Naggsia Pall-Gergely & Muratov

Pall-Gergely, Barna, Muratov, Igor V. & Asami, Takahiro, 2016, The family Plectopylidae (Gastropoda, Pulmonata) in Laos with the description of two new genera and a new species, ZooKeys 592, pp. 1-26 : 11-12

Taxon classification Animalia Pulmonata Plectopylidae

Naggsia Pall-Gergely & Muratov gen. n.

Type species.

Helix laomontana L. Pfeiffer, 1862.

Content.

Naggsia laomontana (L. Pfeiffer, 1862).

Diagnosis.

Shell flat, widely umbilicated, body whorl rounded; protoconch with dense, regular, slightly waved ribs with extremely fine spiral striation. Epiphallus ab sent, diverticulum and gametolytic sac are both very short, but diverticulum is still shorter than the gametolytic sac. Cusp of central tooth missing, only basal plate of central tooth present. Marginals bicuspid.

Differential diagnosis.

Naggsia gen. n. differs from the genera having ribbed embryonic whorls ( Endothyrella , Gudeodiscus , Halongella , Sicradiscus , Sinicola ) by the absence of an epiphallus and the presence of a very short diverticulum. Moreover, although the protoconch of Naggsia gen. n. is ribbed, the ribs (radial lines) are not straight, as in the other genera, but are somewhat wavy. Naggsia gen. n. differs from the genera without a ribbed protoconch ( Chersaecia , Endoplon , Plectopylis ) by the presence of regular, slightly waved ribs on the embryonic whorls. The latter genera are insufficiently known anatomically. Plectopylis bensoni Gude, 1914 (mentioned as Plectopylis achatina Pfeiffer, 1845) and Plectopylis cyclaspis Benson, 1859 have a well-developed epiphallus ( Stoliczka 1871). Interestingly, these Plectopylis species have a relatively short and thickened diverticulum, which is somewhat similar to that of Naggsia laomontana . Similarly to Naggsia laomontana , Chersaecia simplex Solem, 1966 lacks the epiphallus (see Solem 1966), but it at has no diverticulum, which is well developed in Naggsia . See differential diagnosis under Hunyadiscus and Table 1.

Etymology.

The new genus is dedicated to Fred Naggs (NHM) in acknowledgement of his help with our studies on the Plectopylidae .

Distribution.

Northern Laos (Figure 15).

Remarks.

The anatomy of Naggsia laomontana is rather similar to that of Plectopylis in the short diverticulum and to Chersaecia in the absence of epiphallus. The shell characters, namely the ribbed protoconch and the reduced parietal plication is similar to the genera Endothyrella , Gudeodiscus , Halongella , Sicradiscus and Sinicola . The radula of Naggsia laomontana shows similarities with those of Gudeodiscus (Veludiscus) , Halongella and Plectopylis (see Stoliczka 1871, Páll-Gergely et al. 2015a) in terms of the small central tooth and the simple marginals. In contrast, the central tooth of Endothyrella , Gudeodiscus (Gudeodiscus) , Sicradiscus and Sinicola species is large (as large as or larger than the ectocones of the first laterals), ( Páll-Gergely et al. 2015a, 2015b), and the marginals are tricuspid or even quadricuspid. Before examining ethanol-preserved Naggsia laomontana specimens, we considered grouping the plectopylid genera into two tribes, namely one with a ribbed, and another with a smooth or granulated protoconch. The examination of Naggsia laomontana revealed that the character states considered to be primarily important do not allow the placement of Naggsia gen. n. in any of the two groups, and that the character states rather show a mosaic structure across genera.