Osteocephalus vilarsi Melin 1941

Abstract

Osteocephalus vilarsi (Melin, 1941) nov. comb. (Fig. 7) Hyla (Trachycephalus) vilarsi Melin, 1941 Osteocephalus taurinus – Bokermann 1966 (synonymized vilarsi with taurinus) Osteocephalus leprieurii – Cochran and Goin 1970 (synonymized vilarsi with leprieurii) Osteocephalus taurinus – Trueb and Duellman 1971 Osteocephalus taurinus – Frost 2009 Hyla vilarsi (GNM 488) was described by Melin (1941) from a single female that he had obtained from indigenous people at Taracuá (on modern maps also Taracua or Missão Taraquá; for information on the type locality see Caldwell et al. 2002), about 100 m a.s.l., Rio Uaupés, in the upper Rio Negro drainage of Estado Amazonas, Brazil, on 7 April 1924. The holotype is a female of 62.2 mm snout-to-vent length (SVL) that contains eggs and therefore must be an adult. A striking feature are two distinct, almost parallel longitudinal frontoparietal ridges on the head, a character found in a few species of Osteocephalus. Bokermann (1966) listed the taxon without explanation as a synonym of Osteocephalus taurinus Steindachner, 1862. Cochran and Goin (1970) considered vilarsi and Osteocephalus planiceps Cope, 1874, to be synonymous with Osteocephalus leprieurii (Duméril and Bibron, 1841). Trueb and Duellman (1971) included vilarsi and O. planiceps, among others, in the synonymy of O. taurinus, a widespread species ranging from the Guyanas and southern Venezuela throughout the Amazon Basin southward to Bolivia. Duellman and Mendelson (1995) resurrected O. planiceps as a valid species. The status of vilarsi was not addressed by them. Thus, according to those previous authors, the taxon should either be a synonym of O. leprieurii, O. planiceps, or O. taurinus. Redescription of the holotype: Melin (1941) described the species in some detail. This is expanded here in order to facilitate the comparison between species, for while he mentioned the similarity between vilarsi and O. taurinus, he did not explicitly state the differences between them. Adult female of 62.2 mm SVL. Snout bluntly rounded in dorsal and lateral view. Head slightly longer than wide. Lateral edges of frontoparietals raised, forming two almost parallel ridges. Canthus rostralis very distinct, almost straight (very slightly curved inwardly). Loreal region deeply concave. Nostrils elevated, opening laterally. Dentigerous processes of vomers in contact with each other, bearing 11 teeth on the left and 15 on the right, angular, in between choanae, their anterior edges at about midlevel of the choanae, their posterior edges reaching slightly beyond the posterior edges of the choanae. The latter are large, oblique and bean-shaped though somewhat angular. Tongue elliptical, about 1.4 times longer than wide. Supratympanic fold from the anterior edge of the tympanum sloping towards the upper edge of the arm insertion in an almost straight line. Tympanum large, conspicuous, elliptical, slightly wider than high and about 77 % of the eye diameter. Skin on dorsum smooth with a few scattered, small, flat tubercles (under magnification) in the posterior half of the back. Dorsal surfaces of head rugose. Loreal region granulate. Skin loose or missing (removed) above the sphenethmoid and on the right nostril. Skin of body smooth laterally and on lateral and dorsal surfaces of the extremities. Ventrally smooth in thoracic area and on chin, granulate on belly and posterior two thirds of the thighs. Axillary membrane absent. Cloacal opening at about three fourths of thigh height. The finger and toe discs are desiccated. Melin described them as being scarcely half the size of the tympanum and slightly oblong, but it is not clear whether they were in a better state then. The disc of Finger III is 52 % of the tympanum width. The thumb bears a large elliptical thenar tubercle and there is a prominent supernumerary tubercle proximal to the proximal subarticular tubercle. A few low tubercles are present on the outer edge of the fourth finger. The distal subarticular tubercle on Finger IV is barely bifid, the others are simple. The relative length of the adpressed fingers is I 1400 m on Mount Ayanganna has about the same size as vilarsi and also shares cranial ridges, but vilarsi lacks an axillary fold (one half of humerus length in phasmatus) and the width of the disc of Finger III is about half the tympanum width (larger than tympanum). Since vilarsi can be distinguished from all other species in the area it is here considered a valid member of the genus Osteocephalus characterized by (1) medium size (female 62.2 mm SVL), sexual dimorphism unknown; (2) skin on dorsum of females smooth anteriorly, interspersed with small flat tubercles on the posterior 2 / 3 of the back, unknown in males; (3) skin on flanks smooth; (4) very prominent, almost straight canthus rostralis; (5) frontoparietal ridges present, well visible through skin; (6) dentigerous processes of vomers angular; (7) straight supratympanic fold, sloping in a fairly straight line posterior to the tympanum; (8) web on inner edge of third finger reaching distal end of penultimate subarticular tubercle; (9) distal subarticular tubercle on Finger IV barely bifid; (10) dorsum uniform tan; (11) venter cream with some small brown spots posterior to the clavicle; (12) narrow white labial stripe to posterior edge of tympanum, extended into large subocular spot; (13) flanks brown with a few small irregular tan spots; (14) position of vocal sacs unknown; (15) juvenile coloration unknown; (16) tadpole habitat and labial tooth row formula unknown; (17) color of bones white (?). Distribution: Osteocephalus vilarsi is still only known from the type locality in the extreme northwest of Brazil, close to the Colombian border.Published as part of Jungfer, Karl-Heinz, 2010, The taxonomic status of some spiny-backed treefrogs, genus Osteocephalus (Amphibia: Anura: Hylidae), pp. 28-50 in Zootaxa 2407 on pages 41-46, DOI: 10.5281/zenodo.29392