Atelopus spumarius Cope, 1871

Atelopus spumarius Cope, 1871 View in CoL

Figs. 3–4 View FIGURE 3 View FIGURE 4

Atelopus spumarius Cope, 1871: 222 View in CoL from “Ambyiacu R.“ (= PERU: Loreto: Río Ampiyacu), syntypes lost (2 specimens at ANSP, leg. John Hauxwell); Lötters et al. 2002a: 168; Lötters et al. 2002b: 97; Lötters et al. 2003: 173; Lötters et al. 2005: 345; Rueda Almonacid et al. 2005: 126; De la Riva et al. 2011: 162; Frost 2024; Lötters 1996: 47; Lötters et al. 2023: Supplementary Table 1; Plewnia et al. 2024b: 241.

Atelopus spumarius spumarius View in CoL . — Rivero 1968: 23; Lescure “1973” 1974: 144; Lescure 1981: 894 (designation of a neotype, MNHNP 1979.8382) from “Colonia, bassin de la rivière Ampiyacu (Depto. Loreto), Pérou” (= PERU: Loreto: Río Ampiyacu basin, Colonia); Lescure & Gasc 1986: 717.

Neotype. PERU: Loreto: Colonia (= Colonia Ancón on the right shore of Río Zumún close to the juncture with the Río Yaguasyacu , a tributary to the Río Ampiyacu ; 3°12’S, 71°59’W, 100 m asl), MNHNP 1979 View Materials /8382 ( Fig. 3 View FIGURE 3 ), adult female, leg. May 1978 by Jean Lescure. GoogleMaps

Referred material. PERU: Loreto: 3 km NE Pebas, AMNH A 103030–103035 About AMNH , 6 adult females (leg. April 1977 by Charles W. Myers and John W. Daly), MUBI 18222–18224 , 1 female, 2 males (leg. 26 August 2022 by Philipp Böning, Angel Chujutalli, Jaime Culebras, Christopher H. Heine, Alisha Jung, Karl-Heinz Jungfer, Stefan Lötters and Amadeus Plewnia); Pebas , NHMW 3886 View Materials /1–2, 2 adult females (leg. unknown) .

Definition. Atelopus spumarius sensu stricto is placed in the genus Atelopus based on its mt and nc markers nested within Atelopus (and with the 16S rRNA fragment showing uncorrected p-distance <4% to the genus type species A. flavescens Duméril and Bibron ), and on having presacrals I and II fused. The species is dinstinguished from all other species by the combination of the following characters: (1) A small-sized species with SVL of adult males 22.2 and 23.4, N = 2, and females 25.8 ± 1.80, N = 10; (2) slender body ( SW / SVL = 0.261 and 0.270 in 2 males, 0.287 ± 0.021 in 10 females) with (3) long legs ( TIBL / SVL = 0.457 and 0.495 in 2 males, 0.461 ± 0.029 in 10 females) and (4) acuminate to subacuminate snout in males and subacuminate to truncate in females, protruding slightly beyond apex of lower jaw; (5) tympanic membrane absent, tympanic annulus not visible, columella present, ostia pharyngea present; (6) phalangeal formula of hand 1-2-3-3; webbing absent on hand; (7) first finger short ( THBL / HAND = 0.423 and 0.455 in 2 males, 0.412 ± 0.020 in 10 females), in adult males with keratinized light brown nuptial pad; (8) phalangeal formula of foot 2-2-3-4-3, webbing formula of toes I 0–0 to 1 / 2 II 0 to 1 / 2 –1 to 11 / 2 III 1 to 11 / 2 –3 IV 3–0 to 11 / 2 V; (9) skin smooth to areolate, dorsally and laterally covered with dense, almost indistinct minute spiculae; they are sometimes aggregated in small groups; ventrally smooth to areolate, cloaca and adjacent thighs most areolate; (10) vertebral column conspicuous, neural processes absent; (11) in life: dorsum black to brown with few yellow, greenish or whitish asymmetric circles, dots or lines; dorsolaterally yellow, greenish or whitish foam-like reticulation forming a band from above eye to groin with numerous black or brown rounded irregular spots (smaller than EYDM); laterally a black or brown band from tip of snout almost to groin, rarely interrupted by yellow, greenish or whitish lines; limbs and dorsal surfaces of hand and foot with yellow, greenish or whitish foam-like reticulation with black or brown spots (smaller or larger than EYDM), thumb and sometimes tips of fingers and toes dorsally yellow to yellowish orange; in males, throat and venter cream, posteriorly becoming orange, sometimes with few tiny brown dots (smaller than or equal to diameter of finger III) on throat and small brown dots (smaller than EYDM) on lateral and posterior vent; in females, throat and chest orange or yellow, venter anteriorly cream yellow, posteriorly orange or yellow, anteriorly with numerous brown or black dots (smaller than or equal to EYDM), sometimes as a continuous chest band; in both sexes palms, plants and ventral surface of cloaca and underside of thighs and upper arm in both sexes and forearm in females bright orange; iris black with a narrow golden ring surrounding horizontally oriented pupil; (12) in preservative: above brown with cream to brownish white pattern; below whitish to cream with brown dots; bright orange life markings faded to pale orange, pale yellow or cream; (13) pulsed call 922 ± 24 ms at dominant frequency 3,404 ± 22 Hz .

