# Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand

Parin Jirapatrasilp, Gilles Cuny, László Kocsis, Chirasak Sutcharit, Nom Ngamnisai, Thasinee Charoentitirat, Satapat Kumpitak, Kantapon Suraprasit

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Parin Jirapatrasilp, Gilles Cuny, László Kocsis, Chirasak Sutcharit, Nom Ngamnisai, et al., Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand. Zookeys, 2024, 1202, pp.1-110. 10.3897/zookeys.1202.119389. hal-04590679v2

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# Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand

Parin Jirapatrasilp¹,²✉, Gilles Cuny³✉, László Kocsis⁴✉, Chirasak Sutcharit¹✉, Nom Ngamnisai⁵, Thasinee Charoentitirat⁶, Satapat Kumpitak⁶, Kantapon Suraprasit⁷✉

1. Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

2. Leibniz-Institut zur Analyse des Biodiversitätswandels - Standort Hamburg, Martin-Luther-King-Platz 3, Hamburg 20146, Germany

3. Université Claude Bernard Lyon 1, LEHNA UMR 5023, CNRS, ENTPE, F-69622, Villeurbanne, France

4. Institute of Earth Surface Dynamics, University of Lausanne, Rue de la Mouline, 1015 Lausanne, Switzerland

5. Department of Geography, Faculty of Social Sciences, Srinakharinwirot University, Bangkok 10110, Thailand

6. Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

7. Center of Excellence in Morphology of Earth Surface and Advanced Geohazards in Southeast Asia (MESA CE), Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

Corresponding author: Kantapon Suraprasit (Kantapon.S@chula.ac.th)

## Abstract

Based on several field investigations, many molluscan shells and chondrichthyan teeth, together with other invertebrate and actinopterygian remains were found from the marine Bangkok Clay deposits in Ongkharak, Nakhon Nayok, at a depth of ~ 5–7 m below the topsoil surface. Animal macrofossils recovered from these Holocene marine deposits were identified and their chronological context was investigated in order to reconstruct the paleoenvironments of the area at that time. The majority of marine fossils recovered from the site consist of molluscs, with a total of 63 species identified. Other invertebrate species include a stony coral, a mud lobster, barnacles, and a sea urchin. The vertebrates are represented by fish remains, including carcharhinid shark teeth from at least nine species, stingray and trichiurid teeth, and one sciaenid otolith. The molluscan fauna indicates that the paleoenvironments of the area corresponded to intertidal to sublittoral zones, where some areas were mangrove forests and intertidal mudflats. The fish fauna is dominated by the river shark *Glyphis*, indicating freshwater influences and possibly occasional brackish conditions. The carbon-14 analysis of mollusc and charcoal remains shows that deposition of the marine sediment sequence began during the mid-Holocene, spanning approximately from 8,800 to 5,300 cal yr BP. This study provides in-depth insights into the diversity of fishes, marine molluscs, and other invertebrates from the Bangkok Clay deposits, supporting the existence of a marine transgression onto the Lower Central Plain of Thailand during the mid-Holocene.

**Key words:** carbon-14 dating, Chao Phraya River Basin, Chondrichthyes, marine transgression, mollusc, paleoenvironment

OPEN ACCESS

Academic editor: Fedor Konstantinov

Received: 25 January 2024

Accepted: 24 March 2024

Published: 15 May 2024

ZooBank: https://zoobank.org/D04EE090-0D05-4EB2-ADA6-3EE4E19F59D9

**Citation:** Jirapatrasilp P, Cuny G, Kocsis L, Sutcharit C, Ngamnisai N, Charoentitirat T, Kumpitak S, Suraprasit K (2024) Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand. ZooKeys 1202: 1–110. https://doi.org/10.3897/zookeys.1202.119389

**Copyright:** © Parin Jirapatrasilp et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0).
# Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand

Parin Jirapatrasilp¹,²✉, Gilles Cuny³✉, László Kocsis⁴✉, Chirasak Sutcharit¹✉, Nom Ngamnisai⁵, Thasinee Charoentitirat⁶, Satapat Kumpitak⁶, Kantapon Suraprasit⁷✉

1. Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

2. Leibniz-Institut zur Analyse des Biodiversitätswandels - Standort Hamburg, Martin-Luther-King-Platz 3, Hamburg 20146, Germany

3. Université Claude Bernard Lyon 1, LEHNA UMR 5023, CNRS, ENTPE, F-69622, Villeurbanne, France

4. Institute of Earth Surface Dynamics, University of Lausanne, Rue de la Mouline, 1015 Lausanne, Switzerland

5. Department of Geography, Faculty of Social Sciences, Srinakharinwirot University, Bangkok 10110, Thailand

6. Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

7. Center of Excellence in Morphology of Earth Surface and Advanced Geohazards in Southeast Asia (MESA CE), Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

Corresponding author: Kantapon Suraprasit (Kantapon.S@chula.ac.th)

## Abstract

Based on several field investigations, many molluscan shells and chondrichthyan teeth, together with other invertebrate and actinopterygian remains were found from the marine Bangkok Clay deposits in Ongkharak, Nakhon Nayok, at a depth of ~ 5–7 m below the topsoil surface. Animal macrofossils recovered from these Holocene marine deposits were identified and their chronological context was investigated in order to reconstruct the paleoenvironments of the area at that time. The majority of marine fossils recovered from the site consist of molluscs, with a total of 63 species identified. Other invertebrate species include a stony coral, a mud lobster, barnacles, and a sea urchin. The vertebrates are represented by fish remains, including carcharhinid shark teeth from at least nine species, stingray and trichiurid teeth, and one sciaenid otolith. The molluscan fauna indicates that the paleoenvironments of the area corresponded to intertidal to sublittoral zones, where some areas were mangrove forests and intertidal mudflats. The fish fauna is dominated by the river shark *Glyphis*, indicating freshwater influences and possibly occasional brackish conditions. The carbon-14 analysis of mollusc and charcoal remains shows that deposition of the marine sediment sequence began during the mid-Holocene, spanning approximately from 8,800 to 5,300 cal yr BP. This study provides in-depth insights into the diversity of fishes, marine molluscs, and other invertebrates from the Bangkok Clay deposits, supporting the existence of a marine transgression onto the Lower Central Plain of Thailand during the mid-Holocene.

**Key words:** carbon-14 dating, Chao Phraya River Basin, Chondrichthyes, marine transgression, mollusc, paleoenvironment

OPEN ACCESS

Academic editor: Fedor Konstantinov

Received: 25 January 2024

Accepted: 24 March 2024

Published: 15 May 2024

ZooBank: https://zoobank.org/D04EE090-0D05-4EB2-ADA6-3EE4E19F59D9

**Citation:** Jirapatrasilp P, Cuny G, Kocsis L, Sutcharit C, Ngamnisai N, Charoentitirat T, Kumpitak S, Suraprasit K (2024) Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand. ZooKeys 1202: 1–110. https://doi.org/10.3897/zookeys.1202.119389

**Copyright:** © Parin Jirapatrasilp et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0).
Table of contents

<table><tr><td>Introduction</td><td>3</td></tr><tr><td>Geological settings of the study area</td><td>4</td></tr><tr><td>Materials and methods</td><td>7</td></tr><tr><td>Results</td><td>8</td></tr><tr><td>Systematic palaeontology</td><td>8</td></tr><tr><td>Phylum Cnidaria</td><td>8</td></tr><tr><td>Class Anthozoa Ehrenberg, 1834</td><td>8</td></tr><tr><td>Family Rhizangiidae d'Orbigny, 1851</td><td>8</td></tr><tr><td>Phylum Mollusca</td><td>9</td></tr><tr><td>Class Gastropoda Cuvier, 1795</td><td>9</td></tr><tr><td>Family Colloniidae Cossmann, 1917</td><td>9</td></tr><tr><td>Family Neritidae Rafinesque, 1815</td><td>9</td></tr><tr><td>Family Potamididae H. Adams & A. Adams, 1854</td><td>12</td></tr><tr><td>Family Naticidae Guilding, 1834</td><td>16</td></tr><tr><td>Family Calyptraeidae Lamarck, 1809</td><td>20</td></tr><tr><td>Family Bursidae Thiele, 1925</td><td>21</td></tr><tr><td>Family Cancellariidae Forbes & Hanley, 1851</td><td>21</td></tr><tr><td>Family Buccinidae Rafinesque, 1815</td><td>23</td></tr><tr><td>Family Melongenidae Gill, 1871</td><td>23</td></tr><tr><td>Family Nassariidae Iredale, 1916</td><td>25</td></tr><tr><td>Family Muricidae Rafinesque, 1815</td><td>26</td></tr><tr><td>Family Borsoniidae Bellardi, 1875</td><td>29</td></tr><tr><td>Family Clathurellidae H. Adams & A. Adams, 1858</td><td>30</td></tr><tr><td>Family Clavatulidae Gray, 1853</td><td>30</td></tr><tr><td>Family Horaiclavidae Bouchet et al., 2011</td><td>32</td></tr><tr><td>Family Pseudomelatomidae Morrison, 1966</td><td>32</td></tr><tr><td>Family Terebridae Mörch, 1852</td><td>33</td></tr><tr><td>Family Architectonicidae Gray, 1850</td><td>36</td></tr><tr><td>Family Cylichnidae H. Adams & A. Adams, 1854</td><td>36</td></tr><tr><td>Family Ellobiidae Pfeiffer, 1854</td><td>37</td></tr><tr><td>Class Bivalvia Linnaeus, 1758</td><td>39</td></tr><tr><td>Family Nuculanidae H. Adams & A. Adams, 1858</td><td>39</td></tr><tr><td>Family Arcidae Lamarck, 1809</td><td>41</td></tr><tr><td>Family Noetiidae Stewart, 1930</td><td>45</td></tr><tr><td>Family Ostreidae Rafinesque, 1815</td><td>46</td></tr><tr><td>Family Placunidae Rafinesque, 1815</td><td>47</td></tr><tr><td>Family Pectinidae Rafinesque, 1815</td><td>49</td></tr><tr><td>Family Lucinidae J. Fleming, 1828</td><td>49</td></tr><tr><td>Family Cyrenidae Gray, 1840</td><td>50</td></tr><tr><td>Family Mactridae Lamarck, 1809</td><td>50</td></tr><tr><td>Family Tellinidae Blainville, 1814</td><td>53</td></tr><tr><td>Family Ungulinidae Gray, 1854</td><td>53</td></tr><tr><td>Family Veneridae Rafinesque, 1815</td><td>54</td></tr><tr><td>Family Corbulidae Lamarck, 1818</td><td>56</td></tr><tr><td>Family Pholadidae Lamarck, 1809</td><td>58</td></tr><tr><td>Family Pharidae H. Adams & A. Adams, 1856</td><td>60</td></tr><tr><td>Class Scaphopoda Bronn, 1862</td><td>62</td></tr></table>
Table of contents

<table><tr><td>Introduction</td><td>3</td></tr><tr><td>Geological settings of the study area</td><td>4</td></tr><tr><td>Materials and methods</td><td>7</td></tr><tr><td>Results</td><td>8</td></tr><tr><td>Systematic palaeontology</td><td>8</td></tr><tr><td>Phylum Cnidaria</td><td>8</td></tr><tr><td>Class Anthozoa Ehrenberg, 1834</td><td>8</td></tr><tr><td>Family Rhizangiidae d'Orbigny, 1851</td><td>8</td></tr><tr><td>Phylum Mollusca</td><td>9</td></tr><tr><td>Class Gastropoda Cuvier, 1795</td><td>9</td></tr><tr><td>Family Colloniidae Cossmann, 1917</td><td>9</td></tr><tr><td>Family Neritidae Rafinesque, 1815</td><td>9</td></tr><tr><td>Family Potamididae H. Adams & A. Adams, 1854</td><td>12</td></tr><tr><td>Family Naticidae Guilding, 1834</td><td>16</td></tr><tr><td>Family Calyptraeidae Lamarck, 1809</td><td>20</td></tr><tr><td>Family Bursidae Thiele, 1925</td><td>21</td></tr><tr><td>Family Cancellariidae Forbes & Hanley, 1851</td><td>21</td></tr><tr><td>Family Buccinidae Rafinesque, 1815</td><td>23</td></tr><tr><td>Family Melongenidae Gill, 1871</td><td>23</td></tr><tr><td>Family Nassariidae Iredale, 1916</td><td>25</td></tr><tr><td>Family Muricidae Rafinesque, 1815</td><td>26</td></tr><tr><td>Family Borsoniidae Bellardi, 1875</td><td>29</td></tr><tr><td>Family Clathurellidae H. Adams & A. Adams, 1858</td><td>30</td></tr><tr><td>Family Clavatulidae Gray, 1853</td><td>30</td></tr><tr><td>Family Horaiclavidae Bouchet et al., 2011</td><td>32</td></tr><tr><td>Family Pseudomelatomidae Morrison, 1966</td><td>32</td></tr><tr><td>Family Terebridae Mörch, 1852</td><td>33</td></tr><tr><td>Family Architectonicidae Gray, 1850</td><td>36</td></tr><tr><td>Family Cylichnidae H. Adams & A. Adams, 1854</td><td>36</td></tr><tr><td>Family Ellobiidae Pfeiffer, 1854</td><td>37</td></tr><tr><td>Class Bivalvia Linnaeus, 1758</td><td>39</td></tr><tr><td>Family Nuculanidae H. Adams & A. Adams, 1858</td><td>39</td></tr><tr><td>Family Arcidae Lamarck, 1809</td><td>41</td></tr><tr><td>Family Noetiidae Stewart, 1930</td><td>45</td></tr><tr><td>Family Ostreidae Rafinesque, 1815</td><td>46</td></tr><tr><td>Family Placunidae Rafinesque, 1815</td><td>47</td></tr><tr><td>Family Pectinidae Rafinesque, 1815</td><td>49</td></tr><tr><td>Family Lucinidae J. Fleming, 1828</td><td>49</td></tr><tr><td>Family Cyrenidae Gray, 1840</td><td>50</td></tr><tr><td>Family Mactridae Lamarck, 1809</td><td>50</td></tr><tr><td>Family Tellinidae Blainville, 1814</td><td>53</td></tr><tr><td>Family Ungulinidae Gray, 1854</td><td>53</td></tr><tr><td>Family Veneridae Rafinesque, 1815</td><td>54</td></tr><tr><td>Family Corbulidae Lamarck, 1818</td><td>56</td></tr><tr><td>Family Pholadidae Lamarck, 1809</td><td>58</td></tr><tr><td>Family Pharidae H. Adams & A. Adams, 1856</td><td>60</td></tr><tr><td>Class Scaphopoda Bronn, 1862</td><td>62</td></tr></table>
<table><tr><td>Family Dentaliidae Children, 1834</td><td>62</td></tr><tr><td>Phylum Arthropoda</td><td>62</td></tr><tr><td>Class Malacostraca Latreille, 1802</td><td>62</td></tr><tr><td>Family Thalassinidae Latreille, 1831</td><td>62</td></tr><tr><td>Class Thecostraca Gruvel, 1905</td><td>63</td></tr><tr><td>Family Balanidae Leach, 1817</td><td>63</td></tr><tr><td>Phylum Echinodermata</td><td>64</td></tr><tr><td>Class Echinoidea Schumacher, 1817</td><td>64</td></tr><tr><td>Family Temnopleuridae Agassiz, 1872</td><td>64</td></tr><tr><td>Phylum Chordata</td><td>65</td></tr><tr><td>Family Carcharhinidae Jordan &amp; Evermann, 1896</td><td>65</td></tr><tr><td>Family Dasyatidae Jordan &amp; Gilbert, 1879</td><td>82</td></tr><tr><td>Class Actinopterygii Klein, 1885</td><td>82</td></tr><tr><td>Family Trichiuridae Rafinesque, 1810</td><td>82</td></tr><tr><td>Family Sciaenidae Cuvier, 1829</td><td>85</td></tr><tr><td>Discussion</td><td>85</td></tr><tr><td>Acknowledgments</td><td>89</td></tr><tr><td>Additional information</td><td>89</td></tr><tr><td>References</td><td>90</td></tr></table>

## Introduction

The Holocene began approximately 11,700 years ago and belongs to one of the interglacial periods. Prior to the Holocene, during the period of the Last Glacial Maximum (LGM), the global climate was much colder and dryer and was a period of significant landscape changes in many areas due to a lowered sea level, approximately 120 m below the present-day stands (Clark et al. 2009). During the Holocene, however, the climate became warmer, and the sea level rose and inundated a previously emerged landmass. Southeast Asia is one of the regions impacted by sea level inundations (Sathiamurthy and Voris 2006), due in part to an increase in precipitation level after the cold and dry period (Chabangborn 2017). Differences in climatic and environmental conditions between the Pleistocene and Holocene have therefore had impacts on the ecological adaptations of both terrestrial and marine organisms, leading to dispersal, migration, and extinction of species.

