears very

probable, however, that other individuals might have the two halves

fused at the middle into one continuous ring of bone, although Sternberg found the same divided condition in the type of Edmontonia
longiceps.^^ The ring is broadly arched and has a length, measured
in a straight line across the arch, of 350 millimeters, a width on the
median line of 90 millimeters. The medial scute is rectangular inoutline with its greatest diameter transverse. Viewed from above,
however, this scute is pentagonal in shape due to the low lying projecting spine, which strongly overhangs the posterior border of thescute.

The keel on this scute is placed nearest the external side andTheis slightly divergent from the median line as it runs backward.

median scute has the keel nearest to the inner side, and the overhanging spinous projection is more rounded and pointed than on the scutepreviously described.

The outer of the three scutes is subrhombic

in outline when viewed from above and the keel which originates on

the inner, anterior corner, pursues a diagonal course outward andbackward, the conical spine strongly overhanging its outer border.
On the anterior border at the junction of the scutes there areroughened indentations that suggest the points of attachment ofsmaller dermal elements. Otherwise this border is beveled from^ Matthew, W. D., Natural History, vol. 22, 1922, pp. 334-335.
21

Sternberg, C. M., Trans. Royal See. Canada, vol. 22, 1928, sec. 4, p. 104.

AET. 16

FOSSIL REPTILES FROMMONTANAGILMORE27

below upwards, leaving a narrow rounded edge whose surface is
The scutes vary from 26 to 36 millimeters inthickness around their borders. From the rounded character of theouter border of the third or lateral scute, it seems quite probableslightly roughened.

that it represents the lateral termination of the first ring.
The two coossified scutes, shown in Figure 1, Plate 5, are thought
to represent the median pair of the second dermal row Avhich in thisinstance are fully coossified on the median line as in Panoplosaurus.

These scutes in transverse curvature, thickness, outline of posteriorborder, and keel development show a close resemblance to the homologous elements of Panoplosaurus mirus. In proportion and outline
as a whole and in minor features they show many dissimilarities andstrongly suggest that differences found in the armor of Palaeoscincus

and PanoijlosauTus when fully
tinguishing these genera.

known will greatly assist in dis-

The median coossified plates of the second row measured in astraight line across the ventral side have a greatest transverse width

on the median line a length antero-posteriorly ofof 390 millimeters;

130 millimeters.

The keels of these scutes are placed nearest theouter border, whereas in Panoplosaurus they are near the inner edge.

The posterior end of the keel develops a low, obtusely rounded spinethat overhangs this edge.

The third plate consisting of the two coossified scutes shown in
Figure 2, Plate 5, is identified as completing the right half of thesecond ring. That the smaller one represents a lateral scute seems
to be indicated by the rounded outer border and the strong diagonal
trend of the keel.

—

Spined scutes. Massive, long, sharply pointed spined scutes, suchon the shoulders and along the sides of Palaeoscincus(see pi. 8) are present, and are illustrated in Plate 6, Figures 1, 2,
3, and 4.
A pair of moderately sized spinous scutes apparently corresponding
as are foundto those lateral to the ends of the second transverse ring (fig. 3, pi. 6)in the Palaeoscincus skeleton are in perfect preservation.

Theirbases are subovate in outline, measuring 205 millimeters in thelongest diameterand 133 millimeters in the shortest.

These ends

are deeply concave and around the borders a rugose band indicatesclearly the depth of their insertion in the integumentary covering.

On the superior surface, a high, triangular-shaped spinous keel isOver all, this scute hasa greatest height of 290 millimeters. The surface of these bones
is covered by the usual shallow vascular pits and grooves.
single scute, the largest of the series, doubtless corresponds tothe second in this row of lateral spines, and occupies a position overdeveloped, overhanging the basal portion.

A

PROCEEDINGS OF THE NATIONAL MUSEUM

28

vol. 77

the left shoulder and lateral to the third transverse ring in the
Palaeoscincus skeleton (pi. 6, fig. 1). Viewed from below the baseof this scute is subrectangular in outline, having a greatest lengthof 350 millimeters, and a width at the center of 120 millimeters.

