Fossil freshwater mollusks from the Early Pleistocene (Calabrian) of northern Taiwan

2025  47  20 geodiversitas Geodiversitas est une revue en flux continu publiée par les Publications scientifiques du Muséum, Paris Geodiversitas is a fast track journal published by the Museum Science Press, Paris Les Publications scientifiques du Muséum publient aussi / The Museum Science Press also publish: Adansonia, Zoosystema, Anthropozoologica, European Journal of Taxonomy, Naturae, Cryptogamie sous-sections Algologie, Bryologie, Mycologie, Comptes Rendus Palevol Diffusion – Publications scientifiques Muséum national d’Histoire naturelle CP 41 – 57 rue Cuvier F-75231 Paris cedex 05 (France) Tél. : 33 (0)1 40 79 48 05 / Fax : 33 (0)1 40 79 38 40 [email protected] / http://sciencepress.mnhn.fr © Publications scientifiques du Muséum national d’Histoire naturelle, Paris, 2025 ISSN (imprimé / print) : 1280-9659/ ISSN (électronique / electronic) : 1638-9395 Directeur De la publication / Publication director : Gilles Bloch, Président du Muséum national d’Histoire naturelle réDacteur en chef / editor-in-chief : Didier Merle réDacteur associé / associate editor: Sylvain Charbonnier assistant De réDaction / assistant editor : Emmanuel Côtez ([email protected]) Mise en page / Page layout : Emmanuel Côtez coMité scientifique / scientific board : Christine Argot (Muséum national d’Histoire naturelle, Paris) Beatrix Azanza (Museo Nacional de Ciencias Naturales, Madrid) Raymond L. Bernor (Howard University, Washington DC) Henning Blom (Uppsala University) Gaël Clément (Muséum national d’Histoire naturelle, Paris) Ted Daeschler (Academy of Natural Sciences, Philadelphie) Cédric Del Rio (Muséum national d’Histoire naturelle) Gregory D. Edgecombe (The Natural History Museum, Londres) Ursula Göhlich (Natural History Museum Vienna) Jin Meng (American Museum of Natural History, New York) Brigitte Meyer-Berthaud (CIRAD, Montpellier) Zhu Min (Chinese Academy of Sciences, Pékin) Isabelle Rouget (Muséum national d’Histoire naturelle, Paris) Sevket Sen (Muséum national d’Histoire naturelle, Paris, retraité) Stanislav Štamberg (Museum of Eastern Bohemia, Hradec Králové) Paul Taylor (The Natural History Museum, Londres, retraité) couverture / cover : Réalisée à partir des Figures de l’article/Made from the Figures of the article. Geodiversitas est indexé dans / Geodiversitas is indexed in: – Science Citation Index Expanded (SciSearch®) – ISI Alerting Services® – Current Contents® / Physical, Chemical, and Earth Sciences® – Scopus® Geodiversitas est distribué en version électronique par / Geodiversitas is distributed electronically by: – BioOne® (http://www.bioone.org) Les articles ainsi que les nouveautés nomenclaturales publiés dans Geodiversitas sont référencés par / Articles and nomenclatural novelties published in Geodiversitas are referenced by: – ZooBank® (http://zoobank.org) 721 GEODIVERSITAS • 2025 • 47 (20) © Publications scientifiques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com MOTS CLÉS Taïwan, Pléistocène inférieur, Escargots d’eau douce, vivipare, biogéographie, paléoenvironnement. KEY WORDS Taiwan, Early Pleistocene, freshwater snails, viviparid, biogeography, paleoenvironment. urn:lsid:zoobank.org:pub:989E2C23-E304-4855-85D2-9017A92FC609 Hsu C.-H., Osipova D. & Lin C.