Synapturanus danta, Chávez & Thompson & Sánchez & Chávez-Arribasplata & Catenazzi, 2022

Chavez, German, Thompson, Michelle E., Sanchez, David A., Chavez-Arribasplata, Juan Carlos & Catenazzi, Alessandro, 2022, A needle in a haystack: Integrative taxonomy reveals the existence of a new small species of fossorial frog (Anura, Microhylidae, Synapturanus) from the vast lower Putumayo basin, Peru, Evolutionary Systematics 6 (1), pp. 9-20 : 9

Synapturanus danta sp. nov.

Synapturanus sp. ( Chávez et al. 2021)

Holotype.

Male CORBIDI 21050 (Figs 4A-E , 5A, B ), collected by Michelle E. Thompson, David Sánchez, and Germán Chávez at Campamento Quebrada Federico (02°31'34.7"S, 70°39'17.2"W; 110 m a.s.l.), Putumayo Province, Loreto Department, Peru, on 7 November 2019.

Paratopotypes.

Juvenile CORBIDI 21013 (Fig. 5E, F ), collected by Michelle E. Thompson, David Sánchez, and Germán Chávez at the same site on 6 November 2019; male CORBIDI 21051 (Fig. 5C, D ), same data as holotype .

Definition and diagnosis.

(1) A small-sized Synapturanus (SVL of 17.6-17.9 mm in adult males, females unknown); (2) head dorsally flat in lateral view; (3) eyes small, slightly larger than half the size of the eye-naris distance; (4) fingertips tapering without discs; (5) subarticular tubercles not visible on fingers; (6) thenar tubercle indistinct, palmar tubercle distinct; (7) fingers with preaxial and postaxial fringes (except preaxially on Finger IV), strongly visible on Fingers II and III pre and post axially; (8) toe tips slightly expanded in toes II and III; (9) inner metatarsal tubercle indistinct, outer metatarsal tubercle indistinct; (10) dorsal color pattern chocolate brown without spots or blotches, a stripe along the canthus rostralis and upper eyelid only present in juveniles; (11) throat and ventral surface of limbs cinnamon brown or pinkish brown, chest and belly cyan white; (12) call consisting of a tonal note 0.054-0.063 seconds in length with a slight downward frequency modulation (delta 0-94 Hz) and a dominant frequency at 1.73-1.81 kHz (Table 3 ).

Table 1 summarizes morphological differences between the new species and the current described congeners. In appearance, Synapturanus danta sp. nov. is easily distinguishable from most of its congeners, except for S. rabus and S. salseri , by bearing a flat head in lateral view (vs convex in the rest of species). The new species can be further distinguished from S. rabus (data for S. rabus taken from Pyburn 1977 and Fouquet et al. 2021b) by having an indistinct tympanum (vs visible), an eye slightly larger than half of the size than eye-naris distance (vs slightly smaller than half of the size of eye-naris distance), lacking canthal stripe in adults (vs present), and an advertisement call with a note length of 0.054-0.063 seconds (vs 0.03 seconds). From S. salseri , by being smaller with a mean SVL of 17.8 mm in adult males (vs 26.4 mm), and by having a visible palmar tubercle (vs absent), no metacarpal and inner metatarsal tubercles (vs present), no spots or stripes on dorsal surface of body (vs orange or gray spots and a discontinuous canthal stripe present), and by having an advertisement call with a dominant frequency ranging from 1.73-1.81 kHz (vs 1.10-1.47 kHz in S. salseri ). Furthermore, the new species can be differentiated from S. ajuricaba by having a non-visible tympanum (vs visible), eyes being slightly larger than half the eye-naris distance (vs slightly smaller than half the eye-naris distance), an advertisement call with a dominant frequency of 1.73-1.81 kHz (vs 1.01-1.12 kHz); and by lacking spots on dorsum (vs present). Moreover, the new species is differentiable from S. mesomorphus , S. mirandariberoi and S. zombie by having a slender body shape (vs robust in S. mirandariberoi and S. zombie ), non-rounded fingers (vs rounded in S. mesomorphus and S. mirandariberoi and having a rounded disc on fourth finger in S. zombie ), a palmar tubercle present (vs absent), lacking thenar and metatarsal tubercle (vs present), having an advertisement call with a higher dominant frequency, ranging from 1.73 kHz to1.81 kHz (vs 1.06-1.13 kHz in S. mesomorphus , 1.10-1.47 kHz in S. mirandariberoi , and 1.06-1.19 kHz in S. zombie ), and by lacking spots or speckles on dorsum (vs present). Additionally, the new species differs from a genetically related undescribed species (Fig. 2 ) from Serra do Divisor National Park, western Brazil ( Synapturanus sp. “Divisor” voucher number MZUSP 159223, Fouquet et al. 2021a), by having a longer head which is in average 27% of the SVL, n=3 (vs 19%, n=3), a shorter nose being 33% of the head length, n=3 (vs 47%, n=3) and shorter tibia which is about 32% of the SVL, n=3 (vs 40%, n=3).