This surface is traversed by a median longitudinal depression that
gradually deepens toward the spinous end. The base is concave fromend to end with a torqued posterior end. The shape of the basal
surface is probably an adaptation in better conformation with theunderlying bones of the shoulder region. Its depth of insertion in
the skin is clearly indicated by a rugosely roughened band that
extends entirely around the basal portion of the scute. On the dorsal

surface is a high, sharp edged keel that has its origin on the posterior
internal angle and extends diagonally across the scute.

This keel
gradually increases in height from its point of origin terminating
in a high, sharply-pointed but compressed spine that strongly overhangs the posterior basal part of the scute. Measured from thebase to the tip this spine is 242 millimeters long.

A dermal plate illustrated by Lambe^^and provisionally associ-ated with Euoplocephalus tutus, may, on account of its close
resemblance to the plate just described, be quite certainly referred to
the genus Palaeoscincus.

A pair of large triangular shaped, sharply pointed spines, eachwith a smaller scute carrying a very much smaller andblunter spine undoubtedly represent the next two spines of thecoossified

lateral series

which project outward from the side of the body

above the fore leg. In Palaeoscincus, however, these two elements
appear to remain distinct. These coossified plates have a greatest
basal length of 460 millimeters. The taller spine measures 400
millimeters in height, the shorter only 180 millimeters. These
spines are figured in Plate 6, Figure 4.
Among the dermal elements there are three other scutes which
may be classified as spines but no clue has yet been obtained as totheir position. These are of much smaller size than those previously
described and one is shown in Plate 6, Figure 2. These have subovate, concavely excavated bases, low asymmetrically placed keels,that pass into two obtusely pointed compressed or angularly roundedspines that project backward at a low angle. Two of these are theright and left elements of a pair.
The position of this lateral row of spined dermal elements in the
Palaeoscincus, skeleton (pi. 8), having the spines projecting outward and forward seems entirely opposed to a natural placing. In
such a position they would have been a source of constant annoyanceand trouble to the animal by constantly catching on small trees-5

CoDtrib. Canadian Paleont., vol.

3,

1902,

p.

57,

fig.

1.3.

ART. 16

FOSSIL REPTILES FROMand shrubbery.

MONTANAGILMORE29

Had they not been found in situ, a study of living

creatures on the basis of analogy would not have placed them as they

Reversed in position or at most having the spines directedfrom the body, would be more in accord with thosespined quadrupedal creatures known to-day. Furthermore, thespecimen of Scolosaurus in the British Museum has somewhat similar scutes preserved along the neck in situ, and these are in accord
with living lizards. It is not my purpose to question the position of
the spines in the Palaeoscincus skeleton but I do seriously doubtthat during the life of the animal they occupied their present
forwardly directed position.
Sacral armor. That Palaeoscincus had a shield-like bony covering over the sacrum as in Nodosaurus seems to be indicated by thepresence of a number of large fragmentary plates. These plateare.

straight out—

pieces are clearlyshown to consist of a number of thin, coossified
and varying shapes, although most of themscutes of several sizes

seem to be suboval in outline. From this fragmentarj'^ evidence itwould appear that there may be a row or rows of large scutes surrounded by smaller ones. It would seem quite probable that allof these pieces may have been parts of one continuous bony shield.
The nodular prominences on these scutes are almost obsolete, except
for a slight thickening near the center of the largest.

On the dorsal

surface shallow depressions follow the course of the sutures, clearly

A few detached scutes of the same natureprobably represent elements that pertain to nearby areas. Good
examples of these are shown in Plate 7, Figure 1.
Undetermined scutes. In addition to the dermal scutes describedabove and whose position on the animal has been determined withsome degree of assurance, there are in the collection no less thantwenty other dermal elements whose origin at this time is unknown.
These scutes are of various dimensions, strongly keeled, short spined,
broadly to narrowly suboval in outline, always excavated below, but
usually deepest beneath the highest part of the keel or spine. On
either side of the keel the external surface slopes both ways to theedge, either flatly or with a varying amount of concavity, dependinglargely upon the height of the keel or spine. In none of thesesmaller scutes does the spine overhang the border. The shortspines, if they may be so designated, show a great variety of form;
some are obtusely pointed, others compressed and sharp edged,
others have the keel running the full length of the scute, whilestill others have only a nodular projection.
great many small rounded granular ossifications were foundscattered through the quarry. These filled the interspaces between
the larger scutes, and are well shown in specimens of Palaeoscincus
marking out their limits.

