(Figs 7–10) QCAZ 49572 (field no. PUCE 18835), adult male from Ecuador, Provincia Pastaza, Cantón Santa Clara, Río Pucayacu, in the vicinities of the Zanjarajuno Reserve (1.3578°S, 77.8477°W), 940 m above sea level, collected by P. Peña-Loyola, N. Peñafiel, and R. Tarvin on 3 July 2010.

20 adult males, 1 adult female. QCAZ 33256, adult male, collected by I. G. Tapia, D. Almeida-Reinoso and M. Páez on 30 March 2007; QCAZ 39579, 39586–87, adult males, collected by D. Salazar-Valenzuela and G. Diaz between 12 and 14 December 2008; QCAZ 40909–10, adult males, collected by I. G. Tapia, L. A. Coloma, and S. R. Ron on 31 March 2008; QCAZ 40252, 40258, adult males, collected by D. Salazar-Valenzuela, D. Acosta-López and C. Korfel between 23 February and 1 March 2009; QCAZ 45271–72, 45277, 45281, adult males, collected by D. Acosta-López between 30 July and 2 August 2009; QCAZ 45907, 45909, adult males, collected by P. Peña-Loyola on 16 October 2009; QCAZ 49569–71, adult males, collected by N. Peñafiel between 26 June and 3 July 2010; QCAZ 49021–22, adult males, collected by R. Tarvin, and L. Bustamante on 3 August 2010; QCAZ 49439, adult female, collected by R. Tarvin and P. Aguilar on September 2010; QCAZ 48744 adult male, collected by S. R. Ron, L. Bustamante, I. G. Tapia , P. Peña-Loyola and R. Tarvin on 3 July 2010.

42 adult males, 2 adult females. Ecuador: Provincia Morona Santiago: Bobonaza (1.4980°S, 77.8793°W), 660 m above sea level, QCAZ 32506, 32508, 32512, adult males, collected by L. A. Coloma and I. G. Tapia on 18 August 2008; Nuevo Israel (2.165°S, 77.902919°W), 1289 m above sea level, QCAZ 46472, adult male, collected by J. Brito-Molina on 2 January 2010; Provincia Napo: Reserva Yachana (0.8458°S, 77.2287°W), 300–350 m above sea level, QCAZ 48790, 48797, 48803–04, 48811, 48814, adult males, collected by S. North, S. Topp and G. Estevez between 4 June and 18 August 2008; Huino, QCAZ 50198, adult female, collected by W. C. Funk on February 2003; Provincia Orellana: El Edén (0.46147°S, 76.1252°W), 228 m above sea level, QCAZ 39633, adult male, collected by S. Aldás-Alarcón, Dayuma, Pozo Sunka (1.7333°S, 76.7333°W), 279 m above sea level, EPN-H 2752, 2755–56, 6372; Provincia Pastaza: Fundación Hola Vida (1.6285°S, 77.9072°W), 845 m above sea level, QCAZ 25607, 25469, adult males, collected by K. Elmer and I. G. Tapia on 27 June 2003, QCAZ 37175, adult male collected by I. G. Tapia, L. A. Coloma, P. Peña-Loyola and M. Páez on July 2007; Río Maderoyacu (1.3917°S, 77.4139°W), 500–600 m above sea level, EPN-H 6373, 6385, adult males, collected by A. Almendáriz; Provincia Zamora Chinchipe: Centro Shuar Yawi (4.4300°S, 78.6316°W), 945 m above sea level, QCAZ 31016, 31032–33, 31047, 31053, adult males, QCAZ 31051, adult female, collected by D. Almeida-Reinoso and A. Armijos between 13 and 19 September 2003. Peru: Región Loreto: Provincia Datem del Marañón: Cordillera de Kampankis: Pongo de Chinim (3.1130°S, 77.7762°W), 365 m above sea level, CORBIDI 09368, 09370, 09394, 9396, 10534, 10537, MUSM 28050, adult males collected by P. J. Venegas and A. Catenazzi on 3 August 2011; Quebrada Kampankis (4.0431°S, 77.5412°W), 325 m above sea level, CORBIDI 09507, 10535, adult males collected by P. J. Venegas and A. Catenazzi on 13 August 2011; Quebrada Wee (4.2041°S, 77.5298°W), 310 m above sea level, CORBIDI 09545–46, 09553, 09569, 10532–33, 10535–36, MUSM 28051, adult males, collected by P. J. Venegas and A. Catenazzi on 18 August 2011.