-H. 2025. — Fossil freshwater mollusks from the Early Pleistocene (Calabrian) of northern Taiwan. Geodiversitas 47 (20): 721-737. https://doi.org/10.5252/geodiversitas2025v47a20. http://geodiversitas.com/47/20 ABSTRACT Despite the extensive fossil mollusk records in Taiwan, over 99% are marine species. Among the few freshwater deposits, the Tananwan Formation (1.46-1.24 Ma) in northern Taiwan has been recognized as one of the most prolific fossiliferous strata. In a 1-meter thick fossiliferous mudstone layer within the formation, we identified five molluscan taxa. The assemblage is primarily dominated by Sinotaia quadrata (Benson, 1842) and the less common Melanoides aff. tuberculata, which corresponds to the current freshwater ecosystem in northern Taiwan. This study presents detailed descriptions and images of fossil freshwater molluscan assemblage from Taiwan, providing insights into the origins of contemporary freshwater biodiversity in the subtropical West Pacific. Additionally, in several fossil S. quadrata specimens, juvenile shells were found within female shells, marking the second known case of child-carrying in fossil viviparids. RÉSUMÉ Mollusques fossiles d’eau douce du Pléistocène inférieur (Calabrien) du nord de Taïwan. Malgré l’abondance des mollusques fossiles à Taïwan, plus de 99% d’entre eux sont des espèces marines. Parmi les rares dépôts d’eau douce, la formation Tananwan (1,46-1,24 Ma), dans le nord de Taïwan, est reconnue comme l’une des unités fossilifères. Dans une couche de mudstone fossilifère d’un mètre d’épaisseur au sein de la formation, nous avons identifié cinq espèces de mollusques. L’assemblage, principalement dominé par les espèces Sinotaia quadrata (Benson, 1842) et, moins communément, Melanoides aff. tuberculata, correspond à l’écosystème d’eau douce actuel du nord de Taïwan. Cette étude présente des descriptions détaillées et des images d’assemblages de mollusques d’eau douce fossiles à Taïwan, permettant ainsi de mieux comprendre les origines de la biodiversité contemporaine des eaux douces du Pacifique ouest subtropical. En outre, dans plusieurs spécimens fossiles de S. quadrata, des coquilles juvéniles ont été trouvées à l’intérieur de coquilles femelles, ce qui constitue le second cas connu de portage de juvéniles chez les viviparidés fossiles. Chia-Hsin HSU Department of Geosciences, National Taiwan University, no. 1, Roosevelt Road, Sec. 4, Taipei 106319 (Taiwan) [email protected] Diana OSIPOVA Chien-Hsiang LIN Biodiversity Research Center, Academia Sinica, no. 128, Academia Road, Sec. 2, Nankang, Taipei 11529 (Taiwan) [email protected] [email protected] (corresponding author) Submitted on 23 October 2024 | accepted on 25 November 2024 | published on 6 November 2025 Fossil freshwater mollusks from the Early Pleistocene (Calabrian) of northern Taiwan 722 GEODIVERSITAS • 2025 • 47 (20) Hsu C.-H. et al. INTRODUCTION Molluscan fossils are among the most abundant biological remains in the sedimentary archives of Taiwan. More than 1000 species belonging to at least 430 genera have been recorded, ranging from the Oligocene to the Quaternary (e.g., Hu& Tao 2003; Senan etal. 2023). Most of them co-occur with corals (e.g., Ribas-Deulofeu etal. 2021), echinoids (e.g., Hsu etal. 2024; Chen etal. 2025), fish (e.g., Lin etal. 2021; Lin& Chien 2022; Přikryl etal. 2024), and crabs (e.g., Hu& Tao 1996). Despite the abundant fossil mollusk records in Taiwan, more than 99% are recognized as marine species (Hu& Tao 2003), with fewer than 20 freshwater mollusk species sporadically reported (Hu& Tao 1991; Hu 1992a; Hu& Wang 1995; Lee 2000). TAIWAN Holocene deposit Holocene deposit Tananwan Formation Linkou Formation Highway no. 61 Tatun Volcano Group (Pleistocene) Taoyuan Terrace (Late Pleistocene) Linkou Terrace (Early Pleistocene) Western Foothills (Oligo-Pliocene) Fault Taipei Basin Taipei Basin II I I 1 12 –1 0 0 km 120°E 121° 122° 25°N 24° 23° 22° II A C B C B 50 km 5 km 1 km fig. 1. — Locality and geological background of sampling