Ansonia infernalis, Suwannapoom & Grismer & Pawangkhanant & Poyarkov, 2022

Suwannapoom, Chatmongkon, Grismer, L. Lee, Pawangkhanant, Parinya & Poyarkov, Nikolay A., 2022, A new species of stream toad of the genus Ansonia Stoliczka, 1870 (Anura: Bufonidae) from Nakhon Si Thammarat Range in southern Thailand, Zootaxa 5168 (2), pp. 119-136 : 127-131

Ansonia infernalis sp. nov.

Suggested Common Name: Infernal Stream Toad (English), คางคกห้วยนรก (Kang Kok Huay Narok) (Thai). Figures 3–5

Holotype. AUP-00327, an adult male collected on 28 May 2018 along a forest stream within lowland evergreen forest at Thungsong , Thungsong District, Nakhon Si Thammarat Province, Thailand (N 8.2703°, E 99.6883°; 305 m a.s.l. in elevation) by Parinya Pawangkhanant and Thanawut Worranuch ( Fig. 3A–C ).

Paratypes (n=2).AUP-00328–29, two adult females with same collection information as holotype ( Fig. 4A–B ).

Diagnosis. Ansonia infernalis sp. nov. is recognized as a member of the genus Ansonia based on the results of the molecular phylogenetic analyses that recover it as the sister species of clade of eight other species of Ansonia from north of the Isthmus of Kra ( Figs 1 , 2A ) as well as by a combination of the following morphological characters: moderate body size (maximum SVL 24.5 mm in the male and 29.1 mm in females); absence of parotoid glands; long slender limbs bearing long slender digits with bulbous tips form small adhesive pads; weak subarticular tubercles; and membranous foot webbing ( Chan et al. 2014; Grismer et al. 2016; Inger 1960, 1966, 1992; Wilkinson et al. 2012; Quah et al. 2019). It can be differentiated from all congeners by the following combination of characters: maximum SVL in males 24.5 mm and females 29.1 mm; snout projecting beyond lower jaw; vocal sac opens on right side; tympanum visible; no interorbital ridges; dorsal tubercles present; dorsolateral row of enlarged tubercles present but none on back; spiny tubercles on dorsum and flanks; abdomen coarsely granular; submandibular tubercles present; no oblique flaps of skin bordering vent; finger and toe tips bulbous, slightly dilated, forming weak discs; first finger shorter than second; approximately three phalanges free of web on fourth toe and two phalanges free of web on fifth toe; inner and outer metatarsal tubercles present; no tarsal ridges; no light-colored streaks on canthus rostralis; light-colored patch below eye; yellow rictal tubercle at angle of jaw; no white postorbital patch; iris black with gold flecks; no light-colored vertebral stripe; dorsum black, lacking an X-shaped marking surrounding interscapular spot; no dark-colored markings on rump; no dark dorsolateral stripe; no distinct, red-tipped, dorsal tubercles; light-colored, interscapular spot; fore- and hind limbs bearing irregularly shaped, light-colored crossbars; large, discrete, white, submandibular spots; gular spotting/blotching present; venter and undersides of limbs black bearing thick, white reticulations; palmar surfaces of hands and thenar surfaces of feet reddish-orange in life.

Description of holotype ( Fig. 3 ). Adult male, SVL 24.5 mm ( Fig. 3 ); head longer than wide (HL/HW=1.14); snout shorter than wide (SL/SW=0.84), projecting beyond lower jaw, weakly tuberculate, truncate in dorsal view, truncate and sloping in lateral view ( Fig. 3B ); canthus rostralis distinct, lores vertical, flat; nares open anterolaterally just below canthus, located much closer to end of snout than to eye; keratinized submandibular spinules present; distance between nares smaller than snout length (IND/SL=0.71) and snout width (IND/SW=0.59); eyes large, protruding beyond upper jaws in ventral view ( Fig. 3C ), diameter less than snout length (ED/SL=0.87) and interorbital distance (ED/IOD=1.08); pupils horizontal; interorbital region flat, weakly tuberculate, distance smaller than snout width (IOD/SW=0.68) and snout length (IOD/SL=0.81); tympanum distinct, suboval, taller than wide ( Fig. 3 ), horizontal axis less than eye diameter (TD/ED=0.70); choanae subcircular, separated by a distance larger than their diameter; vomerine ridges and teeth absent; tongue narrow, ending in median point, posterior one-half free.