Throughout this section, coloration refers to preserved specimens unless otherwise noted. Osteocephalus cannatellai is a medium-sized species of Osteocephalus having the following combination of characters: (1) size sexually dimorphic; maximum SVL in males 57.21 mm (n = 33), in females 70.88 (n = 3); (2) skin on dorsum bearing scattered tubercles in males, smooth in females; (3) skin on flanks areolate; (4) hand webbing formula varying from I basal II1½ —2¹/₃III2⁺—2IV to I basal II2^–—3^–III2²/₃—2½IV; foot webbing formula varying from I1—2½II1—2III1⁺—2IV2½—1⁺V to I0⁺—1^–II0⁺—1⁺III0⁺—1½IV1^–—0⁺V; (5) dorsum varying from dark brown with light gray marks to cream with brown marks; (6) venter varying from light gray to dark brown with lighter dots and/or dark brown blotches; (7) cream suborbital mark present, clear labial stripe absent; (8) flanks cream with darker reticulations anteriorly and dark marks; (9) dermal roofing bones of the skull weakly exostosed; (10) in life, bones green; (11) in life, iris bronze with irregular reticulations; (12) paired vocal sacs small, located laterally, behind jaw articulation, (13) in life, juveniles with bronze iris, without pale elbows, knees, and heels; (14) larvae unknown.

Osteocephalus cannatellai is most similar to Osteocephalus buckleyi and Osteocephalus vilmae sp. n. The three species differ from other Osteocephalus by the combination of a bronze iris with irregular black reticulations (in life), areolate skin on the flanks, prominent tubercles in the tarsus and absence of a row of conspicuous tubercles in the lower jaw. Osteocephalus cannatellai differs from Osteocephalus buckleyi in having: (1) scattered and weakly keratinized dorsal tubercles (more abundant and keratinized in Osteocephalus buckleyi), (2) smaller tympanum (1/5 of head length in Osteocephalus cannatellai vs. 1/4 in Osteocephalus buckleyi; Fig. 5), (3) larger size (Osteocephalus cannatellai mean male SVL = 46.83, SD = 4.31, n = 33; Osteocephalus buckleyi mean male SVL = 41.12, SD = 2.45, n = 24; differences are significant: t = 5.82, P < 0.001; Fig. 5), (4) darker venter (cream with brown speckling in most Osteocephalus buckleyi; Figs 4 and 9.), (5) more extensive areolate area on flanks (from axillary region to groin in Osteocephalus cannatellai, restricted to anterior one third of flank in Osteocephalus buckleyi), (6) contrasting coloration between flanks and venter (change in coloration is gradual in Osteocephalus buckleyi), and (7) advertisement call (Fig. 11). Our phylogenetic analyses show that Osteocephalus cannatellai and Osteocephalus buckleyi are not sister species (Fig. 1).

Osteocephalus cannatellai differs from Osteocephalus vilmae in having a narrower head (relative to SVL, mean male HW/SVL = 0.323, SD = 0.034, n = 33; Osteocephalus vilmae mean male HW/SVL = 0.355, SD = 0.012, n = 5; differences are significant: t = 2.06, P = 0.046) and a smaller tympanum (relative to SVL, mean male TD/SVL = 0.069, SD = 0.007, n = 33; Osteocephalus vilmae mean male TD/SVL = 0.087, SD = 0.006, n = 5; differences are significant: t = 5.17, P < 0.001). According to the phylogeny, Osteocephalus cannatellai and Osteocephalus vilmae are not sister species (Fig. 1). Osteocephalus cannatellai differs from Osteocephalus cabrerai in (1) lacking prominent tubercles on the lower jaw, (2) having smooth to tuberculate outer edge of Finger IV (outer edge with fringe in Osteocephalus cabrerai), and (3) having less webbing in the hands (in Osteocephalus cannatellai webbing reaches two thirds of the distance between the ultimate and penultimate tubercle of Finger IV, in Osteocephalus cabrerai it reaches the proximal border of the ultimate tubercle; Fig. 12). Osteocephalus cannatellai differs from other species of Osteocephalus (except Osteocephalus buckleyi, Osteocephalus cabrerai, and Osteocephalus vilmae)in having a combination of prominent tubercles in the tarsus and areolate skin in the flanks. A bronze iris with black reticulations further distinguishes Osteocephalus cannatellai from Osteocephalus deridens, Osteocephalus oophagus, Osteocephalus planiceps, and Osteocephalus taurinus which have black straight lines radiating from the pupil; iris coloration also differs in Osteocephalus carri, Osteocephalus festae, Osteocephalus heyeri, Osteocephalus subtilis, and Osteocephalus verruciger which have predominantly dark irises (Jungfer 2010; Jungfer and Lehr 2001; Lynch 2002). Osteocephalus cannatellai is larger than Osteocephalus exophthalmus (maximum male SVL in Osteocephalus cannatellai 57.21, n = 33; in Osteocephalus exophthalmus 32.7 mm, n = 3; Smith and Noonan 2001) and Osteocephalus fuscifacies (maximum SVL 44.17, n = 21). Skin texture in the flanks distinguishes Osteocephalus cannatellai (areolate) from Osteocephalus mutabor (smooth). Osteocephalus inframaculatus differs from Osteocephalus cannatellai in coloration of the ventral surfaces of hindlimbs (bold brown blotches in Osteocephalus inframaculatus are absent in Osteocephalus cannatellai; Jungfer 2010).

