Review of the Frog GenusSilverstoneia, with Descriptions of Five New Species from the Colombian Chocó (Dendrobatidae: Colostethinae)

Abstract

The dendrobatid genus Silverstoneia is a clade of forest-dwelling frogs that share small adult size (<22 mm snout-vent length), basal webbing between toes III–IV, a solid blackish brown flank divided by a conspicuous pale oblique lateral stripe from the groin to the eye, a pale ventrolateral stripe, finger I > II, male nurse frogs (known in four species), and larvae possessing an umbelliform oral disc with few to many submarginal papillae and medially emarginate posterior labium (also known in four species).The clade is distributed from Costa Rica to southern Departamento del Valle del Cauca in western Colombia and includes eight species, five of which are described herein as new species. As in all species of Dendrobatoidea, in Silverstoneia the distal tendon of insertion of the m. semitendinosus inserts dorsad to the distal tendon of the mm. gracilis complex and is strapped to the dorsal edge of the inner surface of the mm. gracilis complex by a unique binding tendon. The species of Silverstoneia may be diagnosed on the basis of adult size, adult ventral coloration, thigh coloration, and degree of expansion of finger III in adult males; additionally, there are clear species differences among the known tadpoles.Taxonomic comments are given for three previously named species: Silverstoneia erasmios (Rivero and Serna), S. flotator (Dunn), and S. nubicola (Dunn). We were unable to distinguish erasmios from nubicola. However, only females of erasmios are known and its validity needs confirmation. The species S. flotator sensu lato and S. nubicola sensu lato occur north through Panama to Costa Rica; they are distinct from one another, but some intraspecific variation suggests the possible presence of unnamed sibling species. The specimen long recognized as the type of S. flotator is not the holotype, which we consider lost; however, ample material is available from the well-known type locality (Barro Colorado Island) and neotype designation is not needed.Five new species are described—all endemic to low and moderate elevations on the Pacific versant of Colombia: Silverstoneia dalyi (p. 5), S. gutturalis (p. 17), S. minima (p. 22), S. minutissima (p. 29), and S. punctiventris (p. 34).