site: A, study area; B, general geological background and sections of Taipei Basin (modified from Teng 2007); C, geological map of sampling site (modified from Lin 1981). Red star represents the sampling site. Map: Chia-Hsin Hsu. 723 Pleistocene freshwater mollusks of Taiwan GEODIVERSITAS • 2025 • 47 (20) The difference between marine and freshwater fossil records can potentially be attributed to the relatively young geological history of Taiwan. The ongoing orogeny of Taiwan started around the Miocene and Pliocene transition (Lin etal. 2003), and most of the typical terrestrial strata were deposited later than the Pleistocene (Chen 2016), making freshwater mollusk faunas in Taiwan extremely rare. Moreover, within terrestrial fossiliferous strata, vertebrate fossils have received more attention (e.g., the Chochen Vertebrate Fauna; Wei 2007), resulting in relatively limited research on freshwater mollusks. The Tananwan Formation, which contains both marine and terrestrial fossiliferous deposits, possesses one of the best-preserved freshwater mollusk assemblages. Lee (2000) first reported eight species from five families of freshwater mollusk (i.e., Bithyniidae Gray, 1857, Semisulcospiridae Morrison, 1952, Viviparidae Gray, 1847, Lymnaeidae Rafinesque, 1815, and Planorbidae Rafinesque, 1815), although without specimen figures or descriptions. Chuang etal. (2012) mentioned this assemblage but provided no further taxonomical analysis. As for other fossils found in the Tananwan Formation, Yokoyama (1928) reported 17marine mollusk species from the formation in his general report on Taiwanese mollusk fossils. Vertebrate fossils have also been found on the tidal plain of the coastal Linkou Plateau, recognized as belonging to the Tananwan Formation (Shieh 2007). Here, we describe the taxonomic composition of an Early Pleistocene freshwater mollusk assemblage from the Tananwan Formation, providing a framework for understanding the regional freshwater biogeography during the Pleistocene. Altitude (m) Sd, Sandstone M, Mudstone W Linkou Formation Tananwan Formation Mudstone Sandstone Conglomerate Freshwater mollusk Pleistocene Calabrian E 70 60 50 40 30 20 14 MS G AB E C B C M2 Sd2 M1 Sd1 M2 Sd2 M1 Sd1 fig. 2. — Geological column and field observations on the Tananwan Formation, Linkou Plateau, northwestern Taiwan: A, geological column of the sampling outcrop (modified from Chuang et al. 2012), red star represents the relative time scale of the outcrop; B, sampling outcrop, black arrow indicates the fossil beds; C, field photos of fossils and the bedrock. Photos and drawing: Chia-Hsin Hsu. 724 GEODIVERSITAS • 2025 • 47 (20) Hsu C.-H. et al. GEOLOGICAL BACKGROUND Fossils were collected from the Tananwan Formation (25°07’13.1”N, 121°19’11.7”E; Figs 1, 2), a sedimentary unit regionally exposed only on the Linkou Plateau in northwestern Taiwan. This formation is characterized by its horizontal strata, consisting of loosely cemented sandstones and mudstones intercalated with thin conglomerate beds (Horng 2014). The Tananwan Formation is indented and overlain by the Linkou Formation, which is composed of massive conglomerate (Chen 2016). Both formations are interpreted as part of a west-flowing paleo-fan-delta system, known as the Linkou Fan-Delta, supported by paleocurrent analysis and geological structures (Chen& Teng 1990; Chuang etal. 2012). The sedimentary environments of the Linkou Formation and the Tananwan Formation are therefore recognized as alluvial fan and river to shallow marine, respectively (Chen& Teng 1990; Chuang etal. 2012). On the other hand, the age of the Tananwan Formation has been debated for a long