Diagnosis. Atelopus spumarius sensu stricto ( Figs. 3–4 View FIGURE 3 View FIGURE 4 ) can be readily distinguished from all other Atelopus (as far known) by molecular genetics, with an uncorrected p-distance of the 16S rRNA fragment of 3.66% to its closest known described relatives, A. franciscus Lescure and the A. hoogmoedi Lescure complex (Appendices 8, 9). It can be morphologically distinguished from all congeners, except from A. colomai Plewnia, Terán-Valdez, Culebras, Boistel, Paluh, Quezada Riera, Heine, Reyes-Puig, Salazar-Valenzuela, Guayasamin and Lötters , A. histrionicus sp. nov., and A. manauensis Jorge, Ferrão and Lima, by the combination of small size, dorsal and lateral skin covered with dense, almost indistinct minute spiculae, ventral skin smooth to areolate, presence of a columella and dorsal pattern. From these species, it differs in call duration (922 ± 24 ms vs. 2,049 ± 220 ms in A. colomai ; 807 ± 80 ms in A. histrionicus sp. nov.; 744 ± 84 ms in A. manauensis ; Jorge et al. 2020b) and in palmar and plantar coloration in life (orange vs. red). It differs from A. colomai and A. histrionicus sp. nov. in female ventral coloration and pattern in life (throat and chest orange or yellow, venter anteriorly cream yellow with numerous brown or black dots smaller than or equal to EYDM, sometimes forming a continuous chest band, posteriorly orange or yellow vs. below entirely yellow with large black rounded dots all over the ventral side, except throat, in A. colomai ; below entirely whitish to cream with large rounded to irregular dark brown markings in the gular region, on chest and venter in A. histrionicus sp. nov.). Further, it differs from A. colomai in having a subacuminate to truncate snout in lateral view in females (vs. acuminate and more protruding). From A. manauensis , A. spumarius sensu stricto differs in having a longer head (males, HLSQ/HDWD = 1.100 –1.151, N = 2, vs. 1.054, N = 11; Jorge et al. 2020b).

