Ingwenascaris n. g. (Nematoda: Ascaridida: Heterocheilidae) established for I. sprenti n. sp. and I. assymmetrica (Ortlepp, 1932) n. comb., parasites of African crocodiles, and an identification key to the genera of the Heterocheilidae.

Ingwenascaris n. g. (Nematoda: Heterocheilidae) is established to accommodate Ingwenascaris sprenti n. g., n. sp., described from the stomach of Crocodylus niloticus Laurenti (Reptilia: Crocodylidae) in South Africa, based on light and scanning electron microscopy studies of its morphology. The new genus can be distinguished from other heterocheilid genera through a combination of its characters, including the pronounced asymmetry of each subventral lip due to an alate ventral margin and a non-alate margin facing the dorsal lip, the presence of continuous ridges of triangular denticles along the free labial margins, the lack of interlocking processes or a rostral plate, interlabia being indistinct or represented by small lateral interlabia between the dorsal and ventral lips only, the absence of prominent interlabial longitudinal cuticular ridges, the presence of lateral alae that are fused with the subventral lips, the presence of lateral caudal alae in both sexes, spicules of males that are composed of handle and alate blade, the presence of a gubernaculum, the number and arrangement of male caudal papillae and the position of the vulva near the anterior and middle third of the body in females. Ingwenascaris sprenti n. g., n. sp. represents the sixth heterocheilid genus parasitising African crocodilians. Trispiculascaris assymmetrica (Ortlepp, 1932) (syn. Porrocaecum assymmetricum Ortlepp, 1932) from a Central African crocodile is transferred to the new genus as I. assymmetrica (Ortlepp, 1932) n. comb. The genus Trispiculascaris Skrjabin, 1916 is considered a genus incertae sedis. An identification key to the genera of the family Heterocheilidae is presented.