Adult male, 52.85 mm SVL, head length 18.61, head width 18.53, eye diameter 5.08, tympanum diameter 3.31, femur length 25.84, tibia length 30.05, foot length 22.73. Head narrower than body, slightly longer than wide; snout truncate in lateral and dorsal views; distance from nostril to eye longer than diameter of eye; canthus rostralis distinct and rounded; loreal region concave; internarial area depressed; nostrils moderately protuberant, directed laterally; interorbital area flat, lateral margins of the frontoparietals inconspicuous through skin; eye large, strongly protuberant; tympanic membrane clearly evident, large, slightly wider than high, about two thirds of eye diameter, separated from eye by ca. 85% of its diameter; tympanic annulus distinct except dorsally where it is covered by supratympanic fold; posterior end of supratympanic fold reaches arm insertion. Arm slender, axillary membrane present, reaching one third of arm length; four small low tubercles present along ventrolateral edge of forearm; relative length of fingers I<II<IV<III; fingers bearing large, oval discs, that of third finger about three fourths of tympanum diameter; subarticular tubercles prominent, round to ovoid, single; supernumerary tubercles present; palmar tubercle small, elongated; prepollical tubercle large, flat, elliptical; prepollex enlarged; large dark keratinous nuptial excrescences covering inner surface of prepollex up to half the distance between subarticular tubercle and proximal border of disk of thumb; webbing formula of fingers I basal II1²/₃—2²/₃III2½—2⁺IV. Medium sized to small tubercles on tibiotarsal articulation; scattered tubercles on tarsus, more abundant on outer edge; small tubercles scattered along ventrolateral edge of foot; toes bearing discs slightly wider than long, smaller than those of fingers; relative length of toes I<II<V<III<IV; outer metatarsal tubercle ill defined, small, round; inner metatarsal tubercle large, ovoid; subarticular tubercles single, round, protuberant; supernumerary tubercles restricted to the soles; webbing formula of toes I1—2II1—2⁺III1⁺—2⁺IV2^–—1V. Skin on dorsum, head, and dorsal surfaces of limbs smooth, with scattered tubercles; skin on flanks areolate; skin on venter coarsely granular; skin on ventral surfaces of head and thighs granular, those of shanks smooth. Cloacal opening directed posteriorly at upper level of thighs; short simple cloacal sheath covering cloacal opening; round tubercles below vent; two conspicuous white tubercles ventrolateral to vent. Tongue cordiform, widely attached to floor of mouth; dentigerous processes of the vomer angular, adjacent medially, posteromedial to choanae, bearing 12 and 9 (left/right) vomerine teeth; choanae trapezoidal, oblique; vocal sac barely distinct above the arm and below the ear.

Color of holotype in preservative. Dorsum brown with light gray to cream peripheral marks; dark brown, ill defined, transversal bar between orbits (Fig. 8); cream middorsal line from tip of snout to end of sacrum; dorsal surfaces of forearms brown with light gray and dark gray marks, dorsal surfaces of thighs light gray with dark gray transversal bands, dorsal surfaces of shanks and feet brown with dark gray marks. Venter brown with light cream yellowish spots, more abundant on posterior half of the body (Fig. 9); ventral surfaces of hindlimbs and forelimbs brown with dark brown marks and conspicuous white tubercles on forearms; outer half of ventral surfaces of forearms dark brown; sides of head brown with oblique white bar from posteroventral border of orbit to border of jaw, below tympanum (Fig. 10); vertical dark brown bar below eye, anterior to white bar; area behind white bar and eye dark brown except for brown periphery of tympanum; iris light gray with black reticulations; flanks light gray anteriorly, cream posteriorly, areolate region with gray reticulation.

