Kaloula baleata [partim]—Orlov et al. (2002: 99); Nguyen et al. (2005: 43); Orlov and Ananjeva (2007: 148); Nguyen et al. (2009: 94).

Kaloula indochinensis [partim]—Chan et al. (2013: 334, 2014: 577); Chandramouli and Prasad (2018: 52); Poyarkov et al. (2021b: 39); Vassilieva (2021: 72–73); Holden (2023: 149).

ZMMU A-8134 (field number NAP-14688), adult male, from a pond in Cat Tien National Park, along the road from park headquarters to the Bau Sau Lake, Dong Nai River valley, Dac Lua Commune, Tan Phu District, Dong Nai Province, Vietnam, collected by N.A. Poyarkov, A.M. Bragin, and V.A. Gorin on 15 June, 2024 (11.44121°N, 107.41312°E; elevation 137 m a.s.l.) (Figs 6, 7C).

(n = 14).ZMMU A-8135–A-8140 (field numbers NAP-14689–14694), six adult males with collection data same as the holotype; ZMMU A-8141–A-8143 (field numbers NAP-14688–14694), three adult males with collection data same as the holotype; ZISP 15285–15287 (field numbers NAP-14687, NAP-14695–14696), three adult males with collection data same as the holotype; ZMMU A-4739 (field number NAP-01674), adult male from Cat Tien National Park, Dong Nai River valley, Dac Lua Commune, Tan Phu District, Dong Nai Province, Vietnam, collected by N.A. Poyarkov on June 1, 2011 (11.44576°N, 107.38673°E; elevation 128 m a.s.l.); ZMMU A-4642 (field number NAP-00630), adult female from Cat Tien National Park, Dong Nai River valley, Dac Lua Commune, Tan Phu District, Dong Nai Province, Vietnam, collected by N.A. Poyarkov and A.B. Vassilieva on June 2, 2009 (11.44576°N, 107.38673°E; elevation 128 m a.s.l.) (Fig. 8).

(n = 3).ZMMU-A-4602-1–3 (field numbers NAP-02010, NAP-02086, and NAP-02122), adult female and two subadult females from Cat Tien National Park, Dong Nai River valley, Dac Lua Commune, Tan Phu District, Dong Nai Province, Vietnam, collected by E.A. Galoyan on August 22, 2011, September 15, 2011, and November 11, 2011 (11.419503°N, 107.426442°E; elevation 117 m a.s.l.).

Kaloula discordia sp. nov. is distinguished from its congeners by the following combination of morphological characters: (1) medium body size (SVL 42.9–56.2 mm); (2) eyes comparatively small (eye length comprising 60%–75% of snout length); (3) dorsally uniform dark olive-brown; (4) beige-gray ventrally with irregular white mottling on belly and limbs; (5) pale yellow or orange-brown 8-shaped patch on either side of the neck posterior to eyes; (6) yellowish to orange axillary patch present; (7) grayish to beige-yellow inguinal patch present edged with black markings; (8) from gray to beige spot on tibiotarsal articulation present; (9) dark interorbital bar absent; (10) enlarged, widened finger disks (3FDD 6.5%–7.5% of SVL), ca. 1.27 times wider than toe disks; (11) finger subarticular tubercle formula: 1:1:2:2; (12) toe subarticular tubercle formula: 1:1:2:2:2; (13) two metacarpal tubercles not in touch with each other; (14) two metatarsal tubercles, outer metatarsal tubercle rounded, smaller than elongated inner metatarsal tubercle.

(Fig. 6). Adult male in a good state of preservation, habitus robust, head wider than long (HW/HL 1.27), snout projecting beyond lower jaw, gently rounded in lateral view (Fig. 6C); truncated in dorsal view; top of head flat; upper eyelid lacking supraciliary tubercles; eye length less than snout length (EL/SL 0.74) and less than interorbital distance (EL/IOD 0.76); pupils round; nostrils rounded, placed more towards the lateral sides of the snout, located closer to tip of snout than to eye, relatively close to each other (IND/IOD 0.60); supratympanic fold flat, glandular, rather thin; tympanum not visible (Fig. 6C); dorsal surfaces of body and limbs with sparse tubercules, getting denser backwards; ventral surfaces of body and limbs with flat tubercules (Fig. 6A, B). Cloacal opening unmodified, directed posteriorly. Forelimbs relatively long, more than a half of hind limb length (FLL/HLL 0.53); hand long, comprising more than a half of lower arm length (HAL/LAL 0.60) and almost half of forelimb length (HAL/FLL 0.49); fingers rather robust, notably flattened in cross section; relative finger lengths: I<II<IV<III; fingers free of webbing; terminal digits flattened forming wide transversely expanded disks (Fig. 6E); finger subarticular tubercles distinct, large and round, finger subarticular tubercle formula 1:1:2:2; inner metacarpal tubercle elongate; outer metacarpal tubercule triangular-shaped, dilated, bigger than inner metacarpal tubercle (OPTL/IPTL1.18), two metacarpal tubercles not in touch with each other (Figs 6E, 9C); hindlimbs robust, relatively short, not much longer than body length (HLL/SVL 1.16); relative toe lengths: I<II<V<III<IV; tarsal fold on inner surface of tarsus absent; tips of all toes widened, forming rounded terminal disks; all toe disks having dorso-terminal groves; the disk on toe IV the largest (Figs 6D, 9C); toe webbing well developed between all toes, reaching disks at all toes except toe IV; webbing formula i1-2ii1.5-2.5iii1.5-3iv3-1.5v; toe subarticular tubercules distinct, rounded; toe subarticular formula 1:1:2:2:2; two metatarsal tubercles, inner metatarsal tubercle elongated, oval; outer metatarsal tubercle smaller, rounded (Figs 6D, 9C).

