Diplommatina scalaroidea Theobald 1870

Information from the abstract

1Diplommatina scalaroideaTheobald, 1870 Figs 2, 3 A Diplommatina scalaroidea Theobald, 1870: 399, pl. 18, fig. 5. Type locality: Mandalay, regno Burmanico. Pfeiffer 1875: 80. Hanley and Theobald 1876: 56, pl. 141, fig. 10. Theobald 1876: 42. Nevill 1878: 285. Gude 1921: 333. Diplommatina (Eudiplommatina) scalaroidea — Kobelt and Möllendorff 1898: 138. Diplommatina (Diplommatina) scalaroidea — Kobelt 1902: 445. Type material examined. The type series could not be located in the Natural History Museum, London, nor the National Museum of Wales, Cardiff (T. White, B. Rowson, and J. Gallichan, pers. comm.). Other material. Myanmar • CUMZ 15442 (2 shells; Fig. 2 A), CUMZ 15443 (1 shell; Figs 2 B, 3 A) and CUMZ 15444 (12 shells + 3 juveniles) from Pyiyaung city, Mandalay Region; 20°50'47.5"N, 96°24'12.4"E; P. Tongkerd and S. Panha leg. Description. Shell sinistral, ovoid-fusiform, pale yellowish to whitish colour. Shell height 4.6–5.2 mm; shell width 2.3–2.6 mm. Whorls ~ 7–8, convex; spire conical; suture wide and deep. Protoconch ~ 1 ¾ whorl, with fine growth lines, wrinkles, and roundish malleated pits. Teleoconch with strong, nearly regularly spaced radial ribs; penultimate whorl with widest spacing ribs, ~ 3–4 ribs / mm; last whorl before aperture with ~ 5–6 ribs / mm. Spiral striations very thin, fine and appear from teleoconch to about fourth whorl. Penultimate whorl wider than last whorl. Constriction externally inconspicuous; internal constriction marked by distinct vertical ridge. Aperture circular, with four barriers: parietalis very strong and prominent ridge; two horizontal palatalis situated beyond constriction – upper palatalis elongate with prominent ridge, lower palatalis short and strong; columellaris distinctly prominent ridge, continuous with peristome, and slightly deflected downward toward palatal wall (Fig. 3 A). Peristome broadly expanded, double; outer peristome broader than inner peristome. Lip thickened, multi-layered; parietal callus thin, expanded. Columellar angulate, with distinct sinulus below. Umbilicus closed. Distribution. This species was originally described from the Mandalay Region. During our surveys across multiple localities in the Mandalay Region and Shan State, the species was found exclusively on limestone karsts near Pyiyaung City, suggesting that its distribution is likely restricted to the Mandalay Region (Fig. 1 A). Remarks. Theobald (1870: 398) described four Diplommatina species, namely D. affinis Theobald, 1870, D. pupaeformis Theobald, 1870, D. salwiniana Theobald, 1870 and D. scalaroidea, consecutively in the same publication but without clearly indicating the number of specimens examined, illustrations, or specifying the type localities. However, in the introduction, Theobald (1870) mentioned that the specimens were obtained from Mr. Fedden, who had collected them after returning from the Upper Salwin. The type series of these four species could not be located in the NHM, London, nor the NMW, Cardiff collections, except for D. pupaeformis (see under D. pupaeformis; T. White, B. Rowson, and J. Gallichan, pers. comm.). Although the type specimen of D. scalaroidea is not available, the diagnostic characters given in the original description and the type locality correspond well with the specimens examined in this study. This species is readily distinguished from all other congeners by its sinistral shell coiling, whereas all other species possess dextral shells. The most closely related species in Myanmar is D. exilis Blanford, 1863 from Ava, which differs in having a dextral shell and more narrowly spaced radial ribs (Hanley and Theobald 1876).

Why this record is monitored

This record has an Impact Signal of 73/100 based on recency, source, collaboration, and bibliographic signals. It prioritizes monitoring and is not a judgment of research quality.

Related topics: Diatoms and Algae Research · Marine Bivalve and Aquaculture Studies · Mollusks and Parasites Studies