Color of holotype in life. Based on digital photographs. Dorsum brown with green peripheral marks; dark brown, ill defined, transversal bar between orbits (Fig. 7E); dorsal surfaces of forearms brown with green and dark brown marks, dorsal surfaces of thighs dark green with dark brown transversal bands, dorsal surfaces of shanks and feet brown with dark brown marks. Sides of head brown with oblique lime bar from posteroventral border of orbit to border of jaw, below tympanum; vertical dark brown bar below eye, anterior to lime bar; area posterior to lime bar and eye dark brown except for brown periphery of tympanum; flanks light green, areolate region with dark reticulation.

The specific name cannatellai is a noun in the genitive case and is a patronym for David C. Cannatella, who with his research has enriched the understanding of the evolution of Neotropical amphibians. He has also contributed to amphibian studies in Ecuador by providing funding and training to local scientists.

Variation in dorsal and ventral coloration of preserved specimens is shown in Figures 8 and 9. Dorsal background coloration varies from cream to light gray or brown; irregular dark brown or dark gray marks are always present (Fig. 8). Some specimens have a cream middorsal line from the tip of the snout to the mid sacrum (QCAZ 49570) or the vent (QCAZ 39633). In females, the dorsum always lacks tubercles while in males it varies between lacking tubercles (QCAZ 32508) and having scant and ill-defined non-keratinized tubercles (e.g., QCAZ 48814 and 49569). The prominence of the tubercles seems to decrease in preserved specimens: when collected, QCAZ 48744 had large conspicuous dorsal tubercles (Fig. 7), in preservative tubercles are barely noticeable.

Ventral surfaces of preserved specimens (Fig. 9) vary from light gray (QCAZ 40909) to brown (QCAZ 31031). In most specimens, there are dark brown or dark gray spots, more abundant posteriorly (e.g., QCAZ 49439); QCAZ 39633 has brown blotches on the chest and venter; QCAZ 48804 has similar marks that also reach the gular region. In two Peruvian specimens ventral surfaces are light gray with few brown spots posteriorly (CORBIDI 09553) or with light brown spots, slightly visible, on gular region and belly (MUSM 28050). The gular regions in some Peruvian specimens are brown (e.g., CORBIDI 09507, 10532). Ventrally, limbs vary from light gray or light brown to dark brown; in QCAZ 33256 and 39587 black dots are present on limbs; scant cream tubercles can be present in the external edge of the forearm (e.g., QCAZ 32512). The skin of the anterior and posterior surfaces of thighs and the concealed surfaces of shanks are pale in the Peruvian specimens. The vent region is light gray to dark brown with dark brown dots. Flanks are cream to light gray, areolate in the anterior two-thirds and smooth posteriorly. In specimens from Peru the flanks are completely areolate. The areolate portion has a dark brown reticulation.

Head shape is truncate in dorsal and lateral view (e.g., QCAZ 39579). Lateral head coloration varies between dark brown (QCAZ 49569) to cream (QCAZ 32506). There is a cream subocular mark. The tympanic annulus is concealed dorsally and has lighter color than the background. The distal subarticular tubercle on Finger IV is single (e.g., QCAZ 40909) or bifid (e.g., QCAZ 45272).

Morphometric data pertain to adults and are summarized in Table 3.In the examined series, the largest male has a SVL of 57.21 mm and the largest female 72.77 mm; mean male SVL = 46.84 mm (n = 33, SD = 4.31), mean female SVL = 66.55 mm (n = 3, SD = 5.44). Females are significantly larger than males (t = 7.66, df = 33, P < 0.001). A MANOVA on the residuals of the regressions between SVL and the other measured variables indicates lack of significant differences between sexes in size-free morphometry (F = 0.239, df = 17, P = 0.060).

Based on digital photograph of adult male QCAZ 48744 (Fig. 7 C–D): dorsum green with irregular light and dark brown marks; canthal region green with cream subocular mark and olive green diffuse band along the posterior half of upper lip; tympanum light brown; flanks light green with dark brown reticulation anteriorly and irregular dark brown blotches posteriorly; dorsal surfaces of thighs, shanks and forelimbs green with transversal brown bands; venter brown with irregular dark brown and cream marks; iris bronze with diffuse brown mid-horizontal line and black reticulations.