Forelimbs and fingers long and slender (HAL/SVL=0.26; FLL/SVL=0.70); finger length from shortest to longest: I<II<IV<III; basal webbing not extending beyond proximal subarticular tubercle; fingertips bulbous, slightly dilated not forming discs; subarticular tubercles indistinct; inner and outer metacarpal tubercles weak, oval, slightly raised, inner smaller than outer. Hind limbs and toes long and slender (FL/SVL=0.32; HLL/SVL 1.65), toe length from shortest to longest: I<II<V<III<IV; toes with lateral dermal fringes continuing up to the toe tips; webbing formula: I 0.5–0.5 II 0.5–2 III 1.5–3.5 IV 3.5–1 V; toe tips bulbous, not forming discs; subarticular tubercles indistinct; inner metatarsal tubercle small, oval, slightly raised; outer metatarsal tubercle raised, rounded, somewhat smaller than inner (OMTL/IMTL=0.91). Upper eyelid, interorbital region, dorsal part of snout and canthus covered with numerous small and larger tubercles; no bony interorbital ridges; single row of small spinules on upper lip and outer margin of upper eyelid; single enlarged rictal tubercle; no supratympanic folds or parotoid glands; dorsum, flanks, and dorsal surfaces of limbs bearing irregularly spaced, large and small tubercles most of which have brown keratinized spinules, some larger tubercles have more than one spinule; concentration of larger tubercles above tympanum and in scapular region forming an indistinct dorsolateral row extending to insertion of hind limbs; series of brown conical, keratinized tubercles along edges of underside of mandible, absent in gular region; abdomen coarsely granular; all ventral surfaces except for manus and pes covered with coarse, evenly spaced, rounded glandular tubercles.

Coloration in life ( Fig. 3 ). Dorsal surfaces of limbs and lower flanks flushed with orange coloration. Top of head black; dorsum and flanks black, punctuated with widely spaced, red-tipped tubercles; round, darkly mottled, orange, insterscapular spot; forelimbs bearing irregularly shaped, light-colored orange bands, most prominent on brachia; top of manus and fingers orange with faded dark mottling; orange, irregularly shaped bands on hind limbs; orange patch on ankles; large, white, widely spaced, submandibular blotches; gular region, abdomen, and undersides of limbs grey large white blotches; and bottoms of manus, pes and digits bright-orange.

Variation ( Table 4 ). The female paratypes approach the male holotype in all aspects of coloration ( Fig. 4 ). They are larger than the males (29.1 mm vs 24.5 mm) and have fewer keratinized submandibular spinules present.

Distribution. Ansonia infernalis sp. nov. is currently known from the type locality in Thungsong, Thungsong District, Nakhon Si Thammarat Province, Thailand ( Fig. 1 ) and from the adjacent Ron Phibun District, Nakhon Si Thammarat Province, Thailand, based on a photographic record. The two localities are separated by ca. 15 km straight-line distance and are located on the western and eastern slopes of the Nakhon Si Thammarat Mountain Range, respectively.

Natural history. The type series was collected at night between 2000–2330 h along a small rocky stream in degraded tropical lowland forest adjacent to an agricultural area. During our surveys in Thungsong and Ron Phibun districts of Nakhon Si Thammarat Provice, we recorded the new species from elevations of 300–900 m a.s.l. The microhabitat of the new species represents a small stream ca. 1–2 m wide with numerous large rocks forming small cascades of water. The tropical forest is dominated by two Dipterocarpus spp. species, Parashorea stellata Kurz , Anisoptera scaphula (Roxb.) Pierre , and Macaranga triloba (Thunb.) Müll. Arg. During the evening, specimens were observed to slowly move along the stream or call while perched on stones and leaves near the water ( Fig. 5 ). During the day, (1200–1500 h), adults were observed sitting on rocks near the stream. Adults were recorded at the type locality from May to June but during our survey in September 2018, we did not observe any specimens. We have observed similar apparent seasonal activity patterns in A. malayana Inger , A. tiomanica Hendrickson , and A. smeagol Davis, Grismer, Klabacka, Muin, Quah, Anuar, Wood & Sites in Peninsular Malaysia.