In life, the dorsal surfaces of the head and body olive-brown, dorsal surfaces of the limbs grayish-olive with grayish-white spots (Fig. 6A); flanks of the body and lateral sides of the head grayish olive; orange-brown 8-shaped patches on the neck posterior to eyes; bright-orange axillary patch continuing on elbows (Fig. 7C); grayish-white inguinal patch; small grayish-beige spots near tibiotarsal articulation; ventral surfaces of head and body gray, darker on the throat near the jaw; belly and ventral surfaces of limbs pinkish with weak white mottling (Fig. 6B). Iris golden with brown reticulations ventrally and dorsally from the pupil (Figs 6C, 7C). In preservation after one year of storage in ethanol, dorsal coloration faded to dark gray, light patches became less pronounced, and they faded to light gray or grayish-beige, though the pattern generally remained unchanged.

(in mm): SVL 51.5; HL 11.7; HW 14.8; SL 5.5; EL 4.1; N-EL 3.9; IND 3.2; IOD 5.3; UEW 3.0; FLL 31.9; LAL 26.4; HAL 15.7; HLL 60.0; TL 45.0; FL 30.2; IPTL 3.0; OPTL 3.5; 1FL 8.1; 1TOEL 7.9; OMTL 2.1; 3FDD 3.6; 4TDD 2.3.

Table 4 presents the morphometric variation of the type series. Fig. 8 displays the variation in dorsal coloration of the paratypes. In general, all paratypes agree well with the description of the holotype, differing only in the brightness of light inguinal and axillary markings. In male paratypes ZISP 15285 and ZMMU A-8138, the right foot is poorly developed; in male paratype ZMMU A-8139, the right hand is poorly developed.

Vassilieva (2021) provided morphometric data and a detailed description of tadpoles of Kaloula discordia sp. nov. (as K. indochinensis). Vassilieva (2021) noted that tadpoles of ‘K. indochinensis’ from Cat Tien NP, Dong Nai Province, southern Vietnam (corresponding to Kaloula discordia sp. nov.) differ from K. indochinensis sensu stricto from Kon Ka Kinh NP, Gia Lai Province, and Chu Mon Ray NP, Kon Tum Province, central Vietnam, by having comparatively longer spiracle tubes (markedly longer than the vent tubes), a narrower mouth relative to body width, more developed tail musculature (tail base width more than a third of the body width), and a rather contrasting tail coloration.

Kaloula discordia sp. nov. is currently reliably known from Dong Nai, Lam Dong, Tay Ninh, and Binh Phuoc provinces of Southern Vietnam and was also reported from the adjacent Mondulkiri Province of eastern Cambodia; the known distribution of the new species is shown in Fig. 5, and the locality information is detailed in Appendix 1. The single Cambodian record of the new species from Phnom Prich Wildlife Sanctuary in Mondulkiri Province, originally reported as K. indochinensis by Chan et al. (2013) and Holden (2023), can be confidently assigned to Kaloula discordia sp. nov. based on the external morphology and coloration of the recorded specimen and the geographic proximity of the locality to the population of Kaloula discordia sp. nov. in Binh Phuoc Province of southern Vietnam. The new species was recorded mostly from relatively low elevations of ca. 70–300 m a.s.l.; in Bao Loc forestry of Lam Dong Province, the new species was recorded at elevations up to 550 m a.s.l. Kaloula discordia sp. nov. is restricted to lowland and hilly, seasonally dry, semi-deciduous, and evergreen monsoon forests of southern Vietnam (see Vassilieva et al. 2016). Male frogs were recorded calling from small temporary pools and flooded areas from May to November (Fig. 7A, B); the peak of the breeding season coincides with heavy rains in June–August. The new species is semi-fossorial and quite elusive and is usually active only after periods of heavy rains; frogs are aestivating during dry periods in leaf litter, underground borrows, or tree hollows (Vassilieva et al. 2016; Holden 2023). Diet consists of ants and beetles (Vassilieva et al. 2016); the new species is a good climber; males can call when perching a few meters above ground level (Holden 2023). The actual distribution of K. discordia sp. nov. is still insufficiently known, but we suppose that this species is likely to occur in those provinces of southern Vietnam where forests similar in composition are still preserved, including Dak Nong, Binh Duong, Binh Thuan, and Ba Ria-Vung Tau provinces. Syntopic species of amphibians included Microhyla butleri Boulenger, 1900; M. heymonsi Vogt, 1911; M. mukhlesuri; Kaloula pulchra; Fejervarya limnocharis (Gravenhorst, 1829); Occidozyga martensii; Polypedates megacephalus Hallowell, 1861; and Rhacophorus annamensis Smith, 1924.

