Amolops attiguus, Sheridan & Phimmachak & Sivongxay & Stuart, 2023

Sheridan, Jennifer A., Phimmachak, Somphouthone, Sivongxay, Niane & Stuart, Bryan L., 2023, Systematics of the Lao torrent frog, Amolops cremnobatus Inger & Kottelat, 1998 (Anura: Ranidae), with descriptions of four new species, Vertebrate Zoology 73, pp. 931-956 : 931

Amolops attiguus sp. nov.

Figure 12 "Clade E"

Holotype.

NCSM 80907 (field number BLS 15852), adult male, Laos, Bolikhamxay Province, Viengthong District, Nam Kading National Protected Area, Nam Xouang, 18.42676°N, 104.39136°E, 343 m elev., coll. 2200 h on wet rock face next to series of waterfalls over exposed sandstone bedrock with potholes on 1 March 2013 by Bryan L. Stuart, Jennifer A. Sheridan, Sengvilay Seateun, and Niane Sivongxay.

Paratypes.

Laos, Xieng Khouang, Mork District, tributary of Nam Mork: NCSM 80761 (one adult male), 19.07075°N, 103.95870°E, 454 m elev., coll. 12 April 2012 by Somphouthone Phimmachak. - Vietnam, Nghe An Province, Anh Son District, Pu Mat National Park, Cao Ven: AMNH A 191846 (one adult male), 18.81050°N, 104.95150°E, 273 m elev., coll. 16 May 2010 by David A. Kizirian, Truong Quang Nguyen, and Sinh Van Nguyen; AMNH A 191848 (one adult male), AMNH A 191849, NCSM 79166 (two adult females), coll. 18 May 2010 by David A. Kizirian, Truong Quang Nguyen, and Sinh Van Nguyen.

Etymology.

The specific epithet taken from attigua (L.) for neighboring or adjacent, in reference to the new species’ nested geographic distribution between its morphologically similar relatives A. tanfuilianae sp. nov. and A. kottelati sp. nov. (Fig. 1 ).

Suggested Common Names.

Similar Lao torrent frog (English), ຂຽດເກາະຜາລາວແອດທ ີກຸສ (Khiat Korpha Lao Sumphan; Lao).

Diagnosis.

A member of the Amolops larutensis group having the combination of 2-3 vomerine teeth, sometimes faint or absent; relative finger lengths I <IV<II <III; mean ± SE SVL of adult males 30.2 ± 0.9 mm (range 28.9-31.3 mm; n = 5) and of females 39.2-39.4 mm (n = 2); EYE 4.7 ± 0.3 mm (range 4.1-4.8 mm) in males and 5.3-6.1 mm in females; TEY 0.7 ± 0.1 mm (range 0.5-0.9 mm) in males and 1.1-1.3 mm in females; SNT 4.1 ± 0.1 mm (range 4.5-4.7 mm) in males and 5.4-5.5 mm in females; and FTL 15.8 ± 0.7 mm (range 15.0-16.8 mm) in males and 18.6-18.7mm in females.

Description of the holotype.

Habitus moderately slender. Head length subequal to head width. Snout weakly pointed in dorsal view. Snout projecting slightly beyond lower jaw in lateral view, sloping obliquely back to lip. Nostril lateral, nearer to tip of snout than to eye. Canthus rostralis distinct. Lores obliquely and slightly concave. Eye diameter approximately equal to snout. No pineal body visible. Tympanum distinct, round, approximately one-third of eye diameter, slightly depressed relative to skin of temporal region, tympanic rim elevated relative to tympanum. Rictal glands slightly oval and pronounced. Vomerine teeth obliquely angled, closer to each other than to choanae, and extremely small, with 2-3 teeth each. Tongue cordiform, notched posteriorly. Vocal slit opening near corner of jaw. No gular pouch, but with some extra skin at edge of jaw.

Forelimb moderately slender. Tips of all four fingers expanded into wide discs with circummarginal grooves. Fingers slender. Relative finger lengths I <IV<II <III. Minimal basal webbing on hands. Subarticular tubercles conspicuous, surfaces rounded, formula 1, 1, 2, 2. One supernumary tubercle at base of fingers 2-4. Irregularly-shaped palmar and oval thenar tubercles present. Well-developed nuptial pad on Finger I, on dorsal surface to level of distal end of subarticular tubercle.

Hindlimbs moderately long and slender. Toes slender. Tips of toes expanded into wide discs with circummarginal grooves. Web on all toes to base of disc. Subarticular tubercles conspicuous, surfaces rounded, formula 1, 1, 2, 2, 2. Inner metatarsal tubercle oval. No outer metatarsal tubercle. Discs of toes smaller than that of finger, but larger than or equal to that of outermost finger. Outermost toe disc slightly wider than toe. Widest toe disc narrower than all finger discs except for that of thumb. Subarticular tubercles conspicuous, surfaces rounded; formula 1, 1, 2, 2, 2. Inner metatarsal tubercle oval; outer metatarsal tubercle barely visible, small, round.

Dorsal surface with weakly spinose glands. No supra-tympanic fold. Glandular dorsolateral fold. Flanks glandular. Spinose glands behind tympanum above arm. Glands around vent. Ventral surfaces weakly granular.

