Nototriton lateomuscus, Kubicki & Reyes & Arias, 2022

Kubicki, Brian, Reyes, Aura & Arias, Erick, 2022, Revised taxonomy and distributions of Costa Rican moss salamanders (Caudata: Plethodontidae: Nototriton), with descriptions of new taxa, Zootaxa 5194 (4), pp. 451-496 : 481-485

Nototriton lateomuscus sp. nov.

San Ramon moss salamander

Holotype. UCR 23694 ( Figs. 14–16 ), an adult female from Costa Rica: Provincia de Alajuela: Cantón de San Ramón: Distrito de Angeles: Edge of road, approximately 3 kilometers west of Balsa , ca. 1200 m a.s.l., collected by Brian Kubicki in the company of Aura Reyes on 21 October 2016.

Paratopotypes. UCR 23695, same collection data as the holotype . UCR 23696, same locality data as the holotype, but collected by Brian Kubicki in the company of Aura Reyes on 12 October 2013 .

Generic Placement. Assigned to the genus Nototriton due to having fewer than 14 costal grooves, reduced manus and pes that are longer than wide, and the molecular evidence (16S, COI, and cyt b mtDNA distances) presented herein.

Subgeneric Placement. Nototriton lateomuscus is assigned to the subgenus Nototriton due to its known geographic distribution (endemic to Costa Rica), its small hands and feet with the majority of the lengths of fingers II, III, and IV and toes II, III, IV, and V being free of extended palmar or plantar tissue, and by the molecular evidence (16S, COI, and cyt b mtDNA distances) presented herein.

Diagnosis. Nototriton lateomuscus is distinguished from the other described species of the subgenus Nototriton by its16S, COI, and cyt b mtDNA distances.

Comparisons. Since the molecular evidence presented herein strongly supports N. lateomuscus forming part of clade with N. abscondens and N. gamezi , and due to the fact that all three of these species have adjoining distributions, morphological comparisons are only going to be focused on distinguishing N. abscondens and N. gamezi from N. lateomuscus .

Contrasting characteristics for Nototriton lateomuscus are presented in parentheses. Nototriton abscondens ( Taylor, 1948) can be distinguished from N. lateomuscus by having relatively smaller nostril openings, average LNH = 0.16 mm and RNW = 0.16 (average LNH = 0.21 mm and RNH = 0.2 mm); wider internarial distance, average IND = 0.9 mm (average IND = 0.7 mm). Nototriton gamezi ( García-París & Wake, 2000) has larger nostril openings, average LNH = 0.29 mm and RNH = 0.24 mm (average LNH = 0.21 mm and RNH = 0.2 mm).

Description of holotype. Adult female having a total length of 66.2 mm and SL of 29.3 mm. Head slightly wider than neck and shoulders (HeW 4.0 mm, NeW 3.3 mm, ShW 3.4 mm), with greatest width of head just posterior to the articulation of the jaws; snout raised anterodorsally, spadate to rounded in dorsal outline, and rounded in profile; snout relatively short (SnL 1.0 mm, 3.4 % of SL), with nearly terminal non-protruding large nostrils (LNH 0.25 mm, RNW 0.25 mm) directed anterolaterally; internarial area convex in dorsal outline. Eyes relatively large (EW = 130 % of SnL), protruding beyond dorsal outline of head, directed anterolaterally, with a distinct suborbital groove. Top of head flat and smooth, tapering slightly toward anterior terminus, lacking contrasting interorbital or other dermal structures. Canthus rostralis rounded; intercanthal area flat to slightly convex; and loreal region flat to slightly concave. No obvious cirri (nasolabial protuberances) present, but nasolabial grooves weakly discernible on tip of snout; nasolabial grooves start at lateral margins of nares and extend ventrally with a slight outward orientation; nasolabial grooves start at lateral margins of nares and extend ventrally at first, but take a drastic backwards curve about halfway to lip; nasolabial grooves terminate just prior to reaching margin of upper lip. Gular fold welldefined, starting on lateral portion of neck, below postorbital groove, wrapping around posterolateral section of head at a slightly anterior angle and crossing venter as a smooth and anterior-oriented curve. Nuchal grooves very weak to indiscernible. Postorbital grooves discernible, starting at posterior corner of eyes and traveling horizontally along the inferior margin of parotoid glands, terminating at gular fold on the lateral portion of neck. Horizontal mandibular grooves indiscernible, but vertical mandibular groove well-defined.Vertical mandibular grooves starting at inferior margins of postorbital grooves and extending vertically to and crossing onto gular region, but becoming indiscernible just medially of inner mandibular grooves. Inner mandibular grooves evident, nearly forming a single curving structure, but become indiscernible at anterior portion of gular patch. Pair of very weakly but discernibly raised parotoid glands present on dorsolateral margin of head between orbits, postorbital grooves, and occiput. Upper lip protruding slightly beyond edge of lower lip in ventral and lateral views; no mental gland discernible under skin of anterior intermandibular region.