The Central Plain of Thailand is an important area where the topography and climate changes were under the influence of a sea level rise starting at ~ 12 ka. The region covers the plains between the mountain ranges along the lower northern part of Thailand, including the Yom and Nan River basins, and the low-lying plains of the Chao Phraya, Tha Chin, Mae Klong and Bang Pakong River basins near the Gulf of Thailand (Sinsakul 2000). During the Holocene, the Sing Buri Plain (5–15 m above mean sea level (amsl)) and the Bangkok Lowland (0–5 m amsl), forming the Central plain of Thailand, were inundated (Takaya 1969). Approximately 8–7 ka, the sea level was 2–4 m higher than present-day stands and inundated the whole lowland areas of Bangkok. Later, the sea level subsided along with a new sedimentation regime and a new land-mass started to develop, shaping the current coastal shorelines (Umitsu et al. 2002; Tanabe et al. 2003).
<table><tr><td>Family Dentaliidae Children, 1834</td><td>62</td></tr><tr><td>Phylum Arthropoda</td><td>62</td></tr><tr><td>Class Malacostraca Latreille, 1802</td><td>62</td></tr><tr><td>Family Thalassinidae Latreille, 1831</td><td>62</td></tr><tr><td>Class Thecostraca Gruvel, 1905</td><td>63</td></tr><tr><td>Family Balanidae Leach, 1817</td><td>63</td></tr><tr><td>Phylum Echinodermata</td><td>64</td></tr><tr><td>Class Echinoidea Schumacher, 1817</td><td>64</td></tr><tr><td>Family Temnopleuridae Agassiz, 1872</td><td>64</td></tr><tr><td>Phylum Chordata</td><td>65</td></tr><tr><td>Family Carcharhinidae Jordan &amp; Evermann, 1896</td><td>65</td></tr><tr><td>Family Dasyatidae Jordan &amp; Gilbert, 1879</td><td>82</td></tr><tr><td>Class Actinopterygii Klein, 1885</td><td>82</td></tr><tr><td>Family Trichiuridae Rafinesque, 1810</td><td>82</td></tr><tr><td>Family Sciaenidae Cuvier, 1829</td><td>85</td></tr><tr><td>Discussion</td><td>85</td></tr><tr><td>Acknowledgments</td><td>89</td></tr><tr><td>Additional information</td><td>89</td></tr><tr><td>References</td><td>90</td></tr></table>

## Introduction

The Holocene began approximately 11,700 years ago and belongs to one of the interglacial periods. Prior to the Holocene, during the period of the Last Glacial Maximum (LGM), the global climate was much colder and dryer and was a period of significant landscape changes in many areas due to a lowered sea level, approximately 120 m below the present-day stands (Clark et al. 2009). During the Holocene, however, the climate became warmer, and the sea level rose and inundated a previously emerged landmass. Southeast Asia is one of the regions impacted by sea level inundations (Sathiamurthy and Voris 2006), due in part to an increase in precipitation level after the cold and dry period (Chabangborn 2017). Differences in climatic and environmental conditions between the Pleistocene and Holocene have therefore had impacts on the ecological adaptations of both terrestrial and marine organisms, leading to dispersal, migration, and extinction of species.

The Central Plain of Thailand is an important area where the topography and climate changes were under the influence of a sea level rise starting at ~ 12 ka. The region covers the plains between the mountain ranges along the lower northern part of Thailand, including the Yom and Nan River basins, and the low-lying plains of the Chao Phraya, Tha Chin, Mae Klong and Bang Pakong River basins near the Gulf of Thailand (Sinsakul 2000). During the Holocene, the Sing Buri Plain (5–15 m above mean sea level (amsl)) and the Bangkok Lowland (0–5 m amsl), forming the Central plain of Thailand, were inundated (Takaya 1969). Approximately 8–7 ka, the sea level was 2–4 m higher than present-day stands and inundated the whole lowland areas of Bangkok. Later, the sea level subsided along with a new sedimentation regime and a new land-mass started to develop, shaping the current coastal shorelines (Umitsu et al. 2002; Tanabe et al. 2003).
The extent of marine intrusion into the Central Plain of Thailand during the Holocene was largely interpreted based on various studies (e.g., geomorphological, sedimentological, paleontological, palynological, and stratigraphical data as well as carbon-14 dating of peat layers). These studies indicated that the ancient coastal shoreline of the Gulf of Thailand was located further north in Phra Nakhon Si Ayutthaya Province during 7.3–6.5 ka (Jarupongsakul and Thiramongkol 1992). The ancient coastal shoreline was also reconstructed based on a 4,500-year-old coastal archaeological site in Chonburi Province (Boyd et al. 1996), open-pit mining of clay deposits at a depth of 7 m under the ground surface in many provinces, dated to ~ 8–7 ka (Songtham et al. 2007, 2015), and geological studies of coastal berms in Chumporn and Prachuap Khiri Khan provinces, dated between 8.9–5.6 ka and 6.5–6 ka, respectively (Nimnate et al. 2015; Surakiatchai et al. 2018).

In addition to the inference of ancient coastal shorelines during the Holocene, studies on faunas and floras along the ancient coast of the Gulf of Thailand are crucial to understand paleoenvironmental and palaeoecological changes in response to climatic oscillations. The ancient coastal habitats occupied by these animals are investigated based on the identification and dating of fossils (e.g., molluscs, arthropods, and vertebrates). According to accurate species-level identification, microhabitats can be investigated based on comparisons between fossils and living species or related taxa. The paleoenvironments of the area are also reconstructed based on the identification of various groups of animals because each of them has a different mode of life in a specific habitat (Negri 2009, 2012; Oliver and Terry 2019).

Marine faunas from the Holocene Bangkok Clay deposits of the Central Plain of Thailand have infrequently been analysed in detail, and we identify the animal macrofossils recovered from the clay pit of Ongkharak, Nakhon Nayok Province in central Thailand (Fig. 1). We also date the Bangkok Clay sequence deposited in the area, using a carbon-14 dating technique. Although the Bangkok Clay deposits have previously been described from some areas of Nakhon Nayok Province (Songtham et al. 2007; Royal Irrigation Department 2009), the fauna and its paleoenvironments have not yet been thoroughly studied and compared to other sites from different regions (e.g., Negri 2009, 2012). This study not only fulfils the gap regarding the paleoenvironments of the Gulf of Thailand during the Holocene, but also illustrates the ancient coastlines in the eastern part of the Central Plain of Thailand to some extent. The reconstruction of ancient coastlines and paleoenvironments is crucial to advance the knowledge of archaeological contexts in terms of prehistoric human settlements and cultures, and probably helpful in forecasting changes in coastal ecosystems and environments in response to sea level oscillations due to the present-day global warming situation.

## Geological settings of the study area

The study area is located at the clay pit in Ban Lad Chang, Chumpon Subdistrict, Ongkharak District, Nakhon Nayok Province (13°59'30.9"N, 100°55'11.5"E) in the Lower Central Plain of Thailand (Fig. 1), which is covered by the thick marine deposits of the Chao Phraya River delta, also known as the Bangkok Clay. These marine clay deposits have been dated between the Late Pleistocene and Holocene (Cox 1968; Moh et al. 1969; Sinsakul 2000). The Bangkok clay sequence comprises three main zones (Ohtsubo et al. 2000): 1) weathered
The extent of marine intrusion into the Central Plain of Thailand during the Holocene was largely interpreted based on various studies (e.g., geomorphological, sedimentological, paleontological, palynological, and stratigraphical data as well as carbon-14 dating of peat layers). These studies indicated that the ancient coastal shoreline of the Gulf of Thailand was located further north in Phra Nakhon Si Ayutthaya Province during 7.3–6.5 ka (Jarupongsakul and Thiramongkol 1992). The ancient coastal shoreline was also reconstructed based on a 4,500-year-old coastal archaeological site in Chonburi Province (Boyd et al. 1996), open-pit mining of clay deposits at a depth of 7 m under the ground surface in many provinces, dated to ~ 8–7 ka (Songtham et al. 2007, 2015), and geological studies of coastal berms in Chumporn and Prachuap Khiri Khan provinces, dated between 8.9–5.6 ka and 6.5–6 ka, respectively (Nimnate et al. 2015; Surakiatchai et al. 2018).

In addition to the inference of ancient coastal shorelines during the Holocene, studies on faunas and floras along the ancient coast of the Gulf of Thailand are crucial to understand paleoenvironmental and palaeoecological changes in response to climatic oscillations. The ancient coastal habitats occupied by these animals are investigated based on the identification and dating of fossils (e.g., molluscs, arthropods, and vertebrates). According to accurate species-level identification, microhabitats can be investigated based on comparisons between fossils and living species or related taxa. The paleoenvironments of the area are also reconstructed based on the identification of various groups of animals because each of them has a different mode of life in a specific habitat (Negri 2009, 2012; Oliver and Terry 2019).

Marine faunas from the Holocene Bangkok Clay deposits of the Central Plain of Thailand have infrequently been analysed in detail, and we identify the animal macrofossils recovered from the clay pit of Ongkharak, Nakhon Nayok Province in central Thailand (Fig. 1). We also date the Bangkok Clay sequence deposited in the area, using a carbon-14 dating technique. Although the Bangkok Clay deposits have previously been described from some areas of Nakhon Nayok Province (Songtham et al. 2007; Royal Irrigation Department 2009), the fauna and its paleoenvironments have not yet been thoroughly studied and compared to other sites from different regions (e.g., Negri 2009, 2012). This study not only fulfils the gap regarding the paleoenvironments of the Gulf of Thailand during the Holocene, but also illustrates the ancient coastlines in the eastern part of the Central Plain of Thailand to some extent. The reconstruction of ancient coastlines and paleoenvironments is crucial to advance the knowledge of archaeological contexts in terms of prehistoric human settlements and cultures, and probably helpful in forecasting changes in coastal ecosystems and environments in response to sea level oscillations due to the present-day global warming situation.

## Geological settings of the study area

The study area is located at the clay pit in Ban Lad Chang, Chumpon Subdistrict, Ongkharak District, Nakhon Nayok Province (13°59'30.9"N, 100°55'11.5"E) in the Lower Central Plain of Thailand (Fig. 1), which is covered by the thick marine deposits of the Chao Phraya River delta, also known as the Bangkok Clay. These marine clay deposits have been dated between the Late Pleistocene and Holocene (Cox 1968; Moh et al. 1969; Sinsakul 2000). The Bangkok clay sequence comprises three main zones (Ohtsubo et al. 2000): 1) weathered
<figure><img src="image_1.png" /><figcaption>**Figure 1.** Map of the lower central plain of Thailand (orange). A red star indicates the location of the study area.</figcaption></figure>

clay with a thickness of 0–2 m in the uppermost part, 2) soft marine clay in the middle part, and 3) medium stiff clay at the bottom. The Holocene Bangkok Soft Clay in the middle part, with a thickness ranging from 10 to 20 m, is olive grey and medium to dark grey in colour, indicating reducing environments (Sinsakul 2000; Choowong 2002; Tanabe et al. 2003). This Bangkok Soft Clay layer is further divided into lower transgressive peaty (mangrove swamp) and upper regressive deltaic sediments (Tanabe et al. 2003). Some marine shells and remains of mangrove trees were found from this middle layer, indicating intertidal and shallow sublittoral inner bay conditions, with local mangrove and freshwater influences (Robba et al. 2002, 2003, 2004, 2007; Songtham et al. 2007; Negri 2009, 2012). This evidence supports the occurrence of a marine transgression into the Central Plain of Thailand after the LGM (Songtham et al. 2015).

The rectangular mine is 1,000 m long × 400 m wide and 30 m deep. It was opened to produce clay material used in construction sites. The active mining operations of the clay pit allow us to have access to the stratigraphic sequence of the Quaternary deposits of the area (Fig. 2). The topsoil (0.5–1 m thick) consists of coarse-grained sand with FeO grains and black mud nodules, underlain by a 5 m thick layer of black clay and organic soil (dark layer) partially interbedded with thin layers of silt to very fine-grained sand. Marine invertebrate and vertebrate remains were only found from this organic-rich clay unit, also known as the Bangkok Clay, which overlies the layers of Pleistocene stiff clay (Rau and Nutalaya 1983). In this site, the Pleistocene stiff clay contains seven different
<figure><img src="image_2.png" /><figcaption>**Figure 1.** Map of the lower central plain of Thailand (orange). A red star indicates the location of the study area.</figcaption></figure>

clay with a thickness of 0–2 m in the uppermost part, 2) soft marine clay in the middle part, and 3) medium stiff clay at the bottom. The Holocene Bangkok Soft Clay in the middle part, with a thickness ranging from 10 to 20 m, is olive grey and medium to dark grey in colour, indicating reducing environments (Sinsakul 2000; Choowong 2002; Tanabe et al. 2003). This Bangkok Soft Clay layer is further divided into lower transgressive peaty (mangrove swamp) and upper regressive deltaic sediments (Tanabe et al. 2003). Some marine shells and remains of mangrove trees were found from this middle layer, indicating intertidal and shallow sublittoral inner bay conditions, with local mangrove and freshwater influences (Robba et al. 2002, 2003, 2004, 2007; Songtham et al. 2007; Negri 2009, 2012). This evidence supports the occurrence of a marine transgression into the Central Plain of Thailand after the LGM (Songtham et al. 2015).

The rectangular mine is 1,000 m long × 400 m wide and 30 m deep. It was opened to produce clay material used in construction sites. The active mining operations of the clay pit allow us to have access to the stratigraphic sequence of the Quaternary deposits of the area (Fig. 2). The topsoil (0.5–1 m thick) consists of coarse-grained sand with FeO grains and black mud nodules, underlain by a 5 m thick layer of black clay and organic soil (dark layer) partially interbedded with thin layers of silt to very fine-grained sand. Marine invertebrate and vertebrate remains were only found from this organic-rich clay unit, also known as the Bangkok Clay, which overlies the layers of Pleistocene stiff clay (Rau and Nutalaya 1983). In this site, the Pleistocene stiff clay contains seven different
<figure><img src="image_2.png" /><figcaption>**Figure 2.** The study area and the sediment profile of the clay pit **A** the clay pit of Ongkharak, Nakhon Nayok Province in central Thailand **B** the Bangkok clay layer bearing numerous *in situ* complete shells of *Placuna placenta* **C** Shells of a bivalve *Anadara inaequivalvis* buried *in situ* in the Bangkok clay deposits **D** lithological profile of the clay pit **E** the contact between two successive layers: coarse-grained sand (upper) and black clay (lower) **F** the contact between three successive layers: black clay (upper), lateritic soil (middle), and yellowish brown clay to silt (lower) **G** the contact between two successive layers: purplish (upper) and greyish (lower) clay to sand **H** the contact between two successive layers: greyish clay to sand (upper) and reddish brown lateritic layer (lower).</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>**Figure 2.** The study area and the sediment profile of the clay pit **A** the clay pit of Ongkharak, Nakhon Nayok Province in central Thailand **B** the Bangkok clay layer bearing numerous *in situ* complete shells of *Placuna placenta* **C** Shells of a bivalve *Anadara inaequivalvis* buried *in situ* in the Bangkok clay deposits **D** lithological profile of the clay pit **E** the contact between two successive layers: coarse-grained sand (upper) and black clay (lower) **F** the contact between three successive layers: black clay (upper), lateritic soil (middle), and yellowish brown clay to silt (lower) **G** the contact between two successive layers: purplish (upper) and greyish (lower) clay to sand **H** the contact between two successive layers: greyish clay to sand (upper) and reddish brown lateritic layer (lower).</figcaption></figure>
lithological units from the top to bottom of the pit: 1) reddish brown lateritic soil (1 m thick), 2) yellowish brown clay to silt-sized sediments with root-trace burrows (4 m thick), 3) reddish brown clay to silt-sized sediments with shell fragments (4 m thick), 4) purplish clay to sand-sized sediments (1 m thick), 5) greyish clay to sand-sized sediments (2 m thick), 6) reddish brown lateritic soil with pale pink and white spots of weathering soil (3 m thick), and 7) yellowish grey clay to silt-sized sediments (5 m thick), respectively (Fig. 2).

The Bangkok clay layer at the clay pit of Ongkharak has yielded nearly *in situ* fossil deposits as indicated by preservation of complete shells with both valves attached (Fig. 2C) as well as the orientation of shell valves of *Pholas orientalis*, which has been recovered in natural position within its burrows during field collection (see also Songtham et al. 2007: fig. 3). Although remains of marine molluscs were found throughout the sequence of dark clay deposits, they were most abundant in the middle part of the layer (Fig. 2D–F), at a depth of ~ 2 m below the upper contact that separates it from the topsoil. Numerous wood fragments, plant remains, and giant oyster shells were found from the lower part of the dark clay unit below the shell-rich layer.

## Materials and methods

Species identification of specimens is mainly based on the existing literature specified under the treatment of each taxon. The specimens are kept at the Department of Geology, Faculty of Science, Chulalongkorn University, and coded as the name of the collection (CUF: Chulalongkorn fossil collection), followed by the locality (NKNY: Nakhon Nayok) and the catalogue number. Fish remains including teeth and otolith as well as some small shells were photographed with a scanning electron microscope (SEM; JEOL, JSM-5410 LV) or a Leica M205C stereo light microscope with fusion optics and the Leica Application Suite Image System. L and R designate left and right valves of bivalve shells, respectively.

