Phyllonastes sardinayacu, Ortega & Cisneros-Heredia & Camper & Romero-Carvajal & Negrete & Ron, 2025

Phyllonastes sardinayacu sp.nov.

LSID: urn:lsid:zoobank.org:act:B12C9470-F32C-4CEA-9A1B-E2DE6D0CDBA3

Holotype ( Figs 22C View Figure 22 , 23B View Figure 23 , 24 View Figure 24 , 25 View Figure 25 ): QCAZ 58822 View Materials (field no. SC-PUCE 49151) adult female from Ecuador, Morona Santiago Province, Canton Morona, Sinaí Parish , Sangay National Park , Sardinayacu , trail to El Enmascarado Lagoon from refuge 3 (2.0500°S, 78.2196°W), 1798 m a.s.l. Collected by Javier Pinto, David Velalcázar, and Darwin Núñez on 23 January 2015. GoogleMaps

Paratype (N = 1; Fig. 24 View Figure 24 ): Same locality, collectors, and date as holotype, QCAZ 58821 adult female GoogleMaps .

Proposed standard English name: Sardinayacu leaflitter frog.

Proposed standard Spanish name: Cutín de Hojarasca de Sardinayacu.

Definition ( Figs 22C View Figure 22 , 23B View Figure 23 , 24 View Figure 24 , 25 View Figure 25 ; Tables 2 View Table 2 and 3 View Table 3 ): We assign the new species to the genus Phyllonastes based on its phylogenetic relationships. The new species is characterized by: (1) skin on dorsum and flanks finely shagreen, dorsolateral folds absent, ventral surfaces smooth, discoidal fold present; (2) tympanic membrane and tympanic annulus present, supratympanic fold absent, postrictal tubercle absent; (3) snout rounded to truncate in dorsal view and rounded in lateral view; (4) upper eyelid without tubercles, cranial crests absent; (5) vomerine teeth absent; (6) vocal slits and nuptial pads unknown; (7) fingers not expanded distally, finger tips subacuminate without papillae, finger I shorter than finger II, supernumerary tubercles present; (8) fingers bearing narrow lateral fringes, ill-defined pads lacking circumferential grooves; (9) distal phalanges blunt to T-shaped, phalangeal formula of hand 2-2-3-3; (10) ulnar tubercles absent; (11) knees and heels without tubercles, outer edge of tarsus without tubercles, inner edge of tarsus bearing one subconical tubercle; (12) inner metatarsal tubercle elongated in ventral view and rounded in lateral view, bigger than rounded outer metatarsal tubercle; (13) toes slightly expanded distally, with acuminate toe tips and lacking papillae, supernumerary tubercles present, narrow lateral fringes on toes, toe webbing absent, all toes bearing ill-defined pads and circumferential grooves, toe V shorter than toe III; (14) in life, brown dorsum, with two dark brown sacral lateral patches with light brown border, triangular cloacal blotch dark brown with light brown border, ventral surfaces dark brown with scattered small white spots, facial mask dark brown extending from tip of snout to groins, groins orange– brown; and (15) SVL in adult males unknown, SVL in adult females 14.21 mm (N = 2) ( Table 4 View Table 4 ).

Diagnosis: Phyllonastes sardinayacu resembles its closest related species, P. macuma , P. lochites , and P. myrmecoides , by having a tympanic annulus, tympanic membrane, fingers not expanded distally, and acuminate toe tips. It differs from P. macuma by having subconical inner tarsal tubercle (rounded in P. macuma ) and a mask extending to groins (mask extending to anterior half of flank in P. macuma ), and by the absence of papillae in toe tips (present in P. macuma ). Phyllonastes sardinayacu also differs from P. lochites and P. myrmecoides by having three phalanges in finger IV (two phalanges in finger IV in P. lochites and P. myrmecoides ). It differs further from P. lochites by having a rounded snout in lateral view (subtruncate in P. lochites ) and from P. myrmecoides by the absence of papillae in fingertips and toe tips (both present in P. myrmecoides ) and by the presence of supernumerary plantar tubercles (absent in P. myrmecoides ). For a comparison with other Phyllonastes species that are more phylogenetically distant, see Tables 2 View Table 2 and 3 View Table 3 .

