Kalophrynus minusculus Iskandar, 1998

Kalophrynus minusculus Iskandar, 1998 View in CoL

( Figs. 4–7 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 , 11B View FIGURE 11 )

Kalophrynus pleurostigma interlineatus : Mertens (1957)

Holotype. Adult female, MZB Amph 367 ( Fig. 4 A–E View FIGURE 4 ), from Cigeunteur or Tjigeunteur (now Cigenter), Ujung Kulon National Park , Ujung Jaya Village, Sumur District, Pandeglang Regency, Banten Province, Indonesia, collected by A.M.R. Wegner on 15 July 1955.

Paratypes (n=8). Total of seven paratypes from Ujung Kulon National Park , Ujung Jaya Village , Sumur District, Pandeglang Regency, Banten Province, Indonesia, collected by A.M.R. Wegner: One male ( MZB Amph 365.2), one female ( MZB Amph 365.1), and one juvenile ( MZB Amph 365.3) [from the museum record this number ( MZB Amph 365) is listed to have three specimens] collected on 4–9 February 1956 (from the museum record these specimens are only listed from Ujung Kulon) ; One male ( MZB Amph 366) from Nyewaan collected on 15 June 1955 . One male ( MZB Amph 371) [previously MZB Amph 375 in Iskandar (1998); however, from the museum record, the previous number ( MZB Amph 375) is listed as Ingerophrynus biporcatus Gravenhorst ] from Tjibunar (now Cibunar) collected on 27 July 1953 ; One male ( MZB Amph 376) collected on 9 February 1956 (only listed from Ujung Kulon Island ) . One female ( MZB Amph 2924) from Cidaon was collected by Hellen Kurniati in August 1990 .

One male ( MZB Amph 2339) from Gelugur, near Kramat, Way Sekampung , South Lampung Regency , Lampung Province (approx 50 m a.s.l) collected by Djoko T. Iskandar on 15 October 1976 .

Topotypes (n=7). Five males ( MZB Amph 27229–33) and one female ( MZB Amph 27234) from Laban , Ujung Jaya Village , Sumur District, Pandeglang Regency, Banten Province, Indonesia (-6.828865, 105.461436, 29 m a.s.l) were collected by Sasi Kirono on 4 August 2019 GoogleMaps . One male ( MZB Amph 1116) from Tjidaon (now Cidaon), Ujung Jaya Village , Sumur District, Pandeglang Regency, Banten Province, Indonesia, collected by A.M.R Wegner on 4 December 1958 .

English common name. Small sticky frog.

Suggested Indonesian common name. Katak lengket kecil.

Etymology. The specific epithet ” minusculus ” in Latin means small, referring to the small size of the adults compared to the larger K. pleurostigma .

Diagnosis. The species is assigned to Kalophrynus based on molecular analyses and the following combination of morphological characters: absence of spine-like projection of skin at heel and elbow; fingers without greatly enlarged tubercles; snout less than twice diameter of eye; inner metatarsal tubercle low, not shovel-like; tympanum visible ( Inger 1966).

The species can be distinguished from its congeners by the following combination of characters: small size (SVL 23.1–29.2 mm in adult males, 29.3–32.3 mm in adult females); inguinal spot usually present, without light border; fourth finger short but not nub-like; hand and foot with distinct subarticular tubercles; light-colored diagonal stripes on the body; webbing on fourth toe only reaches proximal subarticular tubercle; a pair of distinct dark bands from between the eyes to groin.

Description of topotype (MZB Amph 27229). Adult male ( Fig. 4 F–J View FIGURE 4 ); small-sized (SVL 26.6 mm); habitus moderately stocky; head broader (HW 8.1 mm, 30.4 % SVL) than long (HL 7.4 mm, 27.9 % SVL); snout slightly rounded in lateral view, protruding beyond lower jaw; eye diameter (ED 3.0 mm, 11.4 % SVL) longer than snout length (SL 2.9 mm, 11.1 % SVL); pupil horizontal; canthus rostralis distinct; loreal region vertical, slightly convex; nostril below canthus, nearer to tip of snout (SNL 0.9 mm, 3.2 % SVL) than to eye (NEL 2.0 mm, 7.5 % SVL); interorbital distance (IOD 3.4 mm, 12.7 % SVL) wider than internarial distance (IND 2.1 mm, 7.9 % SVL), the latter nearly equal to upper eyelid (UEW 2.2 mm, 8.1 % SVL); pineal spot absent; tympanum distinct, roughly rounded, diameter (TD 2.0 mm, 7.6 % SVL) about two-thirds of eye; upper jaw edentate; tongue smooth, without papillae; pair of long smooth vomerine fold, straight-edged flaps behind choanae, each extending from labial edge of mouth to near midline, separated by very short gap from its opposite fold; postorbital low, smooth; buccal fold distinct, higher than postorbital; vocal slit present, on both sides of mouth floor between base of tongue and angle of jaws; median subgular vocal sac.

