Systematics and phylogeny of Potamotrygonocestus (Platyhelminthes, Tetraphyllidea, Onchobothriidae) with descriptions of three new species from freshwater potamotrygonids (Myliobatoidei, Potamotrygonidae)

Abstract

Specimens of Potamotrygonocestus used in the present taxonomic and phylogenetic study were collected in freshwater potamotrygonids from the Rio Paraná (Puerto Reconquista, Santa Fé, Argentina; 59°42′W, 29°29′S) during February 1995, and from the Amazon region of Brazil during September to December 1996, supplemented by specimens previously deposited in museum collections. Six species of Potamotrygonocestus were recognized (P. amazonensis, P. chaoi sp. n., P. fitzgeraldae sp. n., P. magdalenensis, P. maurae sp. n., P. travassosi), for which an identification key is provided. Potamotrygonocestus orinocoensis is considered a junior synonym of P. travassosi. Additional specimens of Potamotrygonocestus may represent two undescribed species. A phylogenetic analysis of six morphological characters for the six named species of Potamotrygonocestus generated a single tree eight steps long, with a consistency index of 0.87, a retention index of 0.90, and a rescaled consistency index of 0.79 with the following topology: (P. maurae sp. n. ((P. amazonensis + P. magdalenensis) (P. chaoi sp. n. (P. fitzgeraldae sp. n. + P. travassosi)))).