Pristimantis burtoniorum, Reyes-Puig 1 & Reyes-Puig 1 & Franco-Mena 5 & Jost 2 & Yánez-Muñoz 1, 2022

Reyes-Puig 1,2, Juan Pablo, Reyes-Puig 1,3,4, Carolina, Franco-Mena 5,6, Daniela, Jost 2, Lou & Yanez-Munoz 1,2, Mario H., 2022, Strong differentiation between amphibian communities on two adjacent mountains in the Upper Rio Pastaza watershed of Ecuador, with descriptions of two new species of terrestrial frogs, ZooKeys 1081, pp. 35-87 : 35

Pristimantis burtoniorum sp. nov.

Figures 33 , 35 , 36 Proposed standard English name: Burtons’ Robber Frog Proposed standard Spanish name: Cutín de los Burton

Material examined.

Holotype. DHMECN 14479 (adult Female, Fig. 35 ), collected by Mario Yánez-Muñoz, Juan Pablo Reyes-Puig and Daniela Franco-Mena, in the Machay Reserve , Rio Verde Parish, Baños township, Tungurahua Province, Republic of Ecuador (-1.370008, -78.268117; 2970 m elev.) on 2 March 2018.

Paratypes (2 females, 3 males). DHMECN 14482 (♀), DHMECN 14447 (♀) y DHMECN 14480 (♂), DHMECN 14478 (♂), DHMECN 14481(♂), with same data as the holotype .

Generic placement.

We assign the new species to Pristimantis , based on having head about as wide as body; tympanic membrane differentiated t; cranial crests usually; dentigerous process of vomers usually present; “S” condition of the adductor muscles; terminal discs on digits, bearing well-defined circumferential grooves, supported by T-shaped terminal phalanges; comparative lengths of fingers I and II variable; toe V as long as, or longer than, toe III; and subarticular tubercles not protruding; (Hedges 2008).

Diagnosis.

Pristimantis burtoniorum sp. nov. is distinguished from all congeners by the following combination of characters: (1) skin on dorsum and flanks finely shagreen with a slightly defined mid-dorsal fold, which extends from the tip of the snout to the ventre; skin on ventre areolate, dorsolateral folds absent; discoidal fold present and defined; (2) tympanum present; tympanic membrane and annulus present, equivalent to 25% of the eye diameter; with a single subconic postrictal tubercle; (3) snout large and subacuminate in dorsal and lateral profile; with several small subconic tubercles along the upper mandibulae, more evident in females; (4) upper eyelid with 3-4 large subconic tubercles; one subconic interorbital tubercle, followed by a row of rounded tubercles along middle of the snout; upper eyelid wider than interorbital distance; cranial crests absent; (5) dentigerous process of vomer present, oval in outline with 4-5 teeth oval; (6) males lacking vocal slits, nuptial pads weakly defined; (7) finger I shorter than II; expanded digital pads, extended in fingers II-IV; two times the width of the digits; (8) fingers with large lateral fringes; (9) forearms with small conic ulnar tubercles; (10) heel with a small conic tubercle; outer border of the tarsus with small conical tubercles, inner tarsal fold present, weakly defined in the first portion; (11) two metatarsal tubercles, inner oval twice size of the outer tubercle that is round-shaped; (12) toes with fine lateral fringes; plantar supernumerary tubercles present, toe V larger than III, not extending further than distal subarticular tubercle of toe IV; (13) dorsal colouration grey with transversal marks dark brown, legs and arms with diagonal bands dark brown with interspaces pink (red in life), flanks with oblique bands finely delineated by cream, hidden surfaces of the venter and groin red; ventral colour grey dense, marked by dark brown, throat and outer mandibulae with dark brown marks, brown-red iris and (14) SVL in males 16.61-17.45 mm; females 20.81-27.03 mm.

Comparisons with other species.

