Syncuaria mycteriae n. sp. (Nematoda: Acuarioidea) was collected under the lining of the gizzard of a wood stork, Mycteria americana L., from the Area de Conservacion Guanacaste, Costa Rica. The new species can be distinguished from all known species of Syncuaria by having irregular dotted ornamentations on the caudal alae of males, a complex distal end of the left spicule comprising 3 protuberances, and a spicule ratio of 1:9.3. Preliminary phylogenetic analysis of 11 Syncuaria spp. based on 9 morphological characters produced 2 equally parsimonious cladograms with a consistency index of 85%, differing only in the placement of S. hargilae. The phylogenetic analysis suggests that the new species is the sister species of S. leptoptili, whose male members have a single protuberance on the left spicule. Furthermore, the analysis suggests that the plesiomorphic host group for the genus is Ciconiiformes, specifically Ciconiidae (host for 5 species), with 2 species occurring in Threskiornithidae (also Ciconiiformes), possibly as a result of cospeciation, and 2 species each occurring in Pelecaniformes and Podicipediformes, resulting from 4 episodes of speciation by host switching.