Kaloula discordia sp. nov. most closely resembles other frogs of the K. baleata species complex in overall morphology; most specifically, it is similar to K. indochinensis, with which it was previously confused. From K. indochinensis, the new species can be distinguished by having generally smaller eye size in males (EL mean 3.5 ± 0.3 mm [n = 14] vs. mean 3.9 ± 0.2 mm [n = 18]; EL/SVL 0.071 ± 0.004 vs. 0.079 ± 0.004); smaller finger I in males (1FL mean 7.8 ± 0.4 mm [n = 14] vs. mean 8.5 ± 0.7 mm [n = 18]; 1FL/SVL 0.16 ± 0.01 vs. 0.17 ± 0.007); generally smaller inner palmar tubercules in males (IPTL mean 2.8 ± 0.3 mm [n = 14] vs. mean 3.1 ± 0.4 mm [n = 18]; IPTL/SVL 0.056 ± 0.004 vs. 0.062 ± 0.005); and generally smaller outer palmar tubercules in males (OPTL mean 3.2 ± 0.2 mm [n = 14] mm vs. mean 3.3 ± 0.4 mm [n = 18]; OPTL/SVL 0.064 ± 0.004 vs. 0.067 ± 0.005); generally longer hindlimbs in both sexes (HLL mean 59.6 ± 1.9 mm [n = 14] in males, mean 67.5 ± 0.2 mm [n = 2] in females vs. mean 55.2 ± 3.3 mm [n = 18] in males; 62.7 mm [n = 1] in female; HLL/SVL 1.21 ± 0.04 vs. 1.12 ± 0.03 in both sexes); smaller metatarsal tubercule in males (OMTL mean 2.2 ± 0.3 mm [n = 14] vs. mean 2.7 ± 0.3 mm [n = 18]); by having two metacarpal tubercles, see Fig. 9C (vs. three metacarpal tubercles, see Fig. 9B); by having two subarticular tubercles on toe IV, see Fig. 9C (vs. three well-developed subarticular tubercles, see Fig. 9B); and by having olive dorsal coloration (vs. chocolate-brown to dark grayish-brown).

From K. baleata (morphological data taken from Chan et al. 2013), Kaloula discordia sp. nov. can be distinguished by having generally smaller eyes in both sexes (EL mean 3.5 ± 0.3 mm [n = 14] in males, mean 4.2 ± 0.01 mm [n = 2] in females vs. mean 4.1 ± 0.4 mm [n = 10] in males, mean 4.5 ± 1.7 mm [n = 2] in females); larger distance between nares in both sexes (IND mean 3.1 ± 0.1 mm [n = 14] in males, mean 3.7 ± 0.1 mm [n = 2] in females vs. mean 2.7 ± 0.4 mm [n = 10] in males, mean 3.1 ± 0.30 mm [n = 2] in females); wider finger III disks in both sexes (3FDD mean 3.5 ± 0.3 mm [n = 14] in males, mean 3.9 ± 0.1 mm [n = 2] in females vs. mean 1.7 ± 0.2 mm [n = 10] in males, mean 2.1 ± 0.6 mm [n = 2] in females); smaller metatarsal tubercule in males (OMTL mean 2.2 ± 0.3 mm [n = 14] vs. mean 3.2 ± 0.2 mm [n = 10]); and by having two subarticular tubercles on toe IV, see Fig. 9C (vs. three well-developed subarticular tubercles).

