A NEW DESCRIPTION OF SANIWA ENSIDENS LEIDY, 
AN EXTINCT VAEANID LIZARD 
FROM WYOMING. 
By Charles W. Gilmore, 
Associate Curator, Division of Paleontology, United States National Museum, 
INTRODUCTION. 
In 1870 Dr. F. V. Hayden discovered the fossil remains of an ex- 
tinct lizard in the Bridger deposits, Eocene, in the vicinity of 
Granger, Sweetwater County, Wyoming, which Dr. Joseph Leidy 
briefly described ^ as Saniwa ensidens. 
The type specimen was deposited in the United States National 
Museum, where it has remained in the same unprepared condition as 
originally received 50 years ago. It was preserved in a considerable 
number of blocks of ash-colored rock, the only evidence of the em- 
bedded specimen being two vertebrae, which had been uncovered, and 
the numerous bones which protruded from the broken faces of the 
rock. 
Recently this specimen has been fully prepared by Mr. N. H. Boss, 
preparator in the Section of Vertebrate Paleontology, and under his 
skillful manipulation all the contained bones have either been en- 
tirely freed from the matrix or worked out in bold relief. This work 
has resulted in uncovering many elements whose former existence 
was unknown, and especially important was the discovery of a con- 
siderable part of the vertebral column and the greater portion of the 
skull and lower jaws. 
Since paleontology as yet affords ver}- little information concern- 
ing the evolution of the more specialized land lizards, the unusual 
perfectness of the skeletal remains of the present specimen, coupled 
with the fact that Saniwa ensidens was the A^ery first extinct lacer- 
tilian lizard to be described from North America, it is of sufficient 
interest to Avarrant a full and detailed description of the type 
specimen. 
» Proc. Acad. Nat. Scl., Phila., 1870, p. 124. 
No. 2418-PROCEEDINGS U. S. NATIONAL MUSEUM. VOL. 60, ART. 23. 
1 
2 PROCEEDINGS OF THE NATIONAL. MUSEUM. vol.60. 
OSTEOLOGY OF SAN I W A. 
Suborder Sauria. 
Family VARANIDAE. 
Genus SANIWA Leidy. 
SANIWA ENSIDENS Leidy, 1870. 
Haniwa ensidens Leidy, Proc. Acad. Nat. Sci. Phila.. 1870, p. 124 ; U. S. 
Geol. Surv. of Wyo. and contiguous Terr., 2nd (4th) Ann. Rept, F. V. 
Hayden, U. S. Geologist, 1871, p. 368; U. S. Geol. Survey of Montana 
and portions of adjacent Terr., F. V. Hayden, U. S. Geologist, Washing- 
ton, D. C, 1872, p. 370.— King, C. U. S. Geol. Explor. 40th parallel, Clar- 
ence King, Geologist In charge, 1S7S, vol. 1, p. 608. — Hay, O. P. Bull. 
179, U. S. Geol. Survey, 1901, p. 475. 
Saniva ensidens (Leidy), Marsh, O. C. American Jour. Sci., ser. 3, 1871, 
p. 4.57.— Cope, E. D. U. S. Geol. Survey Terr, for 1872, 6th Ann. Rept., 
F. V. Hayden, U. S. Geologist, Washington, D. C, 1873, p. 632.— Leidy, J. 
Report of U. S. Geol. Survey of Terr., F. V. Hayden, U. S. Geologist in 
charge, vol. 1, 1873, pp. 181-344, pi. 15, fig. 15; pi. 17, fig. 35.— Nopcsa, 
F. B. Beitr. Z. Kenntn, foss. Eid., Beitr. Z. Pal. U. Geol. Ost. Ung., vol. 
21. Wien, U. Leipzig, 1908, p. 46.— Ffi.iIi:RVARY, G. J. Ann. Miisei Nntion- 
alis Hungarici, vol. 16, 1918, p. 420. 
Typfi. specimen.— Cat. No. 2185, U.S.N.M. Collected by Dr. F. 
V. Hayden, 1870. 
The following list shows the bones preserved of the type specimen : 
Skull. — Basioccipital ; basisphenoid ; supraoccipital ; exoccipital, right and 
left; opisthotic, right and left; prootic, left; postfrontal, right and left; post- 
orbital, right and left; prefrontal, left; maxilla, right and left; lachrymal, 
left; jugal, left(?); quadrate, left; epipterygoid, right fragment and left; 
pterygoid, right and left; ectopterygoid, right and left; palatine, right and 
left ; vomer, riglit and left ; several teeth. 
Lower jaw. — Dentary, right and left; splenial, left in part; articular + pre- 
articular, right and left ; angular, right and left ; surangular, right and left ; 
coronoid, right. 
yer/e6r«e.— Atlas, axis, third, fourth, fifth, sixth, and seventh cervical 
vertebrae, articulated ; eighth, ninth, tenth, and eleventh vertebrae, articulated ; 
tvi^elfth to twonty-fir.st vertebrae, partially articulated ; 13 caudal vertebrae. 
Ribs. — Thoracic ribs (8 fairly perfect, parts of 10 others). 
Limb bones. — Right humerus; feunir, distal portion, left; tibia, distal portion, 
left. 
Pectoral girdle. — Right coracoid. 
Type locality. — Vicinity of Granger, Sweetwater County, Wy- 
oming. 
Horizon. — Bridger formation. Middle Eocene. 
The original description by Leidy is as follows : 
Saniiva ensidens. — Among the fossils obtained in Professor Hayden's expedi- 
tion are the remains of a lacertian, labeled as having been discovered near 
" Granger." The bones consist of those of most parts of the skeleton, but are 
ART. 23. AN EXTINCT VARANID LIZARD GILMORE. 3 
all in a fragmentary condition, and are embedded in freslily broken pieces of 
an ash-colored rock. Before disturbance they appear to have bs-en mostly entire 
and preserved nearly in conjunction. They are black, and their interior is 
occupied with crystalline calcite. 
Fragments of bones exhibit well-developed limbs, with long toes, strong ribs, 
and a long tail, altogether indicating a form like that of ordinary living lacer- 
tians. The long bones, even to those of the toes, are hollow. The vertebrae 
exhibit the ball-and-socket articulation of their bodies, but only a single pair 
of zygapophyses in front and behind. No zygantral and zygosphenal articula- 
tion appears to have existed. 
The articular ball of the vertebi'al body is much wider than high, and is 
directed upward, with an inclination backward. 
The body of several dorsals is quite straight inferiorly, fore and aft, and 
measures half an inch in length. The ball is four lines wide and about half 
as thick. The breadth at the anterior zygapophyses is eight lines, and at 
tlie articulations for the ribs, just exterior to the latter, three-fourths of an 
inch. 
HjTDophyses for the articulation of chevrons are situated one-fourth the 
length of the body from the posterior extremity. 
A tooth was found, after careful search, in proximity to what appear to be 
traces of the skull. It consisted of the crown, broken from its connection, 
the character of which, therefore, can not be ascertained. 
The crown of the tooth is compressed conical, slightly curved inwardly and 
backward, sharp pointed, with abruptly impressed trenchent borders; is smooth 
and shining. It is hollow and has thick walls. The transverse section is 
rhomboidally oval, with acute poles. The length is about li lines ; the breadth 
three-fourths of a line ; thickness one-half a line. 
The remains would indicate an animal as large as the largest of our living 
iguanians. 
For the generic name of the animal I would propose to use the euphonious 
one of Saniwa which, according to Professor Hayden, is that used by one of 
the Indian tribes of the Upper Missouri for a rock lizard. The species may 
be named Saniwa ensidens. 
DESCRIPTION OF THK TYPE SKELETON OF SANIWA ENSIDENS, 
LEIDY. 
It will be seen from an examination of the preceding list of the 
bones preserved of the type of /Saniwa ensidens Leidy that a very 
considerable part of the skull and lower jaws has been preserved. 
Most of these bones, excepting the palate shown in plate 1, were 
found disarticulated, though none of the bones were far removed 
from one another in the matrix. Curiously enough the larger and 
heavier elements of the skull, such as the parietals, irontals, nasals, 
and premaxillaries, are entirely missing. It is also unfortunate 
that the anterior ends of the articulated maxillaries and vomers, as 
well as the symphysial ends of the dentaries, are wanting. These 
parts extended into another block of the matrix, which was either 
rejected in the field or has since been lost. 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 60. 
The skull of Saniwa^ as may well be inferred from the close re- 
semblance of the various elements to those of the Varanus, had the 
same light, open construction as in that genus. The similarity of 
many of the individual bones is remarkable, especially when the 
Eocene age of the fossil is taken into consideration. 
A skeleton of Varanus salvator (Cat. No. 29551, U.S.N.M.), having 
a skull of practically the same dimensions as the type of Saniwa 
ensidens Leidy, has a greatest length of (473 mm.) 4 feet 10 inches. 
