Dibamus vorisi, Das & Lim, 2003

Das, Indraneil & Lim, Kelvin K. P., 2003, Two New Species Of Dibamus (Squamata: Dibamidae) From Borneo, Raffles Bulletin of Zoology 51 (1), pp. 137-141 : 139-141

Dibamus vorisi , new species

( Fig. 2 )

Material examined. – Holotype – FMNH 230187 , Danum Valley Field Centre (05º 01’N; 118º 03’E), Lahad Datu District, Sabah, East Malaysia (Borneo); adult male; coll. Robert Inger & Sharon Emerson, 30 Nov.1986. The type locality is shown in Fig. 3 .

Paratype – FMNH 246232 , paratopotype, adult female; coll. Harold Voris & Daryl Karns, 8 Nov.1990 .

Diagnosis. – SVL to 90.1 mm; body relatively slender, body width 3.9% SVL, postoculars two; midbody scale rows 20; subcaudals 33 in a male, 11 in a female; frontonasal entire; nasal suture complete; labial suture absent, preanal pores absent; nuchal collar absent; a pale brown (in preservative) body band situated in the anterior half of body; and a relatively short tail (16.8% SVL in a male; 6.1% SVL in a female).

Comparisons. – The new species of Dibamus from Mendolong, Sabah, is compared with all nominal and one undescribed species (from Pulau Tioman, Pahang, in West Malaysia) .

In showing two postoculars, Dibamus ingeri , new species, can be separated from the following congeners that possess a single postocular: D. bogadeki Darevsky, 1992 (distribution: Hong Kong, eastern China), D. bourreti Angel, 1935 (distribution: Vietnam, China, including Hong Kong), D. deharvengi Ineich, 1999 (distribution: Binh Châu, Vietnam), D. greeri Darevsky, 1992 (distribution: Vietnam), D. leucurus Bleeker, 1860 (distribution: Pulau We, Sumatra, Borneo and southern islands of the Philippines), D. montanus Smith, 1921 (distribution: Vietnam), D. nicobaricus Fitzinger in Steindachner, 1867 (distribution: Nicobar Islands, India), D. smithi Greer, 1985 (distribution: Vietnam), D. somsaki Honda et al., 1997 (distribution: Thailand) and new species from Batu Gua Madu (Das & Yaakob, 2003). It differs from D. taylori Greer, 1985 (distribution: Lombok and Wetar in the Lesser Sundas, Indonesia), which has three postoculars.

Its midbody scale row counts of 20 separates it from the following additional species – D. celebensis Schlegel, 1858 (distribution: Sulawesi, Indonesia: 26-30); D. kondaoensis Honda et al., 2001 (distribution: Kondao Island, Vietnam: 23), D. novaeguineae Duméril & Bibron, 1839 (distribution: southern islands of the Philippines, Halmahera, Sulawesi and West Papua Province of Indonesia on western New Guinea: 22-26); and D. seramensis Greer, 1985 (distribution: Seram, Indonesia: 33). In the dichotomous key to the genus by Greer (1985), the new species falls out as D. alfredi Taylor, 1963 (distribution: southern Peninsular Thailand), but can be distinguished from this species in showing complete (vs incomplete) nasal and labial sutures; preanal pores absent (vs present); a relatively short tail (14.8% vs 17-18% of SVL) and lower subcaudal counts for males (36 vs 46-47).

Description (based on the holotype). – SVL 89.2 mm, TL 12.7 mm; snout bluntly rounded, distinctly conical (IN/IO ratio 0.44), projecting beyond jaws; nostril laterally oriented, oval, situated closer to snout-tip than to orbit (E-N/E-S ratio 0.79); head shorter than wide (HL/HW ratio 0.82), not flattened (HL/HD ratio 0.69); rostral pad with a large number of evenly distributed sensory papillae, rostral suture incomplete, nasal suture complete, extending from ocular to nostril; labial suture absent; posterior border of rostral nearly straight; frontal single, width 0.6 mm; frontonasal entire, width 0.6 mm; frontal wider than long, x 1.20 times wider than frontonasal; interparietal single, not enlarged, narrower than frontonasal and frontal, posteriorly bordered by three slightly smaller nuchal scales; postoculars two; supralabial single, elongate, bordering ocular ventrally; infralabial lanceolate, length 1.6 mm (infralabial length/HW ratio 0.73), separated by a smaller, trapezoid mental; scales bordering posterior edge of infralabial, three bilaterally; ear opening absent; eyes dimly visible through ocular; tongue short, undivided anteriorly, pointed; teeth small, acute.