—

A

30

PEOCEEDINGS OF THE NATIONAL MUSEUM

and Scolosaui'us.

vol. 77

Similar ossifications are probably present in theskin of nearly all armored dinosaurs.
Relationshi'ps.

—The genus Palaeoscincus

falls

readily into thefamily Nodosauridae as redefined by Lull,-'' and on the basis of theskull structure it would appear to have its closest relationships with
Panoplosawus and Edmontonia. These three genera should begrouped to form the subfamily Panoplosaurinae recently proposedby Nopsca,^^ Of the other four genera Dyoplosaurus^ Hierosaurus:,/Scolosaurus, and jStegopelta, included by Nopsca in this subfamily.
Dyoplosaurus^ as shown by the recently discovered skull describedlater in this paper, should now be removed to the Ankylosaurinae,
The skull structure of the three remaining genera is unknown andtheir precise systematic position is much in doubt. The presence inall of transverse rows of nuchal plates is one reason for their provisional retention in the Panoplosaurinae.
The definition of this subfamily may now be emended by the
inclusion of the following skull characters /Skull covered superiorly
hy a few large plates; orbits placed far posteriorly; lateral temporalfenestra opening laterally; nostrils later o-ternrdnal ; large quadrate +quadratojugal dermal plate absent.
While it is not my intention to attempt a revision of the Nodosauridae, yet the study of the specimens in hand has disclosed relationships of certain American members of this family which appear:

worthy of record.
Dyoplosaurus^ as mentioned above, is here transferred from the
Panoplosaurinae to the Ankylosaurinae. In establishing this subfamily Nopsca referred to it the following genera Ankylosaurus.^
Euoplocephalus^ HoplitosoMrus^ Palaeoscincus^ Polacanthus^ Polacanthoides^ Sarcolestes. With this grouping I can agree only inpart. AnJcylosaums^ EuoplocephaJus^ Dyoplosaurus and Anodonto:

saurus are true members of this subfamily.

On the basis of the skull

structure I would amend Nopsca's definition of the Ankylosaurinae

by the inclusion of the following cranial characters Skull covered
superiorly hy numerous small plates; orbits placed submediallylateral temporal fenestra covered by dermal bone; nostrils terminal;
large quadrate -\r quadratojugal dermal plate present.
:

The other genera can not be definitely assigned on the basis of
their cranial structure, the skull being unknown.

Polacanthus., withcomplete bony carapace over the sacral region and tail, compressed dermal elements unlike any found with the more typicalAnkylosaurinae, will, I believe, eventually be found to belong toa distinct subfamily. The American Hoplitosauims is apparently
closely allied and should be grouped with Polacanthus.
its=" Dinosaurierrestl,=»

Geologica Hungarica, Budapest, 1929, pt.

Amer. Journ. Sci., vol. 1, February, 1921, p. 123.

5, p.

70.

MONTANAFOSSIL REPTILES FROM

ART. 16

GILMORE

31

In the light of our present knowledge of the genus Nodosaurus,
I can see no justification for its inclusion in a separate subfamily,
the Nodosaurinae, as proposed by Nopsca. Certainly nothing isfound in its known anatomy that would prevent its assignment to
the Ankylosaurinae.

The inclusion of the genus Trobdon in the Nodosauridae by Nopcsa
is so

obviously in error that I take this opportunity to challenge theTroodon is a typically bipedal animal

propriety of the assignment.

with greatly reduced fore limbs, and a slender elongated scapula;premaxillary teeth present ilium with postacetabular portion vertical and subequal in length with preacetabular portion ischium slender, ceratopsian like; ribs slender; tibia and femur subequal inlength; pes having phalanges with tongue and groove joints; a;;segmented abdominal cuirass.
The features briefly reviewed above are certainly an array ofcharacters that, taken together, do not permit of the inclusion of
the genus in the family Nodosauridae.
At the time of describing the osteology of Troodon -^ attention
was directed to the curious mixture of characters found in the skull
and skeleton and it was my conclusion that the relationships ofTroodon would be best expressed by its reference to a distinct familyof the Ornithopoda known as the Troodontidae, a conclusion, after
again reviewing all of the evidence, that I see no reason to alter.
Chronologicallist

Name, authority, and date

American Nodosauridae

Formation and locality

Judith River, Mont..
Arundel,Benton, Wyo
Lance, Wyo
Lakota, S. Dak
Belly River, Alberta.

