Genus Poteriostomum Quiel, 1919

Synonyms: Hexodontostomum Ihle, 1920

General. Medium-sized Cyathostominea. MC inflated, high, ring-shaped, undivided. Posterior edge of MC at anterior edge of BC. Amphids not markedly projected through MC surface. Tip and longer stalk of submedian papillae extend through MC. Tip of submedian papillae cone-shaped, short. Stalk of submedian papillae broader than long. Elements of ELC more numerous than ILC and shorter of them. Elements of ELC longer than broad, tips pointed; insertion point on tips of ILC. Elements of ILC longer than broad, tips pointed; insertion point at on anterior edge of BC. Line formed by insertion of elements of ILC straight. Form of posterior edge of elements of ILC straight, unadorned. Support for ELC continuous with BC, elongate, curving, thin at one end. Septum intracoronare origin on support. Medial insertion of septum intracoronare situated at junction of ELC and ILC. Walls of BC straight, thicker posteriorly, but without ring-like thickening. Buccal cavity wider than deep, cylindrical. Dorsal gutter prominent, broad, less than 1/2 of BC depth. Buccal teeth absent. Esophageal funnel moderately enlarged, lined with thick cuticle. Esophageal teeth not prominent. Anterior muscular portion of esophagus about 1/4 to 1/3 of esophagus length. Excretory pore posterior to NR. Anterior deirids near middle of glandular esophagus.

Male: Dorsal ray with 6 branches; origins of proximal and middle rays close together. Ventral rays shorter than laterals. Dorsal lobe longer then lateral lobes. Externodorsal rays origin on stem of dorsal. Gubernaculum large, with dorsal handle and ventral notch. Genital cone short, conical. Spicule tips hook- or harpoon-shaped.

Female: Vulva more than 1 tail length from anus. Vagina shorter than sphincter of ovejector. Ovejector vestibule oval or Y-shaped, infundibulum shorter than sphincter. Tail conical, long, more than 2x diameter at anus.

Type species: P. imparidentatum Quiel, 1919.

Discussion

This genus is closely related to the genus Parapoteriostomum, especially in characteristics of the leaf-crown, size, and degree of splitting of the dorsal ray. The two genera can be separated easily, however, by characters of the buccal capsule, especially the point of insertion of the internal leaf-crown and the character of the dorsal ray. The species P. imparidentatum and P. ratzii are very similar except for the difference in the internal leaf-crown. Kotlan (1921) considered P. imparidentatum to be a variety of P. ratzii. However, they are recognized almost universally as distinct species.

According to Hartwich (1986) the females described by Galofre and Rosa (1944) as P. imparidentatum var. longum most likely belong to P. ratzii because no difference in size of the elements of the corona radiata interna are mentioned nor pictured; the smaller number of the elements of both leaf crowns corresponds more to that of P. ratzii. and the wall of the mouth capsule is significantly thicker than in P. imparidentatum.

P. skrjabini from horse and ass in Russia; distinguished by a poorly defined dorsal gutter and a short tail with the vulva very close to the anus, is now designated as a species inquirenda.