I am of the opinion that the length of the complete skeleton of the 
fossil specimen would be somewhat less, because of the slightly 
smaller and shorter vertebrae, but it would certainly have exceeded 
4 feet in length. Some of the extinct American species as Saniwa 
major Leidy or Thinosaurus grandis Marsh probably rivaled the 
largest of the existing Monitors {Varanus salvator)^ which often 
QuJ 
Fig. 1. — Skull of Varanus niloticus. Col, Columella ; Exo, exoccipital ; Fr, fkontal ; 
Ju, jucjAL ; La, lachrymal ; Mx, maxillary ; N, external nares ; Na, nasal ; Pa, 
parietal; pi, palatine; Pmx, premaxillary ; Prf, prefrontal; Pro, prootic ; Pt, 
pterygoid ; Ptf, postfrontal + pcstorp-ital ; Qu, quadrate ; Qnj, quadratojugal ; iSf, 
supratem-oral fossa ; So, supraoccipital ; Sq, squamosal ; T, ectopterygoid ; Y, 
supraorbital. (After Cuviek.) 
attains a length of 7 feet. The largest of the American species, how- 
ever, are small as compared with the Megalania prisca from the 
Pleistocene of Australia with an estimated - length of 30 feet for the 
entire animal. 
Basioccipital—The basioccipital is perfectly preserved, except for 
the loss of its posterior median portion, which with the exoccipitals 
forms the occipital condyle. It thus forms the median boundary 
of the base of the foramen magnum, and ventrally is continuous 
laterally with the exoccipitals. which, as in Varanus, develop thin 
winglike plates that extend forward in a horizontal plane from the 
ventral sides of the proximal ends. The anterior, transversely 
broad, wedge-shaped end is received in a corresponding transverse 
depression on the posterior end of the basisphenoid. The dorsal 
surface of the basioccipital is medially depressed, forming a wide 
longitudinal valley. 
» Lydekker. R. Cat. of Fossil Reptilia and Amphibia, Pt. L, 1888, p. 284. 
AHT. iS3. 
AN EXTINCT VAEANID LIZARD GILMORE. 
Basisphenoid. — The basisphenoid of Saniwa as in livinf^ lizards 
generally sends downward two short processes or hypophyses with 
flattened expanded ends that abut against the pterygoids, as in 
Varanus (fig. 1). Between these processes at the middle it is 
drawn out in front into a short truncated rostrum which articu- 
lated with the presphenoid. The posterior margin is broadly notched 
for the articulation of the basioccipital. The dorsal surface slopes 
upward from the back toward the front, this inclination being con- 
tinued on either side as divergent projecting processes which in 
the articulated skull are lapped by a 
slender projecting process of the 
prootic. Between, and ventral to 
these two processes the widened an- 
terior end of the bone is deeply and 
broadly scooped out, forming the sella 
tertica, into which a pair of entoca- 
rotid canals open. On the lateral pos- 
terior surface is a foramen that in 
Va?'amis leads diagonally through the 
wall of bone into the median excava- 
tion described above. This bone in 
size and shape is remarkably similar 
to the basisphenoid of Varanus sal- 
vatoT (Cat. No. 29408 U.S.N.M.). 
Exoecipital and opistliotic. — Both 
exoccipital bones are present, the left 
having the prootic of that side at- 
tached to it. The exoccipital con- 
tributes to the basal as well as form- 
ing all of the side boundary of the 
foramen magnum. The basal portion 
extends backward and forms the lat- 
eral portion of the occipital condyle. 
Articulated it would extend outward 
and backward as a flattened paraoccipital process having a vertically 
expanded, truncated end, which probably articulated with the supra- 
temporal and quadrate as in Varanus. A foramen leads diagonally 
through this bone into the brain cavity, having its external exit ven- 
tral to the lower border of the paraoccipital process. Beneath and 
forward of this vagal foramen, a small, thin, winglike horizontal 
plate is developed which joins the lateral border of the basioccipital. 
In the comparatively limited development of this platelike process. 
with a decided notch between it and its junction with the paraoc- 
cipital process, it resembles the Iguana much more closely than Vara- 
nus, where this process extends outward on the lower side of the para- 
FiG. 2. — Ventral view of sklll 
BONES OF Saniwa ensidens Leidv. 
Cat. No. 2185. U.S.N.M., type. 
All natural size. A, Right 
I'TERYGOID. Ect, PROCESS AUTICn- 
LATING WITH THE ECTOPTERYGOID ; 
P, PROCESS THAT UNITES WITH THE 
PALATINE. B, Basisphenoid ; hyp, 
hypophyses; p,s, presphenoid, 
WHICH is missing. C, Basioc 
cipital ; oc, occipital condyle re 
stored. D, Right ectopterygoid, 
dorsal view ; rnx, a.nterior end 
that meets the maxillary ; pt, 
POSTERIOR bifurcated END THAT 
MEETS THE OUTER BRANCH OF THE 
PTERYGOID. 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 60. 
Fig. ^5.- — Right exoc- 
CIPITAL OF SaNIWA 
ENSIDEN.S LEIDY. 
Cat. No. 2185, 
U.S.N.M.,TYPE. Na- 
tural SIZE. Pos- 
terior VIEW. 
occipital process for fully one-half its total leng-th, while in Saniwa 
its extent Avould be less than one-fourth the total leng^th. On the an- 
terior side of the paraoccipital process, a sharp median longitudinal 
ridge divides the lower nonarticular from the upper articular surface 
with which it unites with the posterior branch of the prootic by 
squamous suture. On tlic inner anterior end a deep pit, a part of 
the auditory capsule, extends down into this bone. Immediately 
Avithin the foramen magnum the exoccipital is perforated by a small 
foramen for the passage of the hypoglossal nerve. 
Avhich makes its exit beneath the base of the lateral 
paraoccipital process. 
In front of this foramen is a slitlike aperture, the 
internal auditory meatus, through which the audi- 
tory nerve leaA^es the cranial cavity and enters the 
external ear. In the crocodile the thin bone above 
and in front of this slitlike opening is the opis- 
thotic, and from the close resemblance of this por- 
tion of the Saniwa brain case to that of the crocodile leads me to 
believe that the thin bone above the slit, forming a wall betAveen the 
auditory capsule and the brain cavity, is the opisthotic, which, as in 
many other reptiles, has become united with the exoccipital early in 
life. Attached to the right exoccipital is a fragment of the rodlike 
columnella auditoris. 
Supraocclpital. — The supraoccipital has a more pronounced 
median keel than in Varanus^ and in this respect is intermediate be- 
tween Iguana and Varanus. As in the latter genus, it forms the 
superior boundai'y of the foramen magnum. The 
upper end terminates obtusely, but is not so broad 
as in Varanus. Latterly it joins the exoccipitals ; 
anteriorly the prootics and opisthotics, superiorly 
the parietal but by cartilagenous attachment only. 
Epipterygoid. — The complete left epipterygoid 
and a portion of the right are present. It is a 
rounded bar with slight, but about equally ex- 
panded ends. The loAver end is cut off obliquely, 
the upper is flattened on the inner side, Avhere it 
laps against the forward extremity of the prootic 
a total length of 16 mm. 
Pterygoid. — The right pterygoid is present in its entirety, the left 
nearly as perfect. The latter Avas found in the matrix but little sepa- 
rated from its proper articulation Avith the ectopterygoid (see pi. 1) 
and palatine bones. The pterygoid in Saniwa is a long, slender, 
slightly curved bone, having a bifurcated anterior end and a flat- 
tened tapering posterior extremity Avhich laps the inner distal side 
of the quadrate (see A, fig. 2). The slender rodlike posterior por- 
FiG. 4. — Right epi- 
pterygoid OF Sa- 
niwa ENSIDENS 
Leidy. Type. Cat. 
No. 2185, U.S.N.M. 
Natural size. 
rOSTERIOK VIEW. 
This bone has 
AiiT.2<i. AN EXTINCT VAKANID LIZARD GILMORE. 7 
tion is grooved on the dorsal and ventral sides by longitudinal sulci. 
On the dorsal surface forward of the center of the bone the develop- 
ment of a shallow pit marks the point of articulation with the epip- 
ter^^goid. Anterior to this cuplike depression the bone rapidly widens, 
being terminated at the anterior extremity by two projecting 
articular processes, the larger inner process uniting with the palatine ; 
the smaller outer process with the ectopterygoid. The thin notchlike 
border connecting these two processes forms much of the inner and all 
of the posterior boundaries of the infraorbital vacuity. The right 
pterygoid has a greatest length of 43 mm. ; greatest width of anterior 
end, 10 mm. 
The resemblance of this bone to the pterygoid of Varanus salvator 
(Cat. No. 29408, U.S.N.M.) is very close both in size, proportions, 
and method of articulation with surrounding elements, the only 
differences observed being the deeper longitudinal sulcus on the 
ventral side of the posterior half of the fossil bone and the higher 
and sharper ridges on both the ventral and dorsal sides of the 
border leading up to the process that meets the ectopterygoid bone. 
There is no evidence of pterygoid teeth. 
