Nematodes collected at postmortem examination from the lungs of a yellow-spotted Amazon River turtle, Podocnemis unifilis, are described and assigned to a new genus, Pneumoatractis, the twenty-first genus of the superfamily Cosmocercoidea, family Atractidae. The new genus is most similar to congeners possessing a noncosmocercid esophagus and lacking anterior cuticularized formations, namely, Atractis, Cyrtosomum, Leiperenia, Monhysterides, Paratractis, and Rondonia. The new genus differs from the above congeners as follows: males of Atractis have 1 lagenoid spicule and 1 lanceolate spicule, males of Pneumoatractis possess 2 lanceolate spicules; males of Cyrtosomum lack a gubernaculum, a gubernaculum is present in Pneumoatractis; in Leiperenia the anterior part of the esophagus is one fourth of total length of esophagus, in Pneumoatractis the anterior part is one half of total length; Monhysterides lacks lips, which are well developed in Pneumoatractis; Paratractis has scale-like cuticular projections along the dorsal surface of the body in contrast to the smooth surface of Pneumoatractis; and females of Rondonia possess a cloaca, females of Pneumoatractis have separate openings for digestive and reproductive tracts. The new genus also differs from other genera of the family in that it was found in the lungs rather than the intestines.