We selected six samples (shells and charcoal) collected from the marine clay deposits at different depths in the clay pit for carbon-14 dating (Table 1). The samples were pretreated and analysed at the DirectAMS (USA), using an accelerated mass spectrometer (AMS). According to the convention outlined by Stuiver and Polach (1977), the ¹⁴C age ± one standard deviation (SD) was calculated using the Libby half-life of 5,568 years and an isotopic fractionation correction based on δ¹³C measurements obtained from the AMS. The Direct-AMS results were calibrated and corrected for the marine reservoir effect, using the Calib 8.2 program with IntCal20.14c for charcoal (Reimer et al. 2020) and with Marine20 (Heaton et al. 2020) for shells.

<table><caption>Table 1. AMS ¹⁴C ages of shells and charcoal collected from the clay pit of Ongkharak in Nakhon Nayok, central Thailand.</caption><thead><tr><th>Lab Code</th><th>Sample type</th><th>Depths (m) below the uppermost part of a marine clay layer</th><th>¹⁴C age (yr BP)</th><th>Calibrated ¹⁴C (2-sigma) age (cal yr BP)</th></tr></thead><tbody><tr><td>D-AMS 044190</td><td>Shell (Tellinides conspicuus)</td><td>2.2</td><td>5303 ± 26</td><td>5882–5464</td></tr><tr><td>D-AMS 044191</td><td>Shell (Pholas orientalis)</td><td>2.2</td><td>5202 ± 28</td><td>5757–5318</td></tr><tr><td>D-AMS 044193</td><td>Charcoal</td><td>2.2</td><td>5047 ± 26</td><td>5899–5726</td></tr><tr><td>D-AMS 044195</td><td>Charcoal</td><td>3.4</td><td>6186 ± 29</td><td>7166–6983</td></tr><tr><td>D-AMS 044194</td><td>Shell (Magallana cf. gigas)</td><td>4</td><td>7241 ± 32</td><td>7901–7510</td></tr><tr><td>D-AMS 044192</td><td>Charcoal</td><td>4.6</td><td>7913 ± 26</td><td>8784–8600</td></tr></tbody></table>
lithological units from the top to bottom of the pit: 1) reddish brown lateritic soil (1 m thick), 2) yellowish brown clay to silt-sized sediments with root-trace burrows (4 m thick), 3) reddish brown clay to silt-sized sediments with shell fragments (4 m thick), 4) purplish clay to sand-sized sediments (1 m thick), 5) greyish clay to sand-sized sediments (2 m thick), 6) reddish brown lateritic soil with pale pink and white spots of weathering soil (3 m thick), and 7) yellowish grey clay to silt-sized sediments (5 m thick), respectively (Fig. 2).

The Bangkok clay layer at the clay pit of Ongkharak has yielded nearly *in situ* fossil deposits as indicated by preservation of complete shells with both valves attached (Fig. 2C) as well as the orientation of shell valves of *Pholas orientalis*, which has been recovered in natural position within its burrows during field collection (see also Songtham et al. 2007: fig. 3). Although remains of marine molluscs were found throughout the sequence of dark clay deposits, they were most abundant in the middle part of the layer (Fig. 2D–F), at a depth of ~ 2 m below the upper contact that separates it from the topsoil. Numerous wood fragments, plant remains, and giant oyster shells were found from the lower part of the dark clay unit below the shell-rich layer.

## Materials and methods

Species identification of specimens is mainly based on the existing literature specified under the treatment of each taxon. The specimens are kept at the Department of Geology, Faculty of Science, Chulalongkorn University, and coded as the name of the collection (CUF: Chulalongkorn fossil collection), followed by the locality (NKNY: Nakhon Nayok) and the catalogue number. Fish remains including teeth and otolith as well as some small shells were photographed with a scanning electron microscope (SEM; JEOL, JSM-5410 LV) or a Leica M205C stereo light microscope with fusion optics and the Leica Application Suite Image System. L and R designate left and right valves of bivalve shells, respectively.

We selected six samples (shells and charcoal) collected from the marine clay deposits at different depths in the clay pit for carbon-14 dating (Table 1). The samples were pretreated and analysed at the DirectAMS (USA), using an accelerated mass spectrometer (AMS). According to the convention outlined by Stuiver and Polach (1977), the ¹⁴C age ± one standard deviation (SD) was calculated using the Libby half-life of 5,568 years and an isotopic fractionation correction based on δ¹³C measurements obtained from the AMS. The Direct-AMS results were calibrated and corrected for the marine reservoir effect, using the Calib 8.2 program with IntCal20.14c for charcoal (Reimer et al. 2020) and with Marine20 (Heaton et al. 2020) for shells.

<table><caption>Table 1. AMS ¹⁴C ages of shells and charcoal collected from the clay pit of Ongkharak in Nakhon Nayok, central Thailand.</caption><thead><tr><td>Lab Code</td><td>Sample type</td><td>Depths (m) below the uppermost part of a marine clay layer</td><td>¹⁴C age (yr BP)</td><td>Calibrated ¹⁴C (2-sigma) age (cal yr BP)</td></tr></thead><tbody><tr><td>D-AMS 044190</td><td>Shell (Tellinides conspicuus)</td><td>2.2</td><td>5303 ± 26</td><td>5882–5464</td></tr><tr><td>D-AMS 044191</td><td>Shell (Pholas orientalis)</td><td>2.2</td><td>5202 ± 28</td><td>5757–5318</td></tr><tr><td>D-AMS 044193</td><td>Charcoal</td><td>2.2</td><td>5047 ± 26</td><td>5899–5726</td></tr><tr><td>D-AMS 044195</td><td>Charcoal</td><td>3.4</td><td>6186 ± 29</td><td>7166–6983</td></tr><tr><td>D-AMS 044194</td><td>Shell (Magallana cf. gigas)</td><td>4</td><td>7241 ± 32</td><td>7901–7510</td></tr><tr><td>D-AMS 044192</td><td>Charcoal</td><td>4.6</td><td>7913 ± 26</td><td>8784–8600</td></tr></tbody></table>
## Results

The ages of the Bangkok Clay deposits in the clay pit of Ongkharak range from 8,784 calibrated years before the present (cal yr BP) to 5,318 cal yr BP (mid-Holocene) based on the radiocarbon dating of several shell and charcoal fragments collected along the stratigraphic section of the layer (Table 1). The majority of marine faunas are molluscs, where a total of 63 species were identified, including 35 gastropod species from 20 families, 27 bivalve species from 15 families, and one scaphopod species. The most common gastropods are *Architectonica perdix*, *Natica stellata*, and *Indothais lacera*, whereas the most common bivalves are *Corbula fortisulcata*, *Magallana cf. gigas*, and *Joannisella oblonga*. Other invertebrate remains include one species of stony corals (*Oulangia cf. stokesiana*), one unidentified species of mud lobsters (*Thalassina sp*.), two species of barnacles (*Fistulobalanus kondakovi* and *Megabalanus cf. tintinnabulum*), and one species of sea urchins (*Temnotrema siamense*).

The vertebrate remains include at least nine species (two families) of chondrichthyan fishes and at least two species (two families) of actinopterygian taxa. Altogether, 100 cartilaginous fish fossils were recovered, including 97 remains identified as belonging to the family Carcharhinidae and three to the family Dasyatidae. The teeth of the latter belong to the stingray genus *Pastinachus*. Among the carcharhinids, the genus *Glyphis* dominates the shark fauna (61%). There are also at least six species of *Carcharhinus*, representing 26% of the shark fauna. The accurate identification of *Carcharhinus* species is often hindered by the preservation of teeth or by the morphological similarities of tooth positions among these taxa. A few teeth among the carcharhinids belong to the genus *Scoliodon*. Few actinopterygian remains were also found, including three teeth that belong to the family Trichiuridae and one sciaenid otolith that represents the genus *Johnius*.

## Systematic palaeontology

**Phylum Cnidaria**

**Class Anthozoa Ehrenberg, 1834**

**Subclass Hexacorallia Haeckel, 1896**

**Order Scleractinia Bourne, 1900**

**Family Rhizangiidae d'Orbigny, 1851**

**Oulangia Milne Edwards & Haime, 1848**

**Oulangia cf. stokesiana Milne Edwards & Haime, 1848**

Figs 3A, 5A

cf. *Oulangia stokesiana* Milne Edwards & Haime, 1848: pl. 7, fig. 4, 4a. Type locality: Philippines. Milne Edwards and Haime 1849: 183. Lam et al. 2008: 742, fig. 4e.

cf. *Oulangia stokesiana stokesiana*. Cairns et al. 1999: 39.

**Referred material.** CUF-NKNY-007 (1 specimen; Figs 3A, 5A).

**Habitat.** Shallow waters as well as in submarine caves (Lam et al. 2008).
## Results

The ages of the Bangkok Clay deposits in the clay pit of Ongkharak range from 8,784 calibrated years before the present (cal yr BP) to 5,318 cal yr BP (mid-Holocene) based on the radiocarbon dating of several shell and charcoal fragments collected along the stratigraphic section of the layer (Table 1). The majority of marine faunas are molluscs, where a total of 63 species were identified, including 35 gastropod species from 20 families, 27 bivalve species from 15 families, and one scaphopod species. The most common gastropods are *Architectonica perdix*, *Natica stellata*, and *Indothais lacera*, whereas the most common bivalves are *Corbula fortisulcata*, *Magallana cf. gigas*, and *Joannisella oblonga*. Other invertebrate remains include one species of stony corals (*Oulangia cf. stokesiana*), one unidentified species of mud lobsters (*Thalassina sp*.), two species of barnacles (*Fistulobalanus kondakovi* and *Megabalanus cf. tintinnabulum*), and one species of sea urchins (*Temnotrema siamense*).

The vertebrate remains include at least nine species (two families) of chondrichthyan fishes and at least two species (two families) of actinopterygian taxa. Altogether, 100 cartilaginous fish fossils were recovered, including 97 remains identified as belonging to the family Carcharhinidae and three to the family Dasyatidae. The teeth of the latter belong to the stingray genus *Pastinachus*. Among the carcharhinids, the genus *Glyphis* dominates the shark fauna (61%). There are also at least six species of *Carcharhinus*, representing 26% of the shark fauna. The accurate identification of *Carcharhinus* species is often hindered by the preservation of teeth or by the morphological similarities of tooth positions among these taxa. A few teeth among the carcharhinids belong to the genus *Scoliodon*. Few actinopterygian remains were also found, including three teeth that belong to the family Trichiuridae and one sciaenid otolith that represents the genus *Johnius*.

## Systematic palaeontology

**Phylum Cnidaria**

**Class Anthozoa Ehrenberg, 1834**

**Subclass Hexacorallia Haeckel, 1896**

**Order Scleractinia Bourne, 1900**

**Family Rhizangiidae d'Orbigny, 1851**

**Oulangia Milne Edwards & Haime, 1848**

**Oulangia cf. stokesiana Milne Edwards & Haime, 1848**

Figs 3A, 5A

cf. *Oulangia stokesiana* Milne Edwards & Haime, 1848: pl. 7, fig. 4, 4a. Type locality: Philippines. Milne Edwards and Haime 1849: 183. Lam et al. 2008: 742, fig. 4e.

cf. *Oulangia stokesiana stokesiana*. Cairns et al. 1999: 39.

**Referred material.** CUF-NKNY-007 (1 specimen; Figs 3A, 5A).

**Habitat.** Shallow waters as well as in submarine caves (Lam et al. 2008).
**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to the Philippines, and central Pacific (Cairns et al. 1999; Lam et al. 2008).

**Taxonomic remarks and comparisons.** This specimen is classified into the genus *Oulangia* based on the descriptions and figures of Cairns and Kitahara (2012) and Baron-Szabo and Cairns (2016). We tentatively identify this specimen as belonging to *O. stokesiana* according to Lam et al. (2008).

**Phylum Mollusca**

**Class Gastropoda Cuvier, 1795**

**Subclass Vetigastropoda Salvini-Plawen, 1980**

**Order Trochida Cox & Knight, 1960**

**Superfamily Trochoidea Rafinesque, 1815**

**Family Colloniidae Cossmann, 1917**

**Homalopoma Carpenter, 1864**

**Homalopoma cf. sangarense (Schrenck, 1861)**

Figs 3F, 5B

cf. *Turbo sangarensis* Schrenck, 1861: 409–410. Type locality: the Sangaric strait near the shore of the island of Jesso [Sangar (Tsugaru) Strait, Hako-date Bay, Hokkaido, Japan].

cf. *Homalopoma sangarense*. Habe 1958: 5, pl. 2, fig. 1. Golikov and Kussakin 1978: 65–66, fig. 40a, b. Egorov 2000: 66, with in-text fig. Kantor and Sysoev 2006: 42, pl. 18h. Lebedev 2014: 57.

**Referred material.** CUF-NKNY-G24 (1 shell; Figs 3F, 5B).

**Habitat.** On silty-sandy or rarely on rocky substrates at a depth from 2 to 22 m (Egorov 2000; Kantor and Sysoev 2006).

**Distribution.** Sea of Japan and southern Kuril Islands (Kantor and Sysoev 2006; Lebedev 2014).

**Record in Thailand.** This is the first record of this species in Thailand.

**Taxonomic remarks and comparisons.** Although there is only one incomplete specimen, it is tentatively identified as *H. sangarense* based on shell size and shape and several strong spiral cords on the surface as in the descriptions and figures in Habe (1958), Golikov and Kussakin (1978), and Egorov (2000).

**Subclass Neritimorpha Golikov & Starobogatov, 1975**

**Order Cycloneritida Frýda, 1998**

**Superfamily Neritoidea Rafinesque, 1815**

**Family Neritidae Rafinesque, 1815**

**Neripteron Lesson, 1831**

**Neripteron violaceum (Gmelin, 1791)**

Figs 3B, 5C

**Nerita violacea** Gmelin, 1791: 3686. Type locality: unknown.

**Neritina violacea.** Tantanasiriwong 1978: 6, fig. 52. Nateewathana et al. 1981: 56. Wilson 1993: 41, pl. 2, figs 18a, b, 19a–d. Hylleberg and Kilburn 2003: 31.
**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to the Philippines, and central Pacific (Cairns et al. 1999; Lam et al. 2008).

**Taxonomic remarks and comparisons.** This specimen is classified into the genus *Oulangia* based on the descriptions and figures of Cairns and Kitahara (2012) and Baron-Szabo and Cairns (2016). We tentatively identify this specimen as belonging to *O. stokesiana* according to Lam et al. (2008).

**Phylum Mollusca**

**Class Gastropoda Cuvier, 1795**

**Subclass Vetigastropoda Salvini-Plawen, 1980**

**Order Trochida Cox & Knight, 1960**

**Superfamily Trochoidea Rafinesque, 1815**

**Family Colloniidae Cossmann, 1917**

**Homalopoma Carpenter, 1864**

**Homalopoma cf. sangarense (Schrenck, 1861)**

Figs 3F, 5B

cf. *Turbo sangarensis* Schrenck, 1861: 409–410. Type locality: the Sangaric strait near the shore of the island of Jesso [Sangar (Tsugaru) Strait, Hako-date Bay, Hokkaido, Japan].

cf. *Homalopoma sangarense*. Habe 1958: 5, pl. 2, fig. 1. Golikov and Kussakin 1978: 65–66, fig. 40a, b. Egorov 2000: 66, with in-text fig. Kantor and Sysoev 2006: 42, pl. 18h. Lebedev 2014: 57.

**Referred material.** CUF-NKNY-G24 (1 shell; Figs 3F, 5B).

**Habitat.** On silty-sandy or rarely on rocky substrates at a depth from 2 to 22 m (Egorov 2000; Kantor and Sysoev 2006).

**Distribution.** Sea of Japan and southern Kuril Islands (Kantor and Sysoev 2006; Lebedev 2014).

**Record in Thailand.** This is the first record of this species in Thailand.

**Taxonomic remarks and comparisons.** Although there is only one incomplete specimen, it is tentatively identified as *H. sangarense* based on shell size and shape and several strong spiral cords on the surface as in the descriptions and figures in Habe (1958), Golikov and Kussakin (1978), and Egorov (2000).

**Subclass Neritimorpha Golikov & Starobogatov, 1975**

**Order Cycloneritida Frýda, 1998**

**Superfamily Neritoidea Rafinesque, 1815**

**Family Neritidae Rafinesque, 1815**

**Neripteron Lesson, 1831**

**Neripteron violaceum (Gmelin, 1791)**

Figs 3B, 5C

**Nerita violacea** Gmelin, 1791: 3686. Type locality: unknown.

**Neritina violacea.** Tantanasiriwong 1978: 6, fig. 52. Nateewathana et al. 1981: 56. Wilson 1993: 41, pl. 2, figs 18a, b, 19a–d. Hylleberg and Kilburn 2003: 31.
Robba et al. 2004: 24–25, pl. 2, fig. 5a, b. Robba et al. 2007: 89 (appendix).
Printrakoon et al. 2008: table 1. Tan and Clements 2008: 490–491, fig. 3-33, 3-34. Nabhitabhata 2009: 39. Sanpanich and Duangdee 2013: 53. Ng et al. 2016: fig. 1-28. Yang et al. 2017: 20, fig. 75. Tudu et al. 2018: table 1.

