We report the finding of 2 species of Pudica (Nematoda: Heligmonellidae: Pudicinae) in 2 rodents endemic to Chile, the common degu Octodon degus (Octodontidae) and the Bennett's chinchilla rat Abrocoma bennettii (Abrocomidae). Pudica degusi ( Babero and Cattan, 1975 ) n. comb., originally described as a species of Longistriata (Heligmosomidae), was found in the common degu; through the study of its synlophe, the species is reassigned to the Heligmonellidae: Pudicinae and the genus Pudica , and it is revalidated through comparison with the remaining species of the genus. Pudica cattani n. sp. is described from both O. degus and A. bennettii . It is characterized by its large body size, bursal pattern of type 1-3-1 on right lobe, 1-3-1 tending to 1-4 on left lobe, synlophe with 11 ridges including a careen, dorsal ray of the bursa dividing proximally and bursal rays 9 and 10 relatively short. Pudica degusi n. comb. and Pudica cattani n. sp. were found in the same host species but not as coparasitic in the same individuals. The common degu is confirmed as the sole and primary host of Pudica degusi n. comb. It is unlikely that it is the primary host for Pudica cattani n. sp., whose host affinities are less clear mainly due to the scarcity of data. Pudica cattani n. sp. is the first helminth reported from the Bennett's chinchilla rat. Both findings enlarge the host range of the Pudicinae to the families Octodontidae and Abrocomidae, i.e., 9 out of the 11 extant families of caviomorphs, thereby establishing the presence of this nematode subfamily as typical parasites of the Neotropical Hystricognathi.

Two species of Hassalstrongylus Durette-Desset, 1971 , coparasitic in Holochilus chacarius Thomas (Rodentia, Cricetidae) and not recorded since their original description in 1937, were newly found in their type host and locality. Hassalstrongylus mazzai ( Freitas, Lent and Almeida, 1937 ) and Hassalstrongylus argentinus ( Freitas, Lent and Almeida, 1937 ) were obtained from Ho. chacarius from 2 different populations: one from Salta Province (northwest Argentina) and another from Chaco Province (northeast Argentina). The species described as Heligmonoides mazzai Freitas, Lent and Almeida, 1937 had been transferred to Hassalstrongylus even though its synlophe had never been studied. We provide the first descriptions and illustrations of the synlophe of males and females of Hassalstrongylus mazzai and the female of H. argentinus and account for morphological and metrical variability. We confirm, through the study of the synlophe, the placement of Hassalstrongylus mazzai in the genus Hassalstrongylus and designate neotypes for the species because the type material deposited by the authors could not be found. Females of both species were morphologically very similar, and a principal components analysis (PCA) performed on some morphometrical characters showed that the body length, uterus length, and an unexpected character as the number of eggs were useful characters in the discrimination of both species.

The species described as Longistriata fortuita Freitas, Lent, and Almeida, 1937 is here redescribed from new material collected from the type host, Holochilus chacarius balnearum Thomas, and the type locality, San Martín del Tabacal, Salta, Argentina. Neotypes are designed for the species since the type material deposited by the authors is lost. The original description did not include the synlophe or the female and both are here described. Several characters of the synlophe as the number of ridges (14–19), the ridges continuous and all around body, and the presence of a gradient of size of the ridges allow us to place the species within the Heligmonellidae, Nippostrongylinae. The species possesses a unique combination of characters as the synlophe having a carene together with characters of the caudal bursa as the pattern 1-3-1 and the strong development of the dorsal lobe and ray, which precludes its inclusion in any known genus of Nippostrongylinae. A new genus Mazzanema n. gen. is proposed for it, resulting in the new combination Mazzzanema fortuita n. comb.

Two species of Guerrerostrongylus Sutton and Durette-Desset, 1991 , are reported in cricetid rodents from the Atlantic rain forest of Misiones, Argentina. Guerrerostrongylus zetta ( Travassos, 1937 ) is redescribed on the basis of material collected from Oligoryzomys nigripes from Argentina and material loaned by CHIOC from Brazil. It is characterized by a synlophe with about 40–45 (35–48) well-developed cuticular ridges, caudal bursa with long rays 6 and dorsal ray divided at mid-length, and well-sclerotized spicules with marked twisting. It was found with a prevalence of 100% in O. nigripes (14 hosts examined); however, it was not found in its type host Nectomys squamipes (4 hosts examined). Guerrerostrongylus ulysi n. sp., which is described from Sooretamys angouya , differs from the remaining species in the genus mainly by a synlophe with a strong reduction of the cuticular ridges and struts on the right side, and by a heart-shaped caudal bursa, with short rays 6 and a dorsal ray divided distally. It was found with a prevalence of 100% in 5 hosts examined.

Two nematode species are redescribed from the type host species Holochilus chacarius Thomas (Rodentia, Cricetidae, Sigmodontinae) and from the type locality of 1 of them, i.e., Ingenio San Martín de Tabacal, Salta Province, Argentina. Rodents were deposited at the Colección Mamíferos Lillo, Tucumán, Argentina. Litomosoides patersoni ( Mazza, 1928 ) (Onchocercidae) possesses a buccal capsule with irregular external walls, a buccal cavity smooth, becoming thinner near the oral opening, a complete set of head papillae, 3–6 pairs of cloacal papillae, and the “ sigmodontis ” type of spicules. Filarioids were found in 3 of 17 examined hosts. Stilestrongylus stilesi Freitas, Lent, and Almeida, 1937 (Heligmonellidae), whose description was based on male specimens, was found in all 17 of the examined hosts. Here, we describe the female and the synlophe of both sexes. Females are characterized by a short uterus with less than 25 eggs, short ovejector, short and conical tail, and the posterior extremity strongly invaginated in a cuticular expansion usually harboring 1 to several eggs. The synlophe is characterized by 29–31 sub-equal cuticular ridges at the mid-body, with single (in males) or double (in females) axis of orientation of the ridges. The present work validates and enlarges the original descriptions of both species and assigns the specimens from L. patersoni , recovered from the type locality and the type host species, as neotypes.