Atelopus spumarius sensu stricto ( Figs. 3–4 View FIGURE 3 View FIGURE 4 ) is similar to its congeners of the flavescens-spumarius clade, and to A. andinus Rivero , A. loettersi De la Riva, Castroviejo-Fisher, Chaparro, Boistel and Padial , and A. tricolor Boulenger complex (including the junior synonyms A. rugulosus Noble , A. willimani Donoso-Barros ) from the eastern Andean versant of Peru and Bolivia. It differs from the nominal A. barbotini Lescure , A. flavescens Duméril and Bibron (including its junior synonym A. vermiculatus McDiarmid ), A. franciscus and the A. hoogmoedi Lescure complex (including the available name A. hoogmoedi nassaui Ouboter and Jairam ) in pattern and coloration (dorsally black to brown with few yellow, greenish or whitish asymmetric circles, dots or line; dorsolaterally yellow, greenish or whitish foam-like reticulation forming a band from above eye to groin with numerous black or brown rounded irregular spots; ventrally cream in males, cream and orange or yellow in females, with small dark dots vs. dorsally black with red to pink markings, ventrally reddish pink in A. barbotini ; dorsally unicolored reddish, brownish or yellow or brown and with olive, brownish reddish and copper-like vermiculation, ventrally reddish pink in males, pink in females in A. flavescens ; dorsally olive to blackish brown, ventrally reddish in A. franciscus ; dorsally dark brown or black with yellow, pink, bluish, white, greenish or orange irregular spots and reticulated dorsolateral bands or solid bars, ventrally yellow, pink, bluish, whitish, greenish or orange, in some specimens with dark spots or blotches in the A. hoogmoedi complex). All these forms, except some populations of the A. hoogmoedi complex, lack orange palmar and plantar surfaces in life (present in A. spumarius sensu stricto). All Guianan harlequin frogs have longer call duration than A. spumarius sensu stricto (922 ± 24 ms vs. 1,490 ± 140 ms in A. barbotini ; 1,530 ± 220 ms in A. flavescens ; 1,490 ±150 ms in A. franciscus ; 1,190 ± 10 ms in the A. hoogmoedi complex from French Guiana; 1,060 -1,240 ms in the A. hoogmoedi complex from Pará, Brazil; Lescure 1981; Cocroft et al. 1990) with the exception of members of the A. hoogmoedi complex from Amapá, Brazil, (1,160 ± 390 ms; Costa-Campos & Carvalho 2018). In addition, A. spumarius sensu stricto can be distinguished from A. barbotini and the A. hoogmoedi complex by smaller female SVL (25.8 ± 1.80, N = 10, vs. 32.9 ± 2.6, N = 9, in A. barbotini from the type locality; 34.5 ± 1.9, N = 11, in A. hoogmoedi from the type locality). It can be distinguished from A. pulcher Boulenger by smaller male SVL (22.2–23.4, N = 2, vs. 27.27 ± 1.07, N = 13, in A. pulcher ; Lötters et al. 2002a), ventral coloration in life (females throat and chest orange or yellow, venter anteriorly cream yellow, posteriorly orange or yellow, anteriorly with numerous brown or black dots, sometimes as a continuous chest band vs. vermillion red with irregular dark spots in A. pulcher ). In addition, it differs from A. pulcher in having shorter calls (922 ± 24 ms vs. 1,200 ± 100 ms in A. pulcher ; Lötters et al. 2002a). Atelopus spumarius sensu stricto differs from A. harlequin sp. nov. in larger male SVL (22.2 and 23.4, N = 2, vs. 20.6 ± 0.51, N = 4, in A. harlequin sp. nov.) and in dorsal coloration in life (black to brown with few yellow, greenish or whitish asymmetric circles, dots or lines, dorsolaterally yellow, greenish or whitish reticulation forming a continuous broad band from above eye to groin bearing numerous black or brown rounded spots vs. yellowish-gold with numerous dark brown, rounded marks and irregular shaped blotches in A. harlequin sp. nov.). In addition, it differs from A. harlequin sp. nov. in having longer calls (922 ± 24 ms vs. 680 ± 30 ms in A. harlequin sp. nov.; Asquith & Altig 1987). Atelopus spumarius sensu stricto differs from A. seminiferus Cope in smaller female SVL (25.8 ± 1.80, N = 10, vs. 40.0, N = 1), absence of lateral warts (present in A. seminiferus ) and dorsal coloration in preservative (brown with brownish pale asymmetric circles, dots or line and dorsolateral foam-like reticulation forming a band from above eye to groin with numerous black or brown rounded irregular spots vs. dark brown without pattern in A. seminiferus ). From A. andinus , A. loettersi and the A. tricolor complex, A. spumarius sensu stricto can be distinguished by the presence of a columella (vs. absence; Lötters et al. 2011; authors’ unpubl. data). From A. loettersi , it can further be distinguished by ventral coloration and pattern in life (females throat and chest orange or yellow, venter anteriorly cream yellow, posteriorly orange or yellow, anteriorly with numerous brown or black dots, sometimes as a continuous chest band vs. mostly red, in some specimens with irregular brown blotches in A. loettersi ; De la Riva et al. 2011). Atelopus spumarius sensu stricto can be distinguished from A. andinus and the A. tricolor complex by the absence of warts (presence) and by presence of dorsolateral reticulation (absence).