Pristimantis burtoniorum is characterised by the presence of red colouration in hidden surfaces of the hind-limbs, this colouration combined with banded patterns of brown and pink. The presence of tubercles on the upper eyelid, interorbital tubercle and a row of rounded tubercles along snout to the tip and a pale red venter with dark brown mottled pattern in life, easily distinguish the new species from other congeners occurring on the eastern Ecuadorian Andes, diagnostic morphological characters avoiding polymorphism of previously-known species (Fig. 33 ). Another rain frog with red colours on the ventral surfaces that may be confused with P. burtoniorunm is P. tungurahua ( Reyes-Puig et al. 2010); however, this species has prominent calcars and dorsolateral folds; P. sacharuna ( Reyes-Puig et al. 2015) exhibits red colours on the groin, but this is much darker red and is restricted to the groin and the digital pads are very much narrower than the new species. Other similar species in the upper Rio Pastaza watershed are P. puruscafeum ( Reyes-Puig et al. 2014) and P. prolatus ( Lynch and Duellman 1980); however, they have brown dorsal and ventral patterns with no flash colours on hidden surfaces and groins. Finally, P. nigrogriseus (Anderson 1945) has yellow hidden marks on the groin and P. ventrimarmoratus ( Boulenger 1912) has black and white marks on the venter and the exhibits orange/yellow marks on the groin.

Description of the holotype.

(Figs 35 , 36 ) Adult female. Measurements in mm: SVL 22.63; tibia length 12.85; foot length 10.56; head length 8.68; head width 7.36; upper eyelid width 1.93; interorbital distance 2.75; internarial distance 2.19; eye-nostril distance 2.32; eye diameter 4.7; tympanum diameter 2.5; hand length 7,17; head slightly wider than long (12.8 mm vs. 11.7 mm); head width 32.5% of SVL; head length 38% of SVL. Snout subacuminate in dorsal view, rounded in lateral profile (Fig. 35 ). Eye-nostril distance 10.25% of SVL; cantus rostralis straight, loreal region slightly concave; nostrils slightly protuberant, orientated laterally, interorbital area flat, wider than upper eyelid; upper eyelid length is 70% of the interorbital distance, cranial crests absent, occipital region prominent with a large rounded tubercle and two tubercles posterior and lower position. Upper eyelid with two rounded tubercles and other low. Row of small rounded tubercles along middle snout. Tympanic membrane differentiated from surrounding skin, tympanic annulus differentiated, low supratympanic fold with rounded shape, tympanum visible in dorsal view, laterally projected, tympanum diameter 35% of eye diameter, three subconical postrictal tubercles; choanae small, rounded in profile covered by the palatal shell of the maxilla; dentigerous processes of vomer present, oval on outline with 4-5 teeth; tongue longer than wide, oval shape, 60% of it fixed to the mouth floor.

Skin of the dorsum finely shagreen with scattered rounded tubercles; slightly defined dermal fold extending from the tip of the snout to the vent; venter areolate, discoidal fold present; without anal ornamentation and with low tubercles. Forearms slender with three lower ulnar tubercles and a row on the anterior region of the forearm, weakly defined or reduced by preservation effects, fingers with fine lateral fringes (Fig. 36 ), palmar tubercle oval three times larger than thenar tubercle that is rounded; subarticular tubercles of the fingers in hand rounded and elevated, supernumerary tubercles rounded at the base of each digit; digital pads truncated and expanded, twice width of fingers II,III, IV, in finger I slightly wider than the digit; all fingers have digital pads defined by circumferential grooves (Fig. 34 ).

Hind-limbs slender, tibia length 56.7% snout-vent length, small subconic tubercle on the heel with a row of three lower tubercles; inner tarsal fold present, outer edge of the tarsus with low tubercles; toes with fine lateral fringes, without digital webbing, toes digital pads expanded to twice the width of the digit; subarticular tubercles rounded, well defined and elevated, small supernumerary tubercles weakly defined; metatarsal tubercles present, inner oval double in size than outer that is rounded; toe V much longer than III, reaching base of distal subarticular tubercle of toe IV.

Colour of holotype in life (Fig. 37 ). Dorsal surfaces dark brown, with irregular light brown marks, subocular and labial marks forming a banded pattern, body dark brown with light brown marks forming bands extending to the flanks, forelimbs and hind-limbs. Shanks and hidden surfaces of groin and armpit red, other ventral surfaces light brown with dark brown marks. Iris reddish-brown.