Description of the holotype.

An adult male (CORBIDI 21050), 17.9 mm SVL; body stout; head slightly wider than long, HL 24% of SVL; dorsal and ventral skin smooth from head to cloaca; linea masculina visible through the translucent ventral skin in life, extending ventrolaterally from axilla to groin; supratympanic fold barely visible, running from the posterior corner of the eye to the level of the neck; snout long and strongly protruding, projecting way beyond the end of the lower jaw (1.34 mm), tip of the nose protruding, rounded in dorsal and lateral view. Eyes small, 66% of EN; nares located laterally, closer to the tip of the snout (0.69 mm) than to the eye (1.51 mm); canthus rostralis acutely rounded, loreal region strongly concave, grooved; IN 19% of HW; EN 35% of HL. Tympanum barely visible; choanae small (less than 50% of ED), oval, located anterolaterally, no odontophores. Forelimb robust, skin smooth; HAND 15% of SVL; Finger II longer than Finger I when fingers adpressed; fingers short, tips tapering excepting Finger III, unwebbed, with pre- and postaxial fringes, particularly developed on Fingers II and III where fringes extend towards the base of fingers; no finger discs; relative length of adpressed fingers III > IV > II > I; subarticular tubercles not visible on fingers; thenar tubercle indistinct, palmar tubercle small, oval. Glandular unpigmented supracarpal pad present. Hind limb robust, skin smooth; TL 28% of SVL; FL 41% of SVL; relative length of adpressed toes IV > III > V > II > I; toes without discs, tapering on I, IV, and V, expanded on II and II. Toes unwebbed with narrow pre- and postaxial fringes. Subarticular tubercles not visible on toes; inner metatarsal tubercle indistinct, outer metatarsal tubercle indistinct. Metatarsal fold absent.

Color of holotype in life.

Dorsum and flanks chocolate brown without spots. Absence of a stripe along the canthus rostralis and upper eyelid. Snout white, unpigmented. Throat cinnamon brown with scattered pale orange or yellow dots; chest and belly translucent cyan with white small melanophores (Fig. 4A, B ). Upper and lower arm and dorsal surfaces of thigh, shank and tarsus similar to the dorsum in color. Glandular supracarpal pad translucent white.

Color of holotype in preservative.

Dorsum dark brown, nose sulphur yellow. Throat creamy yellow with brown speckles. Chest and belly creamy yellow, with brown speckles toward the flanks, ventral surfaces of limbs yellowish brown. (Fig. 4A-E ).

Variation.

For morphometric variation see Table 2 . Sexual dimorphism unknown. A cyan-white discontinuous canthal stripe extending to the upper eyelid and then, reaching the groins is present in juvenile CORBIDI 21013 (Fig. 5E, F ). Dorsal coloration of this juvenile is dark brown with tiny pale orange dots on dorsal surface of limbs. Ventral cyan-white coloration reaching the edge with the flank in male CORBIDI 21051. Ventral surface of feet black in male CORBIDI 21051 (Fig. 5C, D ).

Advertisement call.

Synapturanus danta sp. nov. (n=2) emits single tonal notes (mean note length 0.059, range 0.054-0.063 seconds, SD=0.003) every 4.083 seconds on average (inter-note range 3.777-4.552 seconds, SD=0.300). The dominant frequency is 1.763 kHz on average (range 1.734-1.809 kHz, SD=0.031) with a slight downward modulation (mean 0.059, range 0.000-0.094 kHz, SD=0.049); a harmonic structure is present (Fig. 6 , Table 3 ).

Etymology.

