Genus Cylicostephanus Ihle, 1922

Synonyms: Cylicostomum (Cylicostephanus) Ihle, 1922; Cylicostomum (Cylicotetrapedon) Ihle, 1925; Erschowinema Tshoijo, 1957.

General. Small Cyathostominae. MC flattened, divided into inner and outer rings. Posterior edge of MC posterior to 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-, cone- or bullet-shaped, about 2 - 3 times as long as thick. Stalk of submedian papillae longer than broad. ELC markedly less numerous, or nearly equal in number, and longer than ILC. Elements of ELC longer than broad, tips rounded or pointed; insertion point on tips of ILC or slightly back from tips. Elements of ILC longer than broad, tips pointed or rounded; insertion point about ¼ or less of BC depth. 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, short, triangular in optical section. Septum intracoronare origin on support or BC. Medial insertion of septum intracoronare situated anteriorly to junction of ELC and ILC. Walls of BC straight or S-shaped, thicker posteriorly or anteriorly. Buccal cavity can be deeper than wide, as deep as wide or wider than deep, but wider posteriorly. Dorsal gutter button-like or elongate. Buccal teeth absent. Esophageal funnel shallow or enlarged. Esophageal teeth usually 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 may have different length relatively to laterals. Dorsal lobe longer then lateral lobes. Externodorsal rays origin at junction of dorsal and laterals rays. Gubernaculum large, with dorsal handle, ventral notch evident or inconspicuous. Genital cone short, conical. Spicule tips pick-shaped.

Female: Vulva about one, or less than one, tail length from anus. Vagina longer than sphincter. Ovejector vestibule oval or Y-shaped. Tail conical or digitiform, short, length less than 2x diameter at anus.

Type species: C. calicatus (Looss, 1900) Cram, 1924

Discussion

The name Cylicostephanus was coined by Ihle (1922) as a subgenus to draw attention to the depressed mouth collar of a group of species including C. calicatus, C. longibursatus, C. minutus, C. hybridus, and C. poculatus. These species also share the characteristics of an ILC composed of short rods implanted close to the anterior edge of the buccal capsule; an ELC composed of longer and broader elements; and a buccal cavity that is slightly narrower anteriorly than posteriorly. Most subsequent workers have grouped these five species together. To this group Cram (1925) added the species C. asymetricus. Cylicostephanus bidentatus, a species considered by some workers to be a synonym of C. asymetricus, is recognized as a separate species because of its large esophageal teeth and relative lack of asymmetry of the buccal capsule.

The common species C. goldi fits well the characteristics of this genus, being very similar in cephalic characteristics to C. longibursatus, and is included in Cylicostephanus.

Hartwich compared published descriptions of the two species and concluded that the description of the rarely reported and often misidentified C. ornatum is indistinguishable from C. goldi. Although there are several reports of C. ornatum in North America, all specimens that Lichtenfels (1975) could locate were redetermined as other species.

Trichonema parvibursatum has previously been considered to be a synonym of C. hybridus, but Hartwich (1986) discovered that the original description of this species more closely matches that of C. goldi.

Trichonema tsengi, recently described in China ( ), is considered to by a synonym of C. calicatus. It was separated from C. calicatus by a greater number and different shapes of ELC elements. As Barus (1962) and Braide and Georgi (1974) have shown, however, C. calicatus has a greater range in number of ELC elements (12-18) than given in earlier reports

Cylicotetrapedon was recognized at the level of genus by Dvojnos and Kharchenko (1994) following several earlier workers who all recognized the same two species in this group. However, neither Lichtenfels (1975) nor Hartwich (1986) could find characters without considerable homoplasy to define this group. The consensus of the 1997 Sun City Workshop (Lichtenfels et al., 1998) was that Cylicotetrapedon not be used.