*Dostia violacea*. Way and Purchon 1981: 314. Subba Rao and Dey 2000: 35. Sri-aroon et al. 2004: table 1, fig. 2-1. Dechruksa et al. 2014: fig. 2k.

*Neripteron violacea*. Swennen et al. 2001: 52, 108, text-fig. 275, fig. 275.

*Neritina (Dostia) violacea*. Gemert 2003: 103. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Dey 2006: 22, figs 11, 12. Ramakrishna et al. 2007: 5, 37. Kesavan et al. 2009: 382, with in-text fig. Eichhorst 2016: 392–395, pl. 102, figs 1–15.

*Neritina (Neripteron) violacea*. Thach 2005: 38, pl. 6, figs 8, 9.

*Neripteron violaceus*. Eichhorst 2008: 268, pl. 79, fig. 7a, b.

*Neripteron violaceum*. Baharuddin et al. 2017: fig. 3o. BEDO 2017b: 97, with in-text fig. Kantharajan et al. 2017: table 1, fig. 4-34. Yadav et al. 2019: table 2, fig. 1h. Mustapha et al. 2021: 52–53, figs 3e, f, 4i. Wells et al. 2021: 154–155.

**Referred material.** CUF-NKNY-G26 (28 shells; Figs 3B, 5C).

**Habitat.** On Nipa palms, muddy surfaces, old wood and rocks in brackish habitats and mangrove forests (Swennen et al. 2001; Mustapha et al. 2021) as well as on gravels in high tidal zones (Yang et al. 2017).

**Distribution.** India (Kantharajan et al. 2017; Yadav et al. 2019); Indo-West Pacific, from Japan to Australia (Wilson 1993; Yang et al. 2017).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** The shell of *N. violaceum* is highly similar to that of *N. cornucopia* (Benson, 1836) but differs in having a purple to orangish red ventral side, and denticulations along the columellar edge often only present in the central part (Huang 1997; Tan and Clements 2008). Although the columella edge of the specimens is corroded, there are still some traces of purple colour at the ventral side. Therefore, these specimens are identified as belonging to *N. violaceum*.

**Nerita Linnaeus, 1758**

**Nerita articulata Gould, 1847**

Figs 3C, 5D

*Nerita lineata* Gmelin, 1791: 3684 [junior homonym of *Nerita lineata* Müller, 1774]. Type locality: Strait of Malacca. Way and Purchon 1981: 314. Hylleberg and Kilburn 2003: 29–30. Yang et al. 2017: 20, fig. 67.

*Nerita (Ritena) lineata*. Cernohorsky 1972: 51, pl. 11, fig. 5.

*Nerita articulata* Gould, 1847: 220. Type locality: Tavoy. Wium-Andersen 1977: 5, fig. 8. Tantanasiriwong 1978: 6, fig. 42. Nateewathana et al. 1981: 56. Tan and Clements 2008: 483–485, fig. 2-3, 2-4. Nabhitabhata 2009: 36. Hamli et al. 2013: tables 2, 3, fig. 2g. Tudu et al. 2018: table 1.

*Nerita balteata* Reeve, 1855: pl. 6, fig. 28. Type locality: unknown. Wilson 1993: 40, pl. 2, fig. 9a, b. Nateewathana 1995: 95, with in-text fig. Nabhitabhata 2009: 36. Sanpanich and Duangdee 2013: 53. Chen et al. 2015: 75, fig. 1a-c. BEDO 2017b: 99, with in-text fig. Kantharajan et al. 2017: table 1, fig. 4-36. Tudu et al. 2018: table 1. Raven 2019: figs 4–6. Yadav et al. 2019: table 2, fig. 1i. Mustapha et al. 2021: 48, figs 2m, n, 4g. Wells et al. 2021: 155.
Robba et al. 2004: 24–25, pl. 2, fig. 5a, b. Robba et al. 2007: 89 (appendix).

Printrakoon et al. 2008: table 1. Tan and Clements 2008: 490–491, fig. 3-33, 3-34. Nabhitabhata 2009: 39. Sanpanich and Duangdee 2013: 53. Ng et al. 2016: fig. 1-28. Yang et al. 2017: 20, fig. 75. Tudu et al. 2018: table 1.

*Dostia violacea*. Way and Purchon 1981: 314. Subba Rao and Dey 2000: 35. Sri-aroon et al. 2004: table 1, fig. 2-1. Dechruksa et al. 2014: fig. 2k.

*Neripteron violacea*. Swennen et al. 2001: 52, 108, text-fig. 275, fig. 275.

*Neritina (Dostia) violacea*. Gemert 2003: 103. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Dey 2006: 22, figs 11, 12. Ramakrishna et al. 2007: 5, 37. Kesavan et al. 2009: 382, with in-text fig. Eichhorst 2016: 392–395, pl. 102, figs 1–15.

*Neritina (Neripteron) violacea*. Thach 2005: 38, pl. 6, figs 8, 9.

*Neripteron violaceus*. Eichhorst 2008: 268, pl. 79, fig. 7a, b.

*Neripteron violaceum*. Baharuddin et al. 2017: fig. 3o. BEDO 2017b: 97, with in-text fig. Kantharajan et al. 2017: table 1, fig. 4-34. Yadav et al. 2019: table 2, fig. 1h. Mustapha et al. 2021: 52–53, figs 3e, f, 4i. Wells et al. 2021: 154–155.

**Referred material.** CUF-NKNY-G26 (28 shells; Figs 3B, 5C).

**Habitat.** On Nipa palms, muddy surfaces, old wood and rocks in brackish habitats and mangrove forests (Swennen et al. 2001; Mustapha et al. 2021) as well as on gravels in high tidal zones (Yang et al. 2017).

**Distribution.** India (Kantharajan et al. 2017; Yadav et al. 2019); Indo-West Pacific, from Japan to Australia (Wilson 1993; Yang et al. 2017).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** The shell of *N. violaceum* is highly similar to that of *N. cornucopia* (Benson, 1836) but differs in having a purple to orangish red ventral side, and denticulations along the columellar edge often only present in the central part (Huang 1997; Tan and Clements 2008). Although the columella edge of the specimens is corroded, there are still some traces of purple colour at the ventral side. Therefore, these specimens are identified as belonging to *N. violaceum*.

**Nerita Linnaeus, 1758**

**Nerita articulata Gould, 1847**

Figs 3C, 5D

*Nerita lineata* Gmelin, 1791: 3684 [junior homonym of *Nerita lineata* Müller, 1774]. Type locality: Strait of Malacca. Way and Purchon 1981: 314. Hylleberg and Kilburn 2003: 29–30. Yang et al. 2017: 20, fig. 67.

*Nerita (Ritena) lineata*. Cernohorsky 1972: 51, pl. 11, fig. 5.

*Nerita articulata* Gould, 1847: 220. Type locality: Tavoy. Wium-Andersen 1977: 5, fig. 8. Tantanasiriwong 1978: 6, fig. 42. Nateewathana et al. 1981: 56. Tan and Clements 2008: 483–485, fig. 2-3, 2-4. Nabhitabhata 2009: 36. Hamli et al. 2013: tables 2, 3, fig. 2g. Tudu et al. 2018: table 1.

*Nerita balteata* Reeve, 1855: pl. 6, fig. 28. Type locality: unknown. Wilson 1993: 40, pl. 2, fig. 9a, b. Nateewathana 1995: 95, with in-text fig. Nabhitabhata 2009: 36. Sanpanich and Duangdee 2013: 53. Chen et al. 2015: 75, fig. 1a-c. BEDO 2017b: 99, with in-text fig. Kantharajan et al. 2017: table 1, fig. 4-36. Tudu et al. 2018: table 1. Raven 2019: figs 4–6. Yadav et al. 2019: table 2, fig. 1i. Mustapha et al. 2021: 48, figs 2m, n, 4g. Wells et al. 2021: 155.
<figure><img src="image_3.png" /><figcaption>**Figure 3.** Size comparison of coral and gastropods found in this study **A** *Oulangia* cf. *stokesiana* **B** *Neripteron violaceum* **C** *Nerita articulata* **D** *Natica stellata* **E** *Natica vitellus* **F** *Homalopoma* cf. *sangarense* **G** *Eunaticina papilla* **H** *Ergaea walshi* **I** *Pirenella incisa* **J** *Scalptia scalariformis* **K** *Telescopium telescopium* **L** *Merica elegans* **M** *Cerithidea obtusa* **N** *Bufonaria rana* **O** *Nassarius micans* **P** *Nassarius siquijorensis* **Q** *Paratectonatica tigrina*.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 3.** Size comparison of coral and gastropods found in this study **A** *Oulangia* cf. *stokesiana* **B** *Neripteron violaceum* **C** *Nerita articulata* **D** *Natica stellata* **E** *Natica vitellus* **F** *Homalopoma* cf. *sangarense* **G** *Eunaticina papilla* **H** *Ergaea walshi* **I** *Pirenella incisa* **J** *Scalptia scalariformis* **K** *Telescopium telescopium* **L** *Merica elegans* **M** *Cerithidea obtusa* **N** *Bufonaria rana* **O** *Nassarius micans* **P** *Nassarius siquijorensis* **Q** *Paratectonatica tigrina*.</figcaption></figure>
*Nerita (Ritena) balteata*. Cernohorsky 1978: 42, pl. 11, fig. 1. Dharma 2005: 68, pl. 9, fig. 3a, b.

*Nerita (Amphinerita) articulata*. Subba Rao and Dey 2000: 31. Dey 2006: 20, figs 7, 8.

*Nerita (Nerita) articulata*. Sri-aroon et al. 2004: table 1.

*Nerita (Theliostyla) balteata*. Thach 2005: 37, pl. 6, figs 36, 37.

*Nerita balteata* forma *articulata*. Eichhorst 2008: 280, pl. 85, fig. 1a, b.

*Nerita (Cymostyla) balteata*. Eichhorst 2016: 455–457, pl. 113, figs 1–9.

**Referred material.** CUF-NKNY-G61 (3 shells; Figs 3C, 5D).

**Habitat.** On tree trunks, branches, roots and on muddy banks and rocky areas or near mangrove forests (Tan and Clements 2008; Mustapha et al. 2021) as well as on rocks in intertidal zones (Yang et al. 2017).

**Distribution.** India (Kantharajan et al. 2017; Yadav et al. 2019); Indo-West Pacific, from China to Australia (Wilson 1993; Yang et al. 2017). Also reported from the Hawaiian Islands (Cernohorsky 1978).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by numerous raised spiral cords and a crenulated outer lip (Tan and Clements 2008). Although this species is widely known as *N. balteata* Reeve, 1855, the name *N. articulata* was made available earlier by Gould (1847). Thus, it has a priority over *N. balteata*.

**Subclass Caenogastropoda Cox, 1960**

**Cohort Sorbeoconcha Ponder & Lindberg, 1997**

**Subcohort Cerithiimorpha Golikov & Starobogatov, 1975**

**Superfamily Cerithioidea Fleming, 1822**

**Family Potamididae H. Adams & A. Adams, 1854**

**Cerithidea Swainson, 1840**

**Cerithidea obtusa** (Lamarck, 1822)

Figs 3M, 5E

*Cerithium obtusum* Lamarck, 1822: 71. Type locality: Timor.

*Cerithidea obtusa*. Cernohorsky 1972: 60 (in part). Tantanasiriwong 1978: 7, fig. 70. Nateewathana et al. 1981: 57. Way and Purchon 1981: 315. Nateewathana 1995: 97, with in-text fig. Poutiers 1998b: 450, with in-text figs. Gemert 2003: 104. Hylleberg and Kilburn 2003: 37–38. Robba et al. 2004: 31–32, pl. 3, fig. 4a, b. Dharma 2005: 92, pl. 21, fig. 8; 308, pl. 119, fig. 8a, b. Thach 2005: 49, pl. 10, fig. 4. Dey 2006: 35–36, figs 38–40. Robba et al. 2007: 89 (appendix). Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Hamli et al. 2013: tables 2, 3, fig. 2a. Dechruksa et al. 2014: fig. 2f. Reid 2014: 27–29, 31, figs 2b, 8, 9. BEDO 2017b: 26, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 125–126.

*Cerithidea (Cerithidea) obtusa*. Brandt 1974: 192–193, pl. 14, fig. 52. Houbrick 1984: 15–16, fig. 5c. Sri-aroon et al. 2004: table 1, fig. 3-1. Sri-aroon et al. 2005: tables 2–6. Ramakrishna et al. 2007: 6, 47. Nabhitabhata 2009: 95.

**Referred material.** CUF-NKNY-G14 (23 shells; Figs 3M, 5E).
*Nerita (Ritena) balteata*. Cernohorsky 1978: 42, pl. 11, fig. 1. Dharma 2005: 68, pl. 9, fig. 3a, b.

*Nerita (Amphinerita) articulata*. Subba Rao and Dey 2000: 31. Dey 2006: 20, figs 7, 8.

*Nerita (Nerita) articulata*. Sri-aroon et al. 2004: table 1.

*Nerita (Theliostyla) balteata*. Thach 2005: 37, pl. 6, figs 36, 37.

*Nerita balteata* forma *articulata*. Eichhorst 2008: 280, pl. 85, fig. 1a, b.

*Nerita (Cymostyla) balteata*. Eichhorst 2016: 455–457, pl. 113, figs 1–9.

**Referred material.** CUF-NKNY-G61 (3 shells; Figs 3C, 5D).

**Habitat.** On tree trunks, branches, roots and on muddy banks and rocky areas or near mangrove forests (Tan and Clements 2008; Mustapha et al. 2021) as well as on rocks in intertidal zones (Yang et al. 2017).

**Distribution.** India (Kantharajan et al. 2017; Yadav et al. 2019); Indo-West Pacific, from China to Australia (Wilson 1993; Yang et al. 2017). Also reported from the Hawaiian Islands (Cernohorsky 1978).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by numerous raised spiral cords and a crenulated outer lip (Tan and Clements 2008). Although this species is widely known as *N. balteata* Reeve, 1855, the name *N. articulata* was made available earlier by Gould (1847). Thus, it has a priority over *N. balteata*.

**Subclass Caenogastropoda Cox, 1960**

**Cohort Sorbeoconcha Ponder & Lindberg, 1997**

**Subcohort Cerithiimorpha Golikov & Starobogatov, 1975**

**Superfamily Cerithioidea Fleming, 1822**

**Family Potamididae H. Adams & A. Adams, 1854**

**Cerithidea Swainson, 1840**

**Cerithidea obtusa** (Lamarck, 1822)

Figs 3M, 5E

*Cerithium obtusum* Lamarck, 1822: 71. Type locality: Timor.

*Cerithidea obtusa*. Cernohorsky 1972: 60 (in part). Tantanasiriwong 1978: 7, fig. 70. Nateewathana et al. 1981: 57. Way and Purchon 1981: 315. Nateewathana 1995: 97, with in-text fig. Poutiers 1998b: 450, with in-text figs. Gemert 2003: 104. Hylleberg and Kilburn 2003: 37–38. Robba et al. 2004: 31–32, pl. 3, fig. 4a, b. Dharma 2005: 92, pl. 21, fig. 8; 308, pl. 119, fig. 8a, b. Thach 2005: 49, pl. 10, fig. 4. Dey 2006: 35–36, figs 38–40. Robba et al. 2007: 89 (appendix). Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Hamli et al. 2013: tables 2, 3, fig. 2a. Dechruksa et al. 2014: fig. 2f. Reid 2014: 27–29, 31, figs 2b, 8, 9. BEDO 2017b: 26, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 125–126.

*Cerithidea (Cerithidea) obtusa*. Brandt 1974: 192–193, pl. 14, fig. 52. Houbrick 1984: 15–16, fig. 5c. Sri-aroon et al. 2004: table 1, fig. 3-1. Sri-aroon et al. 2005: tables 2–6. Ramakrishna et al. 2007: 6, 47. Nabhitabhata 2009: 95.

**Referred material.** CUF-NKNY-G14 (23 shells; Figs 3M, 5E).
<figure><img src="image_4.png" /><figcaption>**Figure 4.** Size comparison of gastropods found in this study. **A** *Brunneifusus ternatanus*; **B** *Murex trapa*; **C** *Indothais lacera*; **D** *Pristiterebra miranda*; **E** *Chicoreus capucinus*; **F** *Indothais gradata*; **G** *Ellobium aurisjudae*; **H** *Inquisitor vulpionis*; **I** *Turricula javana*; **J** *Architectonica perdix*; **K** *Pseudoneptunea varicosa*; **L** *Cassidula nucleus*; **M** *Pseudoetrema fortilirata*; **N** *Paradrillia melvilli*; **O** *Duplicaria tricincta*; **P** *Granuliterebra bathyrhaphe*; **Q** *Comitas ilariae*; **R** *Cylichna modesta*; **S** *Maoritomella vallata*.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 4.** Size comparison of gastropods found in this study. **A** *Brunneifusus ternatanus* | **B** *Murex trapa* | **C** *Indothais lacera* | **D** *Pristiterebra miranda* | **E** *Chicoreus capucinus* | **F** *Indothais gradata* | **G** *Ellobium aurisjudae* | **H** *Inquisitor vulpionis* | **I** *Turricula javana* | **J** *Architectonica perdix* | **K** *Pseudoneptunea varicosa* | **L** *Cassidula nucleus* | **M** *Pseudoetrema fortilirata* | **N** *Paradrillia melvilli* | **O** *Duplicaria tricincta* | **P** *Granuliterebra bathyrhaphe* | **Q** *Comitas ilariae* | **R** *Cylichna modesta* | **S** *Maoritomella vallata*.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 5.** Coral and gastropods A Oulangia cf. stokesiana B Homalopoma cf. sangarense C Neripteron violaceum D Nerita articulata E Cerithidea obtusa F Pirenella incisa G Telescopium telescopium.</figcaption></figure>

**Habitat.** On firm mud and on trunks and stilt roots in mangrove forests as well as in fully marine and estuarine areas (Reid 2014).