Paraheligmonella kinsellai n. sp. (Nematoda: Heligmonellidae: Heligmonellinae) is described from the small intestine of a cottontail rabbit Sylvilagus floridanus (Allen, 1890) (Leporidae) from Costa Rica. The new species is similar to P. romerolagi (Gibbons and Kumar, 1980), parasitic in Romerolagus diazi from Mexico and to P. lamothei Digiani, Carreño, and Durette-Desset, 2008 , parasitic in Sylvilagus floridanus from Costa Rica, by the characters of the synlophe at mid-body, i.e., 14 cuticular ridges and a single axis of orientation inclined at 30° to the sagittal axis in both sexes. The males of the new species are distinguished from those of P. romerolagi by a caudal bursa that is not bell-shaped, a bursal pattern of type 2–3 with a tendency to 2–2–1, and a genital cone that is not hypertrophied. They are also distinguished from the males of P. lamothei by having the same bursal pattern in both lobes (in P. lamothei the pattern is 2–2–1 on the right lobe and 2–3, with a tendency to 2–2–1, on the left lobe), rays 3 are much longer than rays 2, rays 2 and 3 diverging more proximally, and rays 8 are longer than the dorsal ray. The females of the new species also differ from those of P. lamothei by the shape of the posterior extremity (long and strongly curved vs. short and nearly straight) and by the synlophe at the ovejector level (ridge no. 1′ hypertrophied and remaining ridges reduced vs. ventral ridges hypertrophied and dorso-lateral ridges reduced).

Vexillata noviberiae ( Dikmans, 1935 ) (Trichostrongylina: Heligmosomoidea), originally described as a parasite of Sylvilagus floridanus from Louisiana, is redescribed from material collected from Sylvilagus palustris in Florida and from S. floridanus in Kansas. New morphometric and morphological data are provided. Stunkardionema halla Arnold, 1941 , described from S. floridanus from Kansas and New York, is proposed as a junior synonym of V. noviberiae . These findings confirm the occurrence of V. noviberiae as a parasite of rabbits and its wide distribution range in North America.

The systematic position of some heligmosomoid nematodes from rodents, deposited in the U.S. National Parasite Collection (USNPC), is revised, mainly through the study of their synlophe, which in all cases was unknown or insufficiently described. The material was registered as different species of Longistriata Schulz, 1926, a genus whose representatives are only parasitic in Holarctic insectivores. Longistriata norvegica Dikmans, 1935 , parasitic in Rattus sp. becomes a synonym of Hassalstrongylus aduncus (Chandler, 1932). Specimens registered as Longistriata dalrymplei Dikmans, 1935 , from Ondatra zibethicus , are confirmed to belong to Carolinensis (Travassos, 1937). Specimens registered as Longistriata noviberiae Dikmans, 1935 , parasitic in Sylvilagus floridanus alacer , were found to belong to Vexillata , and Vexillata noviberiae n. comb. is here proposed. This is the first record of a species of Vexillata in a lagomorph. Other specimens registered as Longistriata norvegica , parasitic in Geomys floridanus austrinus , were also found to be an undescribed species of Vexillata ( Hall, 1916 ), which is named Vexillata chitwoodi n. sp. This is similar to Vexillata chabaudi Yoyotte-Vado, 1972, Vexillata petteri Durette-Desset, 1970, Vexillata scorzai Guerrero, 1984 and Vexillata tejerai Guerrero, 1984 , all having the same number of cuticular ridges (4 dorsal, 5 ventral) and the division of the dorsal ray at its apex. The most related species is V. chabaudi , which is differentiated from the new species by rays 4 not curved distally, by thick rays 8, and by a dorsal ray enlarged at the level of the arising of rays 8.

A new genus of Nippostrongylinae, Malvinema n. gen., with 3 coparasitic species M. frederici n. sp., M. carolinae n. sp., and M. victoriae n. sp. from the intestine of the water rat, Scapteromys aquaticus Thomas (Rodentia: Muridae), from the northeast of Buenos Aires Province, Argentina, is proposed in this study. The new genus shows similarities to 2 Neotropical Nippostrongylinae: Carolinensis (Travassos, 1937) by some characters of the synlophe and Stilestrongylus Freitas, Lent and Almeida, 1937, by the pattern of the caudal bursa. It is characterized by a synlophe with triple or quadruple gradient of size of the ridges, lateromedian, decreasing from the largest left and right ridges. The gradient situated in the right ventral quadrant is always present. The caudal bursa shows a pattern of type 1-4. Malvinema frederici possesses a synlophe with 17 ridges and an axis of orientation inclined at 45° from the sagittal axis; M. carolinae possesses a synlophe with 22–24 ridges and an axis of orientation almost merged with the sagittal axis. Both species have a caudal bursa with the right lobe enlarged transversally. Malvinema victoriae possesses a synlophe with 22–24 ridges, an axis of orientation inclined at 45° from the sagittal axis, and a caudal bursa with the right lobe enlarged vertically.