Diaphera turbanophora Páll-Gergely & Grego, 2020

Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Sajan, Sheikh, Tripathy, Basudev & Chen, Zhe-Yu, 2020, A review of the Diapheridae (Gastropoda: Eupulmonata: Streptaxoidea), with special emphasis on India and Myanmar, Raffles Bulletin of Zoology 68, pp. 682-718 : 692-696

Diaphera turbanophora Páll-Gergely & Grego , new species

( Fig. 8 )

Material examined. Holotype ( H: 3.9 mm, D: 1.3 mm) ( HNHM 104436 ), Myanmar, Kayah State, Hpruso district, Maw Thi Do Village, Entrance of Phruno River Cave , 19°22.744′N, 97°2.570′E (locality code: JG102), coll. J. Grego, 12 December 2019.

Paratypes. 1 shell ( H: 4.05 mm, D: 1.3 mm), same data as holotype; 2 apertural fragments (coll. JG), Myanmar, Kayah State, Hpruso district, Maw Thi Do, road towards Han Li Village, Rocks above bridge over Phruno River ,

19°23.011′N, 97°2.108′E (locality code: JG101), coll. J. Grego, 12 December 2019.

Diagnosis. A Diaphera species with a slender, finely ribbed, glossy shell, a constricted first whorl of teleoconch, a strong parietal lamella, a blade-like columellar tooth, a long upper palatal tooth, and a very small, deeply situated lower palatal denticle.

Description. Shell slender, glossy, off-white (colourless), semitransparent. Ribs very faint, low, equally spaced.

Shell consisting of 6.25–6.5 whorls. Apex acutely pointed, protoconch moderately glossy, rather matte, consisting of 1.5 whorls, boundary of protoconch and teleoconch sharp, teleoconch sculpture glossier, slightly ribbed, its first whorl is constricted, therefore the third whorl from apertural view is narrower than the preceding. Last two whorls are the widest from apertural view. Suture not deep, whorls moderately bulging. Aperture suboval. Parietal callus rounded, thick, not “smeared” onto preceding whorl and only slightly extending beyond the suture. Apertural dentition 5-fold. Parietal lamella strongly developed, elevated, outer portion slightly bent in palatal direction, with a triangular end, inner portion also elevated, rounded, slightly bent towards columella. Sinulus rounded, opens slightly laterally, well isolated (tips of parietal lamella and upper palatal tooth situated close to each other). Palatal wall with a strongly elongated, sharp ridge that corresponds with the parietal lamella, a small, blunt denticle that is situated in the lower edge of the sinulus, and a very slight, blunt denticle that is situated deep inside, at the inner end of the elongated ridge. Out of these three structures, the first two (elongated ridge and denticle inside the sinulus) are probably homologous with the upper palatal tooth, whereas the deeply situated denticle is homologous with the lower parietal tooth. Columellar lamella deeply situated, sharp, lamella-like, vertical (parallel with shell axis). There is a blunt, inconspicuous swelling on the basal side some distance inward from the peristome. Peristome strongly thickened and expanded, slightly reflected. Basal swelling slight, situated a relatively large distance from peristome. Depression anterior to basal swelling on the outer side relatively deep, slightly elongated (corresponding with an elongated ridge on the palatal side). Inner side without depression; umbilicus entirely closed.

Differential diagnosis. The most similar species is Diaphera cylindrelloidea ( Stoliczka, 1871) , which is larger and has a protruding, more circular aperture. The formation and arrangement of the apertural barriers of the two species are strikingly similar. The only difference we found was the parietal lamella, which is of equal height in D. cylindrelloidea , but slightly lowered just behind its outer end in the new species.

Diaphera seatoni Beddome, 1891 is much larger (ca. 1 cm in height), has a protruding aperture, much deeper suture, and different apertural barriers. Namely, anterior to the columellar tooth there is an oblique ridge that descends from near the columellar-parietal angle of the aperture towards the deep basal part, and consists of two elongated knobs. Furthermore, the outer (upper) palatal tooth is not in contact with the deeply situated lower palatal tooth, which, in this case, consists of two small blunt knobs.

Sinoennea woodthorpei , which was described from Fort Stedman (= Maing Thauk), not far from the type locality of the new species, has elongate-ovoid shape with regular ribbing.

Etymology. The first whorl of the teleoconch is constricted compared with the protoconch. Therefore, the apex looks like a head wearing a turban.

Remarks. The Diaphera species of Myanmar have apertures that protrude straight ahead, and are not distorted downwards from apertural view, as in other Diaphera species. This suggests that the free last whorl has probably been developed more than once during the evolution of the Diapheridae , and the Diaphera species of Myanmar are likely closer relatives of Sinoennea of the region than the Diaphera species of the Philippines. However, until more solid evidence is provided, we maintain these taxa in Diaphera .

The body whorl of Diaphera turbanophora , new species, is not free from the penultimate whorl, but the species is classified in the genus Diaphera due to its similarity with other Diaphera species of Myanmar.

Figures

Fig. 8. Diaphera turbanophora Páll-Gergely & Grego, new species (holotype). Scale represents 1 mm.