Palaeoscincus costatus Leidy, 1856

Md

Priconodon crassus Marsh, 1888

Nodosaurus texiUus Marsh, 1889
Palaeoscincus lutus Marsh, 1892
HoplitosauTus marshi Lucas, 1901
Palaeoscincus asper Lambe, 1902
Sterocephalus tutus Lambe, 1902
Stegopelta landerensis Willi^ton, 1905
AnkylosauTUs magnivertus urovvn, 1SG8

Hierosaurus sternbergi Wieland, 1909
Panoplosaurus mirus Lambe, 1919
Dyoplosaurus acutosquameus Parks, 1924.
ScolosauTus cutleri Nopcsa, 1928
Edmontonia longiceps Sternberg, 1928__.
Anodontosaurus lavibei Sternberg, 1929.
Palaeoscincus rugosidens Gilmore, 1830..

2.

of NorthNature of type

Tooth.

Do.
Parts of skeleton and armor.

Tooth.
Parts of skeleton, dermal armor.

Tooth.

do
Benton, Wyo

Fragment of skull, dermal armor.

Hell Creek, Mont.

Skull;

Niobrara, Kans
Belly River, Alberta.

doEdmonton, Alberta,.do.

Tvro Medicine, Mont...

Parts of skeleton, dermal armor.

much of skeleton, andder-

mal armor.
Dermal armor.

,_
'"
''"'
y^
Skull; parts of skeleton and armor.
Fragment of skull; posterior part ofskeleton.
^iMuch of armor and skeleton.
*;.j
Skull, armor, and parts of skeleton.
Skull and armor.
k4
Skull; much of skeleton and armor.

ON A SKULL OF THE GENUS DYOPLOSAURUS
Plate 9, F gures 1 and 2

In 1924 Prof. W. A. Parks ^^ established the genus Dyoplosaurus,
based on a partial but very interesting skeleton, consisting princi=82>

Gilmore, Charlps W., Bull. No. 1, University of Alberta, 1924,
Univ. Toronto Studies, No. 18, 1924, pp. 5-24.

p. 39.

32

PROCEEDINGS OF THE NATIONAL MUSEUM

pally of the posterior part of the axillary skeleton.
only fragmentary skull parts and a few teeth remain.

vol.77Of the headIn the 1928 collection from the Upper Cretaceous of Montana wasa somewhat imperfect skull with four teeth which is identified as
DyoflosauTus acutosquameus Parks. The identification rests verylargely upon similarities found in the teeth. If correct in this assignment, the specimen is of great interest in giving the first adequate knowledge of the skull structure of the genus. This specimen,
No. 11892, U.S.N.M., was collected by George F. Sternberg, May 26,
1928, from the Two Medicine formation, Upper Cretaceous, from thesouth side of Milk River, NW. lA sec. 27, T. 37, N., R. 8 W., on theBlackfeet Indian Reservation, Glacier County, Mont.
The skull has its closest resemblances in Euoplocephalus tutus
Lambe from the Belly River formation, Canada, of which twonearly perfect skulls ^^ are now known in addition to the poorly
preserved type.
The skull before me has the superior surfaces much checked asshown in Plate 9. It lacks the beak in front of the nares, and thepalate is so badly crushed and broken that little can be determinedof the mouth structure.

Viewed from above the skull is subtrianguiar in outline, longer
than broad, and doubtless having a broadly rounded nose as inEuoplocephalus. The anterior half is strongly arched both anteroposteriorly and transversely. Between and behind the line of theorbits the top is depressed, especially on either side of the medianline.
This surface terminates posteriorly as a short overhanging
crest, that is, slightly concave transversely.
Coossified dermal plates cover the surface at the top and side of
the skull, thus completely obscuring all of the underlying cranial
elements. The median posterior border is ornamented by a row offour small quadrangular scutes, the same number as found in the
fragmentary skull of the type of Byoplosaums acutosquameus.
Ankylosaurus also has a similar number, but in Euoplocephalus
there are only two with a plain interspace between. The superior
surface is so badly checked that the form of the scutes can be madeout with great difficulty. They seem to resemble those of Euoplocephalus except for the lack of a large element on the nose. The
surface of these scutes is undulatory, roughly rugose and covered
with vascular pits and grooves. Their edges are usually angular
but none has the depressed central areas found in Euoplocephalus.
Deep circumscribing grooves set off the scutes from one another.
=»Gilmore, C. W., The Canadian Field Naturalist, vol. 37, No. 3, 1923, p. 47; Nopcsa.
P. B., Geologia Hungarica Paleontological Series, vol. 1, 1928, pp. 51-54, pi. 5.

