INTRODUCTION
The newest publication by Thach (2025) described 5 new genera and 208 new species of molluscs from South Asia. Among them, Oophana thaitieni Thach, 2025 was described from “Côn Đảo Island, Southeast Vietnam”, based on a single specimen. Re-examination of the material indicates that this species is a junior synonym of Oophana bulbulus (Morelet, 1863). Similar cases have been noted previously, as Páll-Gergely et al. (2020) pointed out that some species described by Thach were based on minor morphological differences that may fall within the range of intraspecific variation.
TAXONOMY PART
Class: Gastropoda
Subclass: Heterobranchia
Superfamily: Streptaxoidea Gray, 1860
Family: Streptaxidae Gray, 1860
Genus: Oophana Ancey, 1884
Oophana Ancey, 1884: 399
Oophana bulbulus (Morelet, 1862)
Figs 1–5
Shells of Oophana thaitieni Thach, 2025 and Oophana bulbulus (Morelet, 1863): 1–3 – holotype of O. thaitieni (MNHN-IM-2000-40198), Côn Đảo Island, Southeast Vietnam, photographs from Thach (2025); 4 – drawing of O. bulbulus from Tryon (1885); 5 – syntype of O. bulbulus (NHMUK 7787737), Con Dao Island, Ho Chi Minh City, photographs from Natural History Museum, London (NHMUK), Collection Specimens Data Portal. Scale bar 5 mm
Figs 6–12
Shells of Oophana bulbulus (Morelet, 1863): 6 – specimen SMF 136806/1, photographs taken by Sigrid Hof; 7–9 – specimens RMNH.MOL.273691 and their labels, photographs taken by Arike Gill; 10–12 – specimens ZMA.MOLL.388531 and their labels, photographs taken by Arike Gill. Scale bar 5 mm
Ennea bulbulus Morelet, 1862 (Morelet 1862: 477).
Ennea bulbulus – Crosse & Fischer (1863a: 272, pl. X, fig. 3).
Ennea bulbulus – Crosse & Fischer (1863b: 355).
Ennea bulbulus – Mabille & Le Mesle (1866: 128).
Streptaxis bulbulus – Tryon (1885: 80–81, pl. 15, fig. 41, 42, 43).
Streptaxis (Oophana) bulbulus – Möllendorff (1894: 148).
Streptaxis bulbulus – Fischer & Dautzenberg (1904: 1).
Oophana bulbulus – Wenz & Zilch (1960: 562).
Oophana bulbulus – Zilch (1961: 85).
Oophana bulbulus – Schileyko (2000: 796, fig. 1038 A).
Oophana bulbulus – Schileyko (2011: 25).
Oophana thaitieni Thach, 2025 (Thach 2025: 71, figs 362a, c, d (3 figs)) new synonym.
Material examined. Photos of comparative material were used for comparison. They contained: “Côn Đảo Island, Southeast Vietnam”, Muséum National d’Histoire Naturelle, Paris, France (MNHN), MNHN-IM-2000-40198 (holotype of O. thaitieni; Figs 1–3); “insula Poulo-Condor” [Con Dao Island, Ho Chi Minh City (formerly Ba Ria – Vung Tau Province), Vietnam], The Natural History Museum, London, UK (NHM), NHMUK 7787737 (2 syntypes of Oophana bulbulus; Fig. 5); “Cochinchina”, Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt am Main, Germany (SMF), SMF 136806/1 (1 shell of O. bulbulus; Fig. 6); “Pulo-Condore (Annam)” [Con Dao Island, Ho Chi Minh City, Vietnam], Rijksmuseum voor Natuurlijke Historie (Mollusca collection), merged into the Naturalis Biodiversity Center, Leiden, The Netherlands (RMNH.MOL), RMNH.MOL.273691 (2 shells of O. bulbulus; Figs 7–9); “Poulo-Condor” [Con Dao Island, Ho Chi Minh City, Vietnam], Zoölogisch Museum Amsterdam (Molluscs collection), merged into the Naturalis Biodiversity Center, Leiden, The Netherlands (ZMA.MOLL), ZMA.MOLL.388531 (1 shell of O. bulbulus; Figs 10–12).
Remark. The differences between Oophana thaitieni and O. bulbulus proposed by Thach (2025), based on comparisons with published drawings, are as follows: “body whorl less swollen, spire more dome-shaped, columella straighter, outer lip undulate and narrower at posterior end, parietal lamella more oblique in frontal view, columellar lamella lower, palatal lamella shorter, basal lamella narrower”. These characters, however, are the result of variation in each individual. These include: body whorl can be swollen with penultimate whorl not extended beyond last whorl (Figs 5, 7, 8, 10, 11) or slightly beyond last whorl (Fig. 6); spire generally conical and very obtuse; aperture consistently bears a sinulus in all specimens; the anterior edge of the sinulus which near palatal lamella has a straight peristome (Fig. 8), or slightly undulate peristome (Figs 7, 10, 11), or clearly undulate peristome (Figs 1, 5, 6). The aperture dentition of Oophana thaitieni and O. bulbulus is identical in both number and position of lamellae, consisting of one large, strong parietal lamella, one small palatal lamella, one small basal lamella, and one small columellar lamella. No diagnostic characters were found to support the recognition of O. thaitieni as a distinct species from O. bulbulus. Moreover, both nominal taxa share the same distribution on Con Dao Island, Ho Chi Minh City, Vietnam. Thus, Oophana thaitieni Thach, 2025 should be treated as a junior subjective synonym of O. bulbulus (Morelet, 1863).
