Ischnocnema rubridactyla Silva-Soares & Campos & Pirovani-Silva & Costa & Monjardim 2026, sp. nov.
Year: 2026
Type: article
Abstract: Ischnocnema rubridactyla sp. nov. (Fig. 1–5) Holotype. MNRJ 95353, adult male from Parque Nacional do Caparaó (20°30'05"S 41°49'08"W, WGS84; 1,443 m a.s.l.), located near the researchers’ accommodation named “Beija-Flor”, district of Pedra Menina, municipality of Dores do Rio Preto, state of Espírito Santo, southeastern Brazil. Collected by Thiago Silva-Soares & Diego Henrique Santiago on 17 January 2020. Paratopotypes. Four adult males MNRJ 95355–95358; and one adult female MNRJ 95354, all collected with the holotype. Etymology. The specific epithet combines the Latin ruber (“red”) and the Greek daktylos (“finger”), alluding to the conspicuous red coloration on the digits of this tiny frog. Common name. Given the remarkable red coloration on the tips of its fingers and toes, we have designated the Portuguese common name ‘rãzinha-dos-dedos-vermelho-do-Caparaó’. In English, it referred to as ‘ Caparaó red-fingered robber frog’. Diagnosis. Ischnocnema rubridactyla sp. nov. belongs to the Ischnocnema lactea series based on its phylogenetic placement (see Discussion), and it is diagnosed by the following combination of characters: (1) Small-sized species within the I. lactea series (adult males average SVL 15.6 mm, and the single adult female measures 19.4 mm); (2) body aspect slender, with smooth dorsum to granular flanks and undersurfaces; (3) snout subovoid in dorsal view; (4) tip of snout rounded in lateral view; (5) eyelid tubercles oval, poorly developed; (6) prevomerine odontoids present; (7) single, subgular vocal sac, not expanded; (8) discs expanded, T-shaped truncate on fingers III–IV; (9) single glandular-appearing nuptial pad present; (10) toes relative length I<II<V≤III<IV; (11) calcar tubercle present, poorly developed; (12) hidden areas of the inguinal region, thigh, tibia, and tarsus exhibit a vivid red color; (13) discs on the hands and on the toes exhibit a vivid red color (14) black stripe present on perianal region, tarsus, and feet. Description of holotype. Small-sized adult male with SVL 16 mm. Body overall aspect slender, with dorsum smooth, and flanks and undersurfaces smooth to granular. Abdominal or pectoral fold indistinct. Head length 38.1% of SVL, longer than wide; snout subovoid in dorsal view, with tip rounded in lateral view; upper jaw projecting beyond lower; large eyes, protuberant, anterolaterally oriented, corresponding to 35.1% of HW; pupil horizontal, elliptical, translucent palpebral membrane, pigmented on the edge; both eyelids with few poorly developed oval tubercles; tympanum poorly distinct with membrane hidden beneath skin and annulus evident only ventrally; supratympanic fold absent; one postcommissural small oval tubercle is evident on both sides, located just before arm insertion. Canthus rostralis distinct, straight; loreal region oblique, dorsolaterally directed, slightly concave; nostrils rounded, protruding in both dorsal and lateral views, latero-posteriorly directed; inter-nostril distance 28.1% of HW; choanae rounded, distant from one another by about four times their size; prevomerine odontoids small, present in two rounded processes, situated between and posterior to choanae; premaxillary teeth present; thick, medium-sized tongue, ovally disposed, covering almost all mouth floor, notched medially; vocal slits large, conspicuous, laterally oriented; vocal sac single, subgular and not externally expanded. Arms and forearms slender, skin smooth to granular; few lined-up tubercles weakly developed are present on each forearm. Fingers long, not fringed, with ungual flaps present; relative length I<II<IV<III; finger III length 58.4% of hand length; subarticular tubercles single, oval, moderately developed; outer metacarpal tubercle cordiform poorly developed; inner metacarpal tubercle oval moderately developed; few supernumerary tubercles on palmar region poorly developed; glandular-appearing nuptial pad present, beginning on the ventral base of the inner metacarpal tubercle, extending ventrally to the base of the distal phalanx. Notably, the left hand of the holotype exhibits a malformation. Discs expanded, T-shaped truncate on fingers III–IV, and rounded and not indented on finger II; disc pads even and broadened. Disc on finger I is not expanded. Legs slender; thigh almost as long as tibia, which is slightly longer. Dorsal surfaces of thighs, tibia, tarsus, feet, and cloacal area smooth to granular; tarsus with some poorly developed lined-up conical tubercles on their lateral edge; foot with small, oval outer metatarsal tubercle, and moderate, inner spatulate metatarsal tubercle; subarticular oval tubercles poorly developed, some with pigmentation; few small supranumerary tubercles. Toes long, not webbed nor fringed, with ungual flaps present; relative lengths I<II<V≤III<IV; Toe IV length 53.4% of FL; discs on toes II–V expanded, indented on Toes IV and V; disc pads even, broadened, following their disc sizes; calcar tubercle