Genus Petrovinema Ershov, 1943

General. Middle to large-sized Cyathostominea. MC flattened, divided into inner and outer rings. 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 spindle-shaped or bullet-shaped, 2 – 3 times long as thick. Stalk of submedian papillae longer than broad. Number of elements of ILC about 3 times as numerous as ELC; nearly equal in length. Elements of ELC longer than broad, tips pointed; insertion point on tips of ILC. Elements of ILC rod-shaped, longer than broad, tips rounded; insertion point 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. Buccal cavity deeper than wide or as deep as wide, cylindrical. Dorsal gutter nipple- or button-like. Buccal teeth absent. Esophageal funnel shallow. 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. Ventral rays shorter than laterals. Dorsal lobe longer then lateral lobes. Externodorsal rays origin on stem of dorsal. Gubernaculum with small handle, enlarged distal tip. Genital cone elongate, extends beyond bursal edge. Spicule tips hook- or harpoon-shaped.

Female: Vulva about one, or less than 1 tail length from anus. Vagina longer than sphincter of ovejector. Ovejector vestibule oval or Y-shaped, infundibulum longer than sphincter. Tail conical or digitiform, it can be short or long.

Type species: P. skrjabini (Ershov, 1930) Ershov, 1943.

Discussion

Previously Lichtenfels (1975) included the two species of Petrovinema in Cylicostephanus, but the characteristics of the mouth collar, buccal capsule wall and support of the ELC described by Hartwich (1986) place Petrovinema closer to Cylicocyclus than to Cylicostephanus. The molecular data of Hung et al. (2000) and a morphological phylogeny of the Cyathostominea (Lichtenfels and Hoberg, unpublished) support the recognition of Petrovinema as a separate genus, basal to the rest of the Cyathostominea.