The specific epithet is a noun in apposition and refers to the Amazon Tapir ( Tapirus terrestris ), a large mammal locally known as “Danta”. During our expedition, the first time that local people and other researchers in the team spotted one of these frogs, they called it "Rana Danta", because its head profile reminded them of the head of the Amazon Tapir.

Distribution, habitat and natural history.

Synapturanus danta sp. nov. is only known from a population in the Lower Putumayo River Basin, Loreto, Peru (Fig. 1 ). All individuals were captured at night in galleries underneath roots of Clusia spp. in habitats classified as Amazon Peatlands ( Xu et al. 2018; Figs 1 , 7 ), at the beginning of the rainy season. This peatland ecosystem is thought to occur over large areas in the Putumayo Basin (Figs 1 , 7 ; Gumbricht et al. 2017, Xu et al. 2018,); however, some of the areas predicted to be peatlands have yet to be validated with field surveys. Synapturanus danta sp. nov. inhabits the soils of stunted pole forests growing on peat. The vegetation at the type locality consists of treelet species which are common in stunted varillal and chamizal forests on white sand in Loreto, Perú (e.g., Mauritiella armata , Macrolobium limbatum , Retiniphyllum concolor , Dendropanax resinosus , Remijia ulei , as well as the filmy ferns in the genus Trichomanes ), treelet species only known to grow in Loreto in stunted forests on peat soils (e.g., Tabebuia insignis var. monophylla, Diplotropis purpurea , Graffenrieda limbata , Macrolobium sp., Rapatea ulei ) and small populations of other common wetland species such as Mauritia flexuosa and Euterpe precatoria ( Ríos Paredes et al. 2021). These peatlands are seasonally saturated ecosystems, with periods of high-water levels resulting in a matrix of pools formed by rainwater and unsaturated land sitting above the pooled water, and periods of drying down of the landscape when there is low to no rainfall. We sampled during a period of rising water levels at the beginning of the rainy season; however, many unsaturated areas were present, scattered throughout the habitat around root chambers of individual trees and palms. Adult males were caught in those unsaturated areas within chambers and galleries of 15-30 cm depth, underneath roots of Clusia spp. Instead, the only juvenile collected (CORBIDI 21013) was captured only 5 cm depth, jumping between roots of the same species of tree where the adults were calling from. All individuals were observed 3-4 meters apart from each other.

Figures

Figure 1. Map showing the type locality of Synapturanus danta sp. nov. (black star), and the localities of the closest populations of Synapturanus. Those correspond to four undescribed taxa (Fouquet et al. 2021 a): S. sp " Ica 1 " (pale blue circle). S. sp. " Ica 2 " (yellow circle) from Brazil, S. sp " Divisor " from Brazil and Peru (red circles), and S. sp. " Nanay " from Peru (pink circle). Green patches represent Amazon peatlands present in the area (Xu et al. 2018).

Figure 2. Phylogenetic analysis based on a fragment of 16 S, showing the relationship among Synapturanus danta sp. nov. (in red), its congeners, and species of Adelestes and Otophryne (Microhylidae). ML bootstrap values are indicated at each node. Taxa assignation to central, eastern and western clade follows Fouquet et al. (2021 a).

Figure 4. Lateral (A.), dorsal (B.) and ventral (C.) views of the head; Dorsal (D.) and ventral (E.) views of the body of the holotype (CORBIDI 21050, SVL = 17.9 mm) of Synapturanus danta sp. nov. Photographs by Eduardo Quispe-Salcedo.

Figure 5. Type series of Synapturanus danta sp. nov. in life. A, B. Dorsal and ventral view of male CORBIDI 21050 (holotype, SVL = 17.9 mm); C, D. Dorsal and ventral view of male CORBIDI 21051 (SVL = 17.6 mm); E, F. Dorsal and ventral view of male CORBIDI 21013 (SVL = 7.5 mm). Photographs by German Chavez.

Figure 6. Audio spectrograms and oscillograms of the advertisement call of the holotype (CORBIDI 21050) of Synapturanus danta sp. nov .. recorded at night, in the Lower Putumayo River basin. A. Single call; B. Series of two calls

Figure 7. Panoramic view of the type locality (A.) and a view of the landscape in the Amazonian Peatlands inhabited by Synapturanus danta sp. nov. (B.). Photographs by Alvaro del Campo (A.) and Luis Montenegro (B.).