From K. latidisca (morphological data taken from Chan et al. 2014), the new species can be distinguished by having shorter head in males (HL mean 11.2 ± 0.6 mm [n = 14] vs. mean 14.4 ± 0.8 mm [n = 4]); narrower head in males (HW mean 14.7 ± 0.7 mm (n = 14) vs. mean 18.7 ± 1.1 mm [n = 4]); smaller distance between nares in males (IND mean 3.1 ± 0.1 mm [n = 14] vs. mean 4.0 ± 0.1 mm [n = 4]); smaller distance between eyes in males (IOD mean 5.0 ± 0.2 mm [n = 14] vs. mean 5.7 ± 0.4 mm [n = 4]); smaller eye in males (EL mean 3.5 ± 0.3 mm [n = 14] vs. mean 4.6 ± 0.3 mm [n = 4]); smaller metatarsal tubercle in males (OMTL mean 2.2 ± 0.3 mm [=14] vs. mean 3.4 ± 0.1 mm [n = 4]); and by having two subarticular tubercles on toe IV, see Fig. 9C (vs. three subarticular tubercles).

Furthermore, Kaloula discordia sp. nov. differs from K. aureata Nutphand, 1989, by having an olive dorsum with no dark reticulations (vs. golden dorsum with dark brown reticulations); from K. borealis by having wider finger disks (vs. finger tips slightly dilated but not forming wide disks); by yellowish blotches on flanks absent (vs. present); and by olive dorsal coloration (vs. gray-brown). The new species is further diagnosed from K. conjuncta by the stratified coloration on flanks absent (vs. present) and by having distinct outer metatarsal tubercle (vs. weak or indistinct). Kaloula discordia sp. nov. differs from K. ghoshi by having axillary and inguinal light spots (vs. absent); tubercles on dorsum and venter (vs. smooth skin or with small granules dorsally); and olive dorsal coloration (vs. orange-brown). The new species further differs from K. kalingensis by having tubercles on the dorsum (vs. dorsum smooth); by having a distinct outer metatarsal tubercle (vs. indistinct); yellow or orange axillary and inguinal spots (vs. usually absent or small and red if present); lacking light pericloacal ring (vs. present); from K. kokacii by tuberculated dorsum (vs. smooth); axillary and inguinal spots (vs. absent); from K. mediolineata by lacking dorsolateral stripes (vs. present); sacral medial stripe absent (vs. present); and finger disks widened (vs. finger disks slightly dilated but not forming wide disks). Kaloula discordia sp. nov. is distinguished from K. nonggangensis by lacking protuberant tubercles on the upper surface of finger tips (vs. present); from K. picta by lacking dorsolateral stripes (vs. present); by the stratified coloration on flanks absent (vs. present); and by having wide finger disks (vs. finger disks slightly dilated but not forming wide disks). The new species further differs from K. pulchra by the absence of dorsolateral stripes (vs. always present); by having axillary and inguinal spots (vs. absent); from K. rigida by having wide finger disks (vs. finger disks slightly dilated but not forming wide disks); by the stratified coloration on flanks absent (vs. present); by the absence of dorsolateral stripes (vs. present); and by having axillary and inguinal spots (vs. absent). Kaloula discordia sp. nov. differs from K. rugifera by having wide finger disks (vs. slightly expanded small finger disks); by having axillary and inguinal spots (vs. absent); from K. verrucosa by having wide finger disks (vs. slightly expanded small finger disks); by having axillary and inguinal spots (vs. absent); from K. walteri by having wide finger disks (vs. slightly expanded small finger disks); by the stratified coloration on flanks absent (vs. present); having axillary and inguinal spots (vs. absent); and by having a distinct outer metatarsal tubercle (vs. indistinct or absent). Kaloula discordia sp. nov. is geographically isolated from other members of the K. baleata species complex and most of the other congeners, except K. pulchra, with which it occurs in sympatry everywhere throughout its range, and, possibly, K. mediolineata, with which the new species might co-occur in the Tay Ninh, Binh Phuoc, and Ba Ria-Vung Tau provinces of southern Vietnam.

For a comparison of the male advertisement calls of Kaloula discordia sp. nov. with K. indochinensis sensu stricto, see Table 3; data for K. indochinensis are taken from Nguyen et al. (2022). The power call parameters of Kaloula discordia sp. nov. and K. indochinensis are quite similar, with the dominant frequency of the call being the same in the two species (0.38 kHz, range 0.34–0.43 kHz vs. 0.38 kHz, range 0.30–0.45 kHz, respectively) (Table 3). At the same time, Kaloula discordia sp. nov. had a slightly shorter call duration (186.1 ms, range 144–214 ms) than K. indochinensis (215.6 ms, range 194–250 ms) and a significantly longer intercall interval: 1539.4 ms (range 851–8954 ms) in Kaloula discordia sp. nov. vs. 789.3 ms (range 481–1627 ms) in K. indochinensis. These differences have to be taken cautiously as the records of calling of the two species were taken with different ambient temperatures (20.5 °C for K. indochinensis and 24.0 °C for the new species), which also could contribute to the observed differences in call parameters between the two species. Nguyen et al. (2022) did not calculate the number of pulses per call in K. indochinensis and noted the presence of one pulse per call in this species (Nguyen et al. 2022: Table 2), while we recorded 11–13 pulses per call in Kaloula discordia sp. nov. These differences actually result from the different terminology used by Nguyen et al. (2022) and our study, as the waveform oscillograms in Nguyen et al. (2022) clearly show the presence of several pulses in each call.

