Bufo exiguus, Qi & Lyu & Song & Wei & Zhong & Wang, 2023

Qi, Shuo, Lyu, Zhi-Tong, Song, Han-Ming, Wei, Shi-Chao, Zhong, Qi-Feng & Wang, Ying-Yong, 2023, A new species of stream-living toad (Anura: Bufonidae: Bufo) from Guangdong, China, Vertebrate Zoology 73, pp. 677-689 : 677

Bufo exiguus sp. nov.

Figures 3 and 4

Chresonymy.

Bufo cryptotympanicus - Fei et al. (2009, 2010): Longmen County; Li et al. (2011): Mt. Nankun, Longmen County. Torrentophryne cryptotympanicus - Fei et al. (2012): Longmen County; Fei and Ye (2016): Longmen County.

Holotype.

SYS a005790 (Fig. 3 ), adult male, collected on 7 May 2017 by Zhi-Tong Lyu (ZTL), Jian Wang (JW) and Hai-Long He (HLH) from Mt. Nankun (23°38'31"N, 113°50'53"E; 564 m a.s.l.), Longmen County, Huizhou City, Guangdong Province, China.

Paratypes.

Four adult and one subadult specimens from the same locality as the holotype (500-600 m a.s.l.): adult male CIB 19028 (field number: SYS a003605) collected on 14 April 2015 by ZTL, JW and Run-Lin Li; adult females SYS a005715 (Fig. 4A ) and SYS a005716 (Fig. 4C ) collected on 9 April 2017 by ZTL and JW; adult female SYS a005791 collected on 7 May 2017 by ZTL, JW and HLH; subadult female SYS a005584 (Fig. 4B ) collected on 11 November 2016 by ZTL, JW and Ying-Yong Wang.

Diagnosis.

Bufo exiguus sp. nov. is distinguished from other species in the genus Bufo by a combination of the following morphological characters: (1) small body size (adult males with SVL 43.2-43.3 mm, adult females with SVL 48.5-52.4 mm); (2) tympanum absent; (3) parotoid glands small, olive-shaped; (4) tarsal fold absent; (5) dorsal body with a fine vertebral line; (6) numerous white granular nuptial spinules present on dorsal and inner surfaces of fingers I and II in males.

Etymology.

The specific name exiguus means small in Latin and refers to its small body size. According to their distribution and ecological habit, we suggest the common name as "Guangdong stream toad" and Chinese formal name as "guǎng dōng xī chán” (广东溪蟾).

Description of the holotype.

Adult male (Fig. 3 ), body size small and stubby (SVL 43.3 mm); head width slightly larger than head length (HL/HW = 0.98); snout obtusely acuminate in dorsal review, tip of snout vertical in lateral profile; nostrils closer to tip of snout than to eye; canthus rostralis distinct, internarial distance less than interorbital distance (IND/IOD = 0.79); loreal region slightly concave; eye moderate, diameter larger than interorbital distance (ED/IOD = 1.05), pupil horizontal elliptic; tympanum absent; parotoid glands olive-shaped, parallel in position (PW/PL = 0.51); maxillary and vomerine teeth absent; vocal sacs and splits absent.

Radioulnar length almost equal to hand length (RAD/HND = 1.01); hand without webbing, fingers without lateral fringes, relative finger length I = II <IV <III; tips of fingers round, not enlarged, without toe pads; subarticular tubercles prominent, rounded and not divided, present in each phalangeal joint; inner metacarpal tubercle long oval and prominent, lying at the base of finger I; outer metatarsal tubercle rounded, indistinct, boundary unclear; nuptial pad on the medial dorsal surface of the first and second fingers, bearing numerous white granular nuptial spinules.

Hind-limbs short and stout, tibio-tarsal articulation reaching middle point of parotoid gland when hind-limb stretched alongside the body; heels not meeting when flexed hind-limbs held at right angles to body axis; tibia length 0.40 of SVL and foot length 0.60 of SVL; relative toe length I <II <V <III <IV; tips of toes round, not dilated; toes with lateral fringes and with one third webbing, webbing formula I0-1+-II0 - 1-III1-2-IV2-- ½ V; subarticular tubercles rounded, not divided; inner and outer metatarsal tubercle ovoid, the former being much larger than the latter; tarsal fold absent.