**Distribution.** Bay of Bengal; Indo-West Pacific, from southern Vietnam to Java and East Borneo (Reid 2014). Records of fossils from the Late Pliocene in Central and West Java, Indonesia, and from the Holocene in Thailand (Robba et al. 2004; Dharma 2005).
<figure><img src="image_6.png" /><figcaption>**Figure 5.** Coral and gastropods A Oulangia cf. stokesiana B Homalopoma cf. sangarense C Neripteron violaceum D Nerita articulata E Cerithidea obtusa F Pirenella incisa G Telescopium telescopium.</figcaption></figure>

**Habitat.** On firm mud and on trunks and stilt roots in mangrove forests as well as in fully marine and estuarine areas (Reid 2014).

**Distribution.** Bay of Bengal; Indo-West Pacific, from southern Vietnam to Java and East Borneo (Reid 2014). Records of fossils from the Late Pliocene in Central and West Java, Indonesia, and from the Holocene in Thailand (Robba et al. 2004; Dharma 2005).
**Record in Thailand.** Chanthaburi River, Gulf of Thailand and Andaman Sea (Nabhitabhata 2009; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species has a more thickened and flared aperture compared to two similar species, *Cerithidea anticipata*IREDALE, 1929 and *C. reidi* Houbrick, 1986. These two species are also common in Sahul (New Guinea and Australia), whereas *C. obtusa* is present in Sunda (Reid 2014). See also comprehensive taxonomic remarks in Reid (2014).

**Pirenella Gray, 1847**

**Pirenella incisa (Hombron & Jacquinot, 1848)**

Figs 3I, 5F

*Cerithium incisum* Hombron & Jacquinot, 1848: 97, pl. 23, figs 8, 9. Type locality: Borneo.

*Cerithidea (Cerithideopsilla) djadjariensis* [non Martin]. Sri-aroon et al. 2004: table 1, fig. 2-7.

*Cerithideopsilla djadjariensis* [non Martin]. Lozouet 2008: 284, pl. 87, fig. 9; pl. 88, fig. 2.

*Pirenella incisa*. Reid and Ozawa 2016: 30–32, figs 1, 2g, h, 4i, 10, 11a. Zvonareva and Kantor 2016: 415, fig. 5a–d. BEDO 2017b: 28, with in-text fig. Wells et al. 2021: 126.

**Referred material.** CUF-NKNY-G10 (47 shells; Figs 3I, 5F).

**Habitat.** On damp mud in mangrove forests. Also found on open surface areas of intertidal mudflats and on muddy shores of shrimp ponds (Reid and Ozawa 2016; Zvonareva and Kantor 2016).

**Distribution.** East India; Indo-West Pacific, from southern China, the Philippines to West Sulawesi, and Flores Island (Reid and Ozawa 2016).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from the other two similar species, *Pirenella pupiformis* Ozawa & Reid, 2016 and *P. caiyingyai* (Qian, Fang & He, 2013), by the presence of an almost columnar appearance, a more oblique and more flared aperture with the projection of a lip next to a deep anterior canal, and three equal cords on each spire whorl with strong square nodules on axial ribs (Reid and Ozawa 2016). See comprehensive taxonomic remarks in Reid and Ozawa (2016).

**Telescopium Montfort, 1810**

**Telescopium telescopium (Linnaeus, 1758)**

Figs 3K, 5G

*Trochus telescopium* Linnaeus, 1758: 760. Type locality: unknown.

*Telescopium telescopium*. Tesch 1920: 58–59, pl. 132, fig. 191. Cernohorsky 1972: 61, pl. 13, fig. 6. Brandt 1974: 196, pl. 15, fig. 61. Tantanasiriwong 1978: 7, fig. 69. Nateewathana et al. 1981: 57. Way and Purchon 1981: 315. Houbrick 1991: 291–304, figs 1–6. Wilson 1993: 133, pl. 15, fig. 21. Bosch et al. 1995: 56–57, fig. 186. Nateewathana 1995: 97–98, with in-text fig. Pout-
**Record in Thailand.** Chanthaburi River, Gulf of Thailand and Andaman Sea (Nabhitabhata 2009; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species has a more thickened and flared aperture compared to two similar species, *Cerithidea anticipata*IREDALE, 1929 and *C. reidi* Houbrick, 1986. These two species are also common in Sahul (New Guinea and Australia), whereas *C. obtusa* is present in Sunda (Reid 2014). See also comprehensive taxonomic remarks in Reid (2014).

**Pirenella Gray, 1847**

**Pirenella incisa (Hombron & Jacquinot, 1848)**

Figs 3I, 5F

*Cerithium incisum* Hombron & Jacquinot, 1848: 97, pl. 23, figs 8, 9. Type locality: Borneo.

*Cerithidea (Cerithideopsilla) djadjariensis* [non Martin]. Sri-aroon et al. 2004: table 1, fig. 2-7.

*Cerithideopsilla djadjariensis* [non Martin]. Lozouet 2008: 284, pl. 87, fig. 9; pl. 88, fig. 2.

*Pirenella incisa*. Reid and Ozawa 2016: 30–32, figs 1, 2g, h, 4i, 10, 11a. Zvonareva and Kantor 2016: 415, fig. 5a–d. BEDO 2017b: 28, with in-text fig. Wells et al. 2021: 126.

**Referred material.** CUF-NKNY-G10 (47 shells; Figs 3I, 5F).

**Habitat.** On damp mud in mangrove forests. Also found on open surface areas of intertidal mudflats and on muddy shores of shrimp ponds (Reid and Ozawa 2016; Zvonareva and Kantor 2016).

**Distribution.** East India; Indo-West Pacific, from southern China, the Philippines to West Sulawesi, and Flores Island (Reid and Ozawa 2016).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from the other two similar species, *Pirenella pupiformis* Ozawa & Reid, 2016 and *P. caiyingyai* (Qian, Fang & He, 2013), by the presence of an almost columnar appearance, a more oblique and more flared aperture with the projection of a lip next to a deep anterior canal, and three equal cords on each spire whorl with strong square nodules on axial ribs (Reid and Ozawa 2016). See comprehensive taxonomic remarks in Reid and Ozawa (2016).

**Telescopium Montfort, 1810**

**Telescopium telescopium (Linnaeus, 1758)**

Figs 3K, 5G

*Trochus telescopium* Linnaeus, 1758: 760. Type locality: unknown.

*Telescopium telescopium*. Tesch 1920: 58–59, pl. 132, fig. 191. Cernohorsky 1972: 61, pl. 13, fig. 6. Brandt 1974: 196, pl. 15, fig. 61. Tantanasiriwong 1978: 7, fig. 69. Nateewathana et al. 1981: 57. Way and Purchon 1981: 315. Houbrick 1991: 291–304, figs 1–6. Wilson 1993: 133, pl. 15, fig. 21. Bosch et al. 1995: 56–57, fig. 186. Nateewathana 1995: 97–98, with in-text fig. Pout-
iers 1998b: 451, with in-text figs. Subba Rao and Dey 2000: 53. Swennen et al. 2001: 52, 111–112, with in-text fig., fig. 295. Hylleberg and Kilburn 2003: 38. Sri-aroon et al. 2004: table 1, fig. 3-3. Dharma 2005: 92, pl. 21, fig. 1; 308, pl. 119, fig. 4. Thach 2005: 45, pl. 9, figs 4, 7. Dey 2006: 31–32, figs 29–32. Ramakrishna et al. 2007: 48–49. Lozouet 2008: 284, pl. 87, figs 1, 3. Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 97. Hamli et al. 2013: tables 2, 3, fig. 2e. Sanpanich and Duangdee 2013: 54. Dechruksa et al. 2014: fig. 2h. BEDO 2017b: 29, with in-text fig. Kantharajan et al. 2017: table 1, fig. 3-18. Okutani 2017: 797, pl. 63, fig. 11. Yang et al. 2017: 28, fig. 109. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1o. Palanisamy et al. 2020: 2, fig. 1a–d. George et al. 2021: 1532, fig. 2a, b. Wells et al. 2021: 126.

**Referred material.** CUF-NKNY-G64 (2 shells; Figs 3K, 5G).

**Habitat.** On muddy floors of mangrove forests and intertidal mud flats (Poutiers 1998b; Okutani 2017).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to India (Poutiers 1998b; Okutani 2017; Palanisamy et al. 2020). Records of fossils from the Miocene to Quaternary in Indonesia (Tesch 1920; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by its high conical spire with a broad, rather flat base, and a twisted columella with a strong and central spiral ridge (Houbrick 1991; Poutiers 1998b).

**Subcohort Hypsogastropoda Ponder & Lindberg, 1997**

**Superfamily Naticoidea Guilding, 1834**

**Family Naticidae Guilding, 1834**

**Eunaticina Fischer, 1885**

**Eunaticina papilla** (Gmelin, 1791)

Figs 3G, 6A

*Nerita papilla* Gmelin, 1791: 3675. Type locality: Tranquebar [Tharangambadi, Tamil Nadu, India].

*Eunaticina papilla*. Cernohorsky 1971: 201–202, fig. 69. Cernohorsky 1972: 102, pl. 27, fig. 5. Tantanasiriwong 1978: 11, fig. 151. Nateewathana et al. 1981: 58. Way and Purchon 1981: 317. Majima 1989: 68–69, pl. 10, fig. 16, text-figs 15.36, 23.1a–d. Wilson 1993: 223, pl. 36, fig. 7. Bosch et al. 1995: 87, fig. 326. Swennen et al. 2001: 54, 122, fig. 378. Gemert 2003: 105. Hylleberg and Kilburn 2003: 56. Beu et al. 2004: 206, 208–211, fig. 22d–f, h. Robba et al. 2004: 75–76, pl. 9, fig. 7a, b. Dharma 2005: 176, pl. 63, fig. 25a–d; 342, pl. 136, fig. 12a, b. Ramakrishna et al. 2007: 9, 69–70. Robba et al. 2007: 91 (appendix). Hollmann 2008: 500, pl. 195, figs 1, 2. Nabhitabhata 2009: 123. Beu 2010: 152, fig. 21a. Torigoe and Inaba 2011: 55–56, pl. 2, fig. 17. Gopalakrishnan et al. 2012: 73. Öztürk and Bitlis 2013: 7, with in-text fig. Sanpanich and Duangdee 2013: 56. BEDO 2017b: 159, with in-text fig. Okutani 2017: 862, pl. 148, fig. 6. Yang et al. 2017: 52, fig. 215. Tudu et al. 2018: table 1. Albano et al. 2021: 12, fig. 5. Wells et al. 2021: 82.

*Eunaticina papilla papilla*. Thach 2005: 90, pl. 26, figs 3, 5.
iers 1998b: 451, with in-text figs. Subba Rao and Dey 2000: 53. Swennen et al. 2001: 52, 111–112, with in-text fig., fig. 295. Hylleberg and Kilburn 2003: 38. Sri-aroon et al. 2004: table 1, fig. 3-3. Dharma 2005: 92, pl. 21, fig. 1; 308, pl. 119, fig. 4. Thach 2005: 45, pl. 9, figs 4, 7. Dey 2006: 31–32, figs 29–32. Ramakrishna et al. 2007: 48–49. Lozouet 2008: 284, pl. 87, figs 1, 3. Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 97. Hamli et al. 2013: tables 2, 3, fig. 2e. Sanpanich and Duangdee 2013: 54. Dechruksa et al. 2014: fig. 2h. BEDO 2017b: 29, with in-text fig. Kantharajan et al. 2017: table 1, fig. 3-18. Okutani 2017: 797, pl. 63, fig. 11. Yang et al. 2017: 28, fig. 109. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1o. Palanisamy et al. 2020: 2, fig. 1a–d. George et al. 2021: 1532, fig. 2a, b. Wells et al. 2021: 126.

**Referred material.** CUF-NKNY-G64 (2 shells; Figs 3K, 5G).

**Habitat.** On muddy floors of mangrove forests and intertidal mud flats (Poutiers 1998b; Okutani 2017).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to India (Poutiers 1998b; Okutani 2017; Palanisamy et al. 2020). Records of fossils from the Miocene to Quaternary in Indonesia (Tesch 1920; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by its high conical spire with a broad, rather flat base, and a twisted columella with a strong and central spiral ridge (Houbrick 1991; Poutiers 1998b).

**Subcohort Hypsogastropoda Ponder & Lindberg, 1997**

**Superfamily Naticoidea Guilding, 1834**

**Family Naticidae Guilding, 1834**

**Eunaticina Fischer, 1885**

**Eunaticina papilla** (Gmelin, 1791)

Figs 3G, 6A

*Nerita papilla* Gmelin, 1791: 3675. Type locality: Tranquebar [Tharangambadi, Tamil Nadu, India].

*Eunaticina papilla*. Cernohorsky 1971: 201–202, fig. 69. Cernohorsky 1972: 102, pl. 27, fig. 5. Tantanasiriwong 1978: 11, fig. 151. Nateewathana et al. 1981: 58. Way and Purchon 1981: 317. Majima 1989: 68–69, pl. 10, fig. 16, text-figs 15.36, 23.1a–d. Wilson 1993: 223, pl. 36, fig. 7. Bosch et al. 1995: 87, fig. 326. Swennen et al. 2001: 54, 122, fig. 378. Gemert 2003: 105. Hylleberg and Kilburn 2003: 56. Beu et al. 2004: 206, 208–211, fig. 22d–f, h. Robba et al. 2004: 75–76, pl. 9, fig. 7a, b. Dharma 2005: 176, pl. 63, fig. 25a–d; 342, pl. 136, fig. 12a, b. Ramakrishna et al. 2007: 9, 69–70. Robba et al. 2007: 91 (appendix). Hollmann 2008: 500, pl. 195, figs 1, 2. Nabhitabhata 2009: 123. Beu 2010: 152, fig. 21a. Torigoe and Inaba 2011: 55–56, pl. 2, fig. 17. Gopalakrishnan et al. 2012: 73. Öztürk and Bitlis 2013: 7, with in-text fig. Sanpanich and Duangdee 2013: 56. BEDO 2017b: 159, with in-text fig. Okutani 2017: 862, pl. 148, fig. 6. Yang et al. 2017: 52, fig. 215. Tudu et al. 2018: table 1. Albano et al. 2021: 12, fig. 5. Wells et al. 2021: 82.

*Eunaticina papilla papilla*. Thach 2005: 90, pl. 26, figs 3, 5.
**Referred material.** CUF-NKNY-G19 (5 shells; Figs 3G, 6A).

**Habitat.** Fine sandy bottoms in intertidal zones down to 30 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Red Sea to Indian Ocean; Indo-West Pacific, from Japan to Australia and Fiji Islands (Robba et al. 2004; Okutani 2017), as well as the Israeli Mediterranean shelf (Albano et al. 2021). Several records of fossils during the Late Miocene to Holocene in Indonesia, Japan, Taiwan, and Thailand (Beu et al. 2004; Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by a regularly oval shell with a small spire and a large body whorl with low and wide spiral cords, which are broader than their interspaces and crossed by prominent axial ridges (Öztürk and Bitlis 2013). See also comprehensive taxonomic remarks in Beu et al. (2004).

**Natica Scopoli, 1777**

**Natica stellata Hedley, 1913**

Figs 3D, 6B

*Natica stellata* Hedley, 1913: 299–300. Type locality: unknown. Cernohorsky 1972: 94–95, pl. 24, fig. 6. Wilson 1993: 217, pl. 36, fig. 24. Poutiers 1998b: 513, with in-text figs. Robba et al. 2004: 71, pl. 9, fig. 2a, b. Dharma 2005: 176, pl. 63, fig. 18. Robba et al. 2007: 91 (appendix). Hollmann 2008: 492, pl. 191, figs 9, 10a, b. Nabhitabhata 2009: 125. Torigoe and Inaba 2011: 76–77. Mukhopadhyay et al. 2013: 152–153, fig. 6. Sanpanich and Duangdee 2013: 57. Okutani 2017: 862, pl. 149, fig. 7. Wells et al. 2021: 83.

*Natica* (*Natica*) *stellata*. Cernohorsky 1971: 176–177, figs 6, 8–13.