Description of neotype. Adult female. Body slender (SW/SVL = 0.269), head roughly as long as wide (HLSQ/ HDWD = 1.037), snout protruding below apex of lower jaw, truncate in dorsal view; nostrils directed laterally, barely protuberant, not visible in dorsal view, almost at tip of snout in lateral view, situated above apex of lower jaw; canthus rostralis well defined, concave in dorsal view between eye and nostrils; loreal region concave; lips not flared; top of snout depressed; head slightly concave in lateral view; eyelid flared; tympanum absent, tympanic annulus not visible; supratympanic crest poorly developed; choanae small, rounded; ostia pharyngea present; tongue about twice as long as wide, broadest at its tip (situated posteriorly); limbs long and slender (TIBL/SVL = 0.441); webbing absent on hand; fingers and toes lack lateral fringes; palmar tubercle rounded, poorly developed; supernumerary palmar and plantar tubercles absent; thenar and subarticular tubercles indistinct; tips of digits rounded; phalangeal formula of hand 1-2-3-3; first finger short (THBL/HAND = 0.444); inner metatarsal tubercle indistinct, outer metatarsal tubercle rounded, poorly developed; relative length of toes I<II<III<V<IV; phalangeal formula of foot 2-2-3-4-3, webbing formula of toes I 0–0 II 1 / 2 – 11 / 2 III 1–3 IV 3–1 V; tarsal fold absent; foot roughly three quarters of tibia; skin smooth on entire body, dorsally and laterally covered with dense, almost indistinct minute spiculae; skin areolate on loreal region and ventral surfaces of cloaca and adjacent areas of thighs, venter and throat; cloacal opening in an inconspicuous tube, directed posteriorly; vertebral column visible through the skin, neural processes absent.

For live coloration, see Remarks.

In preservative, above brown with brownish pale dorsal spots, circles and dorsolateral irregular reticulation pattern; dorsolateral band posteriorly fused with a narrower band presenting similar reticulation running ventrolaterally from jaws to groin; ventral surfaces of limbs and body pale with brown dots (smaller than or equal to EYDM), which are most dense on lateral and anterior parts of vent and in gular region; smaller dots (smaller than EYDM) on throat and no dots on ventral surface of cloaca and adjacent thighs ( Fig. 3 View FIGURE 3 ).

Measurements: SVL 29.0, TIBL 12.8, FOOT 11.0, HLSQ 8.4, IOD 2.9, HDWD 8.1, EYDM 2.9, ITNA 2.4, FAL 9.2, HAND 7.2, THBL 3.2, SW 7.9.

Variation. For meristic variation of characters see Table 3. Specimens from the Pebas area ( Fig. 4 View FIGURE 4 ) correspond to the neotype description. However, they are slightly smaller than the neotype (and other females from Colonia, examined by Lescure 1981). Skin texture varies from smooth to slightly areolate, with almost indistinct minute spiculae dorsally and laterally which can be aggregated in small groups in some specimens. In dorsal view, the snout varies from acuminate to subacuminate in males and from subacuminate to truncate in females.

In life, dorsal and dorsolateral marks and reticulation pattern varies from yellow to greenish or whitish ( Fig. 4 View FIGURE 4 ).

Sexual dimorphism is apparent in A. spumarius sensu stricto with females being larger than males (SVL 25.8 ± 1.80, N = 10, vs. 22.2–23.4, N = 2). In addition, males possess a light brown keratinized nuptial pad on the dorsal surface of first finger and differ in ventral coloration and pattern as indicated above ( Fig. 4 View FIGURE 4 ).

