A detailed examination (including scanning electron microscopy) of newly collected nematode specimens (subgravid females) referable to Philometroides caudatus Moravec, Scholz and Vivas-Rodríguez, 1995, from the swimbladder of the pimelodid catfish, Rhamdia guatemalensis, in the Papaloapan River in Tlacotalpan, State of Veracruz, Mexico, as well as the paratype specimens of this species, revealed the presence of a small buccal capsule armed with peribuccal teeth in the female. Because of this unique morphological feature within the Philometridae, and considering other taxonomically important characters such as the structure of the male tail and the shape of the anterior end of the esophagus in the gravid female, Neophilometroidinae n. subfam. and Neophilometroides n. gen. are proposed to accommodate this species. Philometra paraguayensis Petter, 1995, is transferred to Neophilometroides as N. paraguayensis (Petter, 1995) n. comb. Newly collected specimens are briefly described and illustrated.