Arms relatively long and slender overall (FLL = 4.9 mm, 16.7 % of SL), without noticeable hypertrophied forearm compared to upper arm. Hands small and slender (HaL = 1.6 mm, 29.1 % of VGS; HaW = 1.4 mm, 25 % of HeW). Fingers II, III, and IV protruding freely, with at least ultimate and all to part of penultimate phalanges being free beyond interdigital tissue margin (LF2 0.74 mm, LF3 0.56 mm). Finger I with minimal indentation at interdgitial space. Tips of fingers rounded, with terminal pads discernible on ventral surfaces. Palmar surfaces appearing to be smooth overall, but with weakly discernible depressions radiating out from palmar section to interdigital margins between fingers. Dorsal surfaces of hands with discernible interdigital depressions or grooves, especially between fingers II-III and III-IV, that start at interdigital tissue margins and cross onto metacarpal region. Relative lengths of fingers on right hand I <IV <II <III.

Legs relatively long and slender overall (HLL 5.9 mm, 20.1 % of SL), without discernible differences between thickness of lower and upper legs. Feet small and slender (FoL 2.1 mm, 38.2 % of VGS; FoW 1.6 mm, 40.0 % of HeW). Toes II, III, IV and V protruding freely, with at least ultimate (toes II and V) and penultimate (toes III and IV) phalanges being free beyond interdigital tissue margin (LT2 0.9 mm, LT3 0.68 mm). Toe I with very minimal indentation at interdgitial space. Tips of toes rounded, with terminal pads discernible on ventral surfaces. Plantar surfaces appearing to be smooth overall, but with very weakly discernible depressions or groove along interdigital spaces. Dorsal surfaces of feet with discernible interdigital grooves, especially between toes II-III, III-IV, and IV-V, that start at interdigital tissue margins and cross onto metatarsal region. Relative lengths of toes on right foot I <V <II <IV <III.

Body subcylindrical (slightly wider than high) in cross section, and relatively slender (TW = 3.3 mm; TW = 19.7 % of AGL). Between axilla and groin, 11 costal grooves visible, 13 if counting axillary and inguinal grooves; costal grooves most visible on ventral and lateral portions of body. Adpressed limbs separated by 4.5 costal folds; 12 costal folds total between axilla and groin. Slight middorsal depression extends longitudinally along length of body, starting at base of head (occiput) and becoming indiscernible on anterior portion of tail. Tail long, 36.9 mm in length, cylindrical in cross section, lacking a discernible constriction at base, evenly tapering from cloaca to pointed terminus. Skin on surfaces of head, body, limbs, and tail smooth.

Coloration in life. The ground color of the dorsal and lateral surfaces of the head and trunk consisted of a brownish-orange coloration. Scattered throughout the dorsal and lateral surfaces of the head and trunk there were numerous dark brownish-black markings of irregular size and shape, in addition to numerous very fine white chromatophores. The parotoid glands where a contrasted paler tone compared to the surrounding dorsal surfaces. The iris was bright copper-orange with a black reticulation.

The upper surfaces of the arms and legs are very similar in coloration and pattern to that of the above-mentioned chromatic characteristics of the dorsal and lateral surfaces of the head and body.

The dorsal and dorsolateral surfaces of the anterior third of the tail were a paler shade of reddish-orange, but the posterior two-thirds of the tail was similar to dorsal surfaces of the trunk. There were also some very fine white chromatophores scattered randomly throughout the tail, but at a much lesser concentration compared to the body and head.

The ventral and ventrolateral surfaces of the head, limbs, and body were contrasted from the superior surfaces by consisting of a concentration of fine white chromatophores on a darker brownish-gray background. The gular patch was slightly more pale in comparison to the ventral surfaces of the trunk. The palmar and plantar surfaces were pale grayish-brown, lacking evident chromatophores. Directly surrounding the cloaca there was a concentration of bright orange chromatophores. The anterior third of the vental surface of the tail had an overall similar pattern and coloration to that of the ventral surface of the trunk. The ventral surface along the posterior two-thirds of the tail had a dark reddish orange ground color with numerous dark brown markings of irregular size and shape in addition to a relatively large concentration of very fine white chromatophores.

