Pristimantis nanus, Zumel & Buckley & Ron, 2022

Zumel, Daniel, Buckley, David & Ron, Santiago R, 2022, The Pristimantis trachyblepharis species group, a clade of miniaturized frogs: description of four new species and insights into the evolution of body size in the genus, Zoological Journal of the Linnean Society 195 (1), pp. 315-354 : 325-330

PRISTIMANTIS NANUS SP. NOV.

( FIGS 5–9 ; TABLES 2 AND 3 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 594B77F6-9A58-49EC-8088-3B79E98891F2

Holotype ( Figs 5 , 6 ): QCAZ 72596 (field no. SC-PUCE 63140 ), adult female from Ecuador, Provincia Morona Santiago, Cantón Gualaquiza, Parroquia Bomboiza , in the buffer zone of El Quimi Biological Reserve , tepui plateau on the eastern side of the Quimi River (3.5182º S, 78.3913º W), 1994 m a.s.l., collected by Diego Almeida, Darwin Núñez, Eloy Nusirquia, Alex Achig and María del Mar Moretta on 23 April 2018.

Paratypes (six: five males, one female): Ecuador: Provincia Morona Santiago: buffer zone of El Quimi Biological Reserve, tepui plateau on the eastern side of the Quimi River , QCAZ 68569 , adult male (3.5187º S, 78.3920º W), 1978 m a.s.l. ; QCAZ 68616 , adult male (3.5189º S, 78.3689º W), 2209 m a.s.l. ; QCAZ 68618 , adult female (3.5188º S, 78.3697º W), 2202 m a.s.l. ; QCAZ 72595 , QCAZ 72598 and QCAZ 72616 , adult males (3.5182º S, 78.3913º W), 1994 m a.s.l. Collected by D. Almeida, D. Núñez, E. Nusirquia, A. Achig , R. Gavilanes and M. Moretta on 5, 11 July 2017 and 23 April 2018 .

Suggested common name: English: dwarf rain frog. Spanish: cutín enano.

Diagnosis ( Figs 5–9 ): A species of Pristimantis characterized by the following combination of characters: (1) dorsal skin smooth with scattered pustules; low scapular folds, \ /-shaped, with two pairs of low scapular subconical tubercles along them, anterolateral and posteromedial; ventral skin weakly areolate on throat and chest, areolate on belly and on posteroventral surface of thighs; discoidal fold distinct; (2) tympanic annulus distinct; tympanic membrane present but hidden by skin and muscle; upper and posterior margins of tympanic annulus covered by low supratympanic fold; one subconical tubercle and several pustules on postrictal region; (3) snout short with a very small rostral papilla at tip, rounded in both dorsal and lateral views; canthus rostralis poorly defined, concave in dorsal view, rounded in lateral view; (4) one to few subconical tubercles and pustules on upper eyelid; (5) cranial crests absent; (6) vocal slits and nuptial pads absent; (7) Finger I shorter than Finger II; discs of digits narrowly expanded, elongately acuminate; (8) fingers bearing narrow lateral fringes; (9) very low subconical ulnar tubercles; (10) one low subconical tubercle on heel; low and subconical outer tarsal tubercles; inner tarsal fold present; (12) toes bearing lateral fringes; basal toe webbing, most distinctive between Toe IV and Toe V; Toe V slightly longer than Toe III; toe discs slightly smaller as those on fingers; (13) in life, dorsal coloration highly variable, generally reddish brown with or without greenish areas; W- shaped paler mark in the scapular region; supratympanic folds darker than background; broad interorbital bar, pale cream anteriorly and dark posteriorly; sides of head usually with diffuse dark labial bars; flanks and dorsal surfaces of limbs with similar colour patterns and several darker diagonal stripes; surfaces adjoining the outline of these stripes are generally paler and have white spots or flecks; pale brown to dark brown venter with some white spots and dark flecks or mottling on throat, chest and belly; dark flecks and white spots of venter may reach the lower halves of flanks and head; throat darker than chest, belly and ventral surfaces of limbs; pale brown groins; dark red to reddish copper iris; and (14) SVL in adult females from 14.08 to 14.82 mm (mean = 14.45 mm; N = 2), adult males from 11.04 to 12.46 mm (mean = 11.67 mm; N = 5; Tables 2 and 3 ).

Comparisons with other species: In this section, coloration refers to live individuals unless otherwise noticed. Pristimantis nanus can be differentiated from the other species of the P. trachyblepharis species group, except P. minimus and P. trachyblepharis , by its tiny size ( Tables 2 and 3 ). Beyond that, P. nanus is similar to P. pramukae because both have W- shaped pale marks in the scapular region and a short snout. However, P. nanus has a chubbier appearance and less expanded, elongate-acuminate discs. Discs of P. pramukae may also be elongate-acuminate in some digits of several specimens, but this condition is not common. Moreover, P. pramukae usually have darker dorsal and ventral colours as compared with reddish, greenish or pale brown colours of P. nanus . Pristimantis nanus cannot be clearly distinguished from P. minimus (SVL range = 9.5–13.7 mm in adult males; 15.3– 18.9 in adult females) and P. trachyblepharis (SVL range = 12.37–15.47 mm in adult males; 15.53–22.24 in adult females) by size ( Tables 2 and 3 ); however, P. minimus is much less tuberculate, lacks tympanic membrane and males have vocal slits, unlike P. nanus males. P. trachyblepharis has a longer snout, a slimmer body and usually shows lighter colorations.

