Contributions to Zoology, 86 (1) – 2017Isabel T Hyman; Irantzu de la Iglesia Lamborena; Frank Köhler: Molecular phylogenetics and systematic revision of the south-eastern Australian Helicarionidae (Gastropoda, Stylommatophora)
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Mysticarion obscurior sp. nov.

Figs 14C, 16B, 19

Material examined. Holotype. AM C.524913 (Matcham, Matcham Road, Wambina Nature Reserve, NSW, 33°24’10” S, 151°26’24” E, leg. Hyman et al., 13/5/2016).

Paratype. AM C.524914 (same data as holotype; Fig. 14C).

Non-type material. See Table S1. Additional material: AM C.340671, AM C.334330, AM C.456540, AM C.500932.

 

Diagnosis. Shell. Small, thin, transparent, pale gold, 3.5 whorls, glossy, globose with a very low spire, whorls rounded. Protoconch with notched spiral grooves, teleoconch with very fine, shallow spiral grooves (Fig. 14C).

Animal. Body beige, pale orange along neck and middle of tail, brown on sides of tail, eye tentacles grey, black line along mantle edge, right shell lappet discontinuously edged with black. Caudal horn large. Right mantle lobe moderately large, other lobes small, none fused. Right shell lappet long, left lappet moderately long, both lappets wide at base, rapidly tapering; with black markings (Fig. 16B).

Genitalia. Bursa copulatrix moderately long, reaching half way along spermoviduct; bursa duct broad at base, then narrowing; sac small, oval-shaped. Penis moderately long, broad, slightly swollen at proximal end, enclosed in penial tunica. Penis interior with two main longitudinal pilasters and multiple wavy ridges. Epiphallus short, approx. 1-1.5 times penis length, containing very few (2-3) internal cryptae near flagellum; entering penis through pyramidal verge of about one third penis length. Epiphallic flagellum slender, with no internal cryptae. Spermatophore not observed (Fig. 19).

FIG2

Fig. 19. Reproductive anatomy of Mysticarion obscurior sp. Nov. A. Genitalia (AM C.374301). B. Penial interior (AM C.524913). Abbreviations: alb, albumen gland; bc, bursa copulatrix; cg, capsule gland; ep, epiphallus; fl, flagellum; her, hermaphroditic duct; ov, ovotestis; p, penis; pp, penial pilasters; pr, prostate; prm, penial retractor muscle; pt, penial tunica; pv, penial verge; ut, uterus; vd, vas deferens. Scale bars = 1 mm.

Remarks. Mysticarion obscurior has a very similar range to M. insuetus, stretching from just north of Gosford on the Central Coast to Bellingen in northern NSW, in subtropical rainforest and wet sclerophyll forest (Fig. 18). The two species co-occur in some areas (e.g. Little Jilliby State Conservation Preserve), although in general M. insuetus appears to be found in drier habitats. Mysticarion obscurior can be distinguished from its congeners by its darker body colouration of brown and pale orange pigmentation and by the discontinuous black edge on the right shell lappet, which is visible in preserved specimens even when the rest of the body pigmentation has faded. This species also has a paler shell with a slightly lower spire than M. insuetus. Unique features of its genital anatomy include a flagellum with no internal cryptae and only a very few cryptae in the epiphallus, indicating that the spermatophore very fewer branching spines. It also has a distinctive pyramidal penial verge and a bursa copulatrix with a long duct with broad and narrow portions and a small, distinct, rounded sac.

Etymology. From obscurior (Latin = darker; adjective), referring to the darker colour of the animal relative to its congeners.