215

RAFFLES BULLETIN OF ZOOLOGY

2020

35 cycles at 94°C for 30 s, 53°C for 30 s, and 72°C for 45

s, and was completed by a nal extension at 72°C for 5 min. Amplication was performed in a 10-μl volume reaction, with Blend Taq (TOYOBO). Amplied PCR products were

electrophoresed on 2.0% agarose gel and viewed under UV light to check for correct fragment size. PCR products

were subsequently puried using 13% polyethylene glycol

(PEG) purification procedures. The PCR products were sequenced with the PCR primers and BigDye v3.1, using ABI 3130xl Genetic Analyzer, and the obtained sequences were deposited in the DDBJ/EMBL/GenBank database with the accession number LC523630. In addition to the newly sequenced data of

X. acanthognathus

(SRC 00961), we used the sequence data of

X. schaeferi

provided by Lawson et al. (2004) and Quah et al. (2018) for comparisons. Sequences were aligned using the MUSCLE algorithm (Edgar, 2004) in MEGA7 (Kumar et al., 2016) with default parameters, and the alignment was checked and unaligned parts were manually revised. Uncorrected

p

-distances among sequences were calculated using MEGA7.

Morphological analysis.

Information on morphological characters of the other four specimens of the genus were obtained from Günther & Manthey (1995), Wallach & Günther (1998), and Quah et al. (2018), and we followed their measurement and scale count methods. We also basically followed morphological characters examined by Günther & Manthey (1995) and Quah et al. (2018) that include snout-vent length (SVL); total length; tail length; presence or absence of internasal and loreal; number of preoculars, supraoculars, posto culars , supra labials , infral abials , dorsal scale rows, ventrals, and subcaudals; cloacal plate undivided or divided. All measurements, except snout-vent length and tail length, were taken with a Mitutoyo caliper to the nearest 0.1 mm. Ventral counts followed that of Dowling (1951). The terminal scute was not included in the number of subcaudals. Dorsal scale row counts were taken at one head length behind the posterior end of head, at midbody, and at one head length before vent. Values for paired head characters were given in left/right order. The sex was determined by presence or absence of hemipenis. Institutional abbreviations are as follows: FMNH—Field Museum of Natural History, Chicago, USA; LSUHC—La Sierra University Herpetological Collection, La Sierra University, Riverside, California, USA; USMHC—Universiti Sains Malaysia Herpetological Collection, Malaysia; ZMB—Museum für Naturkunde der Humboldt-Universität zu Berlin, Germany.

RESULTS Molecular analysis.

The uncorrected

p

-distance for the cyt b gene fragment was 9.9% between

X. acanthognathus

from Lambir NP, Sarawak (SRC 00961) and the holotype of

X. schaeferi

from Templer’s Park, Selangor (ZMB 50534), and 10.1% when compared to

X. schaeferi

from Lata Kijiang, Negeri Sembilan (L SUHC 13481). These values are much

higher than the maximum of intraspecic variation in cyt b

gene observed in other genera of snakes in Southeast Asia (Supikamolseni et al., 2015).

Morphological comparison.

The present specimen (SRC

00961) was identied as belonging to the genus

Xenophidion

based on the following characteristics: a small snake with laterally compressed body and a short tail; nasal undivided; internasals absent; prefrontals greatly enlarged; loreals and suboculars absent; undivided subcaudals; irregular dark zig-zag vertebral stripe bordered by whitish zig-zag stripes running along the length of the body. Furthermore, this specimen was collected in northern Borneo (locality of

X. acanthognathus

) and the following characteristics are closer to

X. acanthognat hus

than

X. schaeferi

: 185 ventrals; 55 subcaudal scales; relatively short tail (SVL/tail length = 4.20) (Günther & Manthey, 1995; Quah et al., 2018). Thus, this specimen is most probably

X. acan thognathus

. Although dentition characters are known to be diagnostic for this genus (Günther & Manthey, 1995), we were unable to examine those characters due to the small size of our specimen. Examination via CT scanning is planned for future studies.

Intraspecific variation (Table 1).

Our specimen (SRC 00961) is generally similar in pholidosis to the holotype of the species (FMNH 235170) reported by Günther & Manthey (1995). Differences between SRC 00961 and the holotype were the number of ventrals (185 vs. 181); number of subcaudals (55 vs. 51); number of dorsal scales rows (22/24/20 vs. 19/23/19); morphology of body scales (slightly keeled only posteriorly vs. strongly keeled); position of the largest supralabial (2

nd

vs. 1

st

and 2

nd

); number of postoculars (3/2 vs. 2/2); SVL/tail length ratio (4.20 vs. 4.52); condition of yellowish-white patch on dorsum behind neck (small and unclear vs. large and clear). Difference in the yellowish- white patch between our specimen and the holotype may be ontogenetic because our specimen is a small juvenile and it is common for some snakes to exhibit change of colour pattern during development (Lillywhite, 2014).

Interspecific comparisons (Table 1).

Xe no ph id io n acanthognathus

can be differentiated from its sister species,

X. schaeferi

by the following characteristics: l arger number of ventrals (181–185 vs. 176–178); larger number of subcaudals (51–55 vs. 43–45); and shorter tail (SVL/tail length = 4.20–4.52 vs. 4.69–4.84).

Description of SRC 00961 (Figs. 1–4, Table 1).

Juvenile female; total length 156 mm; tail length 30 mm; head length 7.1 mm from anterior edge of rostral to posterior end of mandible; head width 3.9 mm at broadest point; head distinct from neck; eyes small, pupils round; snout short and rounded

in dorsal prole; rostral scale triangular, broader than tall,

visible from above; nasals undivided, extending from middle of snout above to nearly the mouth opening below, nares in the distal corners; internasal absent (probably fused with prefrontals or nasals); loreal absent; preocular 1/1, large, extending dorsally on each side contacting prefrontal , frontal, supraocular, one head scale, 2

nd

and 3

rd

supralabials and eye; supraocular 1/1, small; postoculars 3/2, upper smaller than lower; prefrontals two, very large, longer than wide, in broad contact with each other, frontal, preoculars, posterior tip of nasals, and 1

st

and 2

nd