Chersaecia perarcta simplex ( Solem, 1966 ) Páll-Gergely, Barna, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 51-52

Chersaecia perarcta simplex ( Solem, 1966) comb. nov.

Figs 21L–M, 22E–H

Plectopylis (Chersaecia) simplex Solem, 1966: 97–101 , figs 23c–g, 24, pl. 3, figs a–c [“Chieng Dao, North Thailand at 1,200 –1,300 meters elevation”].

Chersaecia simplex – Páll-Gergely et al. 2015c: 10.

Diagnosis

Main plica absent.

Material examined

Paratypes

THAILAND: 2 broken specimens (preserved in ethanol: PL122 used for molecular study, the other, nearly intact shell: D = 12.6 mm), S.E. Asien, N. Thailand, Chieng Dao, O.H., 1200–1700 m a.s.l., 1 Jul. 1960, Degerbøl leg. (nr. 979) (ZMUC-GAS-487).

Description

MEASUREMENTS (in mm). D = 12.6, H = 4.1 (n = 1, ZMUC-GAS-487).

CHARACTERS OF THE GENITAL SYSTEM. I examined the ethanol-preserved Chersaecia perarcta simplex genitalia, which were dissected out by Solem. I found an opened penis of one specimen ( Fig. 22H ), and the complete genitalia separated into two parts of another one ( Fig. 22G ). One part of the second specimen included the penis, its retractor muscle, the vagina, the distal part of the spermoviduct, and the stalk of the bursa copulatrix (the bursa itself was missing), whereas the other part contained the proximal genitalia (remaining part of spermoviduct, albumen gland, etc.). I can confirm that the diverticulum is absent, just as Solem (1966) reported. There were also some eggs in the vial, probably from the same specimen which had the complete genitalia preserved. The structure described by Solem (1966) as a “small vergic papilla” is a thickening of the folds of the penial wall, and not homologous with the penial papilla of Helicoidea, etc., which is an extended part of the epiphallus to the penis lumen.

Differential diagnosis

The shell shapes of Chersaecia perarcta and Plectopylis simplex do not differ. The nominotypical subspecies possesses the main plica, which is lacking in C. perarcta simplex .

Distribution

Chersaecia perarcta simplex is known from the type locality only ( Fig. 9 ).

Remarks

Because of the indistinguishable outer-shell characters, Plectopylis (Chersaecia) simplex is assigned as a subspecies of C. perarcta . The difference between the two forms is only the presence/absence of the parietal plicae.

Figures

Fig. 22 (next page). A–F. Shells of species of Chersaecia Gude, 1899. A. C. nagaensis (Godwin-Austen, 1875), syntype (NHMUK 1903.7.1.753). B. C. nagaensis muspratti (Gude, 1897), syntype (NHMUK 1912.4.16.320). C. C. perarcta perarcta (Blanford, 1865), probable syntype (NHMUK 1903.7.1.753). D. C. perarcta perarcta (NHM 97458). E–F. Shell and protoconch of C. perarcta simplex (Solem, 1966), paratype (ZMUC-GAS-487). G–H. Genitalia of C. perarcta simplex (Solem, 1966) (ZMUC- GAS-487). G. Male part of the genitalia. H. Opened penis (arrow shows thickened part of penial folds). Scale bars: A–E (upper scale) = 10 mm; F–H = 1 mm. Photos: H. Taylor (A–C), T. Deli (D) and B. Páll- Gergely (E–F).

Fig. 9. Shells of Chersaecia dextrorsa (Benson, 1860). A. Holotype (NHMUK 1906.2.2.144). B–C. Adult and juvenile syntypes of Helix (Plectopylis) brachydiscus Godwin-Austen, 1879 syn. nov. (NHMUK 1903.7.1.752). D. Shell from Thailand (UF 76507). E. Shell from Thailand (UF 346181). F. Deciduous periostracal fold (UF 76385). G. Protoconch (same specimen as D). Scale bars: A–E = 10 mm; F–G = 1 mm. Images: H. Taylor (A–C), T. Deli (D–E) and B. Páll-Gergely (F–G).