Pravonitor Iredale, 1937

Hyman, Isabel T. & Ponder, Winston F., 2010, A morphological phylogenetic analysis and generic revision of Australian Helicarionidae (Gastropoda: Pulmonata: Stylommatophora), and an assessment of the relationships of the family 2462, Zootaxa 2462 (1), pp. 1-148 : 62-64

Pravonitor Iredale, 1937

Pravonitor Iredale, 1937c: 3 . Type species Nitor kreffti insularum Iredale, 1937 (OD).

Description. External morphology: Shell of about 5.2 whorls, glossy, spire and apex slightly raised. Protoconch smooth; teleoconch with microscopic spiral grooves. Whorl profile rounded above and below evenly convex periphery. Internal walls of early whorls complete; umbilicus open, very narrow. Mantle laps of medium length, finger-shaped, tapering to a blunt point, not fused, uniform in colour. Mantle lobes small. Sole of foot and caudal apparatus as for family.

Mantle cavity: As for family. Mantle with visible minor blood vessels; pigmentation of black spots.

Digestive system: Oesophageal crop absent.

Genital system: As for family. Carrefour embedded in albumen gland, talon free. Free oviduct very long; capsular gland absent; internal longitudinal pilasters present. Bursa copulatrix inserted on vagina, moderately long, more than half spermoviduct length; duct of bursa copulatrix wide, not distinguishable from bursa copulatrix, internally with pustules. Vagina very short. Epiphallus enters penis through two fleshy lips; penis internally covered in round pustules, pilasters absent, penial diverticulum absent. Penial sheath present, enclosing only base of penis; penis retractor muscle attached to middle of epiphallic caecum. Epiphallus internally with longitudinal pilasters. Epiphallic retractor caecum moderate in size, positioned in middle of epiphallus. Flagellum present; flagellum and distal part of epiphallus with shallow internal cryptae, externally visible. Spermatophore not present in dissected material.

Radula: Relatively long and narrow. Central tooth with small ectocones; mesocone lanceolate, similar in length to tooth base. Lateral and marginal tooth fields distinguishable. Lateral teeth with endocone much smaller than central tooth ectocones; ectocone equal in size to those on central tooth; mesocone similar in length to tooth base. Marginal teeth with endocones absent; ectocones approximately same length and breadth as mesocone, not subdivided into extra teeth.

Remarks. Pravonitor was created as a subgenus of Nitor for Helix kreffti Cox, 1864 and Nitor kreffti insularum Iredale, 1937 ( Iredale 1937c) from far north Queensland (Cape York and islands of Torres Straits). The reason for the subgeneric separation was given as a difference in shell texture and the lack of an angulation or keel. Pravonitor was raised to generic status by Smith (1992), who also synonymised P. kreffti and P. kreffti insularum . In addition to P. kreffti , three undescribed species of Pravonitor are recognised in the AM and QM collections (J. Stanisic, pers. comm.), two from around Cooktown and the third from Rocky River camp, Cape York Peninsula.

Pravonitor can be separated from Nitor based on a number of characters. Firstly, it has a rounded whorl profile in contrast to the more or less angulate periphery seen in Nitor , with the whorl profile flattened above and flattened or rounded below. A peripheral coloured stripe is present on the shell of some specimens of P. kreffti but is absent in Nitor and the spiral grooves on the protoconch of Nitor are absent in Pravonitor . There are also a number of anatomical differences between Pravonitor , Nitor and other helicarionid snails. Pravonitor is included here with taxa that have a smooth, slender flagellum; however, the flagellum is slightly wider than most of the others in this group, and there are some signs of internal cryptae, indicating that the spermatophore (not examined here) probably has short spines on the tail pipe. This was not observed in other helicarionid snail taxa from northern Queensland.