Eungarion Stanisic, 1993

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 : 52-56

Eungarion Stanisic, 1993

Eungarion Stanisic, 1993: 27 . Type species Eungarion mcdonaldi Stanisic, 1993 (OD).

Description. External morphology: Shell reduced, 2.7 whorls, glossy, spire and apex flattened. Protoconch and teleoconch smooth. Whorl profile rounded above and below evenly convex periphery. Internal walls of early whorls incomplete; base of last whorl membranous; umbilicus not visible. Mantle laps large, rounded, mantle laps fused at base, uniform in colour. Mantle lobes of medium size, left and median lobes fused to form lobe over head. Sole of foot and caudal apparatus as for family.

Mantle cavity: As for family. Mantle with visible minor blood vessels, pigmentation absent.

Digestive system: Oesophageal crop present.

Genital system: As for family. Carrefour and talon both not embedded in albumen gland. Free oviduct short; capsular gland present; free oviduct internally with irregular thickenings. Bursa copulatrix inserted on vagina, short, less than half spermoviduct length; duct of bursa copulatrix wide, not distinguishable from bursa copulatrix, internally smooth. Vagina internally with wavy longitudinal pilasters. Epiphallus enters penis through two fleshy lips; penis internally covered in pustules, longitudinal penis pilasters present, penial diverticulum absent. Penial sheath present; thick at base of penis, thinning towards epiphallus, not enclosing entire penis; penis retractor muscle attached to base 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 without internal cryptae and externally smooth and slender. Spermatophore soft capsule with firm tail pipe open at one end, tail pipe sculptured with longitudinal rows of tiny teeth.

Radula (based on Stanisic 1993a): Relatively long and narrow. Central tooth with small ectocones; mesocone lanceolate, longer than 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 longer than tooth base. Marginal teeth with endocones absent; ectocones approximately equal in size to mesocone, not subdivided into extra teeth.

Remarks. This genus was described recently by Stanisic (1993a). The single species was described as differing from Fastosarion superba primarily in the internal sculpture of the penis and the degree of reduction of the shell. Stanisic (1993a) also noted that Eungarion mcdonaldi could be differentiated from Thularion semoni (Martens, 1894) in its weaker mantle laps and lobes, larger caudal horn and the absence of a penial verge.

Eungarion bears similarities to genera such as Fastosarion , Stanisicarion , Thularion and Parmacochlea in the presence of an epiphallic caecum and a long, slender flagellum. All of these genera except Parmacochlea also share the presence of a distinct vagina. Eungarion , Parmacochlea and Thularion have a relatively long epiphallic caecum with the penial retractor muscle attaching to its base. This character is shared with the snail genera Expocystis and Westracystis . Eungarion can be distinguished from the other genera by the degree of shell reduction and by the internal structure of the penis. In addition, it has an extremely large number of marginal radular teeth compared to most other Australian taxa.