time. A recent comprehensive study suggests that the formation was deposited between 1.46 and 1.24 Ma (Early Pleistocene Calabrian Stage), based on magnetostratigraphy and the occurrence of large-sized Gephyrocapsa spp., correlated with well-studied continuous sections of the Gutingkeng Formation in southern Taiwan (Horng 2014). We tentatively followed this age estimation due to its comprehensive sampling and the combination of magnetostratigraphy and biostratigraphy in the analysis. MATERIAL AND METHODS Mollusk fossil specimens were hand-picked directly in the field (25°07’13.1”N, 121°19’11.7”E; Fig. 1) between 2023 and 2024, without the use of sieving. All specimens are from the one-meter-thick mudstone layer pointed out by the arrow in Fig. 2. No other obvious fossils have been found in the other layers exposed at this outcrop. Fragile specimens were reinforced with super glue before being extracted from bedrock using a steel needle. After brief preparation, the specimens were dried overnight in a 40°C oven to remove moisture from the muddy bedrock. Complete specimens were then described, measured (Fig. 3), and photographed. All descriptions and measurements were conducted only on specimens without obvious taphonomic deformation. Specimens of viviparids and thiarids were measured for six parameters (Fig. 3A): width of shell (WSh), height of shell (HSh), height of spire (HSp), height of basal whorl (HBW), height (HA) and width of aperture (WA). Two additional measurements (Fig. 3C) were done for planorbid shells: the diameter of inner whorls from the basal surface (DIWb) and the last whorl width from the basal surface (LWWb). All specimens are deposited in the Biodiversity Research Museum, Academia Sinica, Taiwan (BRMAS) under the code ASIZF. AbbreviAtions DIWb diameter of inner whorls from the basal surface; HA height of aperture; HBW height of basal whorl; HSh height of shell; HSp height of spire; LWWb last whorl; WA width of aperture; WSh width of shell. SYSTEMATIC PALAEONTOLOGY Class GASTROPODA Cuvier, 1795 Order ARCHITAENIOGLOSSA Haller, 1892 Superfamily vivipAroideA Gray, 1847 Family vivipAridAe Gray, 1847 Subfamily bellAmyinAe Rohrbach, 1937 Genus Sinotaia Haas, 1939 type species.— Paludina quadrata Benson, 1842, by original designation. Sinotaia quadrata (Benson, 1842) (Figs 4, 5) Paludina quadrata Benson, 1842: 487. Paludina purificata Heude, 1890: 176, pl. 40, fig. 4, 4a. Viviparus (chinensis var?) formosensis Kobelt, 1909: 413, pl.77, figs6-7. Vivipara quadrata – Odhner 1930: 27. Vivipara cf. lecythoides – Hsu 1935: 32, pl. 3, figs 2a-b, 3-5. Vivipara dispiralis – Hsu 1935: 33, pl. 3, figs 6a-b, 7a-b, pl. 4, fig. 10. †Bithinia viviparoides Hsu, 1936: 32, pl. 2, figs 19a-b, 20. Viviparus quadratus turritus Yen, 1939: 36, pl. 3, fig. 8. Viviparus quadratus limnophilus – Yen 1939: 192; 1943: 284. Viviparus quadratus – Kuroda 1941: 82.— Yen 1941: 191; 1943: 284. Bellamya purificata – Yen 1943: 126. Sinotaia quadrata – Pace 1973: 30, pl. 5, fig. 2. (For an extensive synonymy list of S. quadrata in East Asian, refer to Ye 2020) AB C Hsh Hsh Hsp HBW WSh WSh DlWb LWWb WA HA HA WA fig. 3. — Diagram of freshwater mollusks for measurements used in this study: A, apertural view of viviparid shell; B, apertural view of planorbid shell; C, apical view of planorbid shell. Photos: Diana Osipova. 725 Pleistocene freshwater mollusks of Taiwan GEODIVERSITAS • 2025 • 47 (20) m AteriAl exAmined .