Pristimantis nanus can be confounded with other small congeneric species such as P. coronatus (SVL = 15.3 mm in a single female; Lehr & Duellman, 2007) and P. andinognomus (SVL = 10.0– 14.5 mm in adult males; 12.6–17.9 mm in adult females; Lehr & Coloma, 2008). Whereas P. nanus does not show distinctive colours on groins, P. coronatus show orange reddish colours. Pristimantis andinognomus has a dorsally acuminate snout as compared with the rounded snout of P. nanus and has white or yellow distinctive coloration in the groins (groins pale brown in P. nanus ) Additionally, males of P. andinognomus have vocal slits, which are absent on P. nanus males. Pristimantis nanus is also similar to P. exoristus ( Duellman & Pramuk, 1999) in having a small size (SVL = 15.0– 16.9 mm in adult males; 21.3–23.5 mm in adult females) and a W- shaped mark in the scapular region. However, in P. exoristus that mark is dark, and in P. nanus is paler than the background. Additionally, in P. exoristus the snout is moderately long, while in P. nanus it is short.

Description of the holotype: Adult female (QCAZ 72596). Measurements (in mm): SVL 14.82; tibia length 7.06; foot length 6.16; head length 5.21; head width 4.41; interorbital distance 1.65; width of upper eyelid 1.24; internarial distance 1.10; eye–nostril distance 1.36; eye diameter 1.78; tympanum diameter 0.65. Colour of the holotype in life and in preservative is shown in Figures 5 and 6 , respectively.

Head ( Figs 5 , 6A, B ): Longer than wide, wide as body; snout short with a very small rostral papilla at tip, rounded or slightly subacuminate in dorsal view, and rounded in profile; canthus rostralis poorly defined, concave in dorsal view, rounded in profile; loreal region concave; several pustules on dorsal surface of snout, and one low subconical tubercle anteromedial to the interocular region; tympanic annulus distinct, its upper margin covered by low supratympanic fold; tympanic membrane present but hidden by skin and muscle; one subconical postrictal tubercle and some pustules on each side of head; upper eyelid with three low subconical tubercles; skin on throat weakly areolate; dentigerous processes of vomer slightly posterior to choanae, triangular, widely separated, each vomer bearing four or five teeth; choanae not concealed by palatal shelf of maxilla; tongue slightly longer than wide, posteriorly notched, posterior half not adherent to the mouth floor.

Dorsum and venter ( Figs 5 , 6A, B ): Dorsal skin smooth bedecked with several pustules; low \ /-shaped scapular folds, bearing one pair of subconical tubercles on its anterior part, and another pair near its posterior end; scapular folds continue posteriorly with rows of small pustules to form almost negligible dorsolateral folds; cloacal sheath without tubercles; skin on chest weakly areolate, belly areolate; discoidal fold distinct.

Forelimbs ( Fig. 6C ): Very low ulnar tubercles; Finger I slightly shorter than Finger II; discs narrowly expanded, elongate acuminate, although slightly more rounded than discs on toes; all fingers having ventral pads surrounded by circumferential grooves; palmar tubercles not well defined, outer palmar tubercle bifid, approximately twice the size of the ovoid thenar tubercle; distinct subarticular tubercles; low hyperdistal subarticular tubercles; indistinct supernumerary tubercles; fingers bearing narrow lateral fringes; basal webbing slightly noticeable.

Hindlimbs ( Fig. 6D ): Heel bearing one low subconical tubercle; several subconical tubercles and some pustules on outer surface of tarsus; inner tarsal fold distinct; Toe V slightly longer than Toe III; discs narrowly expanded, elongate acuminate, nearly as large as those on fingers; all toes having ventral pads surrounded by circumferential grooves; ovoid inner metatarsal tubercle, approximately four times the size of the small and rounded outer metatarsal tubercle; subarticular tubercles distinct; hyperdistal subarticular tubercles low; supernumerary tubercles indistinct; toes bearing narrow lateral fringes; basal webbing, most distinctive between Toe IV and Toe V. Skin on anteroventral surface of thighs weakly areolate, posteroventral surface of thighs areolate.

Variation: The four individuals of P. nanus with available sequences show a mean intraspecific uncorrected genetic p- distance of 0.3% in the 16S gene. In the type series, adult males (SVL = 11.04– 12.46 mm) are between 11.51 and 25.51% smaller than adult females (SVL = 14.08–14.82 mm). Below we list character states distinct from those described in the holotype, followed by an example. Colour variation in life and in preservative is shown in Figures 7 to 9.