Measurements of holotype (mm): SVL 30.4, HDL 10.3, HDW 11.0, SNT 4.7, EYE 4.6, IOD 3.2, IND 3.6, TMP 1.7, TEY 0.8, SHK 19.1, TGH 17.2, HND 9.7, FTL 16.8.

Coloration.

In preservative, dorsal coloration black-brown with paler markings. Pale bars on dorsal surface of thighs and arms. Posterior surface of thighs with irregular pale mottling or reticulation on dark surface. Ventral surfaces cream with very fine dark mottling. Ventral surface of feet dark grey-brown, ventral surface of hands dark beige.

In life (from photos of NCSM 80906, Fig. 1 ), dorsal surface greenish-grey with bright green markings. Dorsal surface of legs paler in color than dorsum. Eye mottled gray on lower one-third, mottled yellowish on upper one-third, with orange on anterior and posterior portions. No ventral photos exist for this specimen in life, but photos of this species recently euthanized (NCSM 80907, Fig. 12 ) show chin and chest to be creamy white with dark mottling, belly to be white with very fine mottling, and underside of arms and thighs to be translucent.

Sexual dimorphism.

Males (n = 5) differ from females (n = 2) in being smaller (30.2 ± 0.9 mm SVL vs 39.2-39.4 mm; Table 1 ), and in possessing paired vocal slits and distinct nuptial pads at base of first finger.

Variation.

Pineal body distinguishable in NCSM 80761, and clear and obvious in AMNH A 191845, 191846, 191848, and 191849, but not apparent in NCSM 79166. Rictal glands indistinct, bordering on absent in all paratypes. Vomerine teeth totally absent in AMNH A 191847; almost absent in AMNH A 191846 and A 191848; extremely small in NCSM 80761, and a bit more prominent in AMNH A 191845. Females have oval thenar tubercle. Outermost toe disc variable: in some individuals it is barely wider than toe, but in others appears wider.

Male AMNH A 191845 very slightly spinose. Dorsal surface of females glandular but not spinose. Glandular dorsolateral fold weak in females and in AMNH A 191845, 191846, and 191848. Spinose glands behind tympanum above arm, and in NCSM 79166 (female), coming down to skin in front of arm, though this feature is absent in AMNH A 191845, 191846, and 191848. In NCSM 79166, the pale dorsal markings are extremely sparse, giving the frog a dark appearance overall with few markings, while in the others, the dorsal surfaces are much more mottled with the paler markings. Pale bars on dorsal surface of thighs and arms less apparent in NCSM 79166 than in other individuals. Ventral coloration of NCSM 79166 creamy on the belly, and white on chin and chest with dark mottling. AMNH specimens A 191845, 19148, and 19149 have white chin and chest with yellow-cream belly (no dark mottling). AMNH A 19146 has white chin and chest with some dark mottling, and yellow-cream belly. Ventral surfaces of feet are dark brown to black, and ventral surfaces of hands are dark beige to black.

Distribution and natural history.

This species is known from clear streams with torrents in eastern Bolikhamxay and Xieng Khouang Provinces of northern Laos and southern Nghe An Province of northern Vietnam. Larvae of the new species remain unknown.

Comparisons.

Amolops attiguus sp. nov. differs from A. tanfuilianae sp. nov. and A. kottelati sp. nov. by having a smaller number (2-3) of vomerine teeth (3-4 in A. tanfuilianae sp. nov. and A. kottelati sp. nov.). Amolops attiguus sp. nov. differs from A. cremnobatus and further differs from A. tanfuilianae sp. nov. by having relative finger lengths I<IV<II<III (I<II<IV<III in A. cremnobatus and A. tanfuilianae sp. nov.). Amolops attiguus sp. nov. further differs from A. sengae sp. nov. by having spinose glands above the arm usually present (absent in A. sengae sp. nov.). Amolops attiguus sp. nov. further differs from A. cremnobatus and A. sengae sp. nov. by having larger EYE and smaller TEY (Fig. 11 ). Amolops attiguus sp. nov. further differs from A. sengae sp. nov. by having smaller SNT and FTL (Fig. 11 ).

Figures

Figure 1. Map of specimen sampling locations of Amolops cremnobatus (orange stars), A. tanfuilianae sp. nov. (blue circles), A. sengae sp. nov. (green diamonds), A. kottelati sp. nov. (red triangles), and A. attiguus sp. nov. (purple squares). Filled symbols are adults and open symbols are tadpoles. Symbols with black dots are sequenced individuals, and symbols without black dots are unsequenced individuals. The sample in Thailand is provisionally referred to A. sengae sp. nov. (see text).

Figure 11. Box and whisker plots of measurements (mm) of morphological features of males of Amolops cremnobatus (B; n = 12), A. sengae sp. nov. (C; n = 5), and A. attiguus sp. nov. (E; n = 5). Measurements are snout-vent length (SVL), snout length (SNT), eye diameter (EYE), tympanum-eye distance (TEY), tarsus length (SHK), and foot length (FTL). Boxes show interquartile range and median (thick black line). Whiskers represent range up to 1.5 x interquartile range (IQR); dots show range beyond 1.5 x IQR. Clusters with the same symbol (* and †) are not significantly different, as determined by paired two-tailed t-tests following ANOVA.

Figure 12. Amolops attiguus sp. nov. NCSM 80907 in life (top row) and in preservative (bottom row).