FOSSIL EEPTILES FROM

AET. 16MONTANAGILMOEE

33

The nearly vertical lateral surface between the orbits and theexternal nares is covered by two large plates, the anterior one bending over to contribute to the dorsal surface. It also forms a partof the posterior boundary of the narial opening.

In Euoflocepha-lus three plates cover this area.

On the angle of the skull above each orbit is a large, blutly edged
scute that slightly overhangs the eye but to a lesser degree than in
Euoplocephalus. On each posterior external angle of the skull isa large subtriangular spinelike scute that projects prominently
backward beyond the posterior border much as in Anhylosaurus.
Euoplocephalus has somewhat similar protuberances but sharper
edged and extending more upward. It is quite apparent that these
two scutes are missing from the posterior part of the Dyoflosaurus
skull figured by Parks.^^

The posterior end of the skull is in fair preservation and presents
a good idea of the arrangement of the occipital region, but many ofthe palatial elements are entirely missing, or so badly crushed that

but little conception of its normal condition can be obtained.
The occipital condyle is reniform in outline and directed backwardand downward. It seems quite apparent that the basal portions of
the exoccipitals participate in its formation much as they do in
Stegosaurus.^^ The condyle has a greatest transverse diameter of
54 mm., a greatest vertical diameter of 32 millimeters. The reniform shape of the condyle offers a striking contrast to the muchlarger subspherical condyle in Palaeoscincus as shown in specimen

The foramen magnum is suboval in outline
and the supraoccipital border above it deeply notched.

No. 11868, U.S.N.M.

The basioccipital is about as long as it is broad.

The ventral

surface between the condyle and the expanded anterior end is broadand deeply concave with a shallow longitudinal depression occupying

The basioccipital processes are very short.

the central area.

The

outward nearly horizontal and with but little
angulation posteriorly. As mentioned above, their pedicles contribute somewhat to the formation of the occipital condyle. At theirouter ends they join the quadrates by means of the paraoccipital
processes resting against a rugose area on the posterior sides of thosebones. They do not seem to be coalesced with the paraoccipital asexoccipitals extend

in Palaeoscincus rugosidens.

The supraoccipital can not be
relatively long, straight,

differentiated.

The quadrate is

and slender as compared with the more

The thin process that
extends forward and inward to meet the pterygoid is less than halfplate-like element in the Palaeoscincus skull.

81 Univ.

Toronto Studies, No. 18, 1924, pi. 4, fig. 1.

82 Gilmore,

C. W., Bull. No. 89, U. S. Nat.

2601—30

3

Museum, 1914, p. 92, flg. 4.

PROCEEDINGS OF THE NATIONAL MUSEUM

34

vol. 77

the width of this process in the type of Palaeosincus rugosidmis;
likewise the articular distal end is much smaller.
There are some remnants of the palate present but a descriptionof these would add nothing of interest.
The lateral temporal fenestra opens outward and backward be-

tween the quadrate and the enveloping armor.
Beneath and somew^hat posterior to the orbit on either side is alarge scute whose strongly developed keel is directed downward andoutward. Its anterior outer border is acutely edged and rounded offfrom the front toward the back. This process completely hides thearticulation of the lower jaw with the quadrate, and furnishes it with
ample protection.
The orbits are suboval in outline, with a diameter anteroposteriorly of 76 millimeters and dorso-ventrally about 30 millimeters.
The skull is widest across the orbits and much constricted transversely in front, a feature that will at once distinguish Dyoplosaurus
from Euoplocephalus and Ankylosaurus.
Measurements of tJie skull

Mm.
Greatest length (estimated) median line
Greatest breadth across center of orbits
Greatest breadth immediately posterior to nares

Teeth.