Skull osteology. General osteological features of two females (MNHNP 1979/8382, neotype, MorphoSource Media ID 000618620; AMNH A103034, MorphoSource Media ID 000436646) are depicted in Figures 5–6 View FIGURE 5 View FIGURE 6 and Appendix 4. The skull of A. spumarius sensu stricto is triangular in dorsal view. The skull length is 7.8, the skull width is 7.0, and the skull height is 4.8 in AMNH A1033034. The skull roof is slightly rugose. In anterior view, the septomaxilla is U-shaped with medial and lateral rami that extend posteriorly towards the vomer. The lateral ramus is much broader than the medial ramus and bears a nasal process. The ossified sphenethmoid is smooth and underlies the posterior and medial margins of the nasals, as well as the anterior margins of the frontoparietals. The posterior limit of the sphenethmoid is about one-half the length of the margin of the orbit. The prootics are slightly rugose and are fused to the posterolateral edge of the frontoparietals. The exoccipitals encircle the foramen magnum and are fused to the frontoparietals dorsally, the prootics laterally, and the parasphenoid anteroventrally. The otic capsule is well-ossified. Columellae are present, cylindrical in shape. The pars media plectra of the columella is slender and bowed, and the pars interna plectra is broad. The operculum in the fenestra ovalis is cartilaginous. The nasals are triangular and bear an acuminate maxillary process that extends ventrolaterally toward the maxilla and nearly contacts the pars facialis of the maxilla. The nasals are narrowly separated medially. The anterior roof of the braincase has a triangular appearence given by the coarsely rectangular frontoparientals, which bear a short triangular suprarobital flange (more evident in the neotype) with nearly even, non-straight orbital edges. Medial articulation is incomplete in both specimens with the anterior one fourth of the bones lacking articulation in the neotype and the anterior three-fourths of the bones lacking articulation in AMNH A1033034. Suture lines are visible where articulation is present. Occipital groves, which are canals for the carotid artery, are present and partially roofed with bone. In the neotype, the left groove is mostly open, while the right grooves irregularly covered along the midpoint. In AMNH A1033034, the left and right groove are covered only at the anterior and posterior tips. Posteriorly, the frontoparietals are fused posterolaterally to the prootics and posteromedially to the medial anterodorsal margins of exoccipitals. The vomers are small, edentate, medially separated, crescent-shaped, and triradiate with an anterior ramus, prechoanal ramus, and postchoanal ramus. The anterior ramus is directed anterolaterally, pointed at the anterior tip, and is roughly the same size as the postchoanal ramus. The prechoanal ramus is short. The pre- and postchoanal rami form the anteromedial margin of the choana. The prechoanal ramus is directed towards the maxilla, and the postchoanal ramus is directed posterolaterally. The postchoanal ramus is fused to the overlying sphenethmoid. The neopalatine is elongate and triangular. It underlies, and is partially fused to, the sphenethmoid and extends towards the maxilla, making contact with the preorbital process. The neopalatine is narrow and pointed at its medial tip, widens as it approaches the maxilla, and is cylindrical and rounded at its anterior border. The parasphenoid has an inverted T-shape. The cultriform process does not contact the sphenethmoid. The cultriform process extends beyond the midpoint of the orbit. The terminal end of the cultriform process is spear-shaped in the neotype and roughly rounded in AMNH A1033034. The parasphenoid alae are directed posterolateral to the cultriform process and are fused to the overlying otic capsule. The posterior margin of the parasphenoid and a medial posterior process is present (more evident in the neotype). The maxillary arcade is complete and edentate. The paired premaxillae each possess a dorsal alary process that is directed anterolaterally. The lower half of the alary process is wider than the upper half. The pars palatina is biradiate with medial and lateral processes. The lateral process is more than twice as long as the medial process. The medial process is well developed and triangular. A concave border is present where the lateral and medial processes of the pars palatina come together. The posterior tip of the pars dentalis is pointed and articulates with the maxilla. Small, irregular sesamoids are present at the contact zone joint between the pars palatina of the premaxilla and the pars palatina of the maxilla in AMNH A1033034. The external surface of the maxillae is slightly rugose. The pars palatina, which extends along the lingual margin of the maxilla, is narrow, and the posterior half of this shelf articulates with the anterior ramus of the pterygoid. The pars fascialis of the maxilla is directed medially and is short and jagged; its dorsomedial margin nearly contacts the neopalatine, sphenethmoid, and the maxillary process of the nasal. The anterior end of the maxilla is truncate and abuts the premaxilla. The posterior end of the maxilla is pointed and contacts the quadratojugal. The quadratojugal is a small, L-shaped bone that underlies the ventral arm of the squamosal and contacts the posterior process of the maxilla at is anterior margin. The quadratojugal of the neotype is much shorter than that of AMNH A1033034. The paired squamosals possess an otic ramus posterodorsally, a zygomatic ramus anterodorsally, and a ventral ramus. The otic ramus is expanded dorsally and has a broad articulation with the crista parotica of the otic capsule, leaving only the posterior end of the prootic free. The zygomatic ramus is small, triangular, and directly medially. The angle between the dorsal surface of the squamosal and the anterior margin of the ventral ramus is nearly perpendicular. The ventral ramus is flat and blade-like.A squamosal keel is present, extending along the outer surface from the zygomatic ramus to the upper half of the ventral arm. The pterygoid is triradiate, bearing anterior, medial, and posterior rami. The anterior ramus articulates with the pars palatina of the maxilla. The medial and posterior rami are of equal length. The medial ramus nearly contacts the prootic. The posterior ramus is flat and blade-like. The palatoquadrate is cartilaginous and therefore not visible in the microCT dataset. The lower jaw is composed of three ossified elements and Meckel’s cartilage, which is not visible in the microCT dataset. The mentomeckelian is the most anterior element that forms a cartilaginous symphysis at the midline of the jaws. Posterodorsally, the mentomeckelian is fused to the dentary. The dentary is slender, thin, and edentate; this element overlays the anterior half of the angulosplenial. The angulosplenial is the largest mandible element and forms the lingual surface of the lower jaws. The lower jaw length is 6.3 in AMNH A1033034, slightly shorter than the length as the skull from the occipital condyle to the premaxilla.