Body relatively slender, BW 3.5 mm (BW/SVL ratio 0.04); head slightly distinct from neck and from body; tail short (TL/SVL ratio 0.14), its tip rounded, not bulbous, wider than rest of tail; tail base thick (TW/TL ratio 0.28); body scales smooth, subcycloid, including near preanal region; transverse scale rows posterior to head 22, at midbody 20; and anterior to vent 18; ventrals 147; subcaudals 33; presacral vertebrae 97; postsacral vertebrae 20; hind limbs reduced; flattened left hindlimb 3.1 mm, covered with three scales basally, three pairs of scales along its length, and terminating in a single scale; an enlarged median scale on preanal region, overlapped by those on sides; preanal pores absent; postanal scales not reduced.

Measurements (in mm; holotype followed by paratype in parentheses). – SVL 79.2 (90.1); BW 3.5 (3.5); TL 13.3 (5.5); TW 3.6 (3.1); E-N 1.1 (1.4); E-S 1.4 (1.9); IN 0.7 (0.8); 1O 1.6 (1.8); HL 1.8 (1.7); HW 2.2 (2.2); HD 2.6 (2.1).

Variation in paratype. – The paratype, an adult female, differs in the following additional characters: hindlimbs absent; frontonasal partially divided; subcaudals 11.

Colouration. – Colour in life unknown. In preservative, dorsum brown, unpatterned; venter slightly paler; snout-tip, sides of head, including supralabials, throat, hindlimbs and preanal region yellowish-cream; no nuchal band; a pale brown body band on anterior half of body, in holotype, commencing 30.6 mm from snout-tip, measuring 13.5 mm in width both dorsally and ventrally; in paratype, commencing 34.4 mm from snout-tip, measuring 13.9 mm in width both dorsally and ventrally; tip of tail cream.

Etymology. – The species name honours Harold Knight Voris, Curator at the Division of Herpetology, Field Museum of Natural History, Chicago, an important worker on the herpetology of Southeast Asia, and also one of the collectors of the type series of the new species.

Natural history. – The holotype was found 5 cm below the surface of the soil, within the confines of the buttresses of a tree, within a primary forest; the paratype from under dead leaves, also within a primary forest ( R. F. Inger, pers. comm., 2002). Danum Valley is situated in eastern Sabah State, is at an elevation of under 300 m ASL. The Danum Valley Conservation Area, located at the upper catchment of the Segama River , is a 43,800 ha area of undisturbed forest within the 972,000 ha concession area of the Sabah Foundation, most of which have been selectively logged. The topography is hilly, supporting primary lowland dipterocarp forest (Inger & Voris, 1993). Rainfall averages about 2,700 mm per year, although droughts are of regular occurrence, especially associated with the El Niño Southern Oscillation years .

Comparisons. – The new species of Dibamus from Danum Valley, is compared with all nominal and one undescribed species (from Pulau Tioman, Pahang, in West Malaysia), besides the species from Mendolong described above.

In showing two postoculars, Dibamus vorisi , new species, can be separated from the following congeners that possess a single postocular: D. bogadeki , D. bourreti , D. greeri , D. leucurus , D. montanus , D. nicobaricus , D. somsaki , D. smithi , a new species from Batu Gua Madu (Das & Yaakob, 2003) and an undescribed species from Pulau Tioman. The new species differs from D. taylori which shows three postoculars.

The midbody scale row counts of the new species (20) separates it from the following additional species- D. celebensis , 26-30; D. kondaoensis , 23; D. novaeguineae , 22- 26; and D. seramensis , 33. The new species can be distinguished from D. alfredi in showing complete (vs incomplete) nasal suture, preanal pores absent (vs present); and fewer subcaudals in males (33 vs 46-47).

Finally, D. vorisi differs from D. ingeri in showing a relatively slender body (width 3.9 vs 4.7% of SVL); presence of a midbody band (vs a nuchal collar); frontonasal scale entire (vs divided); labial suture absent (vs present), and tail with a cream-coloured tip (vs unicoloured).

Figures

Fig. 2. Head of holotype of Dibamus vorisi, new species (FMNH 230187) in dorsal (top), lateral (middle) and ventral (bottom) views. Scale bars = 5 mm.

Fig. 3. Relief map of Borneo, showing the type localities of Dibamus ingeri, new species, at Mendolong (1) and Dibamus vorisi, new species, at Danum Valley (2), both within Sabah State, East Malaysia.