Palatine. — Both palatine bones, but slightly displaced from their 
proper position in the palate, are shoAvn in plate 1. Only their 
dorsal surfaces have been uncovered, but so far as they can be 
compared they appear very similar to the corresponding bones in 
the Varanus palate. The wide, flattened posterior end unites with 
the pterygoid. On the external side, near the middle of the bone, 
a heavy process extends outward to meet the posterior end of the 
maxilla. As in Varanus, this process is perforated by a longitudi- 
nal foramen, which leads into a cavity within the maxilla. A slen- 
der, pointed projection of this process extends backward along the 
maxilla, that, when articulated, probably met the ectopterygoid and 
entirely excluded the maxilla from participation in the formation 
of the boundary of the pterygoid or infraorbital aperture. Ante- 
riorly the palatine sends forward a slender tapering process that 
laps the posterior end of the vomer on the inner side. The for- 
ward ends of the palatines are in contact on the median line, as 
shown in plate 1, but I am inclined to the belief that this has been 
brought about by transverse crushing and that originally they were 
separated, but probably not so wide apart as in the living Varanus. 
The character of the dorsal surface appears to indicate that it was 
in contact with the prefrontal and lachrj^mal bones as in Varavus. 
Vomers. — The vomers are relatively wider transversely than in 
Varanus and they also differ in having a broader and deeper longi- 
tudinal depression on the dorsal surface. They appear to have been 
in contact on the median line throughout the greater part of their 
3136— 22— Proc.N.M.Vol.60— 44 
8 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 60. 
Fig. 5. — Left lach- 
rymal OF Saniwa 
BNSIDENS LEIDT. 
T Y p E J Cat. No. 
2185, U. S. N.M. 
Natural size. A, 
LATERAL VIEW ; B, 
POSTERIOR VIEW. 
length. Viewed from above, the outer border, which stands up as 
a vertical plate, curves in toward the median line and nearly if not 
quite meets the ridge on the vomer of the opposite side. From this 
point forward the outer border curves outward to meet the maxil- 
lary. The anterior ends of the vomers are missing in the type, as 
shown in plate 1. 
Ecfopteri/goid. — Both ectopterygoid bones are 
present, but the right element is the more perfectly 
preserved. It is a curved bone, having a bifurcated 
posterior end that straddles the small outwardly 
turned process on the pterygoid, lapping above and 
below, thus forming a strong union of these two 
bones. Its curved and rounded inner border forms 
the greater part of the outer boundary of the in- 
fraorbital vacuity. The anterior end tapers out 
to an obtuse point having a groove on the external side that joined the 
posterior end of the maxillary. The anterior, outer border was in 
sutural contact with the jugal for half its entire length. Its greatest 
length over all is 16.5 mm. 
Lachryinal. — The left lachrymal is almost perfectly preserved, 
lacking only a little of its external posterior border. Viewed from 
the side, it is a flat bone, subtriangular in outline, with a thickened 
posterior border that is slightly concave vertically. This end, 
which contributed to the boundary of the orbit, is perforated by two 
oval foramina, one above the other. The larger is above and sepa- 
rated from the lower one by a very narrow filament of bone. These 
appear to have a common exit on the me- 
dian internal side of the bone. In Vara- 
nus the lachrymal is perforated by the 
usual lachrymal foramen, but the larger 
and more dorsal foramen of Sankoa is in 
the Varanus, represented by a notch, the 
inner border being formed by the lower 
branch of the prefrontal. A striated ar- 
ticular surface on the postero-inferior 
border appears to indicate the point of 
articulation with the forward end of the 
jugal as in Varanus. Its greatest length is 7.5 mm. ; greates*; height, 
6.5 mm. 
Maxillaiy. — Both maxillae retain their natural relationships to 
the interposed palatal bones as shown in plate 1. The right is the 
better preserved, though it lacks the anterior extremity and a portion 
of the median superior border. In so far as comparison can be made 
it closely resembles the maxillary of Varanus. The principal differ- 
mt 
'fp-^ 
Fig. 6. — Right maxxllahy of 
Saniwa ensidens L e i d t . 
Type, Cat. No. 2185, U.S. 
N.M. Natural size. Lat 
BRAL VIEW. na, border 
that contributes to the 
boundary op the EXTERNAL 
NARIAL OPENING. 
ART. 2a. AN EXTINCT VARANID LIZARD GILMORE. 9 
ence detected is that the lower posterior extremity of the fossil is 
more slender and tapering. It is pierced by a number of foramina 
that form a row slightly above, but parallel to the dental border. 
The sloping superior border anterior to where it joins the perfrontal 
forms the outer boundary of the anterior nares. This border turns 
inward toward the median line posterior to its anterior extremity, 
but the anterior portion of the bone is missing. 
The right maxillary contains eight teeth and there are spaces for 
five more, making 13 teeth within a space 35 mm. long. The same 
space in Varanus contains only nine teeth. It is estimated that the 
missing portion would have carried two, possibly three more, so that 
in all the maxillary of Saniwa would have had at least 15 teeth, prob- 
ably more. Because of the fragile nature of the 
bone and teeth no attempt has been made to 
free the internal or palatal side from the matrix. 
Posteriorly this bone certainly articulated with 
the palatine, ectopterygoid, prefrontal, and lach- ^ „ „ 
^ ' ^ ''^ •ii'i ^"^- ^- — Right post- 
rymal, and probably also with the jugal. frontal of saniwa 
Postfronfal— The postfrontal is a moderate- f,''^''lf'' \, ^!,'^^- 
' -111- 11 Type, Cat. No. 218.'), 
sized trihedral bone, articulated by its expanded u.s.n.m. natural 
cranial end to the frontal and parietal by a «'^^ Viewed from 
^ '' ABOVE. p.f., CUPPED 
cupped articular area between the divergent an- surface which 
terior and posterior branches (see p.f., fig. 7), articulates about 
^ '' 11 equally with the 
that fits in under and along the outer borders lateral projections 
of these bones at their lunction. On the pos- °^ '^^® parietal and 
•' , . . ^ FRONTAL. 
terior side of the pointed distal projection a 
roughened striated surface indicates the sutural contact of the post- 
orbital, which in Saniwa exists as a distinct element. The left post- 
frontal and postorbital were found articulated (fig. 8), the suture 
distinctly shown, so that the manner of their articulation may be 
considered as absolutely determined. In all of the illustrations of 
the Varanus skull ^ and in three of the four skulls of this animal now 
before me the postfrontal-postorbital complex appears as a single 
bone. It is called postfrontal in all the illustrations of the F«ranw.<? 
skull, there being no mention made of the presence of a postorbital. 
However, on the ventral side of the right postfrontal of the skull 
Varanus (Cat. No. 29408, U.S.N.M.), the suture between it and the 
postorbital is visible under the glass. This suture takes essentially 
the same course as in the fossil specimen. Probably in a juvenile 
specimen the division between these two elements would be more 
clearlj^ indicated. It is evident they coalesce early in life, so that in 
adult specimens all traces of the sutures are obliterated. 
» Gadow, H. Amphibia and Reptilia, 1901, p. 542, fig. 138. Gadow recognizes these 
elements as the fused postorbital and postfrontal. 
10 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 60. 
Fig. 8. — Articulated left 
postfrontal and post- 
ORBITAL BONES OF Sa- 
NIWA ENSIDENS LeIDY. 
Type, Cat. No. 2185, 
U.S.N.M. Natural size. 
P, cupped border FOR 
ARTICULATION WITH PA- 
RIETAL AND FRONTAL I 
PO, POSTORBITAL ; ptf, 
POSTFRONTAL. 
Postorhital. — Both postorbital bones are present, the left articu- 
lated with the postfrontal, the ri^ht detached. The latter has an 
expanded anterior end which articulates with the postfrontal by a 
cupped articular surface developed on the upper anterior border. In 
position it extends downward below the postfrontal as a pointed 
process (see fig. 8), but apparently not reaching the jugal. Extend- 
ing posteriorly the postfrontal develops a 
slender tapering process which articulated 
with the squamosal, thus forming the supra- 
temporal arcade as in other members of the 
Varanidae. 
Prootic. — The left prootic was found at- 
tached by matrix to the left exoccipital, but 
slightly displaced from its proper articulation 
with that element (see fig. 9). It closely re- 
sembles the corresponding bone in Varanus 
salvator, being a curved bone having a nar- 
rowed posterior half that laps along the upper 
anterior side of the paraoccipital process by 
squamous suture, and a flattened broader anterior half that turns 
upward from the horizontal at an angle of 45° to meet the parietal 
on the external side at about the middle of the supratemporal fossa. 
The inner posterior border forms a junction with the supraoccipital, 
exoccipital, and opisthotic. The inner surface of this flattened end 
contributes to the formation of the lateral wall of the brain cavitj'^ 
and to the boundary to the auditory capsule. The ventral process, 
which in Varanus extends forward and 
downward to articulate with the basiphe- 
noid, is missing in the fossil, but presumably 
it will be found to be much like that of 
Varanus. 