The specific epithet “discordia” is a noun in apposition, in the nominative case, given in reference to the Roman mythological goddess Discordia. According to the poet Hesiod, this goddess personified not only strife and discord but also competition and labor (Hesiod, Theogony: 20–24, 226–230; see Most 2006). The duality of this name echoes the two aspects of the discovery of the new species. The first aspect is the authors’ hard work and laborious approach in collecting data for the description of the new species. The second challenge pertains to the authors’ internal struggle to choose a politically correct and neutral name for the new species. In modern taxonomy, international teams often face the common challenge of strife and competition; however, this can also lead to overall scientific progress. We recommend “South Vietnamese Painted Frog” as the common name in English, “Yuzhnovietnamskiy Bychiy Uzkorot” as the common name in Russian, and “Ễnh ương Nam bộ” as the common name in the Vietnamese language.

At present, the new species is reliably known only from four localities in southern Vietnam and a single locality in eastern Cambodia (Fig. 5; Appendix 1). The main threats to this species in Vietnam are habitat loss and degradation. The new species is restricted to the lowland monsoon tropical forests of southern Vietnam; it should be noted that these forests during the last 40 years have been subjected to greater anthropomorphic conversion (including logging, agriculture, road construction, and other human activities) than other areas in Vietnam (e.g., De Koninck 1999; Kuznetsov and Kuznetsova 2011; Laurance 2007; Meijer 1973; Meyfroidt and Lambin 2008). The range of the new species covers several nature conservation areas of southern Vietnam and Cambodia, including Cat Tien NP (Dong Nai Biosphere Reserve), Bu Gia Map NP, Lo Go-Xa Mat NP (Vietnam), and Phnom Prich Wildlife Sanctuary (Cambodia). Given the lack of comprehensive studies on the adjacent territories, we suggest Kaloula discordia sp. nov. be classified as Data Deficient (DD) according to the IUCN’s Red List categories (IUCN 2019).

Kaloula baleata [partim]—Orlov and Ananjeva (2007: 148); Nguyen et al. (2009: 94).

Kaloula indochinensis [partim]—Chan et al. (2013: 334, 2014: 577); Teynié et al. (2014: 29); Chandramouli and Prasad (2018: 52); Poyarkov et al. (2021b: 39); Holden (2023: 148).

ZISP 15284 (field label ZISP 199), adult male, Na Home Village, Bouphala District, near the border of Nakai-Nam Theun National Park, Khammouane Province, Laos, collected by N.L. Orlov, S.N. Nguyen, and K.D. Milto on June 18, 2009 (17.544528°N, 105.695278°E; elevation 174 m a.s.l.).

(n = 1).ZMMU A-8144 (field label ZISP 200), adult female from the same location and with the same collection data as the holotype.

Kaloula laosensis sp. nov. is distinguished from its congeners by the following combination of morphological attributes: (1) medium size (SVL ranging 44.0–54.8 mm); (2) eyes comparatively large (eye length comprising 75%–100% of snout length); (3) dark-brown dorsally, with numerous irregular dark blotches forming pericloacal ring; (4) gray or beige ventrally with dense white mottling on belly and limbs; (5) orange triangular patch on either side of the neck posterior to eyes; (6) bright-orange axillary patch present; (7) orange inguinal patch present; (8) bright-orange butterfly-shaped blotch above cloaca present; (9) gray spot on tibiotarsal articulation present; (10) dark interorbital bar present; (11) enlarged, widened finger disks (7.8%–7.9% of SVL), ca. 1.53 times wider than toe disks; (12) finger subarticular tubercle formula: 1:1:2:2; (13) toe subarticular tubercle formula: 1:1:2:2:2; (14) three metacarpal tubercles, median metacarpal tubercle in contact with inner metacarpal tubercle; (15) two metatarsal tubercles, inner metatarsal tubercle ca. three times larger than outer metatarsal tubercle; (16) three small supernumerary tubercles at the basis of toes I, III, IV.