Description of the holotype ( Figs 24 View Figure 24 , 25 View Figure 25 ): Adult female (QCAZ 58822). Measurements (in millimetres): SVL, 14.10; tibia length, 6.53; foot length, 6.39; head length, 3.77; head width, 4.33; eye diameter, 1.66; tympanum diameter, 0.78; interorbital distance, 1.87; upper eyelid width, 1.26; internarial distance, 1.68; eye–nostril distance, 0.92.

Head wider than long, head wider than body; canthus rostralis slightly convex in lateral view; loreal region straight in dorsal view; cranial crests absent; upper eyelid lacking tubercles. Tympanic annulus beneath skin; tympanic membrane present; supratympanic fold and postrictal tubercles absent. Vomerine teeth absent, vocal slits and nuptial pads absent. Snout short and round in dorsal and lateral views, without rostral papilla.

Skin on dorsum and flanks finely shagreen; dorsolateral folds absent; ventral surfaces smooth; skin on cloacal region areolate; discoidal fold present. Ulnar tubercles absent, palmar tubercles low, outer palmar tubercle rounded, with a small extension pointing towards the centre of the palm, larger than elongate thenar tubercle; subarticular tubercles visible only at base of fingers, round in ventral and lateral view; supernumerary tubercles present; narrow lateral dermal fringes on fingers; discs narrow, bearing round and inconspicuous pads; fingers not expanded distally, tip of fingers subacuminate; circumferential grooves not visible; relative length of fingers is I <IV <II <III; phalangeal formula of hand is 2-2-3-3.

Hindlimbs robust; heels and knees without tubercles; tarsal folds (inner and outer) absent, outer tarsal tubercles absent; inner tarsal tubercle present, small, subconical, and prominent; inner metatarsal tubercle small (ill defined in preservative), elongated in ventral view and rounded in lateral view; round outer metatarsal tubercle well defined and prominent; plantar surface with supernumerary tubercles; round subarticular tubercles, ill defined, visible only at base of toes; toes with narrow lateral dermal fringes; webbing between toes absent; discs on toes ill defined (ill defined in preservative), slightly expanded, with acuminate tip (specially on toe III), papilla on tip absent; ill-defined pads and circumferential grooves; relative lengths of toes I <II <V <III <IV; toe III longer than toe V.

Colour of holotype in life (based on digital photographs) ( Fig. 24 View Figure 24 ): Brown dorsum, slightly darker anteriorly, with two lateral, dark brown circular spots with a light brown border at sacrum level. Triangular cloacal blotch dark brown with light brown border. Ventral surfaces dark brown with scattered small white spots. Ventral surfaces of thighs and lower abdomen with irregular orange–brown blotches. Facial mask dark brown extending from tip of snout to groins and delineated dorsally by a light line. Flanks brown, with dark brown band along anterior half, connecting anteriorly with dark brown face mask. Groins brownish orange. Lips bearing small and white spots. Forearms, elbows, and knees with dark brown blotches delineated by a paler line.

Colour of holotype in preservative ( Fig. 24 View Figure 24 ): Dorsal surfaces brown. Head slightly darker than dorsum. Sacral lateral patches dark brown, with slightly lighter border. Cloacal triangle, spots on knees, and elbows dark brown with lighter margins. Ventral surfaces brown, becoming darker towards the throat. Scattered cream spots on ventral surfaces, more marked posteriorly and on hindlimbs.

Variation ( Fig. 24 View Figure 24 ): This section refers to preserved individuals, unless otherwise mentioned. The only paratype, QCAZ 58821 (adult female), differs from the holotype in having a truncate snout in dorsal view and darker coloration. Morphometric variation is detailed in Table 4 View Table 4 .

Distribution, natural history, and conservation status ( Fig. 3 View Figure 3 ): Phyllonastes sardinayacu is known from a single locality in Sangay National Park, near Sardinayacu, 1700 m a.s.l. Individuals were collected in Eastern Montane Forest at night (22:00–23:00 h) on leaf litter in primary and terra firme forest. Because of the lack of information on population size and geographical range, we suggest assigning P. sardinayacu to the Data Deficient IUCN Red List Category (based on IUCN Standards and Petitions Committee 2023).

Etymology: The specific name sardinayacu is a toponym used in apposition and it refers to a river at the species type locality. Sardinayacu is a compound word of Kichua origin, ‘sardina’ meaning sardine and ‘yaku’ meaning water.