**Referred material.** CUF-NKNY-G05 (126 shells; Figs 3D, 6B).

**Habitat.** Sandy gravel bottoms in sublittoral zones down to 20 m depth (Hollmann 2008; Okutani 2017).

**Distribution.** Indo-West Pacific, from Japan to Australia (Cernohorsky 1972; Wilson 1993; Okutani 2017). Probably present in the Indian Ocean (Poutiers 1998b). Records of fossils from the Holocene in central Thailand (Robba et al. 2003, 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Natica vitellus*, in having a parietal callus forming a tongue-shaped extension over the posterior part of the umbilicus (Cernohorsky 1971). See also comprehensive taxonomic remarks in Cernohorsky (1971).

**Natica vitellus (Linnaeus, 1758)**

Figs 3E, 6C

*Nerita vitellus* Linnaeus, 1758: 776. Type locality: Asiatic Ocean.

*Natica vitellus*. Tesch 1920: 70–71, pl. 132, fig. 207a, b. Cernohorsky 1972: 94, pl. 24, fig. 5. Tantanasiriwong 1978: 11, fig. 141. Nateewathana et al. 1981: 58. Way and Purchon 1981: 317. Majima 1989: 74–76, pl. 10, figs 1–12, text-figs 4.1,
**Referred material.** CUF-NKNY-G19 (5 shells; Figs 3G, 6A).

**Habitat.** Fine sandy bottoms in intertidal zones down to 30 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Red Sea to Indian Ocean; Indo-West Pacific, from Japan to Australia and Fiji Islands (Robba et al. 2004; Okutani 2017), as well as the Israeli Mediterranean shelf (Albano et al. 2021). Several records of fossils during the Late Miocene to Holocene in Indonesia, Japan, Taiwan, and Thailand (Beu et al. 2004; Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by a regularly oval shell with a small spire and a large body whorl with low and wide spiral cords, which are broader than their interspaces and crossed by prominent axial ridges (Öztürk and Bitlis 2013). See also comprehensive taxonomic remarks in Beu et al. (2004).

**Natica Scopoli, 1777**

**Natica stellata Hedley, 1913**

Figs 3D, 6B

*Natica stellata* Hedley, 1913: 299–300. Type locality: unknown. Cernohorsky 1972: 94–95, pl. 24, fig. 6. Wilson 1993: 217, pl. 36, fig. 24. Poutiers 1998b: 513, with in-text figs. Robba et al. 2004: 71, pl. 9, fig. 2a, b. Dharma 2005: 176, pl. 63, fig. 18. Robba et al. 2007: 91 (appendix). Hollmann 2008: 492, pl. 191, figs 9, 10a, b. Nabhitabhata 2009: 125. Torigoe and Inaba 2011: 76–77. Mukhopadhyay et al. 2013: 152–153, fig. 6. Sanpanich and Duangdee 2013: 57. Okutani 2017: 862, pl. 149, fig. 7. Wells et al. 2021: 83.

*Natica* (*Natica*) *stellata*. Cernohorsky 1971: 176–177, figs 6, 8–13.

**Referred material.** CUF-NKNY-G05 (126 shells; Figs 3D, 6B).

**Habitat.** Sandy gravel bottoms in sublittoral zones down to 20 m depth (Hollmann 2008; Okutani 2017).

**Distribution.** Indo-West Pacific, from Japan to Australia (Cernohorsky 1972; Wilson 1993; Okutani 2017). Probably present in the Indian Ocean (Poutiers 1998b). Records of fossils from the Holocene in central Thailand (Robba et al. 2003, 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Natica vitellus*, in having a parietal callus forming a tongue-shaped extension over the posterior part of the umbilicus (Cernohorsky 1971). See also comprehensive taxonomic remarks in Cernohorsky (1971).

**Natica vitellus (Linnaeus, 1758)**

Figs 3E, 6C

*Nerita vitellus* Linnaeus, 1758: 776. Type locality: Asiatic Ocean.

*Natica vitellus*. Tesch 1920: 70–71, pl. 132, fig. 207a, b. Cernohorsky 1972: 94, pl. 24, fig. 5. Tantanasiriwong 1978: 11, fig. 141. Nateewathana et al. 1981: 58. Way and Purchon 1981: 317. Majima 1989: 74–76, pl. 10, figs 1–12, text-figs 4.1,
15.38. Wilson 1993: 217, pl. 36, fig. 28. Bosch et al. 1995: 87, fig. 322. Poutiers 1998b: 515, with in-text figs. Subba Rao and Dey 2000: 78. Swennen et al. 2001: 54, 121, fig. 371. Hylleberg and Kilburn 2003: 57. Robba et al. 2003: table 5. Robba et al. 2004: 71–73, pl. 9, fig. 3a, b. Dharma 2005: 176, pl. 63, fig. 17; 342, pl. 136, fig. 5a, b. Ramakrishna et al. 2007: 8, 67. Robba et al. 2007: 91 (appendix). Hollmann 2008: 492, pl. 191, fig. 7. Nabhitabhata 2009: 125. Torigoe and Inaba 2011: 69–70. Sanpanich and Duangdee 2013: 57. BEDO 2017b: 162, with in-text fig. Okutani 2017: 862, pl. 149, fig. 4. Yang et al. 2017: 56, fig. 230. Harzhauser et al. 2018: 7–8, pl. 1, figs 7–15. Tudu et al. 2018: table 1. Wells et al. 2021: 83.

*Natica (Natica) vitellus*. Cernohorsky 1971: 173–174, 176, figs 2–5. Ladd 1982: 39, pl. 6, fig. 7.

*Natica vitellus vitellus*. Thach 2005: 86, pl. 26, fig. 8.

**Referred material.** CUF-NKNY-G04 (5 shells; Figs 3E, 6C).

**Habitat.** Fine sandy or muddy bottoms in intertidal zones down to ~ 120 m depth (Robba et al. 2004); in clean coral-sand pockets and weedy-sand lagoons (Cernohorsky 1971).

**Distribution.** Persian Gulf to Indian Ocean; Indo-West Pacific, from Japan to Australia (Bosch et al. 1995; Poutiers 1998b; Okutani 2017). Several records of fossils from the Early Miocene to Holocene in India, Indonesia, Japan, Malaysia, Myanmar, the Philippines, Polynesia, Taiwan, Vanuatu, and Thailand (Ladd 1982; Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Natica stellata*, in lacking a tongue-shaped extension of a parietal callus over the posterior part of the umbilicus (Cernohorsky 1971). See also comprehensive taxonomic remarks in Cernohorsky (1971).

**Paratectonatica Azuma, 1961**

**Paratectonatica tigrina (Röding, 1798)**

Figs 3Q, 6D

*Cochlis tigrina* Röding, 1798: 147. Type locality: unknown.

*Natica tigrina*. Tantanasiriwong 1978: 11, fig. 142. Nateewathana et al. 1981: 58. Dheeradilok et al. 1984: pl. 3, figs 9, 10. Wilson 1993: 217, pl. 36, fig. 10. Nateewathana 1995: 98, with in-text fig. Poutiers 1998b: 514, with in-text figs. Swennen et al. 2001: 54, 121, fig. 369. Hylleberg and Kilburn 2003: 57. Dharma 2005: 176, pl. 63, fig. 14. Ramakrishna et al. 2007: 8, 66–67, pl. 4, figs 45, 46. Nabhitabhata 2009: 125. Okutani 2017: 864, pl. 150, fig. 10. Yang et al. 2017: 56, fig. 229. Surakiatchai et al. 2018: table 5, pl. 1, fig. 6a, b.

*Paratectonatica tigrina*. Majima 1989: pl. 14, fig. 18. Robba et al. 2003: tables 2–5. Robba et al. 2004: 73, pl. 9, fig. 4a, b. Robba et al. 2007: 91 (appendix). Torigoe and Inaba 2011: 101–102, pl. 3, fig. 30. Kang et al. 2018: 357–358, 360, fig. 4.

*Tectonatica tigrina*. Thach 2005: 87, pl. 26, fig. 24.

*Notocochlis tigrina*. Gopalakrishnan et al. 2012: 73. Sanpanich and Duangdee 2013: 57. BEDO 2017b: 165, with in-text fig. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1a. Wells et al. 2021: 84.
15.38. Wilson 1993: 217, pl. 36, fig. 28. Bosch et al. 1995: 87, fig. 322. Poutiers 1998b: 515, with in-text figs. Subba Rao and Dey 2000: 78. Swennen et al. 2001: 54, 121, fig. 371. Hylleberg and Kilburn 2003: 57. Robba et al. 2003: table 5. Robba et al. 2004: 71–73, pl. 9, fig. 3a, b. Dharma 2005: 176, pl. 63, fig. 17; 342, pl. 136, fig. 5a, b. Ramakrishna et al. 2007: 8, 67. Robba et al. 2007: 91 (appendix). Hollmann 2008: 492, pl. 191, fig. 7. Nabhitabhata 2009: 125. Torigoe and Inaba 2011: 69–70. Sanpanich and Duangdee 2013: 57. BEDO 2017b: 162, with in-text fig. Okutani 2017: 862, pl. 149, fig. 4. Yang et al. 2017: 56, fig. 230. Harzhauser et al. 2018: 7–8, pl. 1, figs 7–15. Tudu et al. 2018: table 1. Wells et al. 2021: 83.

*Natica (Natica) vitellus*. Cernohorsky 1971: 173–174, 176, figs 2–5. Ladd 1982: 39, pl. 6, fig. 7.

*Natica vitellus vitellus*. Thach 2005: 86, pl. 26, fig. 8.

**Referred material.** CUF-NKNY-G04 (5 shells; Figs 3E, 6C).

**Habitat.** Fine sandy or muddy bottoms in intertidal zones down to ~ 120 m depth (Robba et al. 2004); in clean coral-sand pockets and weedy-sand lagoons (Cernohorsky 1971).

**Distribution.** Persian Gulf to Indian Ocean; Indo-West Pacific, from Japan to Australia (Bosch et al. 1995; Poutiers 1998b; Okutani 2017). Several records of fossils from the Early Miocene to Holocene in India, Indonesia, Japan, Malaysia, Myanmar, the Philippines, Polynesia, Taiwan, Vanuatu, and Thailand (Ladd 1982; Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Natica stellata*, in lacking a tongue-shaped extension of a parietal callus over the posterior part of the umbilicus (Cernohorsky 1971). See also comprehensive taxonomic remarks in Cernohorsky (1971).

**Paratectonatica Azuma, 1961**

**Paratectonatica tigrina (Röding, 1798)**

Figs 3Q, 6D

*Cochlis tigrina* Röding, 1798: 147. Type locality: unknown.

*Natica tigrina*. Tantanasiriwong 1978: 11, fig. 142. Nateewathana et al. 1981: 58. Dheeradilok et al. 1984: pl. 3, figs 9, 10. Wilson 1993: 217, pl. 36, fig. 10. Nateewathana 1995: 98, with in-text fig. Poutiers 1998b: 514, with in-text figs. Swennen et al. 2001: 54, 121, fig. 369. Hylleberg and Kilburn 2003: 57. Dharma 2005: 176, pl. 63, fig. 14. Ramakrishna et al. 2007: 8, 66–67, pl. 4, figs 45, 46. Nabhitabhata 2009: 125. Okutani 2017: 864, pl. 150, fig. 10. Yang et al. 2017: 56, fig. 229. Surakiatchai et al. 2018: table 5, pl. 1, fig. 6a, b.

*Paratectonatica tigrina*. Majima 1989: pl. 14, fig. 18. Robba et al. 2003: tables 2–5. Robba et al. 2004: 73, pl. 9, fig. 4a, b. Robba et al. 2007: 91 (appendix). Torigoe and Inaba 2011: 101–102, pl. 3, fig. 30. Kang et al. 2018: 357–358, 360, fig. 4.

*Tectonatica tigrina*. Thach 2005: 87, pl. 26, fig. 24.

*Notocochlis tigrina*. Gopalakrishnan et al. 2012: 73. Sanpanich and Duangdee 2013: 57. BEDO 2017b: 165, with in-text fig. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1a. Wells et al. 2021: 84.
<figure><img src="image_6.png" /><figcaption>**Figure 6.** Gastropods A Eunaticina papilla B Natica stellata C Natica vitellus D Paratectonatica tigrina E Ergaea walshi F Bufonaria rana G Merica elegans H Scalptia scalariformis.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Figure 6.** Gastropods A Eunaticina papilla B Natica stellata C Natica vitellus D Paratectonatica tigrina E Ergaea walshi F Bufonaria rana G Merica elegans H Scalptia scalariformis.</figcaption></figure>
**Referred material.** CUF-NKNY-G03 (70 shells; Figs 3Q, 6D).

**Habitat.** Sandy mud in intertidal zones down to 30 m depth (Thach 2005; Okutani 2017).

**Distribution.** India (Yadav et al. 2019); Indo-West Pacific, from Japan to Australia (Wilson 1993; Poutiers 1998b; Okutani 2017). Records of fossils from the Late Miocene to Quaternary in Indonesia and from the Quaternary in Thailand (Robba et al. 2003, 2004; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by its tall-spired shell with deeply impressed sutures and spiral rows of reddish-brown spots on a white background (Poutiers 1998b; Robba et al. 2004).

Superorder Latrogastropoda Riedel, 2000

Superfamily Calyptraeoidea Lamarck, 1809

Family Calyptraeidae Lamarck, 1809

Ergaea H. Adams & A. Adams, 1854

Ergaea walshi (Reeve, 1859)

Figs 3H, 6E

*Crepidula walshi* Reeve, 1859: *Crepidula*, pl. 3, sp. 17. Type locality: Singapore; Ceylon [Sri Lanka]. Tantanasiriwong 1978: 9. Bosch et al. 1995: 69, fig. 230. Subba Rao and Dey 2000: 64. Swennen et al. 2001: 54, 117, text-fig. 344, fig. 344. Gemert 2003: 104. Robba et al. 2003: tables 3–5. Robba et al. 2004: 66–67, pl. 8, fig. 8a, b. Ramakrishna et al. 2007: 7, 55–56. Robba et al. 2007: 91 (appendix).

*Ergaea walshi*. Nateewathana et al. 1981: 57. Nabhitabhata 2009: 109. Low and Tan 2014: 11–13, fig. 1. BEDO 2017b: 117, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 75.

*Crepidula walshii* [sic]. Way and Purchon 1981: 316.

*Siphopatella walshi*. Hylleberg and Kilburn 2003: 47. Sanpanich and Duangdee 2013: 55. Okutani 2017: 838, pl. 114, fig. 3. Yang et al. 2017: 32, fig. 117.

*Crepidula* (*Siphopatella*) walshi. Dharma 2005: 78, pl. 14, fig. 13a, b; 342, pl. 136, fig. 15a, b.

*Crepidula* (*Ergaea*) walshi. Thach 2005: 66, pl. 10, fig. 27.

**Referred material.** CUF-NKNY-G25 (10 shells; Figs 3H, 6E).

**Habitat.** Attached to the aperture of other shelled marine organisms, in intertidal zones down to 40 m depth (Robba et al. 2004; Thach 2005; Low and Tan 2014).

**Distribution.** Persian Gulf; Indo-West Pacific, from Japan to the Arafura Sea (Robba et al. 2004; Okutani 2017). Several records of fossils from the Late Miocene to Holocene in India, Indonesia, Japan, Taiwan, and Thailand (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by an irregularly subrectangular and flattened shell, with a small apex close to the posterior margin, and a shelf-like internal septum attached just inside the posterior margin (Robba et al. 2004). See also comprehensive taxonomic remarks in Low and Tan (2014).
**Referred material.** CUF-NKNY-G03 (70 shells; Figs 3Q, 6D).

**Habitat.** Sandy mud in intertidal zones down to 30 m depth (Thach 2005; Okutani 2017).

**Distribution.** India (Yadav et al. 2019); Indo-West Pacific, from Japan to Australia (Wilson 1993; Poutiers 1998b; Okutani 2017). Records of fossils from the Late Miocene to Quaternary in Indonesia and from the Quaternary in Thailand (Robba et al. 2003, 2004; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by its tall-spired shell with deeply impressed sutures and spiral rows of reddish-brown spots on a white background (Poutiers 1998b; Robba et al. 2004).

**Superorder Latrogastropoda Riedel, 2000**

**Superfamily Calyptraeoidea Lamarck, 1809**

**Family Calyptraeidae Lamarck, 1809**

**Ergaea H. Adams & A. Adams, 1854**

**Ergaea walshi (Reeve, 1859)**

Figs 3H, 6E

*Crepidula walshi* Reeve, 1859: *Crepidula*, pl. 3, sp. 17. Type locality: Singapore; Ceylon [Sri Lanka]. Tantanasiriwong 1978: 9. Bosch et al. 1995: 69, fig. 230. Subba Rao and Dey 2000: 64. Swennen et al. 2001: 54, 117, text-fig. 344, fig. 344. Gemert 2003: 104. Robba et al. 2003: tables 3–5. Robba et al. 2004: 66–67, pl. 8, fig. 8a, b. Ramakrishna et al. 2007: 7, 55–56. Robba et al. 2007: 91 (appendix).

*Ergaea walshi*. Nateewathana et al. 1981: 57. Nabhitabhata 2009: 109. Low and Tan 2014: 11–13, fig. 1. BEDO 2017b: 117, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 75.

*Crepidula walshii* [sic]. Way and Purchon 1981: 316.