Based on digital photograph of juvenile QCAZ 40859 (Fig. 7 F): dorsum green with dark brown marks; upper lip cream with transversal brown bars; flanks light green with brown marks; dorsal surfaces of arms, thighs and shanks green with brown transversal bars; external edge of tarsus with white tubercles; iris bronze with black reticulations and diffuse mid-horizontal dark band between the pupil and posterior border of iris.

In life the Peruvian specimens have extensive blue coloration in the groins, concealed surfaces of thighs and tibia, dorsal surfaces of tarsus, armpits and posterior surfaces of arms (e.g., CORBIDI 10534; Fig. 7 G–H). The iris is highly variable from light cream to brownish cream and dark brown (CORBIDI 09394); there are always black reticulations and a diffuse mid-horizontal dark band. Some individuals have a diffuse vertical dark band below the pupil.

Green coloration in life changes to cream in preserved specimens.

Call. Males call from vegetation next to rivers or streams. Acoustic parameters of the advertisement call of Osteocephalus cannatellai are shown in Table 4. The call consists of two components. The first is obligatory and consists of one to five rattle-like notes. The second component is facultative and consists of one to three quacks. The first component is pulsed and lacks harmonic structure; the second component has visible harmonics and reaches higher amplitude than the first component (Fig. 11).

The advertisement calls of Osteocephalus cannatellai differ markedly from those of Osteocephalus buckleyi. Calls of Osteocephalus buckleyi (Fig. 11) consist of a pulsed rattle–like note repeated at irregular intervals and without a second component. Those calls have a shorter duration, higher repetition rate, and fewer pulses than calls of Osteocephalus cannatellai.

Osteocephalus cannatellaihas been recorded at twelve localities, all of them south of the Napo river, in the Ecuadorian and Peruvian Amazon basin (Provincias Morona Santiago, Napo, Orellana, Pastaza, Zamora-Chinchipe, and Datem del Marañón; Fig. 2). Localities with known elevation (El Edén, Huino, Yachana, Zanjarajuno, Río Maderoyacu, Hola Vida, Bobonaza, Nuevo Israel, Yawi, and Kampankis) have a range between 200 and 1290 m above sea level. Maximum airline distance between localities is 531 km. Osteocephalus cannatellai occurssympatrically with Osteocephalus buckleyi at Reserva Yachana and with Osteocephalus fuscifacies and Osteocephalus mutabor at Río Pucayacu, Nuevo Israel and Hola Vida.

Most specimens were collected at Río Pucayacu, a river surrounded by a mixture of primary and secondary forest. Frogs were found next to the river, perching over broad leaves or on tree branches 50 to 230 cm above the ground. At the collection site, the river has an average width of approximately 10 m, fast running water, and a rocky bottom. Males were calling next to the river between June 26 and July 3 2010. Several adults and a juvenile were found on a small stream, tributary of Río Rivadeneira, surrounded by secondary forest, near Río Pucayacu, in March 2008.

Vegetation types (according to the classification of Sierra et al. 1999 ) are: (1) Amazonian Mountain Range Evergreen Foothill Forest, characterized by a mixture of Amazonian and Andean vegetation with a canopy of 30 m (Río Pucayacu, Bobonaza, and Yawi), (2) Amazonian Lowland Evergreen Forests, characterized by high plant alpha-diversity and a canopy of 30 m with emergent trees that reach 40 m (Huino, Río Maderoyacu, Reserva Yachana), and (3) Amazonian Lower Montane Evergreen Forest, with an elevational range of 1300 to 2000 m above sea level, its canopy can reach 25 to 30 m (Nuevo Israel; Sierra et al. 1999, Cerón et al. 1999).

Specimens from Peru were collected in Cordillera de Kampankis within an elevational range of 300 to 365 m above sea level in tall, closed-canopy forest on low hills with well-drained soils at the base of the mountains. The soils have variable proportions of silt, clay and sand, but there are some small patches of sandy soil and limestone outcrops. The forest canopy is about 30 m tall, with emergent trees reaching 45 m. All individuals were collected in riparian vegetation of low-velocity and low-volume streams with rounded slate rocks lining the stream bed. Some individual were found on leafs of dense populations of rheophytic plants or shrubby Pitcairnia aphelandriflora (Bromeliaceae). Other individuals were found on branches of bushes between 50 and 200 cm above the ground. Other arboreal frogs at the site were Osteocephalus mutabor, Hypsiboas cinerascens, and Gastrotheca longipes.