Occidozyga lingnanica Lyu & Wang, 2022

Lyu, Zhi-Tong, Wang, Jian, Zeng, Zhao-Chi, Luo, Lin, Zhang, Yan-Wu, Guo, Chun-Peng, Ren, Jin-Long, Qi, Shuo, Mo, Yun-Ming & Wang, Ying-Yong, 2022, Taxonomic clarifications on the floating frogs (Anura: Dicroglossidae: Occidozyga sensu lato) in southeastern China, Vertebrate Zoology 72, pp. 495-512 : 495

Occidozyga lingnanica Lyu & Wang sp. nov.

Ooeidozyga laevis martensi - Pope 1931; Liu & Hu 1961

Occidozyga martensii - Fei et al. 1990; Zhao & Adler 1993; Li et al. 2011

Phrynoglossus martensii - Fei et al. 2009, 2010, 2012

Type materials.

Holotype. SYS a008846, adult male, collected on 18 July 2021 by Zhi-Tong Lyu from Mt Wugongling (22.5914 N, 114.4927 E), Shenzhen City, Guangdong. Paratypes. Seven adult males and three adult females. Male SYS a008847 CIB 118529, collected at the same time as the holotype; males SYS a005589-90, collected on 15 November 2016 by Zhi-Tong Lyu and Jian Wang from Mt Wugongling; males SYS a007372-7373, and females SYS a07374-7375, collected on 5 September 2018 by Jian Wang and Hong-Hui Chen from Qi’ao Island (22.4140 N, 113.6446 E), Zhuhai City, Guangdong Province, China; female SYS a004650, collected on 14 April 2016 by Jian Wang from Mt Yunkai (22.2786 N, 111.1886 E), Xinyi City, Guangdong; males SYS a007657-7658, collected on 8 April 2019 by Jian Wang from Mt Yunkai.

Other examined specimens.

Five adult males and five adult females. Male SYS a005543 and female SYS a005542, from Mt Jiaoyiling (21.1592 N, 110.3093 E), Zhanjiang City, Guangdong; female SYS a005267, from Mt. Diaoluo (18.6408 N, 109.9317 E), Lingshui Li Autonomous County, Hainan; males SYS a005436-5437, 5440-5441 and females SYS a005438-5439, 5442, from Mt Bawangling (1 9.0944 N, 109.0491 E), Changjiang Li Autonomous County, Hainan.

Etymology.

The specific name Occidozyga lingnanica refers to the lingnan region, a geographic area covering Guangdong, Guangxi, and Hainan in southeastern China, where this new frog species occurs in. This specific name is also dedicated to the former Lingnan University (1888-1952) that was incorporated into Sun Yat-sen University after 1953.

Common name.

"Lingnan floating frog" in English / "岭南浮蛙 (lǐng nán fú wā)” in Chinese.

Diagnosis.

(1) Body stocky, size small, SVL 19.9-22.1 mm in males (n=8) and 26.8-28.8 mm in females (n=3); (2) snout short triangular shaped; (3) nostrils located laterally; (4) eye orientation laterally; (5) canthus rostralis visible, rounded; (6) loreal region vertical, not concave/convex; (7) tongue wide and swollen, unnotched, rounded distally, lingual papilla absent; (8) vomerine ridge and vomerine teeth absent; (9) supratympanic fold distinct and raised, slightly curved on the temporal region; (10) tympanum hidden, edge invisible; (11) relative finger lengths II=I<IV<III, relative toe lengths I<II<V<III<IV; (12) fingers without webs, toes with two third webs; (13) heels not meeting, tibio-tarsal articulation reaching at the posterior margin of supratympanic fold; (14) tarsal fold absent.

Comparisons.

