Tholoarctus Kristensen & Renaud-Mornant 1983

Genus Tholoarctus Kristensen & Renaud-Mornant, 1983 Diagnosis (emended): Styraconyxinae with a barrel-shaped outer epicuticle surrounding the trunk, the body itself is thin and elongated. Complete set of cephalic appendages. Cone-shaped primary clavae and secondary clavae enlarged surrounding both the internal and external cirri. Cirri A and E partially surround by funnel-shaped epicuticle folds. Leg sense organs always present on the first (se 1) and fourth (se 4) legs, though much smaller sense organs may be present on the second (se 2) and third (se 3) legs. Flagellum on the sense organ of the first leg always very long. Sense organ of the fourth leg partially enclosed in funnel-shaped epicuticular folds. Females have claws with a main hook, a basal accessory hook and a terminal accessory spur. Males and larvae might have simple claws in the external digits. Long buccal tube with two lateral projections at ca. the mid-point. Long and thin stylet supports articulate with the furcae. Placoids consist of a non-calcified cuticular lining, but three small calcified apodemes occur in the anterior part of the pharyngeal bulb. Mouth cone is terminal and protruding. Globular coelomocytes seem to be attached to the midgut. Sexual dimorphism in body size and claws. Type species: Tholoarctus natans Kristensen & Renaud-Mornant, 1983. Additional species: The genus is currently monotypic. However a sub-species from Italy, Tholoarctus natans pedunculatus D’Addabbo Gallo, de Zio Grimaldi, Morone De Lucia & Troccoli, 1992, has been described (D’Addabbo Gallo et al. 1992).