(Fig. 10). Adult male in a good state of preservation, habitus robust; head wider than long (HW/HL 1.19); snout projecting beyond lower jaw, truncated in dorsal and lateral views (Fig. 10C); top of head flat; upper eyelid lacking supraciliary tubercles; eye length less than snout length (EL/SL 0.75) and less than interorbital distance (EL/IOD 0.77); pupils round; nostrils rounded, placed more towards the lateral sides of snout, located closer to tip of snout than to eye, relatively close to each other (IND/IOD 0.63); supratympanic fold flat, tubercular; tympanum not visible (Fig. 10C); dorsal surfaces of body and limbs with sparse tubercules, getting denser backwards; ventral surfaces of body and limbs almost smooth (Fig. 10A, B). Cloacal opening unmodified, directed posteriorly. Forelimbs relatively long, more than a half of hind limb length (FLL/HLL 0.63); hand long, comprising more than a half of lower arm length (HAL/LAL 0.6) and almost half of forelimb length (HAL/FLL 0.47); fingers rather robust, flattened in cross section; relative finger lengths: I<II<IV<III; no webbing between fingers; terminal digits flattened into very wide transversely expanded T-shaped disks (Fig. 10E); finger subarticular tubercles distinct, protuberant, large and round, finger subarticular formula: 1:1:2:2; metacarpal tubercles three (Figs 9A, 10E), inner metacarpal tubercle elongate, flattened; outer metacarpal tubercule oval, dilated, slightly bigger than inner (OPTL/IPTL 1.05), median metacarpal tubercle the smallest, oval-shaped, contacting both the inner and outer metacarpal tubercles (Figs 9A, 10E); hindlimbs robust, relatively short, not much longer than body length (HLL/SVL 1.12); relative toe lengths: I<II<V<III<IV; tarsal fold on inner surface of tarsus absent; tips of all toes widened, forming terminal oval-shaped disks (Figs 9A, 10D); all toe disks having dorso-terminal groves; the disk on toe IV the largest; toe webbing well developed between all toes, reaching disks at all toes except toe IV; webbing formula i1.5-2ii1.5-2.5iii1.5-3iv3-2v; toe subarticular tubercules distinct, rounded, protruding; toe subarticular formula: 1:1:2:2:2; two metatarsal tubercles, inner metatarsal tubercle elongated, oval, shovel-shaped; outer metatarsal tubercle smaller, rounded; three small supernumerary tubercles at the basis of toes I, III, IV (Figs 9A, 10D).

In life, dorsal surfaces of head and body dark brown with contrasting black spots and blotches; black interorbital bar between the upper eyelids; irregular black blotch on the snout; a series of black blotches forming a L-shaped chevron pattern in the scapular region; elongated black blotches on mid-dorsum, body flanks, and sacral area, forming a black pericloacal ring with irregular borders (Figs 2, 11); dorsal surfaces of limbs grayish brown with dark-brown to black blotches; flanks of body and lateral sides of head grayish brown; on lateral sides of belly getting dark-brown with white spots and blotches; pale orange patches on the neck posterior to eyes; bright reddish-orange axillary patch edged with dark brown; bright reddish-orange inguinal patch edged with black; bright reddish-orange patch above cloaca in the center of dark pericloacal ring (Fig. 2); small grayish-beige spots near tibiotarsal articulation; ventral surfaces of head and body gray, darker near the jaw; belly and ventral sides of limbs densely mottled with white spots and dots (Fig. 10); iris chocolate brown with copper sparkles dorsally and ventrally (Fig. 11). In preservation after 15 years of storage in ethanol, dorsal coloration faded to dark grayish-brown; dark markings on dorsum are well descernible; light patches became less pronounced and faded to yellowish or beige in color, though the coloration pattern generally remained unchanged (Fig. 10).

(in mm): SVL 44.0; HL 10.6; HW 12.6; SL 4.6; EL 3.3; N-EL 3.2; IND 2.7; IOD 4.3; UEW 2.4; FLL 27.6; LAL 21.7; HAL 13.0; HLL 49.3; TL 37.0; FL 25.4; IPTL 2.7; OPTL 2.8; 1FL 7.5; 1TOEL 7.3; OMTL 2.0; 3FDD 3.4; 4TDD 2.2.

Morphometric variation of the type series is presented in Table 4. A dorsal view of a female paratype specimen is presented in Fig. 12. In general, the female paratype specimen agrees well with the description of the holotype, diverging only in body size, which is larger than in the holotype (SVL 54.8 mm). Female paratype ZMMU-A-8144 has comparatively fewer dark markings on the dorsum (Fig. 12), but generally, the coloration pattern is similar to that of the holotype. Holden (2023: 148, fig. 152) published a photo of the new species from Laos as ‘K. indochinensis,’ which has bright-red axillary, inguinal, and pericloacal patches and lighter grayish-brown dorsal coloration.

Currently, data on the larval morphology of Kaloula laosensis sp. nov. are lacking.

