Elachistocleis tinigua Acosta-Galvis & Tonini & De Sá 2022, sp. nov.

Elachistocleis tinigua sp. nov.

Holotype. IAvH-Am–15251 (field number ARA 8311, Fig. 8) an adult female collected on 3 July 2018 by Andrés R. Acosta-Galvis and Duberley Rayo.

Type locality (Fig. 9). Colombia, Meta Department, La Macarena Municipality, vereda Los Alpes, left margin of Losada River, near Los Alpes School, 02°13’7.1” N, 073°55’16.3” W, 234 m a.s.l.

Paratypes (4 specimens) (Fig. 10, Table 2). IAvH-Am–15200 adult female collected on 1 July 2018., IAvH-Am–15252 collected on 3 July 2018, IAvH-Am–15275 collected on 4 July 2018, adult males, by Andrés R. Acosta-Galvis and Duberley Rayo, same locality as the holotype.

Referred specimens (29 specimens). IAvH-Am–14816, IAvH-Am–14829, juveniles collected on 1 July 2018 in Colombia, Meta Department, La Macarena Municipality, El Silencio Lake. 2°14’55.21”N, 73°45’27.40”W, 223 m a.s.l., IAvH-Am–15172–15199 juveniles, same locality and date as holotype.

Referred specimens. MPUJ- 6118–21 (field numbers DXA 044, 082–4, respectively),

Adult males, from Colombia, Meta Department, San Martin Municipality, vereda Montebello, Tocancipá Farm, 3°39’21.7”N, 73°36’49.40”W, 424 m a.s.l, collected on 4 May 2007, by Xamara Albarán and Andrés R. Acosta-Galvis.

Etymology. The specific epithet tinigua honors the now extinct native ethnic group of the Tiniguas who lived in the Manacacias, Yarí, Caguán, and Guayabero river basins within the distribution range of the species. The last two inhabitants of this ethnic group survived until 1994.

Diagnosis (Fig. 4, 8, 10). A medium size species of Elachistocleis (adult males SVL = 30.4–34.1 mm, χ = 32.2 2.6 mm, females SVL = 35.1–38.8 mm, χ = 36.9 2.6 mm), diagnosed by the following combination of characters: (1) an ovoid body form, (2) triangular head, slightly longer than wide, (3) a barely developed and complete occipital fold, (4) snout rounded in lateral and dorsal views, (5) canthus rostralis slightly concave and loreal region is convex, (6) nostrils laterally oriented, (7) post-commissural glands distinct in adult males, barely noticeable in adult females, (8) tympanic annulus and membrane absent, (9) dentigerous process of vomer absent, (10) upper jaw projects beyond the lower jaw, (11) tongue large, ovoid, and occupying the entire buccal cavity, (12) choanae ovoid, large, and widely separated, (13) arms slender without tubercles on forearm, (14) hands lack interdigital membranes and supernumerary tubercles, (15) finger lengths are I<II<IV<III, (16) subarticular tubercles, ovoid and as wide as fingers, (17) thenar tubercle prominent and palmar tubercle bilobate, (18) foot lacks interdigital membranes and supernumerary tubercles, toes lack discs, (19) inner plantar tubercle equal in size to subarticular tubercles, (20) relative toe lengths I<II<V<III<IV, (21) THL is slightly longer than TBL, (22) dorsal surface of body with sparse dermal spines, (23) cloacal region lacks glands, but bears tubercles, (24) in preservative, dorsal coloration dark gray to dark brown with scattered cream spots, (25) ventral surfaces of fore and hind limbs mottled, (26) mid-dorsal line absent, (27) longitudinal line on posterior surface of thighs (= femoral stripe) broad, light, and irregular, (28) axillae and groin lightly spotted, (29) all toes fringed and slightly webbed in females and males, (30) dermal spines absent on ventral surfaces, except on chin of adult breeding males.

Description of Holotype. (Fig. 8). Body size medium (SVL = 38.8 mm), body slender, slightly ovoid, head triangular in shape, longer than broad (Table 2), snout short, snout tip rounded (Fig. 8), nostrils located closer to the tip of snout than to the eye, protuberant, directed laterally (Fig. 8), inter-nostril distance smaller than eye–nostril distance and wider than eye diameter (Table 2), canthus rostralis slightly defined, loreal region slightly convex, lips flared, eyes small, slightly protruding, inter-orbital slightly concave, occipital fold complete, tympanum indistinct, upper jaw projecting beyond lower one, tongue is big, ovoid, and covers three quarters of the buccal cavity, premaxillae, maxillae, and vomerine teeth absent, choanae small, almost ovoid, widely separated, positioned anterolaterally to eye.

Arms are slender, lacking tubercles on forearms. Hands not webbed, fingers tips rounded, not expanded, and not fringed, fingers lacking dermal spines, finger lengths I<II<IV<III, subarticular tubercles well developed and rounded, proximal subarticular tubercles larger than others, supernumerary tubercles absent, thenar tubercle welldeveloped and subovoid, palmar tubercle longitudinally divided. Legs short, moderately robust, knee and heel lacking tubercles, tibial and tarsal ridges absent. Foot not webbed, toes not fringed, toe tip rounded lacking disks, subarticular tubercles well-developed and rounded, supernumerary tubercles absent, inner metatarsal tubercle oval, no outer metatarsal tubercle. Toe lengths I<II<V<III<IV, toes lack dermal spines, tibia length slightly shorter than thigh length, combined thigh and tibia lengths approximately 43.3% of snout-vent length, foot length approximately 59.5% of snout-vent length. Skin smooth, dorsal surfaces of body lacking dermal spines. Throat smooth, lacks dermal spines on chin and snout. Cloaca with para-cloacal tubercles or glands.