*Siphopatella walshi*. Hylleberg and Kilburn 2003: 47. Sanpanich and Duangdee 2013: 55. Okutani 2017: 838, pl. 114, fig. 3. Yang et al. 2017: 32, fig. 117.

*Crepidula* (*Siphopatella*) walshi. Dharma 2005: 78, pl. 14, fig. 13a, b; 342, pl. 136, fig. 15a, b.

*Crepidula* (*Ergaea*) walshi. Thach 2005: 66, pl. 10, fig. 27.

**Referred material.** CUF-NKNY-G25 (10 shells; Figs 3H, 6E).

**Habitat.** Attached to the aperture of other shelled marine organisms, in intertidal zones down to 40 m depth (Robba et al. 2004; Thach 2005; Low and Tan 2014).

**Distribution.** Persian Gulf; Indo-West Pacific, from Japan to the Arafura Sea (Robba et al. 2004; Okutani 2017). Several records of fossils from the Late Miocene to Holocene in India, Indonesia, Japan, Taiwan, and Thailand (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised by an irregularly subrectangular and flattened shell, with a small apex close to the posterior margin, and a shelf-like internal septum attached just inside the posterior margin (Robba et al. 2004). See also comprehensive taxonomic remarks in Low and Tan (2014).
**Superfamily Tonnoidea Suter, 1913**

**Family Bursidae Thiele, 1925**

**Bufonaria Schumacher, 1817**

**Bufonaria rana (Linnaeus, 1758)**

Figs 3N, 6F

*Murex rana* Linnaeus, 1758: 748. Type locality: Asiatic Ocean.

*Bursa (Bufonaria) rana*. Cernohorsky 1972: 119, pl. 32, fig. 8.

*Bursa rana*. Tantanasiriwong 1978: 12, fig. 170. Nateewathana et al. 1981: 59. Way and Purchon 1981: 317. Swennen et al. 2001: 55, 122, fig. 380.

*Bufonaria rana*. Wilson 1993: 226, pl. 43, fig. 1a, b. Aungtonya and Hylleberg 1998: 319. Poutiers 1998b: 551, with in-text figs. Subba Rao and Dey 2000: 92. Hylleberg and Kilburn 2003: 59. Robba et al. 2004: 76–77, pl. 9, fig. 9a, b. Dharma 2005: 194, pl. 72, fig. 1a–e; 352, pl. 141, fig. 7a–c. Ramakrishna et al. 2007: 10, 81, pl. 6, figs 69, 70. Robba et al. 2007: 91 (appendix). Beu 2008: 618, pl. 254, figs 6, 7a, b. Nabhitabhata 2009: 137. Sanpanich and Duangdee 2013: 58. BEDO 2017b: 112, with in-text fig. Okutani 2017: 867–868, pl. 154, fig. 5. Yang et al. 2017: 64, fig. 266. Harzhauser et al. 2018: 13–14, pl. 3, figs 6–9. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1b. Wells et al. 2021: 89.

*Bufonaria (Bufonaria) rana*. Cossignani 1994: 33–35, with in-text figs. Bosch et al. 1995: 102, fig. 372. Gemert 2003: 105. Thach 2005: 96, pl. 28, fig. 8.

**Referred material.** CUF-NKNY-G06, G07 (18 shells; Figs 3N, 6F).

**Habitat.** Muddy or sandy bottoms at a depth from 20 to 100 m (Okutani 2017; Yang et al. 2017).

**Distribution.** Red Sea to Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017; Yadav et al. 2019). Several records of fossils from the Miocene to Quaternary in Indonesia, Japan, the Philippines, and Taiwan (Robba et al. 2004; Dharma 2005; Harzhauser et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2004) and Harzhauser et al. (2018), specifically in having two prominent varices placed at either periphery, running vertically uninterrupted, or slightly staggered, from apex to base, and bearing three short spines.

**Order Neogastropoda Wenz, 1938**

**Superfamily Volutoidea Rafinesque, 1815**

**Family Cancellariidae Forbes & Hanley, 1851**

**Merica H. Adams & A. Adams, 1854**

**Merica elegans (Sowerby I, 1822)**

Figs 3L, 6G

*Cancellaria elegans* Sowerby I, 1822: *Cancellaria*, pl. 218, fig. 3. Type locality: unknown. Tantanasiriwong 1978: 17. Nateewathana et al. 1981: 61. Robba et al. 2007: 51–52, fig. 19d, e; 93 (appendix).
**Superfamily Tonnoidea Suter, 1913**

**Family Bursidae Thiele, 1925**

**Bufonaria Schumacher, 1817**

**Bufonaria rana (Linnaeus, 1758)**

Figs 3N, 6F

*Murex rana* Linnaeus, 1758: 748. Type locality: Asiatic Ocean.

*Bursa (Bufonaria) rana*. Cernohorsky 1972: 119, pl. 32, fig. 8.

*Bursa rana*. Tantanasiriwong 1978: 12, fig. 170. Nateewathana et al. 1981: 59. Way and Purchon 1981: 317. Swennen et al. 2001: 55, 122, fig. 380.

*Bufonaria rana*. Wilson 1993: 226, pl. 43, fig. 1a, b. Aungtonya and Hylleberg 1998: 319. Poutiers 1998b: 551, with in-text figs. Subba Rao and Dey 2000: 92. Hylleberg and Kilburn 2003: 59. Robba et al. 2004: 76–77, pl. 9, fig. 9a, b. Dharma 2005: 194, pl. 72, fig. 1a–e; 352, pl. 141, fig. 7a–c. Ramakrishna et al. 2007: 10, 81, pl. 6, figs 69, 70. Robba et al. 2007: 91 (appendix). Beu 2008: 618, pl. 254, figs 6, 7a, b. Nabhitabhata 2009: 137. Sanpanich and Duangdee 2013: 58. BEDO 2017b: 112, with in-text fig. Okutani 2017: 867–868, pl. 154, fig. 5. Yang et al. 2017: 64, fig. 266. Harzhauser et al. 2018: 13–14, pl. 3, figs 6–9. Tudu et al. 2018: table 1. Yadav et al. 2019: table 2, fig. 1b. Wells et al. 2021: 89.

*Bufonaria (Bufonaria) rana*. Cossignani 1994: 33–35, with in-text figs. Bosch et al. 1995: 102, fig. 372. Gemert 2003: 105. Thach 2005: 96, pl. 28, fig. 8.

**Referred material.** CUF-NKNY-G06, G07 (18 shells; Figs 3N, 6F).

**Habitat.** Muddy or sandy bottoms at a depth from 20 to 100 m (Okutani 2017; Yang et al. 2017).

**Distribution.** Red Sea to Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017; Yadav et al. 2019). Several records of fossils from the Miocene to Quaternary in Indonesia, Japan, the Philippines, and Taiwan (Robba et al. 2004; Dharma 2005; Harzhauser et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2004) and Harzhauser et al. (2018), specifically in having two prominent varices placed at either periphery, running vertically uninterrupted, or slightly staggered, from apex to base, and bearing three short spines.

**Order Neogastropoda Wenz, 1938**

**Superfamily Volutoidea Rafinesque, 1815**

**Family Cancellariidae Forbes & Hanley, 1851**

**Merica H. Adams & A. Adams, 1854**

**Merica elegans (Sowerby I, 1822)**

Figs 3L, 6G

*Cancellaria elegans* Sowerby I, 1822: *Cancellaria*, pl. 218, fig. 3. Type locality: unknown. Tantanasiriwong 1978: 17. Nateewathana et al. 1981: 61. Robba et al. 2007: 51–52, fig. 19d, e; 93 (appendix).
*Cancellaria asperella* [sic]. Cernohorsky 1972: 179, pl. 50, fig. 3 right.

*Merica elegans*. Verrecken 1986: 40–41, fig. 9. Verrecken 1997: 307–308, fig. 36. Swennen et al. 2001: 57, 133, fig. 461. Hylleberg and Kilburn 2003: 100. Dharma 2005: 134, pl. 42, fig. 1. Thach 2005: 188, pl. 58, figs 6, 10. Hemmen 2007: 128–129, with in-text fig. Verrecken 2008: 818, pl. 704, fig. 5a, b. BEDO 2017b: 221, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 121.

**Referred material.** CUF-NKNY-G18 (3 shells; Figs 3L, 6G).

**Habitat.** Sandy and muddy bottoms at a depth from 10 to 30 m (Robba et al. 2004; Thach 2005).

**Distribution.** Indo-West Pacific, from Japan to the Philippines. Records of fossils from the Miocene in Indonesia, and from the Quaternary in Japan (Robba et al. 2007).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Merica asperella* (Lamarck, 1822), in having a slenderer and more fusiform shell with a narrower aperture and a sculptured shell with finer and more numerous ribs crossed by spiral ridges nearly of the same strength, showing a rectangular reticulated pattern (Robba et al. 2007).

## *Sculptia Jousseaume, 1887*

### *Sculptia scalariformis* (Lamarck, 1822)

Figs 3J, 6H

*Cancellaria scalariformis* Lamarck, 1822: 115. Type locality: unknown.

*Cancellaria (Trigonostoma) scalariformis*. Tesch 1915: 39, pl. 79, fig. 81a, b.

*Trigonostoma scalariformis*. Cernohorsky 1972: 180, pl. 50, fig. 2, 2a. Garrard 1975: 27–29, figs 4 (3, 4). Way and Purchon 1981: 320. Wilson 1994: 178, pl. 37, fig. 7a, b.

*Sculptia scalariformis*. Verrecken 1986: 53–55, figs 28–35. Swennen et al. 2001: 57, 133, fig. 462. Hylleberg and Kilburn 2003: 101. Robba et al. 2004: 129–130, pl. 17, fig. 6. Dharma 2005: 134, pl. 42, fig. 12a, b. Hemmen 2007: 277–278, with in-text figs. Robba et al. 2007: 93 (appendix). Okutani 2017: 1054, pl. 344, fig. 4. Yang et al. 2017: 102, fig. 415. Tudu et al. 2018: table 1. Wells et al. 2021: 121. Chan and Lau 2022: 1–2, figs 1–3.

*Sculptia (Sculptia) scalariformis*. Thach 2005: 188, pl. 58, figs 25, 27, 29.

**Referred material.** CUF-NKNY-G64 (1 shell; Figs 3J, 6H).

**Habitat.** Sand and muddy bottoms at a depth from 20 to 40 m in sublittoral zones (Thach 2005; Okutani 2017; Yang et al. 2017).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017). Several records of fossils from the Pliocene to Holocene in the Indo-Pacific area, including Indonesia and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Sculptia bicolor* (Hinds, 1843), by having a higher and narrower body whorl and a less widely open umbilicus (Robba et al. 2007).
*Cancellaria asperella* [sic]. Cernohorsky 1972: 179, pl. 50, fig. 3 right.

*Merica elegans*. Verrecken 1986: 40–41, fig. 9. Verrecken 1997: 307–308, fig. 36. Swennen et al. 2001: 57, 133, fig. 461. Hylleberg and Kilburn 2003: 100. Dharma 2005: 134, pl. 42, fig. 1. Thach 2005: 188, pl. 58, figs 6, 10. Hemmen 2007: 128–129, with in-text fig. Verrecken 2008: 818, pl. 704, fig. 5a, b. BEDO 2017b: 221, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 121.

**Referred material.** CUF-NKNY-G18 (3 shells; Figs 3L, 6G).

**Habitat.** Sandy and muddy bottoms at a depth from 10 to 30 m (Robba et al. 2004; Thach 2005).

**Distribution.** Indo-West Pacific, from Japan to the Philippines. Records of fossils from the Miocene in Indonesia, and from the Quaternary in Japan (Robba et al. 2007).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Merica asperella* (Lamarck, 1822), in having a slenderer and more fusiform shell with a narrower aperture and a sculptured shell with finer and more numerous ribs crossed by spiral ridges nearly of the same strength, showing a rectangular reticulated pattern (Robba et al. 2007).

## *Sculptia Jousseaume, 1887*

### *Sculptia scalariformis* (Lamarck, 1822)

Figs 3J, 6H

*Cancellaria scalariformis* Lamarck, 1822: 115. Type locality: unknown.

*Cancellaria (Trigonostoma) scalariformis*. Tesch 1915: 39, pl. 79, fig. 81a, b.

*Trigonostoma scalariformis*. Cernohorsky 1972: 180, pl. 50, fig. 2, 2a. Garrard 1975: 27–29, figs 4 (3, 4). Way and Purchon 1981: 320. Wilson 1994: 178, pl. 37, fig. 7a, b.

*Sculptia scalariformis*. Verrecken 1986: 53–55, figs 28–35. Swennen et al. 2001: 57, 133, fig. 462. Hylleberg and Kilburn 2003: 101. Robba et al. 2004: 129–130, pl. 17, fig. 6. Dharma 2005: 134, pl. 42, fig. 12a, b. Hemmen 2007: 277–278, with in-text figs. Robba et al. 2007: 93 (appendix). Okutani 2017: 1054, pl. 344, fig. 4. Yang et al. 2017: 102, fig. 415. Tudu et al. 2018: table 1. Wells et al. 2021: 121. Chan and Lau 2022: 1–2, figs 1–3.

*Sculptia (Sculptia) scalariformis*. Thach 2005: 188, pl. 58, figs 25, 27, 29.

**Referred material.** CUF-NKNY-G64 (1 shell; Figs 3J, 6H).

**Habitat.** Sand and muddy bottoms at a depth from 20 to 40 m in sublittoral zones (Thach 2005; Okutani 2017; Yang et al. 2017).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017). Several records of fossils from the Pliocene to Holocene in the Indo-Pacific area, including Indonesia and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Sculptia bicolor* (Hinds, 1843), by having a higher and narrower body whorl and a less widely open umbilicus (Robba et al. 2007).
**Superfamily Buccinoidea Rafinesque, 1815**

**Family Buccinidae Rafinesque, 1815**

**Pseudoneptunea Kobelt, 1882**

**Pseudoneptunea varicosa** (Röding, 1798)

Figs 4K, 7A

*Neptunea varicosa* Röding, 1798: 116. Type locality: unknown.

*Siphonalia (Pseudoneptunea)* aff. *varicosa*. Tesch 1915: 53, pl. 80, fig. 114a, b.

*Pseudoneptunea varicosa*. Cernohorsky 1975: 217–218, figs 10–12. Way and Purchon 1981: 318. Swennen et al. 2001: 56, 128, fig. 428. Robba et al. 2004: 106–107, pl. 14, fig. 5a, b. Dharma 2005: 100, pl. 25, fig. 7a, b; 312, pl. 121, fig. 9a, b. Thach 2005: 135, pl. 39, figs 12, 15. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 148. Sanpanich and Duangdee 2013: 63. Wells et al. 2021: 95.

**Referred material.** CUF-NKNY-G13, G16, G17 (25 shells; Figs 4K, 7A).

**Habitat.** Shallow water at a depth from 10 to 15 m (Thach 2005).

**Distribution.** Indo-West Pacific, from Vietnam to Indonesia (Robba et al. 2004; Dharma 2005; Thach 2005). Records of fossils from the Pliocene and Quaternary in Indonesia and from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Cernohorsky (1975) and Robba et al. (2004), specifically in having subangulate whorls and a sculpture of crisp main spirals with an occasional intermediate spiral thread.

**Family Melongenidae Gill, 1871**

**Brunneifusus Dekkers, 2018**

**Brunneifusus ternatanus** (Gmelin, 1791)

Figs 4A, 7B

*Murex ternatanus* Gmelin, 1791: 3554. Type locality: Ternate Island, North Maluku, Indonesia.

*Pugilina ternatana*. Tantanasiriwong 1978: 15. Nateewathana et al. 1981: 60. Poutiers 1998b: 586, with in-text figs.

*Hemifusus ternatanus*. Yokoyama 1927: 393. Way and Purchon 1981: 318. Swennen et al. 2001: 56, 130, fig. 445. Gemert 2003: 106, with in-text fig. Hylleberg and Kilburn 2003: 88. Robba et al. 2004: 122–123, pl. 16, fig. 7a, b. Dharma 2005: 108, pl. 29, fig. 2a, b; 316, pl. 123, fig. 7a, b. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 162. Sanpanich and Duangdee 2013: 61. BEDO 2017b: 288, with in-text fig. Tudu et al. 2018: table 1.

*Brunneifusus ternatanus*. Dekkers 2018: 41–42, pl. 2, figs 5, 6. Alf and Thach 2021: pl. 1, figs 1–9, pl. 2, figs 1–3. Wells et al. 2021: 97.

**Referred material.** CUF-NKNY-G21, G22 (71 shells; Figs 4A, 7B).

**Habitat.** Mud and muddy sand bottoms from the low tide mark to ~ 10–50 m depth (Poutiers 1998b; Swennen et al. 2001; Dekkers 2018).
**Superfamily Buccinoidea Rafinesque, 1815**

**Family Buccinidae Rafinesque, 1815**

**Pseudoneptunea Kobelt, 1882**

**Pseudoneptunea varicosa** (Röding, 1798)

Figs 4K, 7A

*Neptunea varicosa* Röding, 1798: 116. Type locality: unknown.

*Siphonalia (Pseudoneptunea)* aff. *varicosa*. Tesch 1915: 53, pl. 80, fig. 114a, b.

