Sunday, August 22, 2021

[Herpetology • 2021] Phrynoglossus swanbornorum • A New Species of Phrynoglossus Peters, 1867 (Anura: Dicroglossidae) from southeastern Bangladesh, with Comments on the Genera Occidozyga and Phrynoglossus

Phrynoglossus swanbornorum
Trageser​, Al-Razi​, Maria, Nobel, Asaduzzaman & Rahman, 2021

We describe a new cryptic species of Phrynoglossus from Chattogram Division, Bangladesh based on an integrative taxonomic analysis based on morphology, phylogenetics, and bioacoustics which unambiguously support the placement of the species in the genus Phrynoglossus. We also present a compilation of published morphological characters for all twelve Phrynoglossus species and two species of Occidozyga as well as comments on taxonomy, morphology, and geographic distribution for the two genera. The new species is found to be most morphologically similar to P. martensii, however a provided set of character states visibly differentiates these two species. Finally, habitat for Phrynoglossus swanbornorum sp. nov. is highly fragmented and faces imminent threats from development and agriculture, and although it is confirmed to occur within government protected areas in the southeastern region of Bangladesh, few wildlife regulations are enforced within them. Thus, following IUCN criteria, we consider the new species as Endangered based on criteria B1ab(i,ii,iii,iv) + 2ab(i,ii,iii,iv).

Figure 3:  Phrynoglossus swanbornorum sp. nov.
live holotype JnUZool-A0719.

Figure 5: Phrynoglossus swanbornorum sp. nov. individuals, in life.
(A) Individual 1 with diamond shaped pupil (B) individual 1 with ovoid shaped pupil
(C) individual 2 exhibiting no dorsolateral line (D) individual 1 exhibiting dorsolateral line.

Phrynoglossus swanbornorum sp. nov.
Recommended vernacular name. English: Swanborn’s Puddle Frog. 
Bangla: “Chattgai ar gata bang,” which translates to
English as “puddle frog from Chattogram.”

Generic placement. The new species is assigned to the genus Phrynoglossus based on the following combination of shared adult characters: lacking vomerine teeth and exhibiting a stocky habitus, flattened snout, dorsum or flanks with scattered tubercles, short arms, nuptial pads, horizontal pupils, bony style, forked omosternum, pigmented eggs, distinct or indistinct supratympanic fold, reduced to absent metacarpal webbing, moderate to extensive metatarsal webbing, an elongated inner metatarsal tubercle, indistinct and small tympanum, feebly to moderately developed toes discs, SVL between 15 mm and 61.6 mm in length, and females are larger than males. These adult characters agree with previous descriptions of the genus (see discussion; Taylor, 1962; Iskandar, 1998; Sailo et al., 2009; Inger et al., 2017; Poyarkov et al., 2020; Köhler et al., 2021). Larval characters are unknown.

Diagnosis. The new species presents the following characteristics: (1) relatively small sized Phrynoglossus (adult males = 23.15–28.56 mm SVL, adult female = 30.56 mm); (2) stocky habitus; (3) short arms relative to body size (FLL/SVL 0.19%; range 0.18−0.20%, n = 5); (4) head wider than long (HL/HW 0.73%; range 0.69−0.77%, n = 5); (5) snout slightly projecting, triangular in ventral aspect, smaller than horizontal diameter of eye, and flat in lateral aspect; (6) nostril closer to tip of snout than to eye (NS 0.48−0.51 mm, EN 0.92–109 mm); (7) brown dorsum transitioning to brownish grey on flanks with black speckling concentrated around scattered tubercles, nares, mouth, and above eyes; (8) venter uniform cream white, becoming brown with white mottling and groups of minute dark-grey flecks present in the gular region; (9) tuberculate dorsum; (10) laterally oriented eyes and nares; (11) horizontal pupils; (12) vomerine teeth absent; (13) tongue rounded without notch behind; (14) vocal sac single, median, internal, and subgular in males; (15) canthus rostralis rounded; (16) tympanum indistinct, small, and rounded; (17) supratympanic fold distinct and transverses interorbitally at the posterior edge of the eye; (18) fingertips rounded without discs; (19) nuptial pads present in males; (20) palmar tubercles present; (21) metacarpal webbing absent; (22) toe discs feebly developed; (23) inner metatarsal tubercle elongated and compressed, present at base of 1st toe; (24) fringe of skin on outer side of fifth metatarsal absent; (25) tarsal tubercle absent; (26) tarsal fold absent; (27) metatarsal webbing moderate; and (28) lateral line absent. Details of these characteristics are provided in Table 3.

Etymology. The specific patronym epithet “swanbornorum” is in genitive plural and refers to members of the Swanborn family, who are generous supporters of the conservation efforts of the Creative Conservation Alliance.

Distribution. Phrynoglossus swanbornorum sp. nov. is currently only confirmed to occur within the Chunati Wildlife Sanctuary (21.937533 N, 92.063010 E), Chattogram District at an elevation of ca. 33 m and Teknaf Wildlife Sanctuary (20.887020 N, 92.298954 E), Cox’s Bazar District at an elevation of ca. 26 m (Fig. 1).

Natural history: Phrynoglossus swanbornorum sp. nov. is only known to inhabit lowland, coastal, mixed-evergreen forests of southeast Bangladesh, which are bounded to the east by the mountainous Chattogram Hill Tracts. Within this habitat, Phrynoglossus swanbornorum sp. nov. has only been observed near lentic water bodies under dense forest canopy and was notably absent from surrounding agricultural fields and degraded forest. An image of P. swanbornorum sp. nov. in amplexus (see Distribution; Ahm, 2014) demonstrates that this species exhibits inguinal amplexus. Additionally, eggs from the single collected female were pigmented.

Figure 6: Type localities of all 14 species of Occidozyga and Phrynoglossus species.

We provide morphological, molecular, and bioacoustic evidence that support the validity of the new species, Phrynoglossus swanbornorum sp. nov. This species is currently only confirmed from a relatively small area in southeastern Bangladesh and is considered to have a high risk of extinction due to conspicuous and ongoing threats to the habitat it relies on. We also review and discuss inconsistencies in the literature regarding the genera Phrynoglossus and Occidozyga, particularly that of morphological characters and provide more accurate generic diagnoses for both.

Although multiple species of Phrynoglossus and Occidozyga are generally perceived to be widespread and common, this study adds to a growing body of literature demonstrating the existence of undescribed diversity within the genus, thereby masking the true extinction risk of these species (Mulcahy et al., 2018). We suggest further research be conducted to either rectify incongruent descriptions of diagnostic characters and/or better understand intraspecific variation within the genus as well as including additional nuclear genetic data. Doing so could result in further refinement of the provided generic diagnoses. We also suggest that further surveys be conducted in the northern part of Chattogram Hill Tracts, Bangladesh e.g., Pablakhali Wildlife Sanctuary and Kassalong Reserve Forest, and throughout Rakhine State, Myanmar to better understand the distribution of Phrynoglossus swanbornorum sp. nov.

Scott Trageser​, Hassan Al-Razi​, Marjan Maria, Fahimuzzaman Nobel, Md. Asaduzzaman and Shahriar Caesar Rahman. 2021. A New Species of Phrynoglossus Peters, 1867; Dicroglossidae) from southeastern Bangladesh, with Comments on the Genera Occidozyga and PhrynoglossusPeerJ. 9:e11998. DOI: 10.7717/peerj.11998