— Taiwan • 37 specimens; Shuiniukeng (=Water Buffalo Valley), New Taipei City; Tananwan Formation; Early Pleistocene, Calabrian; ASIZF0100893-ASIZF0100912, ASIZF0100923-ASIZF0100939. description Shell turbiniform, elongate subconical, appears thin, but not fragile. Medium to large in size, with HSh and WSh of adult shell ranging from 25-40 mm and 15-25 mm, respectively. HBW of adult shell about 70% of HSh. HA longer than WA. Shell solid, whorls profile rounded with distinct periphery, sutures impressed but shallow on early whorls, and deep suture of the body whorl. Surface shiny with weak growth lines, with 1-3 loose spiral keels (better visible on the last whorl), not evident in some specimens. Spire rather short, rounded, consists of 4-5 whorls that enlarged slowly; ratio of 1:1.5 to body whorl. Aperture subovate, broad, and prosocline, well angled posteriorly. Umbilicus small and narrow. Subadult shells (Fig. 4M) with pronounced 2-3 spiral keels that become less prominent with age. Juvenile shell (Fig. 5B-E) conical, turbiniform, early protoconch of 3 whorls with evident 2-3 ridges. remArks Viviparid snails exhibit modest sexual dimorphism within species, due to their ovoviviparous reproductive strategy (Minton& Wang 2011). Additionally, shell shape variation, partly influenced by environmental factors, sometimes leads to slight morphological differences between closely related species (Chiu etal. 2002). For instance, Sinotaia quadrata histrica (Gould, 1859) inhabiting lagoonal environments develops thicker, more elongated shells with narrower apertures comparing to those found outside the lagoon (Kagawa etal. 2019). A similar case involves the often co-occurring invasive Cipangopaludina chinensis (Gray, 1833) and C.japonica (Martens, 1861) in the United States, which are morphologically indistinguishable, likely due to their shared habitats (Van Bocxlaer& Strong 2016). These phenotypic variations make species identification in viviparids challenging if relying solely on shell morphology. Moreover, the taxonomic uncertainty surrounding viviparid species has persisted since the 19th century and remains unresolved (Van Bocxlaer& Strong 2019; Ye 2020; Stelbrink etal. 2020). In this study, the juvenile specimens played a crucial role in identifying S. quadrata. Juvenile shells from the Tananwan Formation closely resemble the outline and microsculpture of extant juvenile shells of S. quadrata (Fig. S1A, B). Compared to C. chinensis juveniles (Fig. S1C), the Tananwan juveniles have a less angular outline and the widest point positioned closer to the anterior. They also differ from C. japonica juveniles (Fig. S1D) in having a larger spire whorl angle, resulting in a distinct outline. While typical adult shells of these species differ significantly from our specimens (Fig. S1E-H), the Tananwan specimens A1 D I JK L M1 M2 EGH F A2 B1 B2 C1 C2 fig. 4 . — Sinotaia quadrata (Benson, 1842) from the Lower Pleistocene Tananwan Formation, Shuiniukeng, northern Taiwan: A-M, ASIZF0100893 to ASIZF0100905, respectively. Scale bars: 10 mm. Photos: Diana Osipova. 726 GEODIVERSITAS • 2025 • 47 (20) Hsu C.-H. et al. share similarity with some of the morphotypes of those species (Fig. S1I-L), though the Tananwan adults are smaller than C.chinensis and C. japonica. Thus, based on both juvenile and adult shell morphology, our specimens are most likely belong to S. quadrata. This species has a wide distribution in East Asia, with records from China (Yen 1943), Korea (Lee 2009), and Japan (Hirano etal. 2015; Saito& Kagawa 2020). In Taiwan, this species was first reported as Viviparus angularis (Müller, 1774), followed by more recent studies (Pace 1973; Chiu etal. 2002). Chen (2011) summarized at least 12 varieties of shell morphotypes of S. quadrata across Taiwan. In addition, the subspecies S. quadrata heudei (Dautzenberg& Fischer 1905) is distinguished