Haploptychius Moellendorff , 1906

Inkhavilay, Khamla, Siriboon, Thanit, Sutcharit, Chirasak, Rowson, Ben & Panha, Somsak, 2016, The first revision of the carnivorous land snail family Streptaxidae in Laos, with description of three new species (Pulmonata, Stylommatophora, Streptaxidae), ZooKeys 589, pp. 23-53 : 25-26

Taxon classification Animalia Pulmonata Streptaxidae

Genus Haploptychius Moellendorff, 1906

Haploptychius Möllendorff in Kobelt 1906: 127. Zilch 1960: 562. Richardson 1988: 211. Schileyko 2000: 796, 797.

Odontartemon (Haploptychius) - Thiele 1931: 730. Forcart 1946: 215.

Oophana (Haploptychius) - Benthem Jutting 1954: 76, 95.

Type species.

Streptaxis sinensis Gould, 1859, by original designation.

Description.

Shell depressed to very distorted, mostly white-hyaline or transparent. Shell surface smooth and glossy or with fine radial ridges. Embryonic shell smooth; following whorls increasing regularly; penultimate whorls slightly to strongly extended beyond body whorl. Last whorl rounded and more or less deviated from the vertical axis. Umbilicus narrowly open and deep. Aperture sub-circular to semi-ovate. Peristome expanded and reflected. Apertural dentition always consisting of a single parietal lamella. Schileyko (2000) includes species with a “smooth” parietal wall, i.e. without a lamella in Haploptychius , but whether such taxa belong in this genus requires further investigation.

Live specimens exhibit a semi-transparent bright yellow body, sometimes with brownish spots; skin reticulated. Upper tentacles yellow to orange, long, with black eye-spot on tip; lower tentacles short. Brownish digestive gland and black kidney may be visible through transparent shell. Foot narrow, undivided and with short tail.

Genitalia with long and slender penis; penial sheath long, about a half to whole length of penis. Internal wall of penis with numerous long and slender penial hooks in longitudinal arrangement. Vas deferens passes under penial sheath before connecting apically to penis. Vagina and free oviduct short. Seminal vesicle present, convoluted and short. Vaginal hooks not found.

Remarks.

Currently, the genus Haploptychius consists of about 40 nominal species distributed from India to Indochina, south of China and Greater Sunda Islands ( Kobelt 1906, Zilch 1961, Richardson 1988, Schileyko 2000). Fifteen species were reported from Indochina, of which only three species: Haploptychius pellucens (Pfeiffer, 1863), Haploptychius porrectus (Pfeiffer, 1863) and Haploptychius fischeri (Morlet, 1887) were recorded from Laos (see Gude 1903, Kobelt 1906, Schileyko 2011).

General shell morphology of Haploptychius is quite similar to Oophana Ancey, 1884 and Indoartemon Forcast, 1946. However, it differs in having only a parietal lamella; while Oophana usually has parietal, palatal, columellar and basal lamellae, and Indoartemon always has parietal and basal lamellae. In addition, the genitalia of Haploptychius have a penial sheath extends about a half to entire the penis length, vas deferens passes through penial sheath, and long slender penial hooks. In Oophana , the vas deferens enter the penial sheath apically with very short vagina ( Berry 1963, Schileyko 2000); and Indoartemon , the vas deferens attached (not pass through) the penial sheath, with small and short penial hooks ( Siriboon et al. 2013).

Carinartemis Siriboon & Panha, 2013 resembles Haploptychius in having only a parietal lamella. However, it differs from Haploptychius in its very sharp peripheral keel and having the last whorl more deviated from the vertical axis. In addition, the genitalia has thick or thin penial sheath, penial hook short and stout, and vaginal hooks present ( Siriboon et al. 2014b).

The relatively large, distorted heliciform shell and dentition restricted to a parietal lamella clearly differentiate Haploptychius from Discartemon Pfeiffer, 1856 and Perrottetia Kobelt, 1905 ( Schileyko 2000, Siriboon et al. 2013, 2014a, b).