Skrjabinura gnedina, 1933 (Nematoda: Seuratoidea: Seuratidae), in birds from the area de conservacion Guanacaste, Costa Rica with description of a new species.

Two species of Skrjabinura Gnedina, 1933, were collected in the intestines of birds from the Area de Conservación Guanacaste (ACG), Costa Rica. Skrjabinura mesoamericana n. sp. inhabits Dendrocincla homochroa, Calocitta formosa, Dendrocolaptes certhia, Basileuterus rufifrons, and Chordeiles acutipennis. The new species differs from all species of the genus by having dissimilar spicules, the right having a distinctive thin and bent handle on the proximal end. The new species can be further distinguished from Skrjabinura pomatostomi and Skrjabinura brevicaudatum by having subequal versus equal spicules. Skrjabinura mesoamericana resembles S. brevicaudatum in the number and arrangement of male caudal papillae but differs in the vulva position and in having smaller eggs. The new species differs from S. potamostomi in having 6 versus 8 pairs of postcloacal papillae. Among those species having subequal spicules, the new species further differs from Skrjabinura spiralis in having 1 pair of paracloacal papillae and 6 pairs of postcloacal papillae, versus no paracloacal papillae and 4 pairs of postcloacal papillae, and in the vulva position. The new species is perhaps most similar to Skrjabinura vali, from which it further differs by having 3 pairs of precloacal, 1 pair of paracloacal, and 6 pairs of postcloacal versus 2 pairs of precloacal, 2 pairs of paracloacal, and 6 pairs of postcloacal papillae in the vulva position and in the shape of the eggs. Skrjabinura vali (Guerrero, 1971) Chabaud, 1978, originally described in Piaya cayana from Venezuela, occurs in the small intestine of P. cayana, as well as the new hosts, Crotophaga sulcirostris and Myiarchus tyrannulus, in the ACG, a new locality. Our specimens differ from the original description in the body length of the female, the numbers of postanal papillae of male tail, and the size of eggs.