Occidozyga lingnanica sp. nov. has been long-term misidentified as O. martensii , however, it differs from the latter by a combination of the following morphological characters: tympanum hidden, edge invisible (vs. tympanum edge raised), relative finger lengths II=I<IV (vs. II=IV<I), relative toe lengths V<III (vs. III<V), tarsal fold absent (vs. present), tibio-tarsal articulation reaching the posterior margin of supratympanic fold (vs. reaching the region of eye).

Occidozyga lingnanica sp. nov. can be distinguished from the remaining three known congeners in Clade VIII (Fig. 1 ) by the canthus rostralis rounded (vs. absent in O. magnapustulosa ), loreal region oblique, not concave or convex (vs. slight convex in O. magnapustulosa and O. swanbornorum comb. nov.), relative finger lengths II=I<IV (vs. II<IV<I in O. myanhessei comb. nov., IV<II<I in O. swanbornorum comb. nov.), tarsal fold absent (vs. present in O. magnapustulosa and O. myanhessei comb. nov.).

For the remaining 13 congeners, Occidozyga lingnanica sp. nov. distinctly differs from O. lima , O. obscura comb. nov., and O. berbeza by the tongue wide and swollen (vs. narrow and slender); from O. rhacoda by the dorsolateral fold absent (vs. present); from O. shiwandashanensis by the tarsal fold absent (vs. present); from O. celebensis , O. laevis , and O. sumatrana by the eye orientation laterally (vs. vertically); from O. baluensis , O. floresiana , and O. semipalmata by the canthus rostralis rounded (vs. absent); from O. diminutiva and O. tompotika by the supratympanic fold curved (vs. straight).

Description of holotype.

SYS a008846, adult male (Fig. 5 ). Body stocky, small-sized, SVL 21.4 mm. Head longer than wide (HDW/HDL 0.97), plat above; pineal ocellus distinct; snout short triangular shaped, distinctly protruding beyond lower jaw, tip of snout rounded in dorsal view and profile; canthus rostralis rounded, loreal region oblique, not concave or convex; nostril rounded, laterally, not raised, at the middle between tip of snout and eye; eye orientation laterally, pupil diamond shaped; interorbital space distinctly narrower than internarial distance; tympanum hidden, edge invisible; vomerine ridge and teeth absent; tongue wide and swollen, unnotched, rounded distally, lingual papilla absent.

Forelimbs short, lower arm 15% of SVL and hand 25% of SVL; fingers relatively thin and long, relative finger lengths II=I<IV<III; tips of fingers rounded, not dilated and without disks; fingers without webs and fringes; subarticular tubercles present at the bases of each finger, prominent and rounded; supernumerary tubercles absent; inner and outer palmar tubercles prominent and rounded.

Hind limbs robust, tibia 44% of SVL and foot 63% of SVL; heels not meeting when hind limbs flexed at right angles to the axis of the body; tibio-tarsal articulation reaching at the posterior margin of supratympanic fold when hind limb is stretched along the side of the body; toes distinctly long and thin, relative lengths I <II <V <III <IV; tips of toes rounded, dilated into rounded disks; toes with two third webs, metatarsal web present, distinct lateral fringes on lateral edges of toes I and V; subarticular tubercles rounded, prominent; inner metatarsal tubercle large and long-elliptic, distinctly raised, length triple the width; outer metatarsal tubercle absent; tarsal fold absent.

Dorsal surface relatively rough, large tubercles scattering on skin of dorsum, flanks, and dorsal limbs, not bearing spinules on the dorsal skin; a faint fold across head between orbits; supratympanic fold distinct, raised, extending from the posterior corner of the eye, slightly curved on the temporal region, to the previous shoulder; dorsolateral fold absent. Ventral surface with large flattened tubercles; a fold across breast; dense granules on the ventral tarsi.

Coloration of holotype.