Kaloula laosensis sp. nov. is currently reliably known only from two localities in the Khammouane Province of Laos; the distribution of the new species is shown in Fig. 5, and the locality information is detailed in Appendix 1. In Nakai-Nam Theun NP and in Hin Nam No NP, Khammouane Province, Laos, the new species was recorded from limestone evergreen tropical forests at relatively low elevations of ca. 100–300 m asl. The data on the natural history of Kaloula laosensis sp. nov. is scarce; it inhabits primarily lowland forests and is quite secretive, emerging only after heavy rains from June to September, when depressions in the forest floor are flooded and form temporary pools. The new species is likely associated with limestone karst landscapes of central Laos; the actual distribution of Kaloula laosensis sp. nov. is unknown, but we suppose that this species is likely to occur in adjacent provinces of Vietnam (Ha Tinh and Quang Binh), which harbor limestone forests similar in composition. Details about the new species’ reproductive biology and diet are unknown.

Kaloula laosensis sp. nov. most closely resembles other members of the K. baleata species complex in overall morphology, and comparison with these species appears to be the most pertinent. Most specifically, the new species superficially resembles K. indochinensis, with which it was previously confused. From K. indochinensis, Kaloula laosensis sp. nov. can be distinguished by having relatively longer head in males (HL/SVL 0.24 [n = 1] by our data or mean 0.25 ± 0.1 [n = 4] reported by Chan et al. 2013) vs. mean 0.23 ± 0.1 [n = 18] by our data or [n = 25] reported by Chan et al. 2013); relatively wider disk of finger III in males (3FDD/HAL 0.26 ± 0.1 [n = 1] vs. mean 0.23 ± 0.1 [n = 18]); relatively longer first toe in males (1TOEL/FL 0.29 ± 0.1 [n = 1] vs. mean 0.26 ± 0.1 [n = 18]); by having three metacarpal tubercles with median metacarpal tubercle touching both the inner and outer metacarpal tubercles, see Fig. 9A (vs. median metacarpal tubercle small, not touching the inner metacarpal tubercle, see Fig. 9B); by having two subarticular tubercles on toe IV, see Fig. 9A (vs. three well-developed subarticular tubercles, see Fig. 9B); by having supranumerary tubercles at the basis of toes I, III, and IV, see Fig. 9A (vs. supranumerary tubercles absent, see Fig. 9B); by the presence of numerous contrasting black markings on dorsum (vs. absent or indistinct); and brownish dorsal coloration (vs. chocolate to dark grayish-brown).

From K. baleata, Kaloula laosensis sp. nov. can be distinguished by having a relatively larger distance between nares in males (IND/HW 0.21 [n = 1] by our data or [n = 6] reported by Chan et al. (2013) vs. 0.18 ± 0.1 [n = 10] reported by Chan et al. (2013)); wider finger III disks in males (3FDD 3.4 ± 0.1 mm [n = 1] by our data) or mean 3.1 ± 0.3 mm [n = 6] reported by Chan et al. (2013) vs. 1.7 ± 0.2 mm [n = 10] reported by Chan et al. (2013)); by having two subarticular tubercles on toe IV, see Fig. 9A (vs. three well-developed tubercles); and by having supranumerary tubercles at the basis of toes I, III, and IV, see Fig. 9A (vs. supranumerary tubercles absent).

From K. latidisca, Kaloula laosensis sp. nov. can be distinguished by having relatively shorter heads in males (HL/SVL 0.24 [n = 1] by our data or mean 0.25 ± 0.1 [n = 4] reported by Chan et al. (2013) vs. mean 0.27 ± 0.1 [n = 4] reported by Chan et al. (2014)); relatively smaller distance between eyes in males (IOD/HW 0.34 [n = 1] by our data or mean 0.33 ± 0.1 [n = 6] reported by Chan et al. (2013) vs. mean 0.30 ± 0.1 [n = 4] reported by Chan et al. ((2014); by the presence of numerous black markings on the dorsum (vs. black markings on dorsum absent or few); and by having two subarticular tubercles on toe IV (vs. three well-developed tubercles).

From Kaloula discordia sp. nov. (described above), the new species can be distinguished by having a relatively longer head in males (HL/SVL 0.24 [n = 1] by our data or mean 0.25 ± 0.2 [n = 6] reported by Chan et al. (2013) vs. mean 0.22 ± 0.2 [n = 14]); relatively shorter snout in males (SL/HL 0.43 [n = 1] by our data or mean 0.40 ± 0.1 [n = 6] reported by Chan et al. (2013) vs. mean 0.47 ± 0.1 [n = 14]); relatively narrower head in males (HW/HL 1.19 [n = 1] vs. mean 1.31 ± 0.2 [n = 14]); wider finger III disks (3FDD/HAL 0.26 [n = 1] vs. mean 0.23 ± 0.10 [n = 14]); shorter toe I (1TOEL/FL 0.29 [n = 1] vs. mean 0.25 ± 0.1 [n = 14]); by having three metacarpal tubercles, see Fig. 9A (vs. two metacarpal tubercles, see Fig. 9C); by having supranumerary tubercles at the basis of toes I, III, and IV, see Fig. 9A (vs. supranumerary tubercles absent, see Fig. 9C); by the brown coloration of the dorsum (vs. olive); and by the presence of numerous black markings on the dorsum (vs. black markings on dorsum absent or few).