The neotype of Atelopus spumarius sensu stricto differs from the species described herein by the posterior end of the maxilla being free and laterally protruding beyond the lateral limit of the squamosal (vs., in A. colomai , protruding beyond the lateral limit of the squamosal, but not free; in A. harlequin sp. nov. and in A. histrionicus sp. nov., the squamosal extends laterally beyond the posterolateral limit of the maxilla; Fig. 6 View FIGURE 6 ), the quadratojugal having a thickened pars glenoidalis and a short pars jugularis (vs., in A. colomai , pars glenoidalis subrectangular, pars jugularis elongated; A. harlequin sp. nov., pars glenoidalis longer but more narrow; in A. histrionicus sp. nov., pars glenoidalis triangular; Fig. 6 View FIGURE 6 ), and the maxilla having a straighter orbital margin ( Fig. 6 View FIGURE 6 ). However, variation in these characters exists between the two populations of A. spumarius sensu stricto, which might be attributed to imaging conditions or natural variation.

Further, A. spumarius sensu stricto can be distinguished from A. colomai by a slightly rugose skull roof (vs. smooth) and the frontoparietals being fused over two posterior thirds of their total length (vs. completely fused). Atelopus spumarius sensu stricto differs from A. harlequin sp. nov. by the posteromedial side of the otic ramus of the squamosal being free (vs. attached along its entire length to the prootic). Atelopus spumarius sensu stricto can be distinguished from A. histrionicus sp. nov. by a less rugose skull roof, the lateral margins corresponding to the maxilla being less straight, the posteroventral incisure of the sphenethmoid being less deep, the dorsal end of the dorsal process of the premaxilla (= pars facialis) and the nasals at the same level (vs. protrudes anteriorly beyond the anterior limit of the nasals). For details see Figures 5–6 View FIGURE 5 View FIGURE 6 and Appendix 4.