Forelimb slender; finger webbing absent; tips blunt, rounded; finger length formula IV <I <II <III, fourth finger (Fin4L 1.8 mm, 6.7 % SVL) slightly shorter than first (Fin1L 1.9 mm, 7.0 % SVL); portion of fourth finger projection from palm longer than terminal phalanx of third finger; subarticular tubercles on fingers and palmar tubercles well-developed, rounded, two on fingers I, II, and IV, three on III; outer palmar tubercle large, oval; humeral spine absent; nuptial pad absent.

Hindlimb slender, moderately long (HLL 39.5 mm, 148.6 % SVL); toe length formula I <II <V <III <IV; fifth toe projecting as far as third toe; foot (FL 10.1 mm, 38.1 % SVL) shorter than tibia (TBL 10.9 mm, 41.0 % SVL); tibio-tarsal articulation of adpressed limb reaching tympanum; toe tips blunt, rounded; toes webbing poorly developed, webbing formula I 1–2 II 1–3 III 2–4 IV 4–2 V; fifth toe projecting as far as the third toe; subarticular tubercles rounded, one on toes I and II, two on III, three on IV, and indistinct on V; inner metatarsal distinct, oval; outer metatarsal present, indistinct.

Dorsum skin finely granular, with many small whitish tubercles, scattered on dorsal of head, body, forelimb, and hindlimb; dorsolateral lined with small whitish tubercles, extended from anterior upper eyelid to groin; gland on side of head, behind tympanum, delimited by sinuous groove; supratympanic fold curved; abdomen, ventral thigh, and cloaca with large flattened glandules; pair of round, whitish, slightly elevated tubercles on pectoral region.

Coloration. In preservatives, dorsal body dark brownish, with a distinct pair of dark bands from between the eyes to groin; edge of the bands with whitish tubercles; several dark stripes near groin and side of the body; small dots and whitish tubercles formed distinct dorsolateral line from tip of snout to groin, forming boundary between dorsum and side of head and flank; dorsal limbs with dark cross bars; inguinal spot absent; chin with paired, dark, longitudinal bars; pectoral region yellowish, covered with dark dots; abdomen and ventral thigh yellowish.

Variation. The morphometric variations are listed in Table 2 View TABLE 2 . Males had smaller than females in SVL, RHL, RHW, RSNL, RToe4L, and RToe 5L. The coloration of paratype specimens varies considerably, ranging from extremely faded dark brown to yellowish brown. A pair of dark bands on the dorsal skin of body were indistinct in three paratypes ( MZB Amph 365.3, 371, 376); this might be due to long storage and color change of the specimens. All type and topotype specimens (excluding MZB Amph 27229, 27231) exhibited an inguinal spot without light border; the coloration of the inguinal spot in type specimens was indistinct. Among the topotype specimens, the coloration of the dorsal body ranged from dark brown ( MZB Amph 27232, 27233) to light grayish ( MZB Amph 27234, 27230) and light brown ( MZB Amph 27231). A male paratype from South Lampung ( MZB Amph 2339) exhibited a pointed snout in lateral view ( Fig. 5E View FIGURE 5 3 View FIGURE 3 ).

Morphological comparison. Kalophrynus minusculus differs from K. pleurostigma by females having smaller body size, SVL 29.3–32.3 mm (vs. 34.5–43.5 mm), thinner dorsolateral line, Fig. 11B View FIGURE 11 (vs. thicker, Fig. 11C, D View FIGURE 11 ), and fifth toe projecting as far as the third toe in females, Fig. 12B View FIGURE 12 (vs. fifth toe not projecting as far as third, Fig. 12C View FIGURE 12 ). Kalophrynus minusculus differs from K. meizon by having a smaller body size, SVL 23.1–29.2 mm in males, 29.3–32.3 mm in females (vs. 37.0–50.0 mm in males, 35.0–60.0 mm in females), and absence of conical spines on the dorsal skin of the body of males [vs. present: Zug (2015)].

Kalophrynus minusculus View in CoL is easily differentiated from the nubicola View in CoL group ( K. nubicola View in CoL , K. puncak , K. dringi ) by having larger body size, SVL 23.1–29.2 mm in males, 29.3–32.3 mm in females (vs. ≤ 22.7 in males, ≤ 24.8 mm in females), distinct subarticular tubercles on hand and foot [vs. indistinct: Fukuyama et al. (2021)], distinct snout projection [vs. indistinct: Fukuyama et al. (2021)], and dorsolateral line present [vs. absent (except K. dringi ): Fukuyama et al. (2021)].