Furthermore, Kaloula laosensis sp. nov. differs from K. aureata by having a brownish dorsum with no reticulations (vs. golden dorsum with dark brown reticulations); from K. borealis by having wide finger disks (vs. finger tips dilated but not forming wide disks); by the absence of yellowish blotches on flanks (vs. present); an by brownish dorsal coloration (vs. gray-brown). Kaloula laosensis sp. nov. further differs from K. conjuncta by the stratified coloration on flanks absent (vs. present); by having distinct outer metatarsal tubercle (vs. weak or indistinct); from K. ghoshi by the presence of axillary and inguinal spots (vs. axillary and inguinal spots absent); by tuberculated dorsum and venter (vs. smooth or with small flat granules dorsally); by brownish dorsal coloration (vs. orange-brown). The new species differs from K. kalingensis in that it has tubercles on the dorsum (vs. dorsum smooth), a distinct outer metatarsal tubercle (vs. indistinct), and yellow or orange axillary and inguinal spots (vs. usually absent or small and red if present). Kaloula laosensis sp. nov. further differs from K. kokacii by the presence of dorsal tubercles, axillary and inguinal spots, and a light pericloacal ring (vs. absent). The new species differs from K. mediolineata by dorsolateral stripes and sacral stripe absent (vs. present); by having enlarged, wide finger disks (vs. finger tips slightly dilated but not forming wide disks); from K. nonggangensis by protuberant tubercles on the upper surface of finger tips absent (vs. present); from K. picta by the absence of dorsolateral stripes and stratified coloration on flanks (vs. present); by having enlarged, wide finger disks (vs. finger tips slightly dilated but not forming wide disks). The new species can be readily diagnosed from K. pulchra by the absence of dorsolateral stripes (vs. present) and by having axillary and inguinal spots (vs. absent). Kaloula laosensis sp. nov. further differs from K. rigida by having enlarged, wide finger disks (vs. finger tips slightly dilated but not forming wide disks), by the absence of dorsolateral stripes and stratified coloration on flanks (vs. present), and by having axillary and inguinal light spots (vs. absent). The new species differs from K. rugifera by having enlarged, wide finger disks (vs. slightly dilated small finger disks) and by having axillary and inguinal spots (vs. absent) and is further different from K. verrucosa by having very wide finger disks (vs. small finger disks) and by having axillary and inguinal spots (vs. absent). The new species differs from K. walteri by having very wide finger disks (vs. slightly dilated small finger disks), by the absence of stratified coloration on flanks (vs. presence), by having axillary and inguinal light spots (vs. absent), and by having a distinct outer metatarsal tubercle (vs. indistinct or absent). Except for K. pulchra, which can be found in central Laos in syntopy with the new species, Kaloula laosensis sp. nov. is geographically separated from most of its relatives.

The male advertisement call of Kaloula laosensis sp. nov. has not been recorded, and the bioacoustic data on this species is absent.

The specific epithet “laosensis” is an adjective in the nominative case, given in reference to the new species’ distribution in central Laos. The name also mirrors the specific epithet of K. indochinensis, with which the new species was previously confused. We recommend “Laotian Painted Frog” as the common English name, “Laosskiy bychiy uzkorot” as the common name in Russian, “Ễnh ương Lào” as the common name in Vietnamese, and “ອື່ງຢາງລາວ” (“Ung Yang Lao”) as the common name in Lao languages.

At present, the new species is known only from two localities in Khammouane Province of Laos (Fig. 5). The main threats to this species in Laos are habitat loss and degradation due to intensified logging and deforestation, namely Nakai-Nam Theun NP and Hin Nam No NP. We propose that the IUCN’s Red List categories (IUCN 2019) classify Kaloula laosensis sp. nov. as Data Deficient (DD) due to the absence of comprehensive studies in the adjacent territories.

We assume, based on the distribution of the new species, that several specimens from the type series of K. indochinensis in the original description by Chan et al. (2013), collected in Khammouance Province of Laos and labeled as ‘K. indochinensis Laos’ or ‘Laos OTU’ throughout the text, actually represent Kaloula laosensis sp. nov. These specimens include six adult males stored in the Field Museum of Natural History (FMNH), Chicago, USA, under voucher numbers FMNH 270360–65. The lack of genetic information on these specimens in the original description of K. indochinensis prevented Chan et al. (2013) from recognizing their taxonomic distinctiveness.