A. spumarius A. histrionicus sp. nov. A. harlequin sp. nov. A. colomai

Squamosal in lateral view

However, the discriminatory power of osteological features needs to be seen with caution as intraspecific variation, sexual dimorphism and taxonomic value remain poorly understood for the species discussed.

Vocalization. Calls were recorded by PB from an uncollected male on 27 August 2022, ca. 01:00 pm, at 3 km NE Pebas with a Comica CVM-VM20 directional microphone attached to a Roland R-05 digital receiver. Distance to recorder was 0.4 m and ambient temperature was ca. 25°C. A 51,125 ms recording was available for analysis (CJ ec.cj.aud.22; Fonozoo Sound Code 14654; Fig. 7 View FIGURE 7 ). It contains 20 pulsed calls with duration 922 ± 24 ms (881–962 ms). Intervals between calls last 1,647 ± 162 ms (1,372 –1,991 ms). Dominant frequency is 3,404 ± 22 Hz (3,373 –3,466 Hz). Amplitude is ascending over the course of the call and slightly decreases over the last 3–6 pulses. Frequency shows harmonics and is modulated with a slight increase towards the end of the call. Each pulsed call consists of 42 ± 3 pulses (37–48), that show a length of 8 ± 4 ms (3–27 ms) each. Pulses slightly increase in length over the course of each call with the last pulse being considerably longer than any other pulse. The first or the first two pulses of each call are detached by a long interval of 122 ± 16 ms (83–147 ms) from all subsequent pulses.

Two additional recordings display other call types. The first (total recording 2,222 ms; same recording data as above; CJ ec.cj.aud.23; Fonozoo Sound Code 14655; Fig. 8 View FIGURE 8 ) consists of two pulsed short calls with a duration of 132 and 225 ms, interval 1,110 ms and dominant frequency 2,997 and 3,110 Hz, respectively. Amplitude peaks in the middle of the call with a slight decrease towards the end. Frequency does not show harmonics and is poorly modulated with a minimal increase towards the mid of each call followed by a minimal decrease towards the end and no modulation within pulses. Pulsed short calls consist of 7–16 pulses that show a length of 8 ± 8 ms (3–40 ms) each. The second additional recording (total recording 10,386 ms; same recording data as above; CJ ec.cj. aud.24; Fonozoo Sound Code 14656; Fig. 9 View FIGURE 9 ) consists of a single pure tone short call with a call duration of 47 ms, dominant frequency of 3,199 Hz and a pulsed short call with a call duration of 68 ms, dominant frequency 3,192 Hz, containing only two pulses with a length of 25 and 38 ms. The interval between the pure tone short call and the pulsed short call is 6,708 ms. In both calls, frequency shows harmonics and is modulated with a decrease towards the end.

Tadpole. The tadpole of A. spumarius sensu stricto is unknown.

Distribution. Atelopus spumarius sensu stricto is known from three localities in the Río Ampiyacu drainage at ca. 80–100 m asl ( Peru, Loreto) ( Fig. 2 View FIGURE 2 ). In addition to the two sites mentioned above, the species has been reported from the nearby Nuevo Peru on the Río Ampiyacu (William Lamar, in litt. 30 July 2022). It is likely present in more localities as the general area is homogenous lowland rain forest and poorly studied, as it is difficult to access. Additional populations from other river drainage systems of unclear taxonomic status may be allocable to A. spumarius sensu stricto suggesting that the species’ range may be larger (see Remarks).