Prefrontal. — The left prefrontal was found 
in the matrix but little disturbed from its 
proper articulation with the underlying 
bones of the palate. It is an irregularly- 
shaped bone (see fig. 10) that forms the 
greater part of the anterior boundary of the 
orbit and contributes to both the dorsal and 
lateral surfaces of the skull. Internally it also develops a partial 
postlateral wall for the rhineocephalic chamber. The contribution 
to the dorsal surface is of considerably greater extent, both trans- 
versel}^ and anteroposteriorly, than in a Varanus skull of equal di- 
mensions. Posteriorly a tapering process extends backward along 
the outer edge of the frontal, which, as in Varanus, probably termi- 
■ exo. 
Fig. 9. — Left prootic at- 
tached TO EXOCCIPITAL OF 
SAME SIDE OF SANIWA EN- 
SIDENS Lbidy. Type, Cat. 
No. 2185, U.S.N.M. Nat 
URAL SIZE. Later A I 
VIEW. eXOj EXOCCIPITAL; 
pro, proOtic. 
ART. 553. 
AN EXTINCT VAEANID LIZARD GILMOEE. 
11 
Fig. 10. — Left pre- 
frontal OF Saniwa 
ENSIDBNS LeIDY. 
Type, Cat. No. 2185, 
U.S.N.M. Natural 
SIZE. la, SURFACE 
FOR ARTICULATION 
FOR lachrymal; 
prf, FRONTAL BORDER. 
nated at about the center of the orbit. The anterior extension of 
this bone is missing. A decidedly roughened ridge is developed 
along the angle where it turns downward to fonn the lateral surface. 
This ridge probably marks the seat of attachment for the supra- 
orbital bone, which is missing in this specimen. On the ventral 
part of the lateral surface there is an indented articular area, which 
marks the point of articulation with the separate 
lachrymal bone. Posterior to the lachrymal ar- 
ticulation the bone turns inward, forming a widv-^ 
contribution to the anterior border of the orbit. 
The ventral edge of this orbital portion is slightly 
expanded anteroposteriorly for articulation with 
the underlying palatine, to which it is joined in 
the articulated skull. Anteriorly it appears to 
have articulated w^ith the maxillary as in Vara- 
nus. It probably was also in contact with the 
nasal, but of this I am not entirely certain. 
Quadrate. — The complete left quadrate shows 
this element in its general characteristics to 
closely resemble the corresponding bone in the Varanus skull. It is 
a strong bone of moderate length, having a wide articular end for 
articulation of the lower mandible. This end has a transverse width 
of 8 mm. Viewed from the side, the quadrate is narrow anteropos- 
teriorly at the lower end but rapidly widens in the same diameter 
Q^ toward the proximal end. This 
widening is brought about by the 
inner half of the bone being inclined 
strongly backv.ard from the perpen- 
dicular. The upper articular end of 
the inner portion rises considerabW 
above the upper extremity of the 
outer portion of the bone. In the 
articulated skull it is presumed that 
the inner articulated with the supra- 
temporal, squamosal, and paraoc- 
cipitat bones as in Varanus. The 
outer half of the quadrate measures 
15 mm. in length; the inner. 18 mm. On the inner side of the distal 
end a flattened facet evidently marks the place of contact with the 
posterior extremity of the pterj^goid. 
Jugal. — A long curved bone is provisionally identified as the left 
jugal. If this determination is correct it shows this bone to be 
considerably more robust than the jugal in a Varanus skull of equal 
dimensions (see fig, 1). The pointed posterior extremity is miss- 
FiG. 11. — Left jugal of Saniwa bn- 
siDENS Lbidy. Type, Cat. No. 
2185, U.S.N.M. Natural size. A, 
internal view ; B, external view ; 
a, anterior end ; p, posterior end. 
12 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 60. 
ing, but at the break it is triangular in section. On the ventral 
and internal sides of the anterior half of the bone it is longitudinally 
grooved for articulation with the ectopterygoid, maxillary, and pala- 
tine bones. 
LOWER JAW. 
Both rami of the lower mandible are fairly well preserved, except 
for the loss of the anterior halves of the dentaries. In their general 
proportions, relative extent of the various elements, and the manner 
of articulation of the component bones they closely resemble the 
rami of Varanus, the chief differences noted being the shorter but 
heavier expanded posterior extension back of the cotylus of the 
Fig. 12. — Left ramus of Saniwa ensidkns Leidy. Type, No. 2185, U.S.N.M. Natural 
SIZE. A, EXTERNAL VIEW ; B, INTERNAL VIEW ; ung, ANGDLAu ; art, articular ; Cj 
coEONOiD ; d, dbntary ; a, splenial ; sur, surangdlab. Anterior end of dentart 
restored from Varanus. 
ramus and the relatively narrower (vertically) posterior end of the 
dentary in Saniwa. 
Dentary. — Viewed laterally the dentary joins the surangular by 
a nearly straight vertical suture at a point very slightly posterior of 
the center, as in Varanus. The union of these two bones, however, 
is not as weak as it would first appear, for the surangular extends for- 
ward on the inside of the dentary, thus forming an effective and 
strong articulation. Dorsally it meets the coronoid and ventrally 
the small angular, which sends forward a short process that is 
wedged in between the dentary and the splenial. The latter bone 
laps along the inner side of the dentary, covering the V-shaped man- 
dibular fossa of that side. 
Viewed from the side the dentary narrows toward the front. Near 
its posterior end the bone is perforated, as in Varanus, by a large 
oval foramina. Smaller perforations at intervals form a row imme- 
diately below and parallel to the dental border (see A, fig. 12). 
ART. 23. AN EXTINCT VARANID LIZARD GILMORE. 13 
The upper internal side of the dentary presents a beveled sur- 
face, on which the expanded bases of the pleurodont teeth are at- 
tached. This surface slopes downward from the outer alveolar 
border of the jaw, and gradually increases in width from the poste- 
rior end to the point where the bone is broken off. 
Sura7igvZar. — The surangular is the largest bone of the posterior 
half of the ramus and forms the greater part of the external view 
of this portion of the jaw (see A, fig. 12). Posteriorly it has a 
pointed extremity which ends posterior to the cotylus of the jaw. 
Ventrally the posterior half of this bone unites by a horizontal 
suture with the underlying articular -f prearticular, the anterior half 
with the smaller angular. The anterior end is truncated, this end 
passing 5 mm. inside the posterior end of the dentary. On the ante- 
rior, superior and upper lateral surfaces depressions of the bone 
distinctly marks the depth of overlap of the dentary. On the supe- 
rior anterior border a grooved surface marks the seat of the coronoid 
bone which is detached. The posterior end of the surangular is 
trasversely expanded and contributes slightly to the formation of 
the anterior border of the cotylus for the articulation of the quad- 
rate. On the inside of the jaw the surangular meets the prearticular 
by a horizontal suture somewhat below the middle of the ramus and 
continues forward to their contact with the overlying splenial. 
Angular. — The angular is a small pointed bone that underlies the 
surangular externally and the forward extension of the prearticular 
internally (see A, fig. 12). As in the living Monitor, a slender 
pointed process continues forward, being intercalated between the 
splenial and dentary, slightly in advance of the vertical surangular- 
dentary suture. On the anterior internal side it is overlapped by a 
posterior projection of the splenial. 
ArtiGular-\-2)reartiGular. — The so-called articular in the lizards is 
considered by Williston^ to be the articular 4-prearticular complex. 
There is no indication of a suture in this specimen to show which part 
of this complex is articular and which is the prearticular portion. As 
a matter of convenience in describing this part of the ramus, that part 
of the complex lying in front of the cotylus will be arbitrarily con- 
sidered the prearticular portion, and the posterior part, including 
the cotylus, the articular portion. 
The articular + prearticular complex is an elongate bone that forms 
the whole of the lower boundary of the ramus posterior to the angu- 
lar and all of the extension of the jaw behind, including the cotylus 
(see fig. 12). The prearticular portion extends forward beneath the 
surangular to meet the angular, where it passes from a lateral view, 
but internally it continues forward, the anterior end being inter- 
calated between the splenial and dentary. Posteriorly it forms the 
*Journ. of GeoL, vol. 22, 1914, p. 411. 
14 PROCEEDINGS OF THE NATIONAL. MUSEUM. vol. 60. 
ventral margin of the posterior inframeckelian foramen. In front 
of this foramen in Varanus the prearticular is in contact with the coro- 
noid and it is presumed that a similar condition would prevail in the 
completely articulated Saniwa ramus. 
The articular portion of this ramus presents from a dorsal view a 
shallow concave, antero-posterior, but wide cotylus, behind which 
the articular is slightly contracted, the truncated end being enlarged, 
this latter expansion being especially pronounced in a ventral-inter- 
nal direction. This posterior extension differs from Varaims in being 
shorter, relatively heavier, and in the development of a hooklike inter- 
nal-ventral expansion of this end. The pointed posterior extremity of 
the surangular laps along the upper external side, ending about mid- 
way between the center of the cotylus and the posterior end of the 
ramus. 
