Oospira Blanford, 1872

Man, Nem Sian, Lwin, Ngwe, Sutcharit, Chirasak & Panha, Somsak, 2023, Further notes on the taxonomy of the land snail family Clausiliidae Gray, 1855 (Stylommatophora, Helicina) from Myanmar with description of two new species, ZooKeys 1160, pp. 1-59 : 1

Genus Oospira Blanford, 1872

Clausilia (Oospira) Blanford, 1872: 205. Boettger 1877: 64. Gude 1914: 332.

Phaedusa (Oospira) - Zilch 1959: 389, 390.

Oospira - Schileyko 2000: 581. Nordsieck 2002b: 86. Nordsieck 2007: 23.

Type species.

Clausilia philippiana Pfeiffer, 1847, by original designation.

Diagnosis.

Shell short to long fusiform, shell surface smooth to with striated ridges, spire blunt to attenuated, whorls few to numerous (6-13). Palatal plicae short to long, mostly developed and 3-10 in number. Superior lamella developed, usually connected to spiralis, distinct or indistinct at transition to spiralis. Inferior lamella steeply ascending and somewhat ending distant from superior lamella in aperture view. Subcolumellaris usually invisible in frontal view; clausilium plate lateral to ventral side and usually narrow.

External features.

Living animals possess reticulated skin; dark gray head; short tentacles; body and tail pale to dark brownish; foot moderately elongated, posterior nearly rounded to bluntly pointed.

Remarks.

Oospira is the most species-rich genus of the Phaedusinae , and more than a hundred species have been reported from a broad range in Southeast Asia (MolluscaBase 2022). Nordsieck (2002b) united two previously recognized genera, Acrophaedusa Boettger, 1877 and Pseudonenia Boettger, 1877 to form Phaedusa Oospira based on their shared steeply ascending inferior lamella, normal clausilium plate, and mostly palatal plicae form. Perhaps this grouping causes Oospira to become widely diverged in shell shape from ovate to fusiform, dark brown to pink, and different aperture shapes which is thought to be a homoplasy. A phylogenetic analysis of phaedusinids genera from Japanese and some southeast Asian taxa, especially from Vietnam, was not in line with traditional taxonomy probably due to parallel or convergent evolution ( Motochin et al. 2017; Mamos et al. 2021). However, none of the Indochinese taxa, including Oospira , were explored in this phylogenetic work.

The genera Loosjesia from Thailand, Messageriella Páll-Gergely & Szekeres, 2017 and Castanophaedusa Páll-Gergely & Szekeres, 2017 from Vietnam, Musaphaedusa Nordsieck, 2018 from Laos, and Oospira have a similar shell morphology, especially in the form of the palatal plicae. However, Loosjesia can readily be differentiated by its predominantly curved basal inferior lamella with a long transverse palatal plica and clearly visible subcolumellaris ( Loosjes 1953; Nordsieck 2002b). Messageriella is distinguished by its marginally ending inferior lamella and subcolumellaris, palatal plicae non-parallel and ventral ( Páll-Gergely and Szekeres 2017); similarly, Castanophaedusa has a rhomboidal aperture which extends to the columellar side and sharply bent basis, marginal and strongly emerged subcolumellaris, palatal plicae ventral and parallel to the principalis ( Páll-Gergely and Szekeres 2017). Meanwhile, Musaphaedusa has strong sutural papillae, principalis very long, palatal plicae ventral (only two) and strong rib-like striations on the shell surface ( Nordsieck 2018).

Regarding the reproductive anatomy of this group, Oospira penangensis (Stoliczka, 1873) and O. philippiana were the first species examined for their genitalia ( Stoliczka 1871, 1873). At present, seven species (including O. decollata and O. malaisei from Myanmar) have been investigated ( Loosjes 1953; Likharev 1962; Nordsieck 1973; Maassen and Gittenberger 2007; Páll-Gergely and Szekeres 2017).

Based on shell morphology, we have divided Oospira from Myanmar into two species groups comprised of those with (i) short and ovate fusiform shells and (ii) long and slender fusiform shells. The short and ovate fusiform group includes the species believed to be Oospira s.s. (type species Clausilia philippiana Pfeiffer, 1847), while the long and slender fusiform group assumed to be the species previously known as ' Pseudonenia Boettger, 1877' (type species Clausilia javana Pfeiffer, 1841).

Oospira species group with short and ovate fusiform shell

In Myanmar, this group is comprised of five species, four of which were collected and examined, while O. vespa (Gould, 1856) was not.