Dorsal surface of head and body relatively smooth, all the tubercles and granules without horny spinules; a few rounded tubercles and granules scattered on dorsum, especially in the region between parotoid glands, without large warts. Loreal region relatively smooth, only with a few flat granules; some small tubercles and granules present in temporal region, two larger tubercles at the mandibular articulation; flanks relatively smooth, only with a few granules; dorsal surfaces of limbs relatively smooth, fore-limbs only with small granules, hind-limbs with small granules, some large flat tubercles scattered on dorsal surfaces of tibia; ventral surfaces of head and body wrinkled, with scattered small granules; ventral surfaces of hands and feet with a few flat tubercles.

Colouration of holotype in preservative.

Dorsal ground colour of head and body faded to greyish-brown; a dark brown “V” -shaped marking between eyes, two "inverted V"-shaped markings on the back of body; an indistinct thin vertebral line running from the snout to the upper part of the vent; dorsal surface of limbs greyish-brown, a dark brown band on forearm, some blurry blotches in upper arm, several distinct dark brown bands on femur, tibia and tarsus. Some dark brown blotches on the edge of the lips and mandibular articulation; a dark brown stripe from the nare across lower part of parotoid gland, extending to the groin. Ventral surface of throat and chest brown with a few blurry spots and worm-like markings; ventral surface of body pale yellow with dark brown worm-like markings, many markings agglomerating into a large blotch in the centre of the belly; ventral surfaces of limbs pale yellow, with dark brown spots and worm-like markings; ventral surface of hands and feet dark brown, tips of digits, subarticular tubercles and metatarsal tubercles fading to pale white.

Morphological variation.

Measurements of all individuals are given in Table 3 and the aspects of three female paratypes are given in Figure 4 .

Adult females are larger than males, SSDi = 0.84. Both males have nuptial pads on the dorsal surfaces of the first and second fingers, bearing granular white nuptial spinules. All the paratypes share similar aspects with the holotype in general, apart from the following differences. The relative finger length I <II <IV <III in four paratypes (CIB 19028, SYS a005584, 5715 and 5716); tibio-tarsal articulation reaching to the posterior edge of the parotoid gland when the hind-limb is stretched alongside the body in SYS a005791. Besides, based on existing specimens, the females have rougher skin texture than males, dorsal surfaces of head and body with many rounded tubercles and granules, but all the tubercles and granules are without horny spinules; in the loreal region and temporal region, small tubercles and granules, two or three larger tubercles at the mandibular articulation are present; dorsal surfaces of limbs rough, fore-limbs with many small granules, hind-limbs with small granules and tubercles, some large tubercles scattered on dorsal surfaces of tibia; ventral surfaces of hands and feet with multiple flat tubercles.

As the general aspect of colouration of the holotype in life is not available, we describe the colouration of three female paratypes in life below.

All female paratypes share similar colouration in life. The dorsal surface of the head and body brown or yellowish-brown with a few separated dark brown and rusty red blotches; a dark brown “V” -shaped or inverted hollow triangularly-shaped marking between eyes, two "inverted V"-shaped markings on the back of body; a thin vertebral line running from the snout to the upper part of the vent. Dorsal surface of limbs have the same colour as the dorsal surface of the body, a distinct dark brown band on forearm, some indistinct blotches on the upper arm, several distinct dark brown bands on the femur, tibia and tarsus (rusty red blotches scattered on the limbs in SYS a005584). Some dark brown blotches on the edge of the lips and mandibular articulation; a dark brown stripe from the nares across the lower part of parotoid glands and flanks, extending to the groin (stripe discontinuous in the flanks in SYS a005716). Ventral surface of throat and chest light brown with a few darker spots and worm-like markings; ventral surface of body white with many dark brown worm-like markings, mostly in the centre of the belly; ventral surfaces of limbs showing the same colour as the ventral surface of the body, with dark brown spots and worm-like markings; ventral surface of hands and feet greyish-brown, tips of digits, subarticular tubercles and metatarsal tubercles faintly white. Pupil black; iris golden with black reticular markings, black blotches in four directions.