Splenial. — Although only the thin vertically expanded posterior 
portion of the left splenial is preserved (see B, fig. 12), an examina- 
tion of the dentary along which this bone laps on the inner side shows 
that in shape and extent anteriorly it is approximately the same as 
in Varanus. It covers the inner side of the meckelian groove on the 
dentary and extends posteriorly, overlapping the anterior ends of the 
surangular, prearticular, and angular. It appears also to have been 
in contact with the coronoid. 
Coronoid. — The right coronoid was found detached from the rest 
of the jaw and in a fair state of preservation. It is a small bone, 
curved from end to end, deeply grooved on the ventral side, which 
sets astride of the striated superior border of the surangular. The 
inner process that extends down to meet the prearticular is missing. 
Anteriorly when articulated it was in contact with the dentary and 
splenial as in Varanvs. 
TEETH. 
The teeth of Saniioa ensidens are pleurodont. The right maxillary 
contains intact five of the six posterior teeth of the series in addition 
to two stumps more anterior, probably the ninth and tenth, counting 
from the back ; the left maxillary contains the basal portions of four 
teeth ; the left dentary two, and the right dentary has the three pos- 
terior teeth of the series, and the fifth from the back. Including three 
detached teeth found in the matrix, there are 20 teeth in all. 
All of these teeth are sharply pointed, slightly curved backward, 
like the saber-shaped fangs of Vararms. The teeth are compressed 
from side to side, with trenchent borders fore and aft. The detached 
teeth as mentioned by Leidy are hollow, with thick walls. 
As in Varanus the bases of the teeth are expanded, being anchy- 
losed by the whole of their bases to the oblique surface of the bone 
which on the outside lead upward to slight depressions in the alveolar 
ART. :i3. AN EXTINCT VAEANID LIZARD GTLMORE. 15 
borders. The base of the teeth are finely striated. The striations 
Owen ^ observes in Varanus are " produced by inflected folds of the 
external cement, as in Ichthyosnumis and Lahyrlnthodon^ but they 
are short and straight as in the former genus." 
The teeth throughout both upper and lower series are smaller than 
in a living Varanus salvator of the same size, and whereas there are 
12 teeth in both the maxillae and dentaries of a Varanus salvator^ in 
Saniwa there are not less than 14, probably more teeth in each series. 
VERTEBRAE. 
The vertebral column of Saniwa is represented by 33 fairly well- 
preserved vertebrae, with fragments of at least two more. Twenty 
of these may be classed as presacral, the remaining 13 as anterior 
caudal. The presacral vertebrae as now preserved are in three 
short series. The first, commencing with the complete atlas, con- 
bists of the first six of the column (see fig. 13) and a remnant of 
the centrum of the seventh, all articulated. The next block con- 
tains a series of four, there probably being one vertebra missing, 
of which only a fragment of the spine is preserved in the matrix. 
Although slightly disarranged, as shown in the matrix, plate 3, 
figure 2, it appears that those preserved were continuous in the 
series with those shown in plate 2, figure 2. Thus, the presacral 
series, with the possible exception of one centrum thought to be 
missing between blocks 1 and 2, form a continuous series from the 
skull back to the twenty-second vertebra. Since the living Varanus 
has 29 presacrals, it appears reasonable to suppose that Sanhna had 
an equal number in the complete series. Thus, there would be onl}'^ 
seven vertebrae missing from the presacral series — one between the 
seventh and eighth, the remainder between the twenty-first and the 
sacrum. The caudal series is now preserved in three separate blocks 
of matrix, though probably all were originally joined, but the con- 
tacts have now been lost. There are 13 vertebrae in all of which the 
larger number, seven (see pi. 3, fig. 1), are so little disassociated as 
to show they were in series and probably form the anterior part of 
the tail. 
Atlas. — The atlas is almost perfectly preserved and was but little 
disturbed from its proper relation with the axis. It consists of the 
strongly-keeled intercentrum, odontoid, and the two lateral neuro- 
pophyses, as shown in figure 13. 
The centrum of the atlas (odontoid) is suturally united with the 
axis, and as in most reptiles its place is taken by the octogenous hypo- 
physes or intercentrum. It presents a cupped articular surface for the 
basioccipital and a similar surface behind for the odontoid. The 
» Owen, R. Anatomy of Vertebrates, 1866, vol. 1, p. 404. 
16 PROCEEDINGS OF THE NATIONAL, MUSEUM. vou 60. 
base of each neurapophyses has an antero-internal articuhir surface 
that contributes to the formation of the cupped end for the recep- 
tion of the occipital condyle, a middle surface for union with the 
neuropophyses, and a postero-internal surface for the upper and 
lateral parts of the odontoid. Above this articular end the neuro- 
pophyses is constricted fore and aft, above which it is widely ex- 
panded and arches over the neural canal, meeting on the median line 
without coalescing. There is no neural spine. Each neuropophyses 
develops from its upper and hinder border short zygapophyses which 
articulate with the axis. From its posterior side below a shorter dia- 
pophyses is developed. 
The odontoid is wider than high and presents a convex face in 
front, which completes the articular cavity for the occipital condyle ; 
below is the surface for the intercentrum, and above and behind it are 
the two articular surfaces for the neuropophyses. The whole pos- 
ox in 
Fig. 13. — Cervical vertebrar of Saniwa knsidens Leidy. Type, Cat. No. 218.5, 
U.S.N.M. Natural size, at, atlas ; ax, axis ; ax in, axis intercentrum ; h, hyopo- 
PHYSES ; in, intercentrum of atlas ; 3, 4, 5, 6, 7, cervicals three to seven, hh- 
spectively. 
terior part is sutured to the centrum of the axis and in part anchy- 
losed to its hypophyses. 
Axis. — The centrum of the axis measured nearly 15 mm. in 
length. Much of the spinous process is lacking. The forward part 
is thin and overhangs the odontoid. On the neural arch there is no 
trace of a diapophysis. On either side of the neural arch in front are 
articular surfaces representing the prezygapophyses, and on the pos- 
terior end the transversely expanded neural arch develops well-defined 
postzygapophyses. The centrum, as in all Varanids, terminates 
in a ball behind. Below this ball it sends downward and backward 
a heavy exogenous process with a cupped end which looks downward 
and backward for the articulation of the hypophysis which is missing. 
(See h, fig. 13.) This process is the heaviest of the series, whereas 
in Varanus they grow progressively heavier from the axis back to 
the sixth cervical. 
Vertebrae posterior to the axis. — Articulated with the axis was 
the third, fourth, fifth, sixth, and anterior end of the centrum of 
the seventh vertrebrae, counting backward from the skull (see fig. 
13). The vertebrae of Saniwa as compared with those of Varanus, 
ABT. 23. 
AN liXTINCT VARANID LIZARD GILMOEE. 
17 
Fig. 14. — Dorsal vertebra of Sa- 
NIWA ENSIDENS LEIDY. TYPE, CaT. 
No. 2185, U.S.N.M. Natural size. 
A VIEWED from left SIDE ; B, 
VIEWED from posterior END ; nc, 
neural canal ; s, spinous proc- 
ess ; t, TKANSVERSE PROCESS ; Z, 
anterior zygapophysis ; 2', pos- 
terior ZYGAPOPHYSIS. 
having a slvuU of equal size, are considerably smaller throughout 
the presacral series. The principal changes to be observed in the 
structure of the vertebrae between the third and seventh are : First, 
the development on the cervicals of forwardly projecting divergent 
anterior zygapophyses, which become longer and heavier in each suc- 
ceeding vertebra back to the sixth of 
the series; second, the exogenous 
process for the h3'pophyses, which is 
largest on the axis, becomes rapidly 
reduced in size posteriorly, until on 
the sixth only a vestige® remains; 
third, the small parapophyses first 
developed on the third vertebra is 
decidedly larger on the fourth and 
increasingly so on each succeeding 
vertebra. It would appear that the 
fourth, fifth, and sixth vertebra bore 
sliort ribs as in Hatteria, whereas in 
Varanus salvator the seventh is the first to have a cervical rib; in 
SauroTTialus the first rib is on the fourth cervical. 
The centra in this series are approximately the same length 
throughout, with a cup in front and ball behind, a feature common 
to most lizards, and which continues throughout the vertebral column. 
The neural spines of the cervical series in 
Saniwa are badly damaged, but they do not ap- 
pear to have been taller than in the succeeding 
dorsals, whereas in Varanus they are higher, and 
wider fore and aft, than any that follow them in 
the presacral series. These spines are thin trans- 
versely, but wide (anteroposteriorly) plates of 
bone that terminate dorsally with truncated ex- 
tremities without transverse expansion. The 
posterior zygapophyses do not protrude beyond 
the ball of the centrum. 
The second series of four articulated vertebrae 
(see pi. 2, fig. 2) are thought to represent 
the eighth, ninth, tenth, and eleventh of the 
vertebral series enumerated from the skull. These exhibit a flat- 
tened ventral surface of the centra so typical of all the members 
of the family Varanidae. The nonarticular surfaces of the centra 
are slightly shorter than in the preceding series, as may be seen by 
referring to the table of measurements. 
