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| Pagodapalaina euphrosyne Sutcharit, in Sutcharit, Srisonchai, Maneewan, Jeratthitikul et Annate, 2026. |
Abstract
A new species of Pagodapalaina from southern Thailand is described. Pagodapalaina euphrosyne Sutcharit, sp. nov. is characterised by a sinistral, elongate-fusiform shell with an open-coiled teleoconch, well-developed radial ribs restricted to the penultimate and last whorls, and the presence of the parietalis and columellaris. Unlike all other congeners, the detached teleoconch subsequently resumes regular coiling, with the last whorl becoming tightly reattached to the preceding whorl. This previously undocumented developmental pattern raises fundamental questions about current understanding of the developmental constraints governing shell coiling in terrestrial caenogastropods.
Keywords: limestone; endemic species; whorl detachment; ecophenotypic plasticity; micro-CT
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| A, approximate locations of the type locality of all Pagodapalaina species. Numbers correspond to: 1) P. acme (Laidlaw, 1949) [= Diplommatina laemsonensis Boonmachai, Bergey & Nantarat, 2023]; 2) P. attenuata (Laidlaw, 1949); 3) P. carinaspinosa (Maassen, 2002); 4) P. diminuta (von Möllendorff, 1891); 5) Pagodapalaina euphrosyne sp. nov.; 6) P. gadutensis (Maassen, 2002); 7) P. hidagai (Panha, 1998a); 8) P. hortulanica Chen, 2025; 9) P. jirasaki (Panha, Kanchanasaka & Burch, 2002); 10) P. karoensis (Maassen, 2002); 11) P. krabiensis (Panha & Burch, 1998); 12) P. lenggongensis (Tomlin, 1941) [= Diplommatina lenggongensis nawawii Davison, 1995]; 13) P. parabates (Laidlaw, 1949); 14) P. pongrati (Panha, Kanchanasaka & Burch, 2002); 15) P. prakayangensis (Panha, 1998b); 16) P. sinistra (Tomlin, 1938) [= Diplommatina prakaiphetensis Boonmachai, Bergey & Nantarat, 2023]; 17.1) P. superba superba (Godwin-Austen & Nevill, 1879); 17.2) P. superba brevior (Laidlaw, 1949); 18) P. suratensis (Panha & Burch, 1998); B, live snail of Pagodapalaina euphrosyne sp. nov. |
Systematics
Superfamily Cyclophoroidea Gray, 1847
Family Diplommatinidae Pfeiffer, 1856
Genus Pagodapalaina Chen, 2025
Pagodapalaina Chen in Chen et al. 2025: 390, 391.
Type species: Diplommatina acme Laidlaw, 1949, by original designation.
Remark: The genus is characterised by a sinistrally coiled, elongate-fusiform shell with tightly to loosely coiled whorls and a shell surface bearing low ridges to prominent and trough-like radial ribs. The internal lamellar system comprises a well-developed columellaris, a parietalis varying from small to well developed, a vertical palatalis that may be absent, and a constriction ranging from weak to strong.
The genus currently comprises 18 recognised species (Chen et al. 2025, MolluscaBase 2026, this study). Of these, three species are known from Sumatra, Indonesia, and nine species, including the new species described herein, are recorded from Thailand. The northern distributional limit of the genus is currently considered not to extend beyond the Isthmus of Kra (Fig. 1A).
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| Pagodapalaina euphrosyne sp. nov., paratypes CUMZ 14506 from the type locality. A, B, adult specimens with narrowly expanded lip; C, juvenile specimen shows an early stage of penultimate whorl, and onset of tall trough-like radial ribs |
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| Pagodapalaina euphrosyne sp. nov. from the type locality. A, holotype CUMZ 14505, insets show the aperture with columellaris; B, paratype CUMZ 14506, juvenile with penultimate and last whorl reattached but lip not yet expanded; C, paratype CUMZ 14506, insets show the protoconch sculpture |
Pagodapalaina euphrosyne Sutcharit, sp. nov.
Diagnosis: Shell small, sinistral, elongate-conical, fusiform, with ∼6 whorls. Earlier teleoconch whorls solute for about two whorls, with smooth surface. Penultimate and last whorls regularly coiled, tightly attached, sculptured with very tall, trough-like radial ribs, and fine spiral striations throughout. Peristome double, expanded. Aperture rounded, with four barriers: one parietalis, two vertical palatalis and one columellaris.
Etymology: The specific epithet, euphrosyne, is a noun in apposition derived from Euphrosyne, one of the Three Graces (Charites) in Greek mythology, the personification of joy, beauty, and elegance. It refers to the graceful and delicate shell morphology of the new species.
Chirasak Sutcharit, Ruttapon Srisonchai, Nattaphong Maneewan, Ekgachai Jeratthitikul and Supunya Annate. 2026. A New open-coiled Microsnail Species of the Genus Pagodapalaina (Caenogastropoda: Diplommatinidae) from Thailand. Animal Taxonomy and Ecology. DOI: doi.org/10.1556/1777.2026.00169 [16 Sep 2026]
𝙋𝙖𝙜𝙤𝙙𝙖𝙥𝙖𝙡𝙖𝙞𝙣𝙖 𝙚𝙪𝙥𝙝𝙧𝙤𝙨𝙮𝙣𝙚 Sutcharit, 2026 หรือ หอยกระสวยจิ๋วคลายเกลียวยูโฟรซีน ค้นพบที่ถ้ำทะลุ อำเภอละงู จังหวัดสตูล โดยตั้งชื่อชนิดตามรูปร่างเปลือกที่ละเอียดอ่อนและสง่างาม เสมือน “ยูโฟรซีน” ผู้เป็น 1ใน 3เทพีแห่งความงามของเทพปกรณัมกรีก