poorly developed. Measurements of holotype (in mm)—SVL 16.0; HL 6.1; HW 5.7; END 1.6; ED 2.0; TD 1.1; AMD 2.3; IND 1.6; FAL 3.3; HAL 3.6; 2FD 0.4; 3FD 0.6; 4FD 0.5; THL 6.6; TL 7.2; TAL 4.4; FL 7.3. General color in life (Figs. 3 & 4). There is a high level of variation in body surface coloration among the type series. Notably, finger and toe tips of all individuals are red-colored, as well as the posterior portion of belly and legs are vivid red. Eyes display several black vermiculations; iris is copper and pupil is black. Most specimens exhibit several blotches, always contrasting with the general background color, reminiscent of a military camouflage pattern (Figs. 3A, B, E & F). These blotches may vary in dimension, shapes, position, and contrast with dorsum. The loreal region may exhibit stripes, while stripes on the posterior dorsum and inguinal region may extend into the legs. The dorsum background coloration varies from light and dark brown to nut-brown and grayish, sometimes with two or more of these colors mixed. The ventral region exhibits variations in marbling, ranging from minimal to highly pronounced. The male paratype MNRJ 95357 displays a light vertebral line extending along its dorsum, as well as in the gular region and belly, terminating before the cloacal region (Fig. 4E). Another specimen exhibits the vertebral line, but no ventrally (Fig. 3D). On both sides, the paratype MNRJ 95355 shows a long triangular-shaped stripe, cream with nut-brown core, beginning behind the eye and ending in the inguinal region, where it encompasses two stripes that continue along thighs, tibia and tarsus (Fig. 3C). Individual MNRJ 95358 displays a large creamcolored blotch covering the entire snout, including part of the loreal region (Fig. 3F). Two paratypes do not present the military camouflage pattern (Figs. 3C & D), the second, MNRJ 95356, being uniformly brown, with a black interorbital stripe, and a dorsolateral black line from the nostril to the inguinal region (Fig. 3D). The forearms exhibit one to two dark bars, which may be faint or barely visible in certain specimens. Similarly, the thighs, legs, tarsus, and feet display two to three dark bars, which may also be faint. The tips of certain toes and fingers are red, with the extent of this coloration varying from a few to several digits. On the venter, the posterior belly, inguinal region, and legs exhibit vivid red coloration in most individuals. In the female MNRJ 95354, red coloration is faintly present in the cloacal region, while in MNRJ 95353 and MNRJ 95357, red is absent from ventral surfaces. However, all individuals consistently exhibit red coloration on the tips of the fingers and toes. Coloration in preservative. The dorsal background color of specimens in preservative became darker, ranging from grayish to dark brown. Vivid colors on the undersurfaces vanished. Overall, all previous patterns of blotches, dots, and stripes on all surfaces were retained; the iris became white. Variation. All specimens exhibit consistent morphological characteristics. Variations in dorsal patterns are described in the Color in Preservative section. Specimen MNRJ 95355 displays notable morphological distinctions, particularly in general body texture and coloration: it is the most rugose and darkest individual in the series, with a unique blackened gular region. Its color pattern is distinct among the type series, as previously described. Nonetheless, this individual conforms to the diagnostic characteristics of this new species. Descriptive basic statistics of measurement variables from adults are presented in Table 1. Geographic distribution. Ischnocnema rubridactyla sp. nov. is endemic to the Atlantic Forest, specifically located in the Serra do Caparaó region. It is known only from its type locality within Parque Nacional do Caparaó, with precise coordinates in the district of Pedra Menina, municipality of Dores do Rio Preto, state of Espírito Santo, southeastern Brazil. The species was discovered at an altitude of 1,443 meters above sea level. Natural history. This species inhabits the leaf litter of forested areas (Fig. 5), particularly near streams bordered by dense vegetation. All individuals in the type series were observed active during the morning hours, suggesting a primarily diurnal behavior. Calling activity was noted during light rainfall between 10 and 11 a.m.; the entire type series was collected at the same time on January 17, 2020. Phylogenetic inference and genetic distances. Our molecular analyses revealed the phylogenetic relationships among several species of the genus Ischnocnema. The inferred phylogenetic tree largely corroborates the relationships previously proposed in the scientific literature (Taucce et al., 2018, 2019), consistently delineating some clades that represent the different species series of the genus, while leaving others open, suggesting the need for specific revisions in future studies. One of the main highlights of this analysis is the position
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7140100943