Chersaecia shiroiensis subnagaensis, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 66-67

Chersaecia shiroiensis subnagaensis subsp. nov.

urn:lsid:zoobank.org:act:7DE71ACE-B30E-4569-8DE7-8CCDA15CEE03

Figs 24K–L, 30B

Helix (Plectopylis) nágáensis Godwin-Austen, 1875b: 609–610 , 612, pl. 73, fig. 4 [“Prowi, head of the Lauier river, Nágá hills, 5000 feet ”] (partim).

Diagnosis

Intermediate and lower plicae absent.

Etymology

This new subspecies was mentioned as a dwarf variety of Helix (Plectopylis) nágáensis Godwin-Austen, 1875 . The name subnagaensis refers to the close resemblance of this subspecies to the latter species.

Material examined

Holotype

INDIA: 1 shell, Sikhami, Lahupa, Naga Hills, coll. Godwin-Austen ( NHMUK 1903.7.1.753.1).

Paratypes

INDIA: 6 shells, same data as for holotype ( NHMUK 1903.7.1.753.2–7).

Description

MEASUREMENTS (in mm). D = 7.6–7.8, H = 3.5–3.7 (type series, n = 3).

Differential diagnosis

Chersaecia shiroiensis subnagaensis subsp. nov. differs from the nominotypical subspecies by the fewer whorls (5.25–5.75 whorls; n = 5); a more prominent periostracum, which results in an overall darker shell; a smoother and smaller protoconch, which is conspicuously large and regularly ribbed in C. shiroiensis shiroiensis ; a blunter periumbilical keel; and the absence of the intermediate and lower plicae on the parietal wall (observed in two opened shells from the type series). Chersaecia shiroiensis subnagaensis subsp. nov. differs from C. nagaensis by the smaller size, the formation of the last whorl and the absence of the lower plica.

Distribution

This new subspecies is known from the type locality only.

Remarks

Observing the palatal plicae was difficult due to the erroded shells and the thick shell walls. Two adult specimens and one juvenile had more or less transparent shells. A very long plica was visible close to the upper ‘keel’ in both adult shells; this long plica is situated at the position of the second plica, but in the position of the first plica (close to the suture) no plicae were found. The juvenile shell, however, had the first, short plica visible. The other plicae of the two adult shells were short, but their morphology and orientation could not be observed without breaking the shell. In the case of the juvenile shell (which was transparent), all six plicae were short and horizontal.