In life (Fig. 5 ), dorsal surface grayish brown with irregular black speckles; dorsal limbs with dark brown transverse bars; mid-dorsal stripe yellowish brown but indistinct; a narrow transverse bar between orbits; supratympanic fold dark brown. Pupil bordered with yellow; iris brown with irregular dark or light speckles. Skin of throat dark with white mottling; skin of chest and belly uniform creamy white; ventral surface of limbs grayish pink with dark speckles. Nuptial pad light yellow, slightly transparent.

In preservative, dorsum light gray; black speckles on dorsum and transverse bars on limbs light brown; mid-dorsal stripe grayish white and more distinct; nuptial pad light gray, slightly transparent; ventral surface grayish white; mottling on throat gray white.

Variation.

The measurements of the type series are given in Table 4 . All individuals were similar in morphology. Dorsal coloration varies in life, from light brown, yellowish brown, to dark brown (Figs 5 , 6 ); mid-dorsal stripe varies among individuals, distinct (Figs 4C , 6C ), indistinct (Fig. 5 ), or absent (Figs 4D , 6A, B, D-F ); an irregular orange marking on the occipital region in some individuals (Fig. 6F ).

Male secondary sexual characteristics.

Male with a single subgular vocal sac; in breeding season, a single, light yellow, swollen, and granular nuptial pad on the dorsal surface of finger I, nuptial spinules invisible. Males (SVL 19.9-22.1 mm) distinctly smaller than females (SVL 26.8-28.8 mm) (Fig. 4C, D ).

Ecology.

This frog inhabits natural or artificial ponds and paddy fields in hilly regions. Males call in the water surface or waterside grass from dusk to dawn. The breeding season is from May to August (this study; Fei et al. 2009). In southeastern China, Occidozyga lingnanica sp. nov. shares a similar environment to that of Occidozyga obscura comb. nov., but prefers to hilly regions compared with the latter in plain areas.

Distribution.

Occidozyga lingnanica sp. nov. can be recognized from multiple localities in Guangdong and Hainan of southeastern China based on the phylogenetic result in this work (Figs 1 , 2 ). The records of O. martensi from Yunnan, southwestern China require further clarifications with morphological examinations (see Discussion).

Conservation status.

Occidozyga lingnanica sp. nov. was previously reported as common and widespread species in southeastern China under the nomen O. martensii . Nevertheless, during our repeated surveys throughout southeastern China, the population quantity of this species is found rapidly declining due to the influence of human activities such as pesticide abuse and urban construction. We recommend Occidozyga lingnanica sp. nov. to be listed as Vulnerable (VU) [IUCN Red List criteria B1b(ii)(iii)].

Figures

Figure 1. Phylogenetic trees of the genus Occidozyga sensu lato based on mitochondrial genes 16 S and CO 1. Bayesian posterior probabilities (BPP) and bootstrap supports (BS) are labeled above and below the nodes respectively. Numbers at the terminal of the lineages correspond to the IDs in Table 1.

Figure 2. Map showing the floating frogs Occidozyga obscura comb. nov., Occidozyga lingnanica sp. nov., and their closest congeners. Numbers correspond to the IDs in Table 1.

Figure 4. Morphological features of Occidozyga obscura comb. nov. and Occidozyga lingnanica sp. nov. in preservative. Occidozyga obscura comb. nov.: A adult male SYS a 008121 B adult female SYS a 008122; Occidozyga lingnanica sp. nov.: C adult male paratype SYS a 007373 D adult female paratype SYS a 007375. 1 dorsal view 2 ventral view.

Figure 5. Morphological features of the adult male holotype SYS a 008846 of Occidozyga lingnanica sp. nov. in life. A dorsolateral view B ventral view C left hand D right foot E dorsal view of right hand showing the nuptial pad F calling in situ showing the subgular vocal sac.

Figure 6. Color variation of Occidozyga lingnanica sp. nov. in life. A adult male paratype SYS a 008847 B adult female paratype SYS a 004650 C adult male paratype SYS a 007373 D adult female paratype SYS a 007375 E adult male SYS a 005437 F adult male SYS a 005440.