—There are

five teeth preserved,

365
325
175

one in the center of theright maxillary and the crowns of four others found in the dirt near

Since there were no other animal remains with this specimen, there can be no doubt of the association.
As the lower jaw
was entirely missing it may be inferred that all of these teeth belong
in the upper or maxillary series.
The teeth are alike in form and
Their very small size appears to be distinctive, a fact that can
size.
not be attributed to their being germ teeth as shown by one muchworn tooth which has the same proportions as the unworn. Eachconsists of a laterally compressed crown with a long cylindrical root.
The crowns measure 4.7 mm. antero-posteriorly, 4 mm. transversely
through the cingulum, and about 5 mm. in height. The crown at
the base has a swollen cingulum that is especially pronounced on
the skull.

the outer side.
The edges of the teeth are denticulate, there beingnine or ten denticles on each tooth, four and five respectively on eitherside of the apical one which is decidedly posterior to the central ver-shown in Figure 18. On the outer side the crown isdivided into five principal columns by vertical fluting (see fig. 18B)
which subsides on the internal side before reaching the cingulum.
The three larger denticles are transversely flattened with acute edges,
the others presenting more or less rounded points.
The teeth areworn on the inner side showing that the lower teeth bite inside thetical line asFOSSIL EEPTILES FROM

AET. 16MONTANAGILMORE

35

upper as would be expected. Both surfaces of the crown are marked
by fine, irregular, vertical wrinkling. The line of smaller denticles
on the anterior border curve inward while those of the posteriorborder curve outward, so that viewed from the end, the line of
The roots of the teeth are long,
denticles form a sigmoid curve.
smooth surfaced, and subcylindrical.
These teeth have the general characteristics of other North American armored Dinosauria; that is, laterally compressed crowns withdenticulated borders, basal cingulum, and long more or less cylindrical roots.
Teeth are now known of the following genera Stegosaurus,
Ankylosaurus^ Stegopelta, Princonodon^ Palaeoscincus^ Panoplosaurus, Ed?nontoma, and Dyoplosaurus. Compared with teeth of thesevarious genera those belonging to the present specimen have their:^nearest resemblances in^cthose of Dyoplosaurus.

Through the kindness

W. A. Parks, amaxillary fragment containing teeth of the typeof Dyoplosaurus acutosquatneus was loaned meof Dr.

for study.

parisonof

A direct comthese

Figure 18. Right maxillary tooth of DyoploNO.
ACUTOSQUAMEUS
PARKS.
saurus11893,
U.S.N.M
A, Inker view; B, Outer view; G,
three
Posterior view. All
times natural size

teethwith those of the specimen from the Two Medicine formation showssuch close similarities in size, proportion, denticulation, and sculpture
as to leave no doubt that the two specimens are cospecific. This maxillary fragment of the type was regarded by Parks ^^ " as the anterior
portion of the dentigerous region of the left maxillary," but, after

comparing it with the broken maxillae of the skull here considered, Iam fully convinced that it represents the posterior portion of the rightmaxillary.

This determination is of importance as definitely fixing

the position of the teeth in the jaws; that is, the highest j)art of thecrowns are toward the posterior border. It was also found that the
published illustration of the tooth does not accurately depict theoriginal, being in error in that the denticles on the anterior border
are too acutely pointed and too widely spaced. The second denticle
posterior to the apical one should be lower, and the first point posterior to the apical denticle should be omitted, a fact recognized by
Doctor Parks; on the posterior border at least two denticles should
be added. These are now plainly shown on the specimen, thoughpreviously hidden by adhering matrix. In the Canadian tooth, however, they are barely visible

from a lateral view, passing more to

Univ. Toronto Studies, No. 18, 1924, p.

9.

PEOCEEDINGS OP THE NATIONAL MUSEUM

36

vol.77the outer side than in the tooth of No. 11892, U.S.N.M., as shown in

Figure 18A, where they are slightly visible from an inner view.
3.

A NEW HORNED DINOSAUR

A fragmentary posterior portion of a ceratopsian frill is amongfrom the Two Medicine formation collected during
The presence of long horn-like processes on
the posterior border of the frill shows its affinities to lie within
the genus Styracosaurus^ but these differ to such an extent in form
and arrangement from those of Styracosaurus albertensis Lambe,
from the Belly River of Alberta; as to indicate a distinct species, forwhich I now propose the name Styracosaw'us ovatus, the specificname being suggested by the ovate character of the horn-likethe specimens

the summer of 1928.

processes.

STYRACOSAURUS OVATUS, new species
Plate 10, Figure 2

Type.

