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NATURAL HIST. SURVEY

FIELDIANA • GEOLOGY

Published by
CHICAGO NATURAL HISTORY MUSEUM

Volume 10 December 6, 1951 No. 12

A MASTODONT TOOTH FROM
SZECHWAN, CHINA

Dirk A. Hooijer

RijKSMUSEUM VAN Natuurlijke Historie, Leidbn, Thb Netherlands
AND

Edwin H. Colbert
The American Museum of Natural History and Columbia University

A short while ago one of us (Hooijer), while visiting Chicago
Natural History Museum, came across a fossil molar labeled as
follows: "Tooth of Young Mastodon; Sze-Chuan, China, gift of
A. W. Bahr, New York, July 26, 1926. Field Museum, P14061."

We are greatly indebted to Mr. Bryan Patterson, Curator of
Fossil Mammals at Chicago Natural History Museum, for having
turned this interesting specimen over to us for description. The
photographs were made in the American Museum of Natural History
in New York.

The specimen here described (see fig. 54) is of considerable interest
because it proves to be the first tooth of the genus Synconolophus
to be found outside of India. The molar, which is thoroughly fossil-
ized, has blue enamel and brown dentine and cement and evidently
represents an upper right intermediate molar.

The tooth is almost completely preserved, and consists of three
full ridge-crests or lophs, and in addition a small talon in front
and a sizable talon behind. The anterior ridge-crest is worn down
completely, while the posterior talon is just touched by wear. All
of the worn cones show the enamel to be strongly corrugated, while
heavy vertical grooves, from 2 to 4 mm. apart, are seen on the
marginal surfaces of the outer and of the inner cones. The middle
cone of the third loph is not yet confluent with the buccal cone,
with which it is fused in the more worn second loph;

Not much is left of the anterior talon. On its anterior surface
the tooth has an extensive contact facet, and the lingual two-thirds

No. 683 129

B

Fig. 54. Synconolophus sp., upper right intermediate molar, Chicago Natural
History Museum, no. P14061. A. Crown view. B. External lateral view. Both
XI.

130

B

Fig. 55. Synconolophus ptychodus Osborn, left DM* and M', American
Museum of Natural History, no. 19442. A. Crown view. B. External lateral
view. Both approximately X /i.

131

132 FIELDIANA: GEOLOGY, VOLUME 10

of the anterior enamel surface has been broken off. There is no
sign of a posterior contact facet. The antero-posterior diameter
of the crown, measured on the buccal side, is 80 mm., the width
at the anterior loph is 49 mm., and at the middle loph it is 50 mm.,
while at the third loph the crown width at the base is 56 mm. Behind
the third loph the tooth is gradually rounded off from side to side.

There are two main roots, both transversely broad in cross
section and constricted in the middle. The anterior root supports
the anterior loph, and the posterior, which is wider, is associated
with the third loph. This so-called third loph is only the penultimate
crest if the posterior talon is regarded as a fourth loph; in that case
the posterior talon is limited to some cingular elevations rounding
the tooth off smoothly at the back.^ While the anterior root is
simply pear-shaped in cross section, the posterior root has a small
median anterior projection just above the central cone of the third
loph. Between these two main roots there are two additional
smaller roots that support the outer and the inner cone of the middle
or second loph, respectively, and these roots, too, have about the
same size relation as have the cones on the crown. No support of
any kind, as remarked above, is given to the posterior talon, nor is
the anterior talon provided with roots.

The cingulum is well developed buccally, forming knobs at the
entrances to the transverse valleys, but it is much less distinct
along the lingual base of the crown. There is little or no crown
cement.

From the heavy crenulations seen in all of the enamel figures,
as well as from the presence of vertical marginal grooves, there
seems to be no doubt that the present molar belongs to the genus
Synconolophus, the Siwalik proboscidean with its "multiplication
of the cones and conules which finally render the molar a bewildering
complex, of a warped, choerodont, ptychoid pattern." (Osborn, 1929,
p. 10.) This genus, which was first described from the Siwaliks of
India and until now has never been found beyond the Indian region,
consists at the present time of four species (Osborn, 1936, pp. 654-
665). In age these species range from the Lower Chinji into the

1 This may seem an immaterial point, but it is always a matter of personal
taste whether a big but not exactly full-sized terminal loph or plate in a pro-
boscidean molar deserves to be counted with the ridges. The ridge formula for
the molar now under discussion might be written as X 3 -(- 1 or as X 4; Osborn
would perhaps have preferred to write the formula as 1/2-3-3/4. In the present
case the roots are fortunately preserved, and the large posterior root is clearly seen
to be placed above the third loph from the front while the hindmost transverse
ridge merely forms a bulging out of the crown and, therefore, would seem to be
most correctly named the posterior talon.