" In this feature Saniwa resembles Varanus griseus, where the hypophyses end with 
the sixth cervical, there being only a slight elevation on the seventh, while in Y. salvator 
hypophyses extend back to the seventh and sometimes a vestige is found on the eighth. 
Fig. 15. — Dorsal ver- 
tebra of Saniwa 
HNS I DEN S LbIDY. 
Type, Cat. No. 2185, 
U. S. N. M. Natural 
SIZE. Superior view. 
t, TRANSVERSE PROC- 
ESS ; Z, ANTERIOR ZYGA- 
POPHYSIS ; «', POS- 
TERIOR ZYGAPOPHYSIS ; 
Zg, ZYGANTRA. 
18 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60. 
The articular ball of the centrum in all the succeeding vertebrae 
available for measurement are nearly twice as wide as high, the artic- 
ular surface being inclined upward and backward. The diapophyses 
extending outward from the anterior side of the centra gradually 
grow more robust, proceeding posteriorly. The anterior zygapo- 
physes also become successively shortened, but with broader articular 
faces. The spinous processes remain about the same height as in the 
preceding series, but appear broader antero-posteriorly. 
The third series of articulated dorsals, consisting of 10 vertebrae, 
probably represent the twelfth to the twenty-first. (See pi. 3, fig. 2.) 
All resemble one another so closely that a description of one will do 
for all. Except for their relatively shorter 
spines and smaller size, I am unable to find 
any other features that would distinguish them 
from the corresponding vertebrae in the skele- 
ton of Varanus salvator^ from Java (Cat. No. 
29551, U.S.N.M.) now before me. 
The anterior articular concavity of the cen- 
trum is a transverse ellipse, obliquely placed, 
looking downward and forward, the under sur- 
FiG. 16.— Dorsal vbrte- face of the body being flattened anteropos- 
BUA OF saniwa ensi- tcriorlv and slightly convex transversely. The 
DENS L E I D Y . Type, . '' . , . . , 
Cat. No. 2185, U.S.N.M. articular coiivcxity corresponds m size and 
Natural size, t, gj^ape witli the anterior cup, with an opposite 
TRANSVERSE PROC- ^ ii- ill! Ij. 
ESSES ; z, ANTERIOR zY- aspcot, lookiug upward and backward at an 
GAPOPHYsis ; z', pos- angle of 45° to the lower surface of tlie centrum 
TERIOR ZYGAPOPHYSIS. , r> \ rm i • Clin 
(see fig. 16). The lateral margins oi the ball 
project a little beyond the narrow constriction which divides it from 
the rest of the centrum. 
In advance of this constriction the sides of the body rise, expand- 
ing outwardly at the anterior end to form the projecting costal 
tubercle, which appears to be supported by both the neurapophyses 
and centrum, though nowhere in the series is there a trace of the 
neurocentral suture to be found. The tubercle for the ribs in this 
section of the column presents a hemispherical articular surface as 
in the living Monitor, In front of the tubercle the heavy support 
of the prezygapophyes rises, extending upward and slightly for- 
ward, the upper articular surface being flat looks inward and, up- 
ward, the whole projecting but slightly anterior to the forward end 
of the centrum. 
The upper surface of the broad neural arch between the anterior 
zj^gapophyses is, roughly speaking, concave, but traversed longi- 
tudinally by a median elevation that develops on its anterior margin, 
ART. 23. 
AN EXTINCT VARANID LIZARD GILMORE. 
19 
ITiG. 17. — Anteuior cau- 
dal VERTEBRAE OF Sa- 
NIWA ENSIDENS LEIDY. 
Type, Cat. No. 2185, 
U.S.N.M. Natural 
SIZE. Viewed from 
LEFT SIDE. h, UTPO 
PHYSIS FOR ARTICULA- 
TION OF CHEVRON ; t, 
TRANSVERSE PROCESS ; 
Z' , POSTERIOR ZYGAPO- 
PHYSIS. 
two flattened forwardly projecting processes between which on the 
median line is a broad notch. I regard these processes as rudi- 
mentary zygosphenes (see zg, fig. 15). Marsh ^ notes a simihir 
articulation on the dorsal vertebrae of Thinosaurus paucidens. The 
absence of zygantry, however, shows that they 
no longer function as a true zygosphene-zygan- 
trum articulation. The posterior half of the 
upper surfaces of the neural arch is convex 
and expands outward at its back part to form 
the posterior zygapophyses (see fig. 14, B), 
the articular surface of which looks downward 
and outward. The median part of the arch 
develops a wide (anteroposterior) spine of 
moderate height. This spine is very thin, but 
thickens posteriorly, especially its posterior 
upper extremity. The posterior part of the 
arch, including the zygapophyses, overhangs 
the centrum, but terminates forward of its 
most posterior extension. 
Caudal vertebrae. — There are 13 caudal vertebrae present, all ap- 
parently from the proximal fourth of the tail. These are in three 
blocks of matrix, of which the better-preserved vertebrae, four in 
number, remain articulated (see pi. 3, fig. 1). These, however, 
indicate one important difference when compared with the tail of 
Varanus and that is the low, broad, spinous processes of the presacral 
region continue back much further in the 
caudal series. Though they do gradually in- 
crease in height posteriorly, it appears very 
doubtful if they ever attained the great height 
found in the living Monitor, Varatius salvator 
(see fig.- 17). Nor do any of the 13 vertebrae 
indicate a fore-and-aft narrowing of this proc- 
ess such as begins to take place in the third 
vertebra back of the sacrum in Varanus. 
The caudal centra are more elongate than in 
the mid dorsal region; the middle ventral 
surface is traversed longitudinally by a shal- 
low depression. They retain the cujD-and-ball articulation found in 
the presacral series. On the posterior third of the ventral surface 
of the centrum a pair of short articular protuberances indicate the 
point of attachment for the chevron (see fig. 18). 
The apparent absence of caudal vertebrae, having high spinous 
processes, suggests that Saniwa was a terrestrial form having a 
Fig. 18. — Anterior cau- 
dal vertj;bra of Sa- 
niwa ENSIDENS LeIDY. 
Type, Cat. No. 2185. 
U.S.N.M. Natural 
SIZE. Ventral view. 
ch, hypophysis for 
chevron ; *, TRANS- 
VERSE PROCESS. 
' Amer^ Journ. Sci., ser. 3, vol. 3, 1872, p. 299. 
20 
PROCEEDINGS OF THE NATIONAL, MUSEUM. 
VOL. 60. 
rounded rather than a transversel3^ flattened tail. The dissection 
of a specimen of Varanus griseus from Egypt, a strictly terrestrial 
form shows that the spinous processes do not increase so rapidly in 
height from the sacrum backward as in V. salvator. 
Measurements of vertebrae of Saniwa ensidens, No. 2185, U.S.N.M. 
GIRDLE AND LIMB BONES. 
Coracoid. — The scapular arch is represented only by the right cora- 
coid which lay in the matrix at the proximal end of the humerus of 
that side and opposite the ninth and tenth 
vertebrae of the series, as shown in plate 2, 
figure 2. Only the ventral side has been ex- 
posed. It is a broadly expanded bone having 
a single deep notch on the anterior border as 
contrasted with the two deep notches in the 
Varanus coracoid. Between the posterior 
border of this notch and the glenoid border 
the bone is perforated by a large coracoid fora- 
men. The pointed posterior projection is more 
slender than in Varavnus. (Compare figs. 19 and 
20.) The precoracoidal process has suffered 
the loss of its articular end, as has the anterior 
extremity of the coracoid internal to the notch. 
The presence of a single notch and the long sweeping convex curve 
of its inner border, this bone resembles the coracoid of Loemanctus 
longifes., as figured by Parker.^ The bone is much thickened dorso- 
ventrally at the border of the glenoid cavity. The ventral surface 
is slightly convex antero-posteriorly as in the Monitor. The cora- 
coid measures 15 mm. in width from the glenoid border to the inner 
edge. As preserved it measures 17 mm. antero-posteriorly. The 
notch at its widest expanse measures 6 mm, across. 
Fig. 19. — Left cok.vcoid 
OF Saniwa ensidens 
Leidy. Type^ Cat. No. 
2185, U.S.N.M. Natu- 
ral size. Ventral 
VIEW, gc, coracoid con- 
tribution to the for- 
mation of glenoid 
fossa ; hcs, border that 
articulates with 
SCAFULA. 
« Reynolds, S. H. The Vertebrate Skeleton, 1897, p. 286, fig. 54. 
ART. 23. 
AN EXTINCT VARANID LIZARD GILMORE. 
21 
Hu77ierus. — The right humerus is present and in a fair state of 
preservation. Some portions of the anterior side of the distal half of 
the shaft and the condylar articular surface 
for the radius on the distal end are missing. 
Compared with the corresponding element 
in a skeleton of Varanus salvator. No. 29551, 
U.S.N.M., it agrees very closely in general 
form except for the more abrupt expansion 
of the ulnar side of the distal end and the 
apparent reduction in extent of the thin 
sharp ridge on the radial or outer border. 
