A new colubrid snake of the genus Pseudorabdion from Sumatra

LIBRARY OF THE

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v. 44
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NArURAL HISTORY.
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Published by
CHICAGO NATURAL HISTORY MUSEUM

Volume 44 November 28, 1961 No. 5

A New Colubrid Snake of the Genus
Pseudorabdion from Sumatra

Robert F. Inger
Curator, Division of Amphibians and Reptiles

AND

Alan E. Leviton

Department of Herpetology, California Academy of Sciences

Recently the Naturhistorisches Museum of Vienna sent a collec-
tion of Indo-Malayan snakes to Chicago Natural History Museum in
connection with a study being carried out by the senior author. This
collection includes a single specimen of a new species of the genus
Pseudorabdion. We are grateful to Dr. J. Eiselt of the Naturhis-
torisches Museum for permission to describe this species, which we
are naming after him.

Pseudorabdion eiselt i, new species. Figure 13.

Holotype. — Naturhistorisches Museum number 16806, a gravid
female from Padang, Sumatra, collected by J. Schild, 1899.

Diagnosis. — No preocular or loreal shields; postocular and supra-
ocular shields not fused together or to the ocular shield; frontal
separated from eye by supraocular; nasal small, undivided; inter-
nasal touches first two supralabials.

Description of holotype. — Rostral as high as wide, portion visible
from above equal to length of internasal suture; internasal small,
greatest length about half that of prefrontal; internasal touches first
and second supralabials; prefrontal three-fourths of length of frontal,
touches second and third supralabials and eye; supraocular distinct
from postocular, about one-third of width of frontal; frontal hexag-
onal, separated from orbit, two-thirds of length of parietal; length of
parietal equal to its distance from tip of snout; nasal undivided,
small, not covering entire dorsal edge of first supralabial; no loreal
or preocular; postocular not as high as eye; diameter of eye equal to

Library of Congress Catalog Card Number: 61-1869U
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46 FIELDIANA: ZOOLOGY, VOLUME 44

vertical distance from eye to mouth; five supralabials and a large
postlabial scale; supralabials increasing in size posteriorly, the fifth
much the largest, the third and fourth bordering the eye; fifth labial
broadly in contact with parietal; a large scale between the post-
labial and parietal; mental touches anterior chin shields; five infra-
labials, the first three touching the anterior chin shields; a gular
scale partly separates the posterior chin shields, which are no larger
than gulars; 10 maxillary teeth.

Scales smooth, without apical pits, in 15 longitudinal rows which
are reduced to 13 opposite the fifth ventral before the anal through

fur

Fig. 13. Dorsal and lateral views of holotype of Pseudorabdion eiselti, new sp.
Actual size 8 mm.

loss or fusion of lateral scale row 3; caudodorsal scales reduced to 4
opposite the tenth subcaudal posterior to vent; ventrals 130, the last
one split; anal undivided; subcaudals 12, paired.

Total length 200 mm., tail 10 mm., head to end of parietals 7.5
mm., diameter of eye 1.4 mm.

Color (in alcohol) faded but evidently dark brown above and be-
low, each dorsal scale with a light network or light apical spot; head
dark brown above, upper lip lighter; an obscure yellowish crescent
along lateral margin of parietals.

Comparisons. — In head scutellation eiselti resembles three Philip-
pine species: ater (Taylor), oxycephalum (Giinther), and montanum
Leviton and Brown. It differs from all three in having distinct su-
praocular and postocular shields, the internasal meeting the first
supralabials behind the nasal (indicating the shortness of the nasal
shield), and a proportionally larger eye. The proportion of eye di-
ameter to eye-mouth distance shown by Leviton and Brown (1959;
fig. 5) for Pseudorabdion montanum is incorrect. The eye is much

INGER AND LEVITON: SNAKE FROM SUMATRA 47

too large, compared to the vertical length of the adjacent supra-
labials, and should be reduced by one- third. The eye diameter /eye-
mouth distance ratio is correctly portrayed for P. oxycephalum (fig. 4,
op. cit.), which P. montanum most closely resembles. The eye diam-
eter/eye-mouth distance ratio in eiselti is similar to that in P. longi-
ceps (fig. 1, op. cit.).

Pseudorabdion ater differs further from P. eiselti in having the
frontal bordering the eye and the nasal divided. Pseudorabdion
oxycephalum and P. montanum have higher ventral and subcaudal
counts than eiselti. The counts for females of these species are:
oxycephalum 144-157 and 16-17; montanum 154-161 and 21-22; eiselti
130 and 12. Data for the Philippine species are from Leviton and
Brown (1959).

The only known species that may be sympatric with eiselti is
P. longiceps (Cantor), which has been recorded from the west coast
of Sumatra at Ayer Bangis (de Rooij, 1917), about 170 km. from the
type locality of eiselti. It differs from eiselti in the presence of a pre-
ocular, the separation of the internasals from the labials, and higher
subcaudal counts (females 17-20). Both longiceps and eiselti have
larger eyes and more maxillary teeth than their Philippine congeners
that also lack loreal shields.

All other species of Pseudorabdion differ from eiselti at least in
the presence of loreals and in having the prefrontals and internasals
separated from the labials (a direct consequence of having distinct
loreals). One, albonuchalis (Gunther), has the frontal bordering the
eye. Two, saravacensis (Shelf ord) and sarasinorum (Muller), have
more maxillary teeth (18-21 and 14 respectively) than eiselti (10).
And at least two, taylori Leviton and Brown and mcnamarae Taylor,
have higher subcaudal counts (females 33-35 and 20-23, respectively).
The counts are from Leviton and Brown (1959).

REFERENCES

Leviton, A. E., and Brown, W. C.

1959. A review of the snakes of the genus Pseudorabdion with remarks on the
status of the genera Agrophis and Typhlogeophis. Proc. California Acad. Sci.,
(4), 29: 475-508, 10 figs.

de Roou, Nelly

1917. The reptiles of the Indo-Australian Archipelago. Vol. II. Ophidia.
xiv+334 pp., 117 figs. Leiden, E. J. Brill, Ltd.