Two new Falcaustra lane, 1915 species (Nematoda : Kathlaniidae) from African pipids (Anura)

Two new species of Falcaustra Lane, 1915 are the first to be reported in am phibians from mainland sub-Saharan Africa. Falcaustra puylaerti n. sp. occu rs in hosts of the Xenopus (Silurana) tropicalis group in Sierra Leone, Tog o and Nigeria. Falcaustra hinkeli n. sp. infects Xenopus (Xenopus) fraseri group hosts at localities in the Cameroon and the Democratic Republic of th e Congo. Falcaustra hinkeli and F. puylaerti are probably sister species wi th respect to described congeners and can be differentiated from each other by the form of the cheilostomal structures, the morphometrics of the anter ior body, and by a large difference in male spicule length. Both lack a pre cloacal pseudosucker and are separated from other Falcaustra spp. which sha re this characteristic by the pattern of male caudal papillae and by a chei lostomal ring with associated sclerotized elements and posteriorly directed projections. Evolutionary aspects of the host-parasite relationship are di scussed. Although alternative hypotheses are possible, the distinctive chei lostomal morphology, the sister species relationship and the host specifici ty pattern of F. hinkeli and I;. puylaerti are consistent with their having undergone an extended evolutionary association with the host genus.