H e a d (F i g s 7 – 9): T h r e e s u b c o n i c a l postrictal tubercles (QCAZ 72595); two subconical postrictal tubercles (QCAZ 72616). Upper eyelid with several pustules (QCAZ 68616); one subconical tubercle (QCAZ 72595). Occipital subconical tubercle (QCAZ 72616).

Dorsum and venter ( Figs 7–9 ): Scapular folds almost undistinguishable (QCAZ 68616); prominent (QCAZ 72616). Pair of high subconical scapular tubercles towards the posterior end of the scapular folds (QCAZ 72616). Dorsolateral folds absent (QCAZ 72598). Distinct subconical sacral tubercles (QCAZ 72616). Dorsal skin uniformly smooth (QCAZ 68616). Belly and posteroventral surface of thighs coarsely areolate (QCAZ 68569).

Forelimbs ( Fig. 9 ): Fingers without lateral fringes (QCAZ 72598). Basal webbing absent (QCAZ 68618). Outer palmar tubercle completely divided (QCAZ 72598). Supernumerary tubercles at base of fingers (QCAZ 72598).

Hindlimbs ( Fig. 9 ): Dorsal surface of shanks highly pustulated (QCAZ 68569). Inner tarsal fold inconspicuous (QCAZ 72616). Toe V longer than Toe III (QCAZ 68618). Basal webbing absent (QCAZ 72598).

Distribution, natural history and conservation status: This species is only known from a single locality in the buffer zone of El Quimi Biological Reserve, in Morona Santiago Province, Ecuador, between 1978 and 2209 m a.s.l. ( Fig. 3 ). The natural region is Eastern Montane Forest. The type locality is on a limestone tepui plateau on the eastern side of the Quimi Valley. It was found on mosses, leaves, branches and bromeliads from the ground up to a height of 100 cm. The new species lives on forest ( Fig. 4 ) composed of thin, scattered trees 10–15 m high, shrubby vegetation 1.5 m high and soils with cushioned consistency, covered by mosses, roots and terrestrial bromeliads. This type of soil is locally known as bamba and is characteristic of limestone tepui formations. Individuals were collected about 3 km or more from the nearest disturbed area (pastureland). All observations were made at night. According to available data, this species has a restricted distribution (Extent of Occurrence 0.078 km 2, Area of Occupancy 12 km 2). However, adjacent areas remain unexplored, so we assign P. nanus to the Data Deficient Red List Category ( IUCN, 2021). The type locality is <1 km from the border with Peru. Therefore, its presence in Peru is almost certain.

Etymology: The specific name is derived from the Latin word nanus , meaning dwarf or small.

Figures

Figure 3. Distribution of Pristimantis trachyblepharis species group. Locality information for examined specimens is shown in Supporting Information, Table S2. UCS: Unconfirmed Candidate Species. Elevations are indicated in metres above sea level.

Figure 4. Land coverage in the Ecuadorian localities where individuals of the eight described species of the Pristimantis trachyblepharis species group were found. Land coverage shapefile was downloaded from Ministerio del Ambiente y Agua of Ecuador, at http://ide.ambiente.gob.ec/mapainteractivo. Locality information for examined specimens is shown in Supporting Information, Table S2.

Figure 5. Photographs of the holotype of Pristimantis nanus sp. nov. (QCAZ 72596; adult female, SVL 14.82 mm) in life. A, dorsolateral view; B, dorsal view; C, ventral view.

Figure 6. Photographs of the holotype of Pristimantis nanus (QCAZ 72596; adult female, SVL 14.82 mm) in preservative. A, dorsal view; B, ventral view; C, ventral view of the left hand; D, ventral view of the right foot.

Figure 7. Colour variation in life individuals of Pristimantis nanus in dorsolateral view. A, QCAZ 68569 (adult male, SVL 12.46 mm); B, QCAZ 68616 (adult male, SVL 11.04 mm); C, QCAZ 68618 (adult female, SVL 14.08 mm); D, QCAZ 72595 (adult male, SVL 11.78 mm); E, QCAZ 72616 (adult male, SVL 11.13 mm).

Figure 8. Colour variation in life individuals of Pristimantis nanus in ventral view. A, QCAZ 68569 (adult male, SVL 12.46 mm); B, QCAZ 68616 (adult male, SVL 11.04 mm); C, QCAZ 68618 (adult female, SVL 14.08 mm); D, QCAZ 72616 (adult male, SVL 11.13 mm); E, QCAZ 72595 (adult male, SVL 11.78 mm).

Figure 9. Colour variation in preserved individuals of Pristimantis nanus: 1, dorsal views; 2, ventral views.A, QCAZ 68618 (adult female, SVL 14.08 mm); B, QCAZ 68616 (adult male, SVL 11.04 mm); C, QCAZ 68569 (adult male, SVL 12.46 mm); D, QCAZ 72595 (adult male, SVL 11.78 mm); E, QCAZ 72616 (adult male, SVL 11.13 mm).