HOOIJER AND COLBERT: MASTODONT TOOTH 133

Dhok Pathan, that is, from the Late Miocene or Early Pliocene
through the Middle to Late Pliocene (Colbert, 1942, pp. 1442-
1447). A specimen in the American Museum, containing the left
DM* and M^ (type of Synconolophus ptychodus Osborn, A.M.N.H.
no. 19442), is so extremely close to the present Chinese find that
it would hardly be possible to separate the molar from Szechwan
even subspecifically (fig. 55). The DM* of the Siwalik specimen
is slightly smaller (length of crown 73 mm., width at first loph 44
mm.), the M^ slightly larger (length 91 mm., width of first loph 55
mm.) than the Szechwan tooth, which is just about half-way between
the two in size. The Siwalik DM* carries three lophs plus a small
talon behind, while the M^ possesses three lophs, plus a posterior
talon fully equal to that of the Szechwan molar in relative and
absolute size. The relation between the cones on the crown and
the individual parts of the root system cannot be studied in the
Indian specimen, but it seems from the visible evidence that the
large posterior root is in the same position as it is in the Chinese
molar.

Because of the great similarity between the Siwalik species and
the Chinese find we prefer not to coin a new specific name for the
Szechwan Synconolophus. This specimen bears evidence that Syn-
conolophus extended into southwestern China.

As to the exact locality of the Synconolophus molar nothing can
be added to the information on the Museum label. At Yenchingkou,
near Wanhsien, Szechwan, Dr. Walter Granger collected fossil
mammals for the American Museum of Natural History between
1921 and 1926. There is therefore a possibility that the mastodont
molar came from the locality at which Dr. Granger worked. In a
previous publication (Hooijer, 1951) the history of the collection
made by Granger is presented, and it need not be repeated here;
suffice it to say that there is no evidence whatsoever of the presence
of mastodonts in the Yenchingkou collection as now preserved in
the American Museum of Natural History.

However, in a note on new fossils from Wanhsien, Young (1939,
pp. 330-331) figures and describes a left upper molar (DM 3) as
Mastodon sp., and from the figure it does not seem improbable
that this tooth represents Synconolophus too. This tooth, with a
length of 44.5 mm. and maximum width of 38 mm., two lophs, a
very large posterior talon and strong inner cingulum, could very
well be a third milk molar (not represented in the Siwalik collection)
of the genus under discussion, but of course the original specimen

134 FIELDIANA: GEOLOGY, VOLUME 10

should be re-examined to determine this point. Most unfortunately
the tooth mentioned by Young is a gift of a native, and though the
collectors were told that it came from the same sites where Granger
had been collecting, there is no certainty about this. Young (loc.
cit.) presumes that in addition to the dominantly Middle Pleistocene^
sites of Szechwan, some older fissure deposits do exist in the region,
exactly as at Choukoutien. He suggests that to this earlier (Pliocene)
series might well be referred the isolated Nestoritherium tooth, the
only find of its kind in the collection made by Granger. However,
the chalicothere tooth, although it does not bear a field number, is
known to have been collected during Granger's 1921 field season
and would consequently have come from one of the limestone pits.
This cannot be said with certainty about the two Szechwan mastodont
molars of which we now have evidence. If the age of the Chinese
representative of this mastodont genus can be taken as roughly the
same as that of the Siwalik species, namely. Late Miocene or Plio-
cene, it would seem to be too old to go with the Yenchingkou fauna
of Szechwan.

REFERENCES

Colbert, E. H.

1942. The geologic succession of the Proboscidea. In Proboscidea, by H. F.
OSBORN, 2, pp. 1421-1521, figs. 1220-1224. New York.

HooiJER, D. A.

1951. Two new deer from the Pleistocene of Wanhsien, Szechwan, China.
Amer. Mus. Nov., No. 1495, 18 pp., 4 figs.

OSBORN, H. F.

1929. New Eurasiatic and American proboscideans. Amer. Mus. Nov., No.
393, 22 pp., 22 figs.

1936. Proboscidea. 1, xl+802 pp., 12 pis., 680 figs. New York.

Teilhard de Chardin, p. and Trassaert, M.

1937. The proboscideans of south-eastern Shansi. Palaeont. Sinica, ser. C,
13, fasc. 1, 58 pp., 6 figs., 13 pis.

Young, C. C.

1939. New fossils from Wanhsien (Szechuan). Bull. Geol. Soc. China, 19,
pp. 317-331, 7 figs.

1 Young actually writes: "Lower Pleistocene," but it now seems probable that
the age of the Yenchingkou pits fauna is Middle Pleistocene; it is definitely post-
Villafranchian. Teilhard de Chardin and Trassaert (1937) distinguish three main
zones in the Upper Cenozoic of southeastern Shansi. These are Zone I, of Pontian
age. Zone II, of "Middle Pliocene" age (with Mastodon borsoni), and Zone III, of
Villafranchian age. We believe that Mastodon borsoni is a definitive Villafranchian
type, as is Archidiskodon planifrons, found at the top of Zone II, but Chilotherium,
still present in this zone, is generally regarded as of Pliocene affinities. Therefore
we suspect that Zone II represents a mixture of faunas and probably should be
subdivided, which is in fact indicated by Teilhard de Chardin and Trassaert
(op. cit., p. 4).

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