Color of holotype in preservative (Fig. 8). Dorsum gray with diffuse black reticulations, a few small white spots, dorsal surface of limbs similar to dorsum, dorsal surfaces of tibia with irregular cream spots on the inner margin, palm of hands pale cream and marbled brown below subarticular region, foot dark brown, with blotches pale cream, and a few small white spots, ventral surfaces of anterior thighs, tibia, throat, and belly, dark brown with irregular cream spots, and absence of distinct lines on the body and limbs.

Color of holotype in life (Fig. 10 A–B). Dorsum surfaces and limbs pale dark brown with light gray reticulations and spots, cephalic region and flanks with coloration similar to dorsal surfaces, ventral surfaces dark brown with irregular yellowish cream spots, axillary region, groin, and anterior thigh orange, iris dark brown.

Measurements of Holotype (in mm). SLV 38.8, HDL3 5.89, HDL4 8.0, HL 8.2, HW 8.0, ED 1.6, IOD 4.6, IND 2.5, END 2.5, THL 17.3, TBL 16.3, FL 14.7, FAL 6.3, FD3 0.7, TD4 0.7.

Variation (Fig. 10, Table 2). Herein, coloration refers to live specimens and is based on field notes and digital photographs, unless otherwise noted. Dorsal coloration varies from dark brown with light gray reticulations (e.g., IAvH-Am–15200, IAvH-Am–15251, Fig. 10) to black with light gray reticulations (e.g., IAvH-Am–15172, IAvH-Am–15175–6, IAvH-Am–15178, IAvH-Am–15181, IAvH-Am–15252, Fig. 10) or uniformly dark brown (e.g., IAvH-Am–15275, Fig. 10). Axillary spots can be present or absent (e.g., IAvH-Am–15172, IAvH-Am–15275, Fig. 10); if present they are orange and visible in lateral view (e.g., IAvH-Am–15251–2, IAvH-Am–15173, IAvH-Am–15178, Fig. 8). Dermal spines on chin are absent (e.g., IAvH-Am–15200, IAvH-Am–15251–2) or present and prominent (e.g., in adult male IAvH-Am–15275). The ratio of TBL added to THL with respect to SVL is 54.9–59.5 % in adult females, in adult males is 46.7–47.7%.

Call analysis (Fig.7). Males of Elachistocleis tinigua sp. nov. called at night on ephemeral ponds and from within natural ground depressions filled with water (<10 cm deep), these are the result of rainwater that circulates freely on the surface of land in open grasslands.

The analyzed call belongs to voucher specimens: IAvH-Am–15252 (https://doi.org/ 10.6084/ m9.figshare.16944193) and IAvH– Am –15275 (https://doi.org/ 10.6084/m9.figshare.16944190), were recorded respectively from Vereda Los Alpes near Losada River, at 255 m a.s.l., in the Municipality of Macarena (2°13’12.4”N, 73°55’27.1W), Meta Department, Colombia, on July 3 and 4, 2018 between 20:18–20:49 hrs., air temperature between 25.6–27.7 °C and relative humidity between 61–72%; and MPUJ– 6118–21 (https://doi.org/ 10.6084/ m9.figshare.16944205) recorded from Vereda Montebello, Tocancipá farm, at 350 m a.s.l., in the Municipality of San Martin (3°39’21.7”N, 73°36’49.5W), Meta Department, Colombia on 4 May 2007 (Table 4).

The call of Elachistocleis tinigua sp. nov. (n = 50 calls) consists of a sustained trill (one pulsed note, Guild C sensu Emmrich et al. 2020) made by a long, strong, and continuous note lasting between 1350 and 3753 ms (χ = 2457 ms 0.58) and interval between notes between 1400 and 18684 ms (χ = 6553 ms 3.71), the dominant frequency is between 2954 and 4655 Hz (χ = 3780 Hz 445). Each note consists of a series of sustained and long multi-pulses (348–926 pulses per note) with a rate of 206 to 236 pulses per seconds (χ = 223.7 pulses/s.), the duration of each pulse is 3.0 ms. The calls have an ascendant modulation frequency where the first segment consist of 12 to 48 initial pulses (χ= 27.2) with lower frequencies between 1759.6 and 2678.5 Hz (χ= 2256.6 Hz) and the maximum frequency, at the end of the call, between 4347 and 4702 Hz (χ= 4514.9 Hz).

Distribution (Fig.7). Elachistocleis tinigua sp. nov. is currently known from three localities in the transitional areas between the Orinoco and the Amazon basins in Meta Department, all the localities are located within sub-basins of the Guayabero and Guaviare rivers, at an elevation between 182 to 424 m a.s.l.

Tadpole. Unknown.

Natural history. Elachistocleis tinigua sp. nov. was collected in open areas (grasslands) associated to tropical forests. It is a nocturnal species, the specimens were found active during the period of greatest rainfall (i.e., July). The annual rainfall in the localities where the species are found varies between 2000 to 4800 mm with monomodal seasonality. Elachistocleis tinigua sp. nov. breeds in small pools in areas associated with runoff at about 5% angle. Males vocalize submerged and hidden at the base of seasonal ponds. At the time of collection of the type series, an individual of a false fer-de-lance snake, i.e., Leptodeira annulata (IAvH-R–8837), was observed feeding on a female at 18:33 h (Fig. 9 B).