Kalophrynus minusculus View in CoL differs from K. barioensis Matsui & Nishikawa View in CoL , K. bunguranus (Günther) View in CoL , K. cryptophonus Vassilieva, Galoyan, Gogoleva & Poyarkov View in CoL , K. robinsoni Smith View in CoL , K. subterrestris Inger View in CoL , and K. tiomanensis View in CoL by having a larger body size, SVL 23.1–29.2 mm in males, 29.3–32.3 mm in females [vs. ≤ 19.8 mm in males (except in males K. bunguranus View in CoL , K. cryptophonus View in CoL , K. subterrestris View in CoL , and K. tiomanensis View in CoL ), ≤ 26.7 mm in females]. K. minusculus View in CoL differs from K. anya Zug View in CoL , K. baluensis Kiew View in CoL , K. calciphilus Dehling View in CoL , K. interlineatus (Blyth) View in CoL , K. intermedius Inger View in CoL , K. kiewi View in CoL , K. orangensis Dutta, Ahmed & Das View in CoL , K. palmatissimus View in CoL , and K. sinensis View in CoL by having a smaller body size, SVL 23.1–29.2 mm in males, 29.3–32.3 mm in females [vs. ≥ 31.2 mm in males (except in males K. calciphilus View in CoL and K. intermedius View in CoL ), ≥ 34.4 mm in females (except in females K. palmatissimus View in CoL )].

Kalophrynus minusculus has an overlapping body size with K. eok Das & Haas and K. punctatus Peters , but can be differentiated from those species by the presence of inguinal spot in most specimens (vs. absent). Additionally, K. minusculus differs from K. eok and K. punctatus by having several dark stripes near groin and side of the body [vs. absent: Das & Haas (2003), Inger (1966)].

Kalophrynus minusculus also has an overlapping body size with K. heterochirus Boulenger , K. honbaensis , K. limbooliati , and K. yongi Matsui. However , it can be differentiated from these species as follows: from K. heterochirus and K. limbooliati by a portion of the fourth finger projection from the palm longer than the terminal phalange of the third finger (vs. shorter); additionally, K. minusculus differs from K. heterochirus by the presence of a black inguinal spot (vs. white-bluish). K. minusculus differs from K. honbaensis by the absence of finger webbing [vs. present: Vassilieva et al. (2014)]; and from K. yongi by the absence of nuptial pad (vs. present).

Call characteristics. An adult male (unvouchered specimen) of Kalophrynus minusculus was captured in Kampung Cikawung, Ujung Jaya village   GoogleMaps , Sumur district   GoogleMaps , Pandeglang Regency   GoogleMaps , Banten Province (-6.800636, 105.499069, 8.8 m a.s.l) on 08 April 2025 and brought to a room. Although the specimen was not preserved as a voucher, its identification was confirmed based on direct morphological examination. We recorded one call of one adult male ( Fig. 7 View FIGURE 7 ) at distances of approximately 1 m at an air temperature of 28.0° C. The call sounds to the human ear like “krek….krek…….krek” with a duration of call 1.14 s and dominant frequency 516–689 Hz (mean 617 ± SD 84.685). Note series consist of 3 notes, with two pulses, duration of note series 0.031 −0.048 s (mean 0.040 ± SD 0.008), pulse duration 0.007 −0.026 s (mean 0.015 ± SD 0.007), inter-pulse interval 0.001 −0.022 s (mean 0.010 ± SD 0.011), pulse period 0.023 −0.029 s (mean 0.026 ± SD 0.003), and pulse rate 34.596 −43.774 s (mean 38.380 ± SD 4.796).

Call comparisons. The call characteristics of 11 species of Kalophrynus have been described, analyzed, and recorded [ K. meizon : Matsui et al. (1996); K. baluensis : Malkmus & Riede (1996), Inger et al. (2017); K. yongi : Matsui (2009); K. barioensis : Matsui & Nishikawa (2011); K. calciphilus : Dehling (2011); K. cryptophonus : Vassilieva et al. (2014); K. interlineatus : Matsui et al. (1996), Ohler & Grosjean (2005); K. limbooliati : Matsui et al. (2012); K. dringi , K. nubicola , K. puncak : Inger et al. (2017), Fukuyama et al. (2021)].

The call of Kalophrynus minusculus differs from K. baluensis , K. barioensis , K. limbooliati , K. meizon , and K. yongi by the well-pulsed note (vs. unpulsed note). The call of K. minusculus differs from K. cryptophonus , K. dringi , K. interlineatus , K. nubicola , and K. puncak by consisting of a series of notes (vs. a single note). Additionally, the call of K. minusculus differs from K. cryptophonus by having a lower dominant frequency, 516−689 Hz (vs. 900−1200 in K. cryptophonus ). The call of K. minusculus differs from K. calciphilus by having two pulses (vs. consisting of only 7 or 8 pulses).

Tadpoles. Unknown.

Distribution and natural history. This species is known from lower elevations about 29–50 m a.s.l. on Peucang Island and the tip of mainland Java (Ujung Kulon National Park), and is also recorded from the southern part of Sumatra (Lampung). Females produce 30 to 50 eggs.