Comparisons.

Bufo exiguus sp. nov. are distinctly different from all other recognised congeners by having a relatively small body size, SVL <50 mm in adult males and <60 mm in adult females (vs. SVL> 50 mm in adult males in B. andrewsi , B. aspinius , B. bankorensis , B. bufo , B. cryptotympanicus , B. eichwaldi , B. formosus , B. gargarizans , B. luchunnicus , B. menglianus , B. minshanicus , B. pageoti , B. praetextatus , B. spinosus , B. stejnegeri , B. tibetanus , B. torrenticola , B. tuberculatus , B. tuberospinius , B. verrucosissimus , B. yongdeensis and B. yunlingensis ; SVL> 60 mm in adult females in B. andrewsi , B. aspinius , B. bankorensis , B. bufo , B. eichwaldi , B. formosus , B. gargarizans , B. menglianus , B. minshanicus , B. pageoti , B. praetextatus , B. spinosus , B. tibetanus , B. torrenticola , B. tuberospinius , B. verrucosissimus , B. yongdeensis and B. yunlingensis ), tympanum absent (vs. present in B. andrewsi , B. bankorensis , B. bufo , B. eichwaldi , B. formosus , B. gargarizans , B. menglianus , B. minshanicus , B. praetextatus , B. sachalinensis , B. spinosus , B. tibetanus , B. torrenticola , B. tuberculatus , B. verrucosissimus and B. yunlingensis ), tarsal fold absent (vs. present in B. andrewsi , B. luchunnicus , B. pageoti , B. sachalinensis , B. stejnegeri , B. tibetanus , B. tuberculatus , B. tuberospinius and B. yunlingensis ) and presence of a thin vertebral line (vs. absent in B. ailaoanus , B. bufo , B. eichwaldi , B. formosus , B. minshanicus , B. sachalinensis , B. spinosus , B. torrenticola , B. tuberculatus and B. verrucosissimus ). Comparative data of Bufo exiguus sp. nov. with other recognised members of the genus Bufo are listed in Table 4 .

Distribution and natural history.

The new species is currently only known from the type locality, Mt. Nankun, Longmen County, Huizhou City, Guangdong Province, China. However, another two historic records (Heyuan City and Shaoguan City), designated as B. cryptotympanicus from Guangdong Province, are worthy of careful re-examination (Fig. 1 ).

This species inhabits slow-flowing montane streams, generally surrounded by evergreen and deciduous broadleaved mixed forest, at elevations of 500-600 m a.s.l. All mature individuals were observed at night after rain in April and May. Both males possessed nuptial spinules, but no eggs were observed in the adult female’s oviduct by dissection, suggesting their breeding season should be earlier than April. Nevertheless, the tadpoles and most of the other ecology and types of behaviour of this toad remain unknown.

Figures

Figure 1. Geographic distribution of Bufo exiguus sp. nov. and B. cryptotympanicus. "? " indicates the unconfirmed historic record of B. cryptotympanicus in Guangdong Province, China.

Figure 3. Morphological features of the adult male holotype SYS a 005790 of Bufo exiguus sp. nov. in preservative. A dorsal; B ventral; C close-up of head; D dorsal view of right hand; E ventral view of left hand; F ventral view of left foot. Photos by Shuo Qi.

Figure 4. Paratypes of Bufo exiguus sp. nov. in life. A 1 adult female SYS a 005715, dorsolateral view; A 2 adult female SYS a 005715, ventral view; A 3 adult female SYS a 005715, ventral view of left hand; A 4 adult female SYS a 005715, ventral view of right foot; B subadult female SYS a 005584; C adult female SYS a 005716. Photos by Lyu Zhi-Tong (A, B) and Jian Wang (C).