A new species of Potamotrygonocestus Brooks & Thorson, 1976 (Eucestoda: Tetraphyllidea) from Plesiotrygon iwamae Rosa, Castello & Thorson (Mylliobatoidea: Potamotrygonidae) and a redescription of Potamotrygonocestus chaoi Marques, Brooks & Araujo, 2003 - Luchetti, Natalia da Mata; Marques, Fernando; Charvet-Almeida, P (Systematic Parasitology, 2008)