—Cat. No. 11869, U.S.N.M., consists of the posterior por-tion of the frill

and numerous detached fragments.

Collected by

George F. Sternberg, 1928.

Type locality.—T. 37 N., R. 8 W., Milk River, Blackfeet Indian
Reservation, Glacier County, Mont.

Horizon.

—Two Medicine formation. Upper Cretaceous.

A nearly entire posterior end of a median frill bone with its
attached processes is present.

(See pi. 10, fig. 2.)

This element in

the ceratopsian frill has been variously designated the parietal,

dermosupraoccipital, interparietal, and fused postfrontal. Sternberg ^* has recently attempted to show it to be the parietal instyracosaurus^ but, although it appears to represent that bone inProtoceratops, it certainly can not be the parietal in American
horned dinosaurs, as evidenced by the juvenile Brachyceratops andother ceratopsian skulls in the National collections. I am unable
as yet to decide certainly on its homologies, and, as a matter of
expediency, shall continue to designate it the dermosupraoccipital.
The outstanding peculiarity of the skull of Styracosaurus albert-,
ensis is the large horn-like processes that project outward and backward from the posterior border of the frill. Somewhat similar
processes are present on the frill before me. The two processes
forming the hindermost pair lack their tips but it is quite evident
they were not as long as in the Canadian specimen.
(Compare figs.
1 and 2, pi. 10.)Furthermore, these two horns are convergent as
opposed to the divergent processes in S. albertensis. It would seem='Trans. Roy. Soc. Canada (ser. 3), vol. 21, 1921, pp. 135-143, pis. 1, 2, and 3.

ART. 16

FOSSIL REPTILES FROM MOIS'TAN-A

GILMORE

37

that if completely preserved the extremities of these two Lorns

would nearly meet on the median line. Those of the next pair in
advance are nearly as large as the hinder pair but point outward
more than backward. That there was a third pair is shown by thepresence of a small lateral section of the frill, from the side of whicha small, stubby process projects outward (pi. 10, j&g. 2). If, as isapparent, this fragmentary part represents the third pair, theseprocesses have their origin considerably forward of the second pairas shown by the smooth, rounded border between them. In S. albertensis these processes are relatively shorter, curved, and twinned withthe second pair at the base.

The central part of the posterior border of the interparietal between the posterior pair of processes is thick and rounded and whenviewed from above (pi. 10. fig. 2) displays a decided notch on the
median line. That large fontanelles were present on either side ofa median bar as in S. albertensis is shown by the rapid thinning of
the bone on the anterior borders on either side of the middle, and alsoof the posterior portion of the bar which is preserved. This part ofthe median bar is broadly rounded transversely on the upper side but
flattened beneath.

The upper and lower surfaces of the frill parts are marked by the
The horn-like processes are much flattened
above and below and cross sections taken from almost any partusual vascular grooves.

would be broadly ovate in cross section.
Measurements

Mm.
Greatest width from tip to tip of second pair of processes
Greatest lengtli of riglit process of second pairGreatest width of same at base
Greatest length of shortest process
Greatest width of median notch

80O
295
93
108
57

Reference of the present specimen to a new species on such fragmentary material is a procedure that may be open to some question,
especially where the specific characters are based upon structures
which may be subject to much variation. However, the difference

noted in these hornlike processes, except for their much greater
appear to be comparable to the changes found in the different
species of living horned lizards {Phrynosoma)
In the latter case,however, the differences in horn structure are confirmed by othercharacters such as coloration and scutellation, features that of course
are not available to the paleontologist. However, in establishing
this species on the available material, fragmentary though it may be,
it is with the hope that more complete specimens will disclose otherand perhaps more stable characters.
size,

.

PROCEEDINGS OF THE NATIONAL MUSEUM

38

vol-. 77

EXPLANATION OF PLATES
Plate 1

View of the excavation where the skeleton of Palaeoscinciis rugosiden^ wascollected.

sacrum.

In the middle foreground is a large plastered block containing the
Photograph bj' George F. Sternberg.

Plate 2Skull of Palaecoscincus rugosidens.
About one-third natural size.

No. 11868, U.S.N.M.

Type.

Superior

view.

Plate 3
Fig.

Fig.

1.

— Skull. Viewed from right—Right ramus of Pala&oscincus rugosidens. Type. No. 11868»
side.

2.

U.S.N.M.

Lateral view.