This ridge is perforated by the ectepicon- 
dylar foramen. The ridge appears to have 
been restricted in height and also in the 
distance it extended upward on the shaft 
of the bone, as contrasted with the Varanus humerus (see fig. 21). 
In the abrupt outward expansion of the ulnar border of the distal 
end, this bone more nearly resembles the humerus of Iguana tuher- 
D 
Fig. 20. — Left coracoid of 
Varands SALVATon. Cat. 
No. 29551, U.S.N.M. Ven- 
tral VIEW. Natural size. 
Compare with Fig 19 
gc, GLENOID cavity ; sc, 
SCAPULA articulation. 
\ 
ro-.c 
Fig. 21. — Left humerus of Saniwa ensidens Leidt. Tvpe, Cat. No. 2185, U.S.N.M. 
A, superior view ; B, oblique inferior view ; C, ventral view ; D, left humerus of 
Varanus salvator. Cat, No. 29551, U.S.N.M. Ventral view, d, deltoid crest; 
ep, epiphysis; /, foramen; oc, outer condyle; ra.c, radial condyle; ul.c, ulnar 
CONDYLE. All natural size. 
culata. In Varanus the same expansion is achieved, but by a gradual 
curve outward, beginning higher up on the shaft of the bone. 
Varanus sivalensis, as figured^ by Falconer, is intermediate in re- 
spect to the contour of this end of the humerus. 
» Paleontologlcal Memoirs, vol. 1, 1888, pi. 32. 
22 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
VOL. 80. 
The shaft is nearly straight and subcylindrical, as in most other 
Lacertilians, with a large medullaiy cavity. The transversely ex- 
panded distal end has two condyles; the one for articulation with 
the radius, however, is missing in this specimen. The proximal ar- 
ticular head is transversely elongated, being suboval in outline. The 
radial crest projects from the shaft at some distance below the head 
of the bone. 
Comparative measurements of humeri. 
Varanus 
salvator, 
25551, 
U.S.N.M. 
Greatest length 
Greatest width, proximal end 
Greatest width, distal end. . . 
Least diameter of shaft 
The distal end of the humerus figured " by Leidy as pertaining to 
Saniwa major is so entirely different in its principal characteristics, 
when compared with the humerus of either Saniwa ensidens or 
Varanus salvator, as to indicate at once that it pertains to a 
different type of animal. It is certainly 
not referable to the Varanidae. Since the 
above comment was written, Fejervary's ex- 
cellent paper" on the Fossil Varanidae 
has come to hand, and I find that he had 
previously reached the same conclusion. He 
says: 
The humerus described (p. 182) and figured (pi. and 
fig. 14) by Leidy as belonging to S. major is un- 
doubtedly not reptiUan and therefore can not belong 
to Satiiwa. 
Femur. — The distal end of the left femur 
and the proximal half of the tibia of the same 
side is all that is preserved of the posterior 
limb of the type specimen. Excepting its slightly smaller size and 
the lesser prominence of the ridge developed on the internal-anterior 
side and which continues down on to the distal end. this portion 
of the femur is very similar to the corresponding bone in the Veranus 
skeleton. The principal features of the distal portion of the femur 
are well shown in figure 22. The articular surface, which is well 
toward the posterior side, is broadly concave transversely. On the 
anterior side external to the center of the bone is a well-defined 
Fig. 22. — Distal e.n'd of 
RIGHT FEMUn OF SANIWA 
ENSIDENS Leidy. Type, 
Cat. No. 2185, U.S.N.M. 
Natural size. A, su- 
FERIOU view ; B, VEN- 
TRAL VIEW. 
""Leidy, J. Rept. U. S. Geol. Survey of Terr. F. V. Hayden, U. S. Geologist in charge, 
vol. 1, 1873. pi. 15, fig. 14, p. 182. 
"Ann. Mus. Nat. Hung., vol. 16, 1918, p. 421. 
ART. a3. AN EXTINCT VARAXID LIZARD GILMORE. 23 
groove which extends for a short distance up on the shaft of the 
bone. The epiphysis of the distal end of tliis bone is as distinctly 
defined as in the living Varanus. The broken end of the shaft shows 
a large medullary cavity, now filled with calcite. The transverse 
diameter measures 13.2 mm. ; the fore and aft diameter at the center 
is 8.5 mm. 
Tibia. — The proximal half of tlie left tibia (see pi. 2, fig. 2) shows' 
the same broad expansion of the upper end with flattened anterior 
surface, and the same contracted subtriangular shaft at the middle 
"with large medullary cavity as in the living Monitor. In fact, I 
fail to find any characters by which it may be distinguished from 
Varanus. The proximal end of the tibia has a greatest transverse 
width of 13 mm. 
Ribs. — In the three blocks of matrix containing the presacral 
vertebrae there are parts of more than 18 ribs (see pi. 3, figi. 2). 
several being nearly complete. All of the ribs appear to be single 
headed. A rib lying in the matrix near the right coracoid has a 
vertically expanded head, indicating that it probably pertains to the 
posterior cervical series, the expansion of the head corresponding 
to the elongation of the parapophj'ses in this region of the neck. 
The thoracic ribs, however, do not have any appreciable enlarge- 
ment of the proximal end, which is cupped for articulation with 
the hemispherical parapophyses of the dorsal vertebrae. The proxi- 
mal half of the larger thoracic ribs is flattened both fore and aft. 
becoming subcylindrical as the distal end is approached, which is 
slightly expanded. These ribs, in fact, all of the ribs, appear to be 
moderately but regularly curved from end to end. 
DISCUSSION OF THE FAMILY, AND GENETIC RELATIONSHIPS OF 
THE GENUS SANIWA. 
Family VARANIDAE. 
Postorbital bar incomplete; temporal arcade complete; supra- 
temporal fossa not roofed over by dermal bones; single premax- 
illary bone; nasals coalesced and narrow; infraorbital vacuity 
bounded by the pterygoid, palatine, and ectopterygoid, the maxil- 
lary being excluded; palate toothless; hameal surfaces of the dor- 
sal vertebrae broad, flat, and devoid of carina;.* vertebrae usually 
without zygosphene or zygantrum, when present a vestigal zygo- 
spliene only. No dermal ossifications. 
In the characterization of the family Varanidae as given above 
1 have selected from the definitions of Lydekker,^^ Boulenger," 
and Fejervary^* such parts of their family characterizations as 
« Catalogue of Fossil Reptilia and Amphibia in British Museum, pi. 1, 1888, p. 281. 
"Fauna Brit. India, Ropt. and Batr.. London, 1890, pp. 160-161. 
" Ann. ]\Ius. Nat. Hung., vol. 16, 1918, p. 3G5. 
313G— 22— I'roc.N.M. Vol .6( t 4 r, 
24 PROCEEDINGS OF THE NATIONAL. MUSEUM. vol.60. 
relate to the bony structure, thus making the definition applicable 
to the fossil members of the family, and add remarks of my own 
on the presence of a vestigal zygosphene. 
The Varanidae or Monitors form a group comprising both recent 
and fossil representatives. In 1918 Fejervary^^ listed 43 forms as 
being referable to the family Varanidae. Forty-one of these pertain 
to the genus Va/ranus and two to the genus Saniwa; the latter, al- 
though included under the Varanidae, was regarded by him of 
" Uncertain s^'stematical position." 
His more extended remarks ^® are quoted in their entirety below : 
It must be here remarked that the genus Saniva described by Leidy and 
originating from the Eocene of Wyoming, in America, is also tield by Noposa 
as a Varanid, and talcing this supposition for granted, the Ne(i7-tis should also 
be involved in the history of the evolution of the Varanidae. However, Lydek- 
ker, Zittel (op. cit.), as well as Broili (1911) (op. cit., p. 216) range this 
problematical genus with the Angiiidae, so that, according to their opinion, it 
would not even be related to the Platynota but to the suborder of Lacertilia 
vera (= Kionocrania) . After a conscientious perusal of Leidy's descriptions 
and drawings, I am obliged to confess to the genus Saniva yet appearing a 
complete mystery to me. Neither the description nor the drawings throw 
sufficient light on even the most important characters. The humerus, for in 
stance, presents a particularly birdlike appearance, as Leidy himself very 
judicially remarks. The vertebrae, on the other hand, do, indeed, resemble 
those of Varanus, although the figures allow no persiiective as to the shape 
of the dorsal surface. It must be taken into consideration, however, that 
the vertebrae of an Angvidae and Vara?iidae in many respects bear great like- 
ness to each other, for which reason the resemblance with Varanus can not 
be judged as a decisive phenomenon. Moreover, it does not seem impossible 
that the vertebrae will ultimately prove to belong to Varanidae and will thus 
have to be separated from at least a part of the remains left. 
The observation recorded above is a very logical and concise sum- 
mary of the status of the genus Saniioa, based on the scanty informa- 
tion then available (1918) to Fejervary. 
The more recent preparation of the t3'pe materials, however, now 
shows the genus Saniwa to be based on an adequate specimen, and 
it thus removes some of the uncertainties of which Fejervary justly 
makes mention. 
