Abstract Cosmocercoides latrans n. sp. (Cosmocercidae) from the small intestine of Leptodactylus latrans (Anura: Leptodactylidae) from Northeastern Province of Buenos Aires, Argentina is described. The new species can be distinguished from their congeners by a combination of the characters, among which stands out the number of rosette papillae, the lack of gubernaculum and the presence of lateral alae in both sexes. There are over 20 species in the genus Cosmocercoides, and Cosmocercoides latrans n. sp. represents the third species from the Neotropical realm and the second for Argentina. Additionally, seven previously known taxa are reported; Pseudoacanthocephalus cf. lutzi, Catadiscus uruguayensis, Rauschiella palmipedis, Aplectana hylambatis, Cosmocerca parva, Schrankiana sp. and Rhabdias elegans; providing literature records and information on distribution and host-parasite relationships.

Tanaisia dubia Freitas, 1951 (Digenea: Eucotylidae) is redescribed on the basis of specimens collected from the urinary tubules of the White-backed Stilt Himantopus melanurus (Charadriiformes: Recurvirostridae), and the Great Kiskadee Pitangus sulphuratus (Passeriformes: Tyrannidae), from Argentina. The specimens studied here are consistent with the original description, which was based on 1 specimen found parasitizing the Gray Yellowlegs Tringa melanoleuca (Charadriiformes, Scolopacidae), from Brazil. This redescription adds new morphological characters and enlarges the range of morphometric data for this species. A key to the genera of Tanaisiinae, as well as one for Neotropical species of Tanaisia Skrjabin, 1924 are presented. The diagnosis of Tanaisiinae is emended to include the presence of a cirrus sac. T. dubia is reported for the first time in Argentina and H. melanurus and P. sulphuratus represent new host records.

Tanaisia dubia Freitas, 1951 (Digenea: Eucotylidae) es redescrita a partir de ejemplares encontrados en los túbulos urinarios del tero real Himantopus melanurus (Charadriiformes: Recurvirostridae) y del benteveo Pitangus sulphuratus (Passeriformes: Tyrannidae) de Argentina. Los especímenes aquí estudiados corresponden con la descripción original, basada en un ejemplar hallado parasitando al pitotoy grande Tringa melanoleuca (Charadriiformes, Scolopacidae), de Brasil. Esta redescripción aporta nuevos caracteres morfológicos y amplía el intervalo de valores morfométricos para esta especie. Se presenta una clave para la identificación de los géneros de Tanaisiinae y otra para las especies neotropicales del género Tanaisia Skrjabin, 1924. La descripción de Tanaisiinae es enmendada para incluir la presencia del saco del cirro. Tanaisia dubia se registra por primera vez para Argentina parasitando 2 especies hospedadoras nuevas, H. melanurus y P. sulphuratus.

Two species of nematodes, Rhabdias cf. elegans (Rhabdiasidae) and Aplectana hylambatis (Cosmocercidae), were recovered from the lungs and intestine of Trachycephalus typhonius (Anura: Hylidae) captured in Formosa Province, Argentina. Morphological and morphometric data of both species are provided, and previous records of Rhabdias spp. in the Neotropical region are summarized. The finding of Rhabdias cf. elegans constitutes the first record of this genus in the Formosa Province, and the finding of A. hylambatis represents the first record of this species as a parasite of hylid frogs, and the first report in Formosa Province. Trachycephalus typhonius represents a new host for both parasites.

Dos especies de nematodos, Rhabdias cf. elegans (Rhabdiasidae) y Aplectana hylambatis(Cosmocercidae), fueron recuperados de los pulmones e intestino de Trachycephalus typhonius (Anura: Hylidae) capturados en la provincia de Formosa, Argentina. Se proveen datos morfológicos y morfométricos de ambas especies y se resumen los registros previos de Rhabdias spp. en la región neotropical. El hallazgo de Rhabdias cf. elegans constituye el primer registro del género Rhabdiasen la provincia de Formosa y el de A. hylambatisrepresenta el primer registro de esta especie en hílidos,y el primer reporteen la provincia de Formosa. Trachycephalus typhonius es un nuevo hospedero para ambos parásitos.