by its smaller shell with three well-defined spiral keels (Chen 2011). However, this subspecies has been recognized as synonym of the S.quadrata (Qian etal. 2014; Ye 2020). Fossil occurrences of S. quadrata are known from Pleistocene deposits in Asia (Taiwan Malacofauna Database 2013; Ye etal. 2020). Yen (1943) referred to this species as Viviparus quadratus Benson, 1843 from the Para-loess Formation (possibly Late Pleistocene) in the Yangtze Valley. This species A F1 F2 G1 G2 B1 B2 C1 DE C2 fig. 5. — Sinotaia quadrata (Benson, 1842) from the Lower Pleistocene Tananwan Formation, Shuiniukeng, northern Taiwan: A, specimen with intact juvenile shells (pointed out by arrows) (ASIZF0100906); B-E, juvenile shells (ASIZF0100907 to ASIZF0100910) extracted from ASIZF0100906; F, non-deformed specimen with bedrock (ASIZF0100911); G, deformed specimen with bedrock (ASIZF0100912). Scale bars: A, F, G, 10 mm; B-E, 1 mm. Photos: Diana Osipova. 727 Pleistocene freshwater mollusks of Taiwan GEODIVERSITAS • 2025 • 47 (20) has also been identified in the Upper Pleistocene deposits in Maping (Liuchow), Kwangsi, and Maoshan, Chuyung, Kiangsu (Yen 1943), as well as from Toning and Hainan (Odhner 1930). Yen (1943) synonymized †Bithinia viviparoides Hsu, 1936 from the Siashu Formation (Late Pleistocene), Nanking, China (Hsu 1936), with S. quadrata. Additionally, Viviparus quadratus limnophilus Mabille, 1886, which Yen (1943) synonymized with Vivipara dispiralis Heude 1890, was recorded from the post-Pleistocene period in Kweilin, Kwangsi (Hsu 1935). Order CAENOGASTROPODA incertae sedis Superfamily cerithioideA Fleming, 1822 Family thiAridAe Gill, 1871 (1823) Subfamily thiArinAe Gill, 1871 (1823) Genus Melanoides Olivier, 1804 type species.— Melanoides fasciolata Olivier, 1804, by monotypy. Melanoides aff. tuberculata (Fig. 6A-G) m AteriAl exAmined .— Taiwan • 8specimens; Shuiniukeng (=Water Buffalo Valley), New Taipei City; Tananwan Formation; Early Pleistocene, Calabrian; ASIZF0100913-ASIZF0100919, ASIZF0100940. description Shell turriculate, thick, elongated, with HSh being greater than twice of WSh. HBW and HSp of adult shell about 60% and 40% of HSh respectively. HA longer than WA. Surface smooth on last two whorls, but adapical whorls covered with widely spaced, prosocline collabral undulations. Spiral threads on abapical part of the base. Spire tall, comprising 2/3 of the shell. Suture shallow, but impressed in adapical whorls, last two whorls with slight shoulder at shallow suture. Whorls 7-8 in number (early whorls missing), increasing in diameter slowly, profile flattened. Aperture ovate, but not well preserved in all specimens. A1 A2 E1 H1 H2 H3 E2 F1 F2 G1 G2 B1 C1 D1 B2 C2 D2 fig. 6 . — Melanoides aff. tuberculata (A-G) and Gyraulus sp. (H) from the Lower Pleistocene Tananwan Formation, Shuiniukeng, northern Taiwan: A-G, ASIZF0100913 to ASIZF0100919, respectively; H, ASIZF0100920. Scale bars: A-G, 10 mm; H, 1 mm. Photos: Diana Osipova. 734 GEODIVERSITAS • 2025 • 47 (20) Hsu C.-H. et al. 2020.— Global diversification dynamics since the Jurassic: Low dispersal and habitat-dependent evolution explain hotspots of diversity and shell disparity in river snails (Viviparidae). Systematic Biology 69 (5): 944-961. https://doi.org/10.1093/sysbio/syaa011 tAiwAn mAlAcofAUnA dAtAbAse. 2013.— Taiwan Malacofauna Database. Biodiversity Research Center, Academia Sinica, Taipei. http://shell.sinica.edu.tw/ tAo h.-j. & hU c.-h. 1992 — Szekou Formation (Pleistocene), Hengchun West Platform, Hengchun Peninsula (addendum), in hU C.-H. (ed.), Mollusk Fauna of Taiwan. National Museum of Natural Science, Taichung: 1427-1493. teng l. s. 2007.