Description
Pristimantis burtoniorum is an Ecuadorian frog that was described from three males and three females, with males ranging from 16.6 - 17.5 mm in snout-vent length and females from 20.8 - 27.0 mm. The head is slightly longer than it is wide. The large snout appears subacuminate in the dorsal view and subacuminate or rounded in profile. The slightly protruding nostrils are directed laterally. There are several subconical tubercles on the upper mandible, which are more obvious in females. There is also a row of rounded tubercles along the middle of the snout. The canthus rostralis is straight and the loreal region is slightly concave. The internarial distance is greater than the upper eyelid but smaller than the interorbital distance. The interorbital area is flat. The distinct occipital region has a large, rounded tubercle, and two additional tubercles that are posterior and lower in position. The eye diameter is about twice the diameter of the tympanum and 170% the interorbital distance. The upper eyelid has three to four large subconical tubercles, and there is another subconical tubercle in the interorbital space. The tympanic membrane and annulus are distinct. The tympanum is smaller than the diameter of the eye. There is a low, rounded supratympanic fold present that is visible in the dorsal view and projects laterally. Subconical postrictal tubercles are present, but it is unclear if there are one or three. Cranial crests are absent. The skin on the dorsum and flanks is shagreen with the dorsum having scattered rounded tubercles, and a slightly defined mid-dorsal fold that runs from the tip of the snout to the vent. There are no dorsolateral folds. The skin of the venter is areolate and a distinct discoidal fold is present with low tubercles around the vent. The forearms are slender, having three low ulnar tubercles and a row of tubercles on the anterior region of the forearm. These tubercles can be weakly defined in life and greatly reduced by preservation effects. The oval palmar tubercle is three times larger than the rounded thenar tubercle. Finger 1 is shorter than Finger II. The fingers have fine lateral fringes, supernumerary tubercles at the base, and round, elevated subarticular tubercles. The truncated digital pads are expanded to twice the width of fingers II-IV and slightly wider than digit I. All digital pads have circumferential grooves. Weakly defined nuptial pads can be found on males. The hind limbs are 56.7% of the snout-vent length and slender in build. The tibia is longer than the foot. The heel has a small subconic tubercle and a row of three lower tubercles. The inner edge of the tarsus has a tarsal fold that is weak in the first portion, and the outer tarsal edge has small conical tubercles. The oval inner metatarsal tubercle is twice the size of the rounded outer metatarsal tubercle. The planter has weakly defined supernumerary tubercles. The toes have fine lateral fringes, no webbing, and distinct subarticular tubercles that are round and elevate. Toe V is much longer than toe III, which reaches the base of the distal subarticular tubercle of toe IV. The toe pads are expanded to twice the width of the digits (Reyes-Puig et al. 2022).

DIAGNOSIS:

Pristimantis burtoniorum is best distinguished from similar species of the Pristimantis genus by its red coloration of the hidden surfaces of the hind limbs, as well as its banded brown to pink patterns on the dorsum. Another way this species can be effectively differentiated from closely related species in the Eastern Ecuadorian Andes is by the presence of a row of tubercles that runs along the eyelids, a row of tubercles that run down the snout, and the pale red venter with brown splotches in life. In comparison, P. tungurahua also has a pale red venter, but it also has prominent calcars and dorsolateral folds, which P. burtoniorum lack. Prisitimantis sacharuna only exhibits red coloration in the groin, which is darker than P. burtoniorum, and the digital pads of P. sacharuna are not nearly as expanded as that of P. burtoniorum. Pristimantis puruscafeum and P. prolatus also resemble P. burtoniorum because they have brown dorsal and ventral patterns, but they lack flashy colors in the hidden surfaces and groin. Pristimantis nigrogriseus and P. ventrimarmoratus can also be distinguished because the former exhibits yellow markings in the groin and the latter exhibits orange/yellow markings in the groin and black and white marks on the venter, which are not found in P. burtoniorum (Reyes-Puig et al. 2022).

COLORATION:

In life, P. burtoniorum’s dorsal surfaces are dark brown with irregular light brown marks, which include marks in the subocular and labial region that form a banded pattern. Lighter brown markings also extend onto the sides of the body, forelimbs, and hind limbs. The ventral surface is predominantly light brown with dark brown marks, with the exception of the hidden surfaces of the shanks, groin, and armpit, which are red. The iris is reddish-brown in color. In preservative (70% ethanol), the head and dorsum are mostly dark brown with light brown and white bands extending to the flanks, forelimbs, and hind limbs. This same banded pattern exists on the subocular and labial regions. The groin, base of the venter, and shanks are red. Other ventral surfaces are marked with light brown, except for the chin, which has large splotches of dark brown and gray. The forelimbs, hind limbs, fingers, and toes are all banded with brown and gray lines (Reyes-Puig et al. 2022).

VARIATION:

The dorsal surface’s base color is dark brown and varies with different tones of light brown and cream bands. They may also have a thin mid dorsal line (Reyes-Puig et al. 2022).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Ecuador

View distribution map in BerkeleyMapper.

At the time of the species description, P. burtoniorum was only known from its type locality in the montane cloud forest at Machay Reserve in Rio Verde Parish, Baños township, Tungurahua Province, in the Republic of Ecuador. This area is characterized by a canopy 15 meters in height, an understory dominated by bromeliads (30 - 60 cm in height from the forest floor), and a dense layer of bryophytes and epiphytes. The species was found at an elevation of 2940 meters where the annual precipitation is about 2000 to 3000 centimeters (Reyes-Puig et al. 2022).

Life History, Abundance, Activity, and Special Behaviors
All specimens of P. burtoniorum were found hiding in the base of bromeliad leaves (Reyes-Puig et al. 2022).

Pristimantis burtoniorum can be found in sympatry with members of the Pristimantis festae complex, P. buckleyi complex, and species of Niceforonia and Hyloscirtus (Reyes-Puig et al. 2022).

Members of the Strabomantidae family are direct developers, hatching as fully formed frogs instead of eggs (Hedges et al. 2008). Thus, it can be inferred that P. burtoniorum is also a direct developer.

Larva
No documented information exists about larvae for this species. However, members of the Strabomantidae family are direct developers, hatching as fully formed frogs instead of eggs (Hedges et al. 2008). Thus, it can be inferred that P. burtoniorum is also a direct developer.

Trends and Threats
At the time of the species description, the authors called for further studies of the species to garner a larger understanding of their threats (Reyes-Puig et al. 2022).

Comments

PHYLOGENETIC RELATIONSHIPS:

References
Reyes-Puig, J. P., Reyes-Puig, C., Franco-Mena, D., Jos,t L., and Yánez-Muñoz, M. 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, 35–87. [link]

Hedges, S.B., Duellman, W.E., and Heinicke, M.P (2008). New World direct-developing frogs (Anura: Terrarana): molecular phylogeny, classification, biogeography, and conservation. Zootaxa 1737, 1-1. [link]

Species Account Citation: AmphibiaWeb 2024 Pristimantis burtoniorum: English name: Burtons’ Robber Frog; Spanish name: Cutín de los Burton <https://amphibiaweb.org/species/9534> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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