Coloration in ethanol. After more than a year and a half in ethanol (70%), the overall coloration of the holotype has changed to principally consisting of a mixture of tan and brown mottling. Two pale tannish-yellow patches are visible on the posterior dorsolateral surfaces of the head, where the parotoid glands are located. The dorsal surface of the anterior third of the tail is also pale tannish-yellow. The ventral surfaces of the body and tail are dark brownishgray. The ventral surface of the head has an evident paler tone compared to that of the rest of the body and tail.

Measurements (in mm), limb interval, and percentages of the holotype. SL 29.3; total length 66.2; tail length 36.9; ShW 3.4; HeW 4.0; NeW 3.3; EW 1.3; SnL 1.0; JSL 3.4; LGFS 6.0; LNH 0.25; RNW 0.25; IND 0.8; NLP 0.5; ICD 1.6; HLL 5.9; FLL 4.9; TW 3.3; VGS 5.5; FSL 8.0; UHL 3.3; AGL 16.7; VL 1.9; HaW 1.4; HaL 1.6; LF2 0.74; LF3 0.56; WF3 0.31; FoW 1.6; FoL 2.1; LT2 0.9; LT3 0.68; WT3 0.31. Limb interval 4.5. Measurements in related percentages: VGS/SL 18.8 %; IND/HeW 20.0 %; AGL/SL 57.0 %; HeW/SL 13.7 %; Hew/AGL 24.0 %; SnL/ HeW 25.0 %; LNH/HeW 6.3 %; LNH/SL 0.85 %; RNW/HeW 6.3 %; RNW/SL 0.85 %; HLL/SL 20.1 %; FLL/SL 16.7 %; HaL/VGS 29.1 %; FoL/VGS 38.2 %; Haw/HeW 35.0 %; FoW/HeW 40.0 %; LT2/FoL 42.9 %; LF2/HaL 46.3 %; WT3/FoW 19.4 %; WF3/HaW 22.1 %.

Measurements (in mm), limb intervals, and percentages of the paratopotypes. SL 19.2–26.6; ShW 2.5–3.0; HeW 3.0–3.3; NeW 2.5–3.1; EW 1.2–1.3; SnL 0.6–1.0; JSL 2.4–3.3; LGFS 4.5–5.7; LNH 0.12–0.25; RNW 0.14– 0.22; IND 0.7; NLP 0.3–0.4; ICD 1.4–1.7; HLL 4.5–4.9; FLL 3.9–4.6; TW 2.5–3.4; VGS 3.9–4.9; FSL 5.7–7.5; UHL 2.4–3.2; AGL 11.4–15.1; VL 1.6; HaW 0.9–1.1; HaL 1.1–1.2; LF2 0.37–0.57; LF3 0.34–0.4; WF3 0.22–0.23; FoW 1.1–1.5; FoL 1.4–1.6; LT2 0.53–0.65; LT3 0.37–0.56; WT3 0.25. Limb interval 4–6. Measurements in related percentages: VGS/SL 18.4–20.3 %; IND/HeW 21.2–23.3 %; AGL/SL 56.8–59.4 %; HeW/SL 12.4–15.6 %; Hew/ AGL 21.9–26.3 %; SnL/HeW 20.0–30.3 %; LNH/HeW 3.6–8.3 %; LNH/SL 0.45–1.3 %; RNW/HeW 4.2–7.3 %; RNW/SL 0.53–1.1 %; HLL/SL 18.4–23.4 %; FLL/SL 17.3–25.5 %; HaL/VGS 24.5–28.2 %; FoL/VGS 32.7–35.9 %; Haw/HeW 30.0–33.3 %; FoW/HeW 36.7–45.5 %; LT2/FoL 37.9–40.6 %; LF2/HaL 33.6–47.5 %; WT3/FoW 16.7–22.7 %; WF3/HaW 18.2–25.6 %.

Etymology. The specific epithet is formed from the Latin words lateo, which means to lie hidden, and muscus, which means moss. This taxon is named due to the fact that it often “lies hidden” within moss.

Habitat and natural history observations. Nototriton lateomuscus is known only from three specimens that have been found exclusively within moss growing on the trunks and branches of trees.

Distribution. Nototriton lateomuscus is endemic to Costa Rica, and currently only known to inhabit a single site on the extreme eastern margin of the Tilaran mountains (ca. 1200 masl), north of the city of San Ramon.

Figures

FIGURE 14. Holotype of Nototriton lateomuscus sp. nov. in life on white background. Photograph by BK.

FIGURE 15. Dorsal, lateral, and ventral views of the body of the holotype of Nototriton lateomuscus sp. nov. in preservation. Photograph by BK.

FIGURE 16. Dorsal views of the hand and foot and detail of the face of the holotype of Nototriton lateomuscus sp. nov. in preservation. Photograph by BK.