The incompleteness of the postorbital bar; the toothless palate; 
pterygoids and palatines, widely separated ; infraorbital fossa 
bounded by pterygoid, palatine, and transverse, the maxillary being 
excluded; pleurodont dentition; teeth pointed; dorsal centra with 
flattened haemal surfaces devoid of carina ; and the absence of der- 
mal scutes constitute a combination of characters, together with the 
close resemblance of most of the bones of the skeleton to the living 
« Ann. Mus. Nat. Hung., vol. 16, 1918, pp. 444-445. " Idem, pp. 362-363. 
ART. 23. AN EXTINCT VARANIP LIZARD GILMORE. 25 
genus Varanus^ indicating Saniwa to be a true member of the family 
Varanidae. 
Although Leidy studied only a few of the bones of the type speci- 
men, he more than any subsequent authority correctly diagnosed its 
true relationships. He says : " 
The remains belong to a lacertain about the size of the existing monitor of 
the Nile, to which it appears to be closely related. The bones indicate a 
robust body, a long tail, and limbs with long toes. 
The vertebrae resemble those of the Nilotic monitor in form and propor- 
tions, and like them possesses no zygosphenal articulation. 
The last statement is now known to be incorrect as there are vestigal 
zygosphenes present on the dorsal vertebrae, but I do not consider 
their presence of sufficient morphological importance to bar the as- 
signment of Saniwa from the Varanidae, especially since they appear 
to be undergoing reduction, tlms tending toward the conditions found 
in the Varanus vertebrae, where they have entirely disappeared. It 
was the discovery of similar reduced zygosphenal articulations of the 
vertebrae that led Marsh" in 1872 to establish the genus Thinosau- 
ru8, which he recognized as being closely related but distinct from 
Saniwa because of the supposed absence of zygosphenes in that 
genus. A careful study of Marsh's description and measurements 
of the genotype Thinosaurus paucidens leads me to the conclusion 
that Thinosaurus and Saniwa are congeneric. The latter being the 
older by two years, Thinosaurus thus becomes a synonym, and the 
described species will hereafter be designated respectively Saniwa 
paucidens (Marsh) , S. leptodus (Marsh) , S. crassv^ (Marsh) , S. gran- 
dis (Marsh), and ^S'. agilis (Marsh). 
It would also appear quite probable that a comparative study of 
the type specimens on which the above species were founded would 
show one or more of them to be referable to Saniwa ensidens Leidy. 
Tinosaurus, which Fejervary ^^ regards as being equivalent of 
Thinosawms, probably represents a distinct genus, as is apparently 
indicated by Marsh's meager description,-" in which the teeth are 
described as having cusps, whereas all of the known Varanidae have 
simple coned teeth without auxilliary cusps. 
The family Varanidae therefore contains the genus VaranvrS, 
largely made up of living species of lizards, and the genus Saniwa, 
which at this time includes six or more extinct species. 
'^ Leidy, J. Kept. U. S. Geol. Survey Terr., F. V. Hayden, U. S. in charge, vol. 1. 1873, 
p. 181. 
" Marsh, O. C. Amer. Journ. Scl., vol. 4, 1872, pp. 299-300. 
"Ann. Mus. Nat. Hung., vol. 16, 1918, p. 362. 
s^Amer. Journ. Sci.. ser. 3. vol. 4. 1872. o. 304. 
26 
PROCEEDINGS OF THE NATIONAL MUSEUM. 
vou GO. 
The distinctness of the two Varanid genera Varanus and San'twa 
is clearly set forth by the enumeration of their more important char- 
acters as contrasted in the two paralled columns below : 
Genus Varanus. 
1. Dorsal vertebrae without zygos- 
pheneal articulations. 
2. Coracoid having two anterior 
notches. 
3. Postorbital usually fused with 
postfrontal. 
4. Hypophyses on first six or seven 
cervical vertebrae, vestigal on the sev- 
enth or eighth. 
5. First rib carried on the seventh 
cervical. 
6. Humerus with gradually ex- 
panded ulnar border at distal end. 
Genus San/iwa. 
1. Dorsal vertebrae having vestigal 
z.vgosphene articulations. 
2. Coracoid having a single anterior 
notch. 
3. Postorbital distinct from post- 
fi'ontal. 
4. Hypophyses on first five cervical 
vertebrae, vestigal on the sixth. 
5. First rib appears to have been 
carried on the fifth cervical, possibly 
the fourth. 
6. Humerus with abruptly expanded 
ulnar border at distal end. 
A critical comparison of jSaniica, especially with the existing 
members of the family, appears to show a few of the evolutionary 
changes undergone bj'^ the Varanid skeleton since INIiddle Eocene 
times. These are: 1. the loss of the vestigal zygosphene: 2, a reduc- 
tion in the number of teeth in the jaws; 3, the complete coalescence 
(usually) of the postfrontal postorbital bones: and 4, an increase 
in the number of cervical vertebrae bearing hypophyses. 
The living members of Varanidae, Monitors as they are often 
called, form a group of about 30 species, all belonging to the one 
genus Varanus. Living members of this genus inhabit the tropical 
parts of Africa, Southern Asia, Malasia, and Australia. All are 
carnivorous in habit, feeding upon small backboned animals, insects, 
and especially upon eggs, which they crush between their teeth while 
holding them aloft. Most species live whollj^ upon the land and 
some are arboreal. Others, especially those found along the Nile, 
live about water and are excellent swimmers. The terrestrial species 
are said^^ to haA'e "'a round tail and small external nostrils, but the 
water species have the tail much flattened and the nostrils have large 
cavities." 
Most of the species liA'e wholly upon the land. V. prasiniis is 
supposed to be arboreal. Others, as V. salvator and F. niloticus, 
owing to the fact of their tail being strongly compressed, are excel- 
lent swimmers and deserve the name of water lizards. The terres- 
trial species, as V. griseus, have rounded tails. The apparent ab- 
sence of caudal vertebrae having high spinous processes suggest that 
Saniwa was also a terrestrial species, having a rounded rather than 
a flattened tail. 
s' Willistoii, S. W. Water Reptiles of the Past and rre.-^ent, 1914, pp. 144-145. 
ART. 23. 
AX EXTINCT VARANID LIZARD GILMORE. 
27 
The extinct members of the genus Varanus have been thoroughly 
reviewed and discussed in Fejerviiry's excellent paper, Contributions 
to a Monography on Fossil Varanidae and on Megalanidae, and, as 
he has so clearly pointed out, are very unsatisfactorily known. Of 
the 10 extinct species described, he regards only four of "established 
specilic value." At this time very little satisfaction was obtained 
in attempting to contrast the extinct American forms with the Euro-, 
pean species, except that Saniwa from the Bridger (Middle Eocene) 
has the distinction of being the most ancient Varanid lizard yet dis- 
covered in North America, if not in the world. 
List of North American fossil Varanidae. 
Names. 
Saniwa ensidens Leidy . 
Saniwa major Leidy . . . 
Sanitva paucidens (Marsh). 
Saniwa leptodus (Marsh)... 
Saniiva crass us (Marsh) . . . 
Saniwa grandis (Marsh) . . . 
Saniwa agilis (^larsh) .... 
Locality. 
Near Granger, Wjoming. . . 
Lodge Pole Trail crossing, 
Dry Creek, Wyoming. 
Grizzly Buttes, Wyoming.. 
do 
Henry's Fork, Wyoming. . . 
Grizzly Buttes, Wyoming. . 
Henry's Fork, Wyoming. .. 
Formation. 
Bridger, Middle Eocene. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
28 PKOCEEDINGS OF THE NATIONAL MUSEUM. vol.60. 
EXPLANATION OF PLATES. 
Plate 1. 
Palate of Saniica emklens Leidy. Cat. No. 2185, U.S.N. M. Type. Twice nat- 
ural size. Viewed from above. Shown as found articulated in the matrix, mx, 
maxillaries ; pi, palatines ; pt, pterygoids ; v. vomers. 
Plate 2. 
Fig. 1. Cervical vertebrae of Sanin-a ensidens Leidy. Cat. No. 2185, U.S.N.M. 
Type. Natural size. Viewed from the left side. Shown as found articulated ex- 
cept that the atlas has been removed. 
Fig. 2. Dorsal vertebrae and other bones of Saniwa ensidens Leidy. Cat. No. 
2185, U.S.N.M. Type. About natural size. Shown as found in the matrix, a, 
four anterior dorsal vertebrae, ventral view ; b, left coracoid ; c, right humerus ; 
d, distal end of femur; e, proximal half of tibia. 
Plate 3. 
Fig. 1. Caudal vertebrae of Saniwa oisidens Leidy. Cat. No. 2185, U.S.N.M. 
Type. About natural size. Shown as found in the matrix. 
Fig. 2. — Dorsal vertebrae and ribs of Saniica ensidens Leidy. Cat. No. 2185, 
U. S. N. M. Type. About natural size. The two vertebrae on the right with ven- 
tral surfaces exposed are the ones figured by Leidy. a, distal end of humerus.