About one-third natural size.
Plate 4

— Sacrum of Palaeoscincus rugosidens. Type. No. 11868, U.S.N.M.
About one-fifth natural
Fig.
—Tooth of Palaeoscincus asper Lambe. Type. After Lambe.
Fig.
—Tooth of .Palaeoscincus costatus Leidy. Type. Inner, end, and outer
After Leidy.
views. Three times natural
natural size;
Fig.
—Tooth of Palaeoscincus lutus Marsh. Type,
Fig.

1.

Ventral view.

size.

2.

3.

size.

4.

a,

twice natural size.

&,

After Marsh.

Plate 5

Dermal bonesof

Palaeoscincus

rugosidens.

Type.

No. 11868,

U.S.N.M.

All viewed from above.

—Median pair of coossified dermal plates of the second nuchal row.
—Lateral coossified platesside) of the second nuchal row.
Fig.
nuchal ring.
—Coossified dermal plates forming the half of the
Fig.

1.

Fig.

2.

(left

3.

left

first

All about one-fourth natural size.

Plate 6

Dermal bones of Palaeoscincus rugosidens.

Type.

No. 11868, U.S.N.M.

—Large spine that occupies a position lateral to the third transverse
row of nuchal plates. Side view.
Fig.
—Dermal plate from side of the animal immediately posterior to thelarge spine shown in Figure
Top view.
Fig.
— Spine, from the end of the second transverse row of nuchal plates.
Side view.
Fig.
—Large double-spined plate that projected outward from the side of
Fig.

1.

2.

4.

3.

4.

the animal immediately above the fore leg.
one-fifth natural size.

Lateral view.

All figures about

FOSSIL REPTILES FROM

ART. 16MOFTANAGILMORE

39

Plate 7

Dermalplatesand ilium of Falaeoscincus rugosidens.

Type.

No. 11868,

U.S.N.M.

—Thin ovate dermal scutes probably from above the sacral region.
About one-fourth natural
Fig.
—Median pair of nuchal plates of the second transverse row. Ventral
view. Same as Figure
About one-fourth natural
Plate—^Anterior end of right ilium, showing ends of three coossified dorsal
Fig.
Fig. 1.

Superior view.

size.

2.

size.

5.

1,

3.

ribs.

Ventral view.

About three and six-tenths natural size.
Plate 8in the American Museum
New York, showing the dermal armor as it was found

Mounted skeleton of Palaeosoincus as exhibitedof Natural History,in situ.

—Viewed from above. After Matthew.
Photograph by Amer. Mus. of—The same viewed from theFig. 1.
Fig. 2.

left side.

Nat. History.

Plate 9Skull of Dyoplosauriis acutosquameus Parks.
Fig. 1.

Fig.

—Viewed from right—Viewed from above.

No. 11892, U.S.N.M.

side.

2.

Both figures one-fourth natural size.
Plate 10Fig.

1.

of Styracosaurus albertensis Lambe. Type.
—Posterior part of
After Lambe.
About one-twelfth natural—Posterior part ofof Styracosaurus ovatus. Type. No. 11869,
frill

Viewed from above.
Fig.

2.

U.S.N.M.

size.

frill

Viewed from above.

About one-ninth natural size.

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r<^

Skull of Palaeoscincus rugosidens
FOR EXPLANATION OF PLATE SEE PAGE 38.

PL. 2

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Sacrum and teeth of Palaeoscincus
For explanation of plate see page 38.

PL. 4

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Dermal scutes of Palaeoscincus rugosidens
FOR EXPLANATION OF PLATE SEE PAGE 38.

1

6

PL. 5

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DERMAL SPINES OF PALAEOSCI NCUS RUGOSIDENSFOR EXPLANATION OF PLATE SEE PAGE 38.

PL. 6

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ILIUM AND DERMAL BONES OF PALAEOSCINCUS RUGOSIDENSFor explanation of plate see page 39.

PL. 7

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PROCEEDINGS, VOL. 77. ART. 16

a;Skeleton of Palaeoscincus
For explanation of plate see page 39.

PL.

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SKULL OF DYOPLOSAURUS
For explanation of plate see page 39.

PL. 9

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NATIONAL MUSEUMPROCEEDINGS. VOL. 77, ART. 16

Frills of Styracosaurus
For explanation of plate see page 39.

PL. 10