— Quaternary Tectonics of Taiwan. Special Publication of the Central Geological Survey 18: 1-24. v An b ocxlAer b. & s trong e. e. 2016.— Anatomy, functional morphology, evolutionary ecology and systematics of the invasive gastropod Cipangopaludina japonica (Viviparidae: Bellamyinae). Contributions to Zoology 85: 235-236. https://doi. org/10.1163/18759866-08502005 vAn bocxlAer b. & strong e. e. 2019.— Viviparidae Gray, 1847, in l ydeArd c. & c Ummings K. S. (eds), Freshwater Mollusks of the World: A Distribution Atlas. Johns Hopkins University Press, Baltimore: 43-50. wei k.-y. 2007.— Quaternary mammalian fossils of Taiwan: An eclectic overview and prospects for future study. Special Publication of the Central Geological Survey 18: 261-286. y e b. 2020.— Morphotypes revision, population genetics, and demographic history of Sinotaia quadrata in East Asia. Unpublished PhD thesis, Tohoku University, Sendai, 129 p. ye b., sAito t., hirAno t., dong z., do v.-t. & chibA s. 2020.— Human-geographic effects on variations in the population genetics of Sinotaia quadrata (Gastropoda: Viviparidae) that historically migrated from continental East Asia to Japan. Ecology and Evolution 10: 8055-8072. https://doi.org/10.1002/ ece3.6456 yen t.-c. 1939.— Die chinesischen landund süsswassergastropoden des Natur-museums Senckenberg. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 444: 1-233. yen t.-c. 1941.— A review of Chinese gastropods in the British Museum. Proceedings of the Malacological Society of London 24: 170-289. https://doi.org/10.1093/oxfordjournals.mollus.a064412 yen t.-c. 1943.— Review and summary of Tertiary and Quaternary non-marine mollusks of China. Proceedings of the Academy of Natural Sciences of Philadelphia 95: 267-309. https://www. jstor.org/stable/4064348 yokoyAmA m. 1928.— Mollusca from the oil field of Taiwan. Report of the Imperial Geological Survey of Japan 101, 128 p. yU t.-t., neUbAUer t. A. & jochUm A. 2021.— First freshwater gastropod preserved in amber suggests long-distance dispersal during the Cretaceous Period. Geological Magazine 158: 13271334. https://doi.org/10.1017/S0016756821000285 Submitted on 23 October 2024; accepted on 25 November 2024; published on 6 November 2025. 735 Pleistocene freshwater mollusks of Taiwan GEODIVERSITAS • 2025 • 47 (20) A E IJ KL F G H B CD appenDix 1. — Figure S1, comparison to resemble species in juvenile shell (A-D), typical adult shell (E-H), and shell with similar morphotypes (I-L): A, Sinotaia quadrata (Benson, 1842) from Tananwan Formation (ASIZF0100907); B, Sinotaia quadrata from Japan (Hirano et al. 2015); C, Cipangopaludina chinensis (Gray, 1833) from Japan (Hirano et al. 2015); D, Heterogen japonica (von Martens, 1861) from Japan (Hirano et al. 2015); E, Sinotaia quadrata from Tananwan Formation (ASIZF0100893); F, Sinotaia quadrata from Ombrone river, Italy (invasive species in Italy; Cianfanelli et al. 2017); G, Cipangopaludina chinensis from Japan (Hirano et al. 2015); H, Heterogen japonica from Japan (Van Bocxlaer & Strong 2016). I, Sinotaia quadrata from Tananwan Formation (ASIZF0100894); J, Sinotaia quadrata from Ombrone river, Italy (invasive species; Cianfanelli et al. 2017); K, Cipangopaludina chinensis (Gray, 1833) from China (Lu et al. 2016); L, Heterogen japonica from Japan (Van Bocxlaer & Strong 2016). Scale bars: A-D, 5 mm; E-L, 10 mm. Photos: Chia-Hsin Hsu. 736 GEODIVERSITAS • 2025 • 47 (20) Hsu C.