Colour of holotype in ethanol 70 % (Fig. 35 ). Head and dorsum predominantly dark brown, banded with light brown and white lines extending to the flanks, forelimbs and hind-limbs as in the lips, a labial mask with a banded pattern is present. Groin and base of the venter and shanks red, other ventral surfaces mottled with light brown, chin with irregular dark brown and grey marks; forelimbs, hind-limbs, fingers and toes banded with brown and grey.

Variation (Fig. 37 ). Specimens of Pristimantis burtoniorum present a dorsal colouration with different tones of dark brown banded with light brown and cream, including variations with a thin mid dorsal line (Fig. 23 ). Variation in morphometric measurements are presented in Table 3 .

Distribution and natural history.

Pristimantis burtoniorum is known only from the type locality in the Machay Reserve, Rio Verde Parish, Baños township, Tungurahua Province, Republic of Ecuador (Fig. 2 ) at an elevation of 2940 m. This locality is comprised of montane cloud forest ( MAE 2012), with a canopy of 15 m with a dense layer of bryophytes and epiphytes and an understorey dominated by bromeliads of 30-60 cm in height from the forest floor. This is the predominant microhabitat for Pristimantis burtoniorum ; all specimens were found hiding in the base of bromeliads leaves. Sympatric species are Pristimantis festae complex, P. buckleyi complex, Niceforonia sp and Hyloscirtus sp.

Etymology.

Species epithet is the genitive plural of “Burton” in Latin, in recognition of John and Viv Burton, who founded and led the World Land Trust for most of its existence. Their impact on nature conservation is worldwide. Without the World Land Trust’s "Forests in the Sky" initiative, it would not have been possible for EcoMinga Foundation to establish the Machay Reserve and complete the Llanganates-Sangay Ecological Corridor.

Figures

Figure 2. Sample points in the Naturetrek-Vizcaya Reserve (black triangles) and the Machay Reserve (black circles). The white triangle is the type locality of Pristimantis maryanneae sp. nov. and the white circle is the type locality of Pristimantis burtoniorum sp. nov. The grey shaded areas are the Reserves of the EcoMinga Foundation within the Llanganates-Sangay Corridor and the green shaded areas represent Llanganates National Park (north) and Sangay National Park (south).

Figure 23. Prisitmantis sp. aff. Prisitmantis eriphus. Lateral view of male (DHMECN 14443) Photograph by Mario H. Yanez-Munoz.

Figure 33. Live photograps of new species and comparison with similar Pristimantis frogs in the region A Pristimantis burtoniorum sp. nov. (DHMECN 16220 from Machay Reserve Cerro Mayordomo.) B P. maryanneae sp. nov. (DHMECN 14454 from Naturetrek Vizcaya Reserve) C P. prolatus (DHMECN 16244 from El Encanto) D P. albujai (DHMECN 12245 from Sardinayacu river) E P. tungurahua (DHMECN 15224 from Naturetrek Vizcaya Reserve) F P. puruscafeum (not collected from Cerro Candelaria Reserve) G P. sacharuna (DHMECN 16723 from Rio Zunag Reserve) H P. ventrimarmoratus not collected from Rio Zunag Reserve I Pristimantis sp (DHMECN 16250 from El Encanto). Photographs Juan Pablo Reyes Puig, Mario Yanez Munoz, Jorge Brito and Lou Jost.

Figure 34. Pristimantis maryanneae, live photographs of Paratypes A lateral view and B dorsal view (DHMECN 14452) C lateral view and D dorsal view (DHMECN 14451). Photographs by Mario H. Yanez-Munoz.

Figure 35. Pristimantis burtoniorum sp. nov. (DHMECN 14479), adult female, holotype, SVL = 22.6 mm A dorsal view B ventral view C lateral view. Photographs by Mario H. Yanez-Munoz.

Figure 36. Pristimantis burtoniorum sp. nov. (DHMECN 14479), adult female, holotype A palmar surface detail B plantar surface detail. Photographs by Mario H. Yanez-Munoz.

Figure 37. Pristimantis burtoniorum A lateral view female paratype (DHMECN 14477) B frontal view, male paratype (DHMECN 14480) C groin view, female paratype (DHMECN 14482) D dorsal view of Holotype (DHMECN 14479). Photographs by Mario H. Yanez-Munoz.