Species of amphibians and reptiles recorded in sympatry with Ansonia infernalis sp. nov. at the type locality include Rhacophorus rhodopus Liu & Hu , Theloderma horridum (Boulenger) , Phrynoidis asper (Gravenhorst) , Limnonectes blythii (Boulenger) , Cyrtodactylus lekaguli Grismer, Wood, Quah, Anuar, Muin, Sumontha, Ahmad, Bauer, Wangkulangkul, Grismer & Pauwels , and Cnemaspis lineatubercularis Ampai, Wood, Stuart & Aowphol. Diet , reproductive biology, larval morphology, and other aspects of the natural history of the new species remain unknown.

Etymology. The specific name “ infernalis ” is a Latin adjective meaning “infernal”, “hellish”, and “lower”. The specific name of the new species is in reference to the bright reddish orange coloration of the limbs and flanks that resemble the flames of hell, and also to the low elevation on which the new species can be found.

Comparisons ( Fig. 2 ; Table 1 ). Ansonia infernalis sp. nov. is clearly separated from all other Ansonia by not being the stem lineage of the Thai-Burmese clade and not phylogenetically nested within any other species and bearing a 5.6–10.1% sequence divergence between it and other species in the Thai-Malay clade. However, having only one adult male and two adult females makes a morphological diagnosis tentative. Additional specimens may render some character states not diagnostic or it may prove that they are. At this point female A. infernalis sp. nov. can be separated from all species of the Thai-Burmese clade except for A. karen and A. khaochangensis by being larger than A. inthanon , A. kyaiktiyoensis , and A. pilokensis (29.1 mm vs 23.3–25.4 mm, collectively), and smaller than A. khaochangensis , A. siamensis , and A. thinthinae (29.1 mm vs 32.2–35.3 mm). It is potentially different from all Thai-Burmese species by having a black iris with gold flecks. It differs from various combinations of Thai-Burmese species based on various combinations of toe webbing. Other potentially diagnostic characters that have proven useful in differentiating species of Ansonia from one another (e.g. Suwannapoom et al. 2021; Quah et al. 2019) are presented in Table 1 .

Figures

FIGURE 1. Distribution of the species of the Thai-Burmese clade of Ansonia.

FIGURE 2. A. Maximum Likelihood and Bayesian Inference topologies of Ansonia based on 2453 bp of concatenated 12S and 16S ribosomal DNA.Ancestral nodes for all species are supported by a UFB and BPP of 100 and 1.00, respectively. Blue circles denote backbone nodes with 1.00/100 nodal support. Green circle denotes backbone nodes with only a BPP of 1.00. Unannotated backbone nodes are only weakly supported (UFB and BPP <95/0.95). B. PCA of selected members of the Thai-Burmese clade of Ansonia for which complete adjusted mensural data sets were available. C. Bar graph of uncorrected pairwise sequence divergence of the Thai-Burmese Ansonia species from A. infernalis sp. nov. based on 477 base pairs of 16S RNA.

FIGURE 3. Male holotype (AUP-00327) of Ansonia infernalis sp. nov. A. Dorsolateral view. B. Lateral view. C. Ventral view. Photographs by Parinya Pawangkhanant.

FIGURE 4. Female paratype (AUP-00328) of Ansonia infernalis sp. nov. A. Lateral view. B. Ventral view. Photographs by Parinya Pawangkhanant.

FIGURE 5. Natural habitat of Ansonia infernalis sp. nov. A and B. Microhabitat at the type locality in Thungsong District, Nakhon Si Thammarat Provice, Thailand. C–D. Male (not collected) in situ at the type locality. E. Male (not collected) in ventral view at Ron Phibun District, Nakhon Si Thammarat Provice, Thailand. F. Female (not collected) in situ in dorsolateral view at Ron Phibun District, Nakhon Si Thammarat Provice, Thailand. Photographs by Parinya Pawangkhanant.