-H. et al. Present-day sea level Present-day sea level Sea level lower by 80 m Sea level lower by 80 m Sea level lower by 150 m Sea level lower by 150 m AB 26°N 25° 24° 23° 22° 119°E 120° 121° 122° 26°N 25° 24° 23° 22° 119°E 120° 121° 122° 26°N 25° 24° 23° 22° 119°E 120° 121° 122° CD EF TAIWAN JAPAN JAPAN TAIWAN JAPAN 38°N 36° 34° 32° 124°E 126° 128° 130° 132° 38°N 36° 34° 32° 124°E 126° 128° 130° 132° 38°N 36° 34° 32° 124°E 126° 128° 130° 132° 5 m 20 50 80 150 300 750 1500 2250 3750 3000 4500 5250 6000 5 m 10 30 50 70 90 150 250 400 750 125 0 175 0 225 0 275 0 325 0 375 0 425 0 475 0 appenDix 2. — Figure S2, simulation of land bridge formations at different sea level in Taiwan Strait (A, C, E) and Tsusshima Strait (B, D, F): A, present-day sea level in Taiwan Strait; B, present-day sea level in Tsushima Strait; C, sea level lowered by 80 m in Taiwan Strait, showing the formation of a land bridge; D, sea level lower by 80 m in Tsushima Strait; E, sea level lower by 150 m in Taiwan Strait, showing the formation of a land bridge; F, sea level lower by 150 m in Tsushima Strait, showing the formation of a land bridge. Figures are generated by Ocean Data View (https://odv.awi.de/). Maps: Chia-Hsin Hsu. 737 Pleistocene freshwater mollusks of Taiwan GEODIVERSITAS • 2025 • 47 (20) appenDix 3. — Table S1, shell measurements of fossil Sinotaia quadrata (Benson, 1842). Species Specimen number WSh HSp HSh HBW HA WA Sinotaia quadrata ASIZF0100893 20.76 11.07 31.27 22.37 17.41 11.87 ASIZF0100894 21.3 12.28 33.66 25.4 17.63 12.79 ASIZF0100895 22.79 12.73 33.67 25.71 18.06 13.38 ASIZF0100896 22.73 12.48 36.13 25.9 18.12 13.8 ASIZF0100897 25.78 15.05 39.35 28.22 19.41 15.15 ASIZF0100898 23.93 12.97 39.45 28.36 20.48 13.11 ASIZF0100899 19.54 10.19 30.7 21.82 15.84 12.4 ASIZF0100900 20.62 11.44 33.05 24.06 16.25 13.29 ASIZF0100901 17.97 10.38 29.08 21.53 15.62 10.67 ASIZF0100902 15.15 6.82 21.14 6.85 13.1 9 ASIZF0100903 12.85 6.57 18.72 14.61 11 8.32 ASIZF0100904 11.41 5.74 16.25 12.75 9.46 6.57 ASIZF0100905 9.78 3.32 10.29 8.98 7.64 5.93 ASIZF0100906 – – – – – – ASIZF0100907 4.33 0.67 4.2 3.4 2.85 1.9 ASIZF0100908 4.09 0.69 3.82 3.14 2.63 1.91 ASIZF0100909 3.1 0.37 2.89 2.43 1.81 1.57 ASIZF0100910 –––––– ASIZF0100911 3.15 0.41 3.5 3.05 2.23 – ASIZF0100912 –––––– ASIZF0100923 –––––– ASIZF0100924 15.92 7.49 25.06 18.27 13.55 9.36 ASIZF0100925 16.96 8.29 25 18.22 12.76 12.17 ASIZF0100926 17.67 9.66 24.64 17.81 15.43 11.64 ASIZF0100927 15.24 8.31 24.14 16.53 12.65 9.65 ASIZF0100928 12.3 5.79 17.89 13.83 11.32 7.66 ASIZF0100929 8.61 3.3 13.01 10.46 8.18 6.03 ASIZF0100930 10.89 4.02 10.85 10.12 – – ASIZF0100931 9.61 4.01 13.61 10.61 8.18 5.77 ASIZF0100932 10.56 4.16 11.91 9.83 – – ASIZF0100933 9.93 3.24 11.21 9.71 8.53 – ASIZF0100934 12.38 6.04 18.06 13.53 9.91 7.15 ASIZF0100935 12.87 6.33 18.41 13.74 10.5 7.63 ASIZF0100936 –––––– ASIZF0100937 –––––– ASIZF0100938 –––––– ASIZF0100939 2.74 0.65 3.1 2.51 1.94 1.08 Average adult 15.9 8.07 23.46 17.17 13.52 10.15 Average juvenile 3.48 0.56 3.5 2.91 2.29 1.62 appenDix 4. — Table S2, shell measurements of fossil Melanoides aff. tuberculata Species Specimen number WSh HSp HSh HBW HA WA Melanoides aff. tuberculata ASIZF0100913 12.17 13.39 30.94 17.88 12.73 5.04 ASIZF0100914 5.76 6.49 13.6 7.85 – – ASIZF0100915 5.38 7.95 1.9 6.07 – – ASIZF0100916 5.58 8.18 – – – – ASIZF0100917 5.76 5.4 12.78 7.71 4.82 – ASIZF0100918 5.34 7.23 12.19 – – – ASIZF0100919 3.11 2.48 5.99 3.5 – – ASIZF0100940 6.04 5.23 13.34 8.14 4.81 2.9 Average 6.14 7.04 12.96 8.53 7.45 3.97 appenDix 5. — Table S3, shell measurements of other fossil mollusks. Species Specimen number WSh DIWb HSh LWWb HA WA Gyraulus sp. ASIZF0100920 3.51 1.37 1.1 1.2 0.84 1.05 Gyraulus sp. ASIZF0100941 – – – – – – Lymnaeidae gen. et sp. indet. ASIZF0100921 – – – – – – Lymnaeidae gen. et sp. indet. ASIZF0100942 – – – – – – Unionidae gen. et sp. indet. ASIZF0100922 – – – – – –