Natural history. The species inhabits terra firme lowland rain forest and can be found in close proximity to small streams. In late August 2022, we recorded life history notes at 3 km NE Pebas. All individuals observed were found no more than 2 m away from the edge of a stream ca. 0.5–1 m wide and up to 20 cm deep, characterized by slow-moving clear water, sandy substrate and abundant fallen logs ( Fig. 10 View FIGURE 10 ). Adults were active during the day perching on the steep loamy slopes of the stream or on vegetation (<30 cm above ground). Sex ratio was skewed towards males (12 of 15 adults found). Male-male interaction was observed suggesting home range defence (as described in related taxa, e.g. Ringler et al. 2023): During mid-day, we observed one male approaching a resident (larger) male perching on a trunk in the stream bed (see Plewnia et al. 2024a: Supplementary Video). The resident male started to call, thus showing its bright cream throat towards the other male. In addition, hand waving behavior was performed. The resident male pursued the other male which moved away by climbing up the steep slopes. In the late afternoon, individuals climbed on leaves along the steep slopes, which likely served as sleeping sites at night. Females found in April and August contained well-developed eggs. Amplexus was never observed; juveniles, tadpoles or eggs are unknown.

Conservation status. We suggest listing A. spumarius sensu stricto under the range of categories for species considered threatened (Critically Endangered to Vulnerable) based on the following criteria. The known EOO of A. spumarius sensu stricto is ca. 50 km ² and AOO is 12 km ². While its distributional limits are poorly known it is unlikely to have an EOO greater than 20,000 km ² or to occur at more than 10 threat defined localities.

Most parts of the Río Ampiyacu drainage are covered in undisturbed primary forest with few human (indigenous) settlements and traditional small-scale agriculture (chacras, slash and burn fields). However, we witnessed deforestation and pollution in the immediate Pebas area, i.e. 3 km NE Pebas. Here, the species was found in high densities in a small forest fragment in August 2022 (15 individuals in approx. 10 person*hours). Our visits to the type locality, Colonia Ancón, and the surroundings (April 2012 and January 2014, SL and collaborators) did not reveal any individuals.

Presence and potential impact of Bd remain unknown, four individuals sampled August 2022 (3 km NE Pebas) tested negative (prevalence 0 %; CI 0–51.6 %; Appendix 5).

Atelopus spumarius sensu stricto is further likely to be threatened by climate change in the near future, which might both impact the species habitat as well as interfer and exacerbate existing threats such as disease ( Lötters et al. 2023). The species from the western Amazon are among the harlequin frogs likely to be most affected by climate change ( Lötters et al. 2023).

Etymology. Cope (1871) did not provide a derivatio nominis. The epithet is Latin (nominative case, singular) meaning ‘foam maker’, obviously referring to the species’ dorsolateral pattern.

Remarks. Lescure (1981) collected 34 specimens in 1978 in Colonia Ancón, including 6 females.All specimens were deposited at MNHNP. However, except the neotype, these specimens have not been traced for more than 20 years (Annemarie Ohler, MNHNP, pers. comm. to SL).

Specimens from Igará-Paraná, Departamento Amazonas, Colombia (BMNH 1905.1.31.10-11) and from Yubineto, Loreto, Peru (MNHNP 1979-8416, AMNH 95815-96005) were additionally assigned to this taxon by Lescure (1981). While these specimens resemble A. spumarius sensu stricto by external morphology and bioacoustics (Yubineto; cf. Lescure 1981), we are currently unable to draw final conclusions on the taxonomic status of this material. For comments on additional populations potentially conspecific with A. spumarius sensu stricto see chapter 3.5.

Lescure (1981) described the neotype in life as above black with yellow dorsolateral pattern; below yellow with black spots. His description of a dorsolateral longitudinal band from orbit to the armpit needs rectification, as this pattern is continued beyond the armpit to the groin. In addition, he refers to the area below cloaca to the inner thighs,

the palms and plants as vermilion red ( Lescure 1981). We are unable to refute this, but this deviation from bright orange coloration as known from specimens in the Pebas area might best be explained by an overinterpretation of this feature. This needs further corroboration once new material becomes available from Colonia Ancón.

Re-examination of the neotype revealed that “small warts behind the eye” (sensu Lötters et al. 2002a; b) were an interpreation in error; the skin is areolate here ( Fig. 11 View FIGURE 11 ). However, still dorsal and lateral sides are covered with dense, almost indistinct minute spiculae.