*Pseudoneptunea varicosa*. Cernohorsky 1975: 217–218, figs 10–12. Way and Purchon 1981: 318. Swennen et al. 2001: 56, 128, fig. 428. Robba et al. 2004: 106–107, pl. 14, fig. 5a, b. Dharma 2005: 100, pl. 25, fig. 7a, b; 312, pl. 121, fig. 9a, b. Thach 2005: 135, pl. 39, figs 12, 15. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 148. Sanpanich and Duangdee 2013: 63. Wells et al. 2021: 95.

**Referred material.** CUF-NKNY-G13, G16, G17 (25 shells; Figs 4K, 7A).

**Habitat.** Shallow water at a depth from 10 to 15 m (Thach 2005).

**Distribution.** Indo-West Pacific, from Vietnam to Indonesia (Robba et al. 2004; Dharma 2005; Thach 2005). Records of fossils from the Pliocene and Quaternary in Indonesia and from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Cernohorsky (1975) and Robba et al. (2004), specifically in having subangulate whorls and a sculpture of crisp main spirals with an occasional intermediate spiral thread.

**Family Melongenidae Gill, 1871**

**Brunneifusus Dekkers, 2018**

**Brunneifusus ternatanus** (Gmelin, 1791)

Figs 4A, 7B

*Murex ternatanus* Gmelin, 1791: 3554. Type locality: Ternate Island, North Maluku, Indonesia.

*Pugilina ternatana*. Tantanasiriwong 1978: 15. Nateewathana et al. 1981: 60. Poutiers 1998b: 586, with in-text figs.

*Hemifusus ternatanus*. Yokoyama 1927: 393. Way and Purchon 1981: 318. Swennen et al. 2001: 56, 130, fig. 445. Gemert 2003: 106, with in-text fig. Hylleberg and Kilburn 2003: 88. Robba et al. 2004: 122–123, pl. 16, fig. 7a, b. Dharma 2005: 108, pl. 29, fig. 2a, b; 316, pl. 123, fig. 7a, b. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 162. Sanpanich and Duangdee 2013: 61. BEDO 2017b: 288, with in-text fig. Tudu et al. 2018: table 1.

*Brunneifusus ternatanus*. Dekkers 2018: 41–42, pl. 2, figs 5, 6. Alf and Thach 2021: pl. 1, figs 1–9, pl. 2, figs 1–3. Wells et al. 2021: 97.

**Referred material.** CUF-NKNY-G21, G22 (71 shells; Figs 4A, 7B).

**Habitat.** Mud and muddy sand bottoms from the low tide mark to ~ 10–50 m depth (Poutiers 1998b; Swennen et al. 2001; Dekkers 2018).
<figure><img src="image_7.png" /><figcaption>**Figure 7.** Gastropods A *Pseudoneptunea varicosa* B *Brunneifusus ternatanus* C *Nassarius micans* D *Nassarius siquijoren-sis* E *Chicoreus capucinus* F *Indothais gradata*.</figcaption></figure>

**Distribution.** Eastern Indian Ocean; Indo-West Pacific, from Taiwan to Indonesia and the Philippines (Poutiers 1998b; Robba et al. 2004). Records of fossils from the Pliocene and Quaternary in Indonesia, Japan, and Taiwan (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).
<figure><img src="image_8.png" /><figcaption>**Figure 7.** Gastropods A *Pseudoneptunea varicosa* B *Brunneifusus ternatanus* C *Nassarius micans* D *Nassarius siquijoren-sis* E *Chicoreus capucinus* F *Indothais gradata*.</figcaption></figure>

**Distribution.** Eastern Indian Ocean; Indo-West Pacific, from Taiwan to Indonesia and the Philippines (Poutiers 1998b; Robba et al. 2004). Records of fossils from the Pliocene and Quaternary in Indonesia, Japan, and Taiwan (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).
**Taxonomic remarks and comparisons.** This species is the sole member of the genus *Brunneifusus*, characterised by a determinate outer lip, compared to the indeterminate growth of the outer lip in *Hemifusus* Swainson, 1840 (Alf and Thach 2021). See also comprehensive taxonomic remarks in Alf and Thach (2021).

**Family Nassariidae Iredale, 1916**

**Nassarius Duméril, 1805**

**Nassarius micans** (A. Adams, 1852)

Figs 30, 7C

*Nassa micans* A. Adams, 1852: 106. Type locality: Cagayan, Misamis, Mindanao.

*Nassarius (Zeuxis) micans*. Cernohorsky 1984: 147–148, pl. 29, figs 8–11. Robba et al. 2003: table 5. Robba et al. 2004: 120, pl. 16, fig. 4a, b. Dharma 2005: 106, pl. 28, fig. 16a, b. Robba et al. 2007: 93 (appendix). Okutani 2017: 914, pl. 202, fig. 11

*Nassarius micans*. Gopalakrishnan et al. 2012: 77. Wells et al. 2021: 99.

**Referred material.** CUF-NKNY-G27 (53 shells; Figs 30, 7C).

**Habitat.** Sandy bottoms in subtidal zones down to 50 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Gulf of Oman to India; Indo-West Pacific, from Japan to Papua New Guinea (Cernohorsky 1984; Robba et al. 2004; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Nassarius comptus* (A. Adams, 1852), by having a longer body whorl with narrowly subcanaliculate sutures, a more prominent varix, and a narrower and more elongate aperture (Cernohorsky 1984). See also comprehensive taxonomic remarks in Cernohorsky (1984).

**Nassarius siquijorensis** (A. Adams, 1852)

Figs 3P, 7D

*Nassa siquijorensis* A. Adams, 1852: 97. Type locality: Island of Siquijor, Philippines.

*Nassa (Zeuxis) siquijorensis*. Tesch 1915: 59, pl. 81, figs 128a, b, 129a, b.

*Nassarius (Zeuxis) siquijorensis*. Cernohorsky 1978: 88, pl. 27, fig. 8. Cernohorsky 1984: 134–136, pl. 25, figs 12–14, pl. 26, figs 1–5. Robba et al. 2003: table 5. Robba et al. 2004: 120–121, pl. 16, fig. 5a, b. Dharma 2005: 106, pl. 28, fig. 14a–c. Robba et al. 2007: 93 (appendix).

*Nassarius siquijorensis*. Nobuhara 1993: fig. 8-1a, 8-1b. Swennen et al. 2001: 56, 130, fig. 442. Hylleberg and Kilburn 2003: 87. Kool 2007: figs 17–20. Martin 2008: 120, pl. 355, fig. 13; 128, pl. 359, fig. 13. Surakiatchai et al. 2018: table 5, pl. 1, fig. 9a, b. Wells et al. 2021: 99.

*Zeuxis siquijorensis*. Thach 2005: 148, pl. 44, fig. 25.

*Nassarius siquinjorensis* [sic]. Yang et al. 2017: 90, fig. 371.
**Taxonomic remarks and comparisons.** This species is the sole member of the genus *Brunneifusus*, characterised by a determinate outer lip, compared to the indeterminate growth of the outer lip in *Hemifusus* Swainson, 1840 (Alf and Thach 2021). See also comprehensive taxonomic remarks in Alf and Thach (2021).

**Family Nassariidae Iredale, 1916**

**Nassarius Duméril, 1805**

**Nassarius micans** (A. Adams, 1852)

Figs 30, 7C

*Nassa micans* A. Adams, 1852: 106. Type locality: Cagayan, Misamis, Mindanao.

*Nassarius (Zeuxis) micans*. Cernohorsky 1984: 147–148, pl. 29, figs 8–11. Robba et al. 2003: table 5. Robba et al. 2004: 120, pl. 16, fig. 4a, b. Dharma 2005: 106, pl. 28, fig. 16a, b. Robba et al. 2007: 93 (appendix). Okutani 2017: 914, pl. 202, fig. 11

*Nassarius micans*. Gopalakrishnan et al. 2012: 77. Wells et al. 2021: 99.

**Referred material.** CUF-NKNY-G27 (53 shells; Figs 30, 7C).

**Habitat.** Sandy bottoms in subtidal zones down to 50 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Gulf of Oman to India; Indo-West Pacific, from Japan to Papua New Guinea (Cernohorsky 1984; Robba et al. 2004; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Nassarius comptus* (A. Adams, 1852), by having a longer body whorl with narrowly subcanaliculate sutures, a more prominent varix, and a narrower and more elongate aperture (Cernohorsky 1984). See also comprehensive taxonomic remarks in Cernohorsky (1984).

**Nassarius siquijorensis** (A. Adams, 1852)

Figs 3P, 7D

*Nassa siquijorensis* A. Adams, 1852: 97. Type locality: Island of Siquijor, Philippines.

*Nassa (Zeuxis) siquijorensis*. Tesch 1915: 59, pl. 81, figs 128a, b, 129a, b.

*Nassarius (Zeuxis) siquijorensis*. Cernohorsky 1978: 88, pl. 27, fig. 8. Cernohorsky 1984: 134–136, pl. 25, figs 12–14, pl. 26, figs 1–5. Robba et al. 2003: table 5. Robba et al. 2004: 120–121, pl. 16, fig. 5a, b. Dharma 2005: 106, pl. 28, fig. 14a–c. Robba et al. 2007: 93 (appendix).

*Nassarius siquijorensis*. Nobuhara 1993: fig. 8-1a, 8-1b. Swennen et al. 2001: 56, 130, fig. 442. Hylleberg and Kilburn 2003: 87. Kool 2007: figs 17–20. Martin 2008: 120, pl. 355, fig. 13; 128, pl. 359, fig. 13. Surakiatchai et al. 2018: table 5, pl. 1, fig. 9a, b. Wells et al. 2021: 99.

*Zeuxis siquijorensis*. Thach 2005: 148, pl. 44, fig. 25.

*Nassarius siquinjorensis* [sic]. Yang et al. 2017: 90, fig. 371.
**Referred material.** CUF-NKNY-G01 (10 shells; Figs 3P, 7D).

**Habitat.** Sandy and muddy bottoms from subtidal zones to 450 m depth (Cernohorsky 1984; Thach 2005; Yang et al. 2017).

**Distribution.** Red Sea to India; Indo-West Pacific, from Japan to Indonesia and New Caledonia (Cernohorsky 1984; Dharma 2005; Yang et al. 2017). Records of fossils from the Pliocene in Indonesia and from the Holocene in Thailand (Cernohorsky 1984; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Nassarius castus* (Gould, 1850), in having a more tapering spire, canaliculate sutures, and considerably more numerous axial ribs (Cernohorsky 1984). See also comprehensive taxonomic remarks in Cernohorsky (1984) and Kool (2007).

**Superfamily Muricoidea Rafinesque, 1815**

**Family Muricidae Rafinesque, 1815**

**Chicoreus Montfort, 1810**

**Chicoreus capucinus (Lamarck, 1822)**

Figs 4E, 7E

*Murex capucinus* Lamarck, 1822: 164. Type locality: unknown.

*Naquetia capucina*. Tantanasiriwong 1978: 13. Nateewathana et al. 1981: 59. Way and Purchon 1981: 318. Bussarawit 1991: 31.

*Chicoreus (Rhizophorimurex) capucinus*. Houart 1992: 106–109, fig. 217. Tan 2000: 504. Dharma 2005: 164, pl. 57, fig. 20; 336, pl. 133, fig. 9a-c. Thach 2005: 114, pl. 36, fig. 2. Merle et al. 2011: 99, text-fig. 39.

*Chicoreus capucinus*. Wilson 1994: 27, pl. 3, fig. 12a, b. Middelfart 1997: 358, pl. 2, fig. 7. Hylleberg and Kilburn 2003: 69. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Houart 2008: 154, pl. 372, fig. 1. Printrakoon et al. 2008: table 1. Nabhitabha-ta 2009: 141. BEDO 2017b: 300, with in-text fig. Sanpanich and Duangdee 2013: 62. Dechruksa et al. 2014: fig. 4d. Wells et al. 2021: 113.

*Chicoreus (Naquetia) capucinus*. Subba Rao and Dey 2000: 100.

*Chicoreus copucinus* [sic]. Sri-aroon et al. 2004: table 1.

**Referred material.** CUF-NKNY-G11, G12 (30 shells; Figs 4E, 7E).

**Habitat.** Muddy sand and rocks in mangrove forests (Thach 2005).

**Distribution.** Indo-West Pacific, from the Philippines to Australia to Fiji Islands (Houart 1992). Records of fossils from the Middle Miocene to Late Pliocene in Indonesia (Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Houart (1992) and Merle et al. (2011), specifically in having a rounded last whorl usually associated with three spineless varices, each with a short and webbed expansion on adapical section, an aperture with a characteristically small callus with straight, adherent columellar lip, and a broad siphonal canal. See also comprehensive taxonomic remarks in Houart (1992).
**Referred material.** CUF-NKNY-G01 (10 shells; Figs 3P, 7D).

**Habitat.** Sandy and muddy bottoms from subtidal zones to 450 m depth (Cernohorsky 1984; Thach 2005; Yang et al. 2017).

**Distribution.** Red Sea to India; Indo-West Pacific, from Japan to Indonesia and New Caledonia (Cernohorsky 1984; Dharma 2005; Yang et al. 2017). Records of fossils from the Pliocene in Indonesia and from the Holocene in Thailand (Cernohorsky 1984; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Nassarius castus* (Gould, 1850), in having a more tapering spire, canaliculate sutures, and considerably more numerous axial ribs (Cernohorsky 1984). See also comprehensive taxonomic remarks in Cernohorsky (1984) and Kool (2007).

**Superfamily Muricoidea Rafinesque, 1815**

**Family Muricidae Rafinesque, 1815**

**Chicoreus Montfort, 1810**

**Chicoreus capucinus (Lamarck, 1822)**

Figs 4E, 7E

*Murex capucinus* Lamarck, 1822: 164. Type locality: unknown.

*Naquetia capucina*. Tantanasiriwong 1978: 13. Nateewathana et al. 1981: 59. Way and Purchon 1981: 318. Bussarawit 1991: 31.

*Chicoreus (Rhizophorimurex) capucinus*. Houart 1992: 106–109, fig. 217. Tan 2000: 504. Dharma 2005: 164, pl. 57, fig. 20; 336, pl. 133, fig. 9a-c. Thach 2005: 114, pl. 36, fig. 2. Merle et al. 2011: 99, text-fig. 39.

*Chicoreus capucinus*. Wilson 1994: 27, pl. 3, fig. 12a, b. Middelfart 1997: 358, pl. 2, fig. 7. Hylleberg and Kilburn 2003: 69. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Houart 2008: 154, pl. 372, fig. 1. Printrakoon et al. 2008: table 1. Nabhitabha-ta 2009: 141. BEDO 2017b: 300, with in-text fig. Sanpanich and Duangdee 2013: 62. Dechruksa et al. 2014: fig. 4d. Wells et al. 2021: 113.

*Chicoreus (Naquetia) capucinus*. Subba Rao and Dey 2000: 100.

*Chicoreus copucinus* [sic]. Sri-aroon et al. 2004: table 1.

**Referred material.** CUF-NKNY-G11, G12 (30 shells; Figs 4E, 7E).

**Habitat.** Muddy sand and rocks in mangrove forests (Thach 2005).

**Distribution.** Indo-West Pacific, from the Philippines to Australia to Fiji Islands (Houart 1992). Records of fossils from the Middle Miocene to Late Pliocene in Indonesia (Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Houart (1992) and Merle et al. (2011), specifically in having a rounded last whorl usually associated with three spineless varices, each with a short and webbed expansion on adapical section, an aperture with a characteristically small callus with straight, adherent columellar lip, and a broad siphonal canal. See also comprehensive taxonomic remarks in Houart (1992).
Indothais Claremont et al., 2013

Indothais gradata (Jonas, 1846)

Figs 4F, 7F

*Purpura gradata* Jonas, 1846: 14–15. Type locality: Indian Ocean, near Singapore.

*Thais gradata*. Bussarawit 1991: 33. Middelfart 1997: 367–368, pl. 4, fig. 1. Tan 2000: 499. Hylleberg and Kilburn 2003: 76. Dharma 2005: 170, pl. 60, fig. 11a, b; 340, pl. 135, fig. 1a–e. Printrakoon et al. 2008: table 1. Yang et al. 2017: 76, fig. 316.

*Stramonita gradata*. Wilson 1994: 47, pl. 4, fig. 5a, b. Thach 2005: 128, pl. 37, figs 33, 37.

*Indothais gradata*. Okutani 2017: 963, pl. 255, fig. 9. Wells et al. 2021: 114.

**Referred material.** CUF-NKNY-G29 (1 shell; Figs 4F, 7F).

**Habitat.** Rocky bottom at a depth from 1 to 5 m (Thach 2005; Okutani 2017).

**Distribution.** Indo-West Pacific, from Japan to Australia (Okutani 2017; Yang et al. 2017). Records of fossils from the Middle to Late Pliocene in Indonesia (Dharma 2005).

**Record in Thailand.** Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Middlefart (1997), specifically in having an erect and crenulate outer lip, which has a pronounced indentation in the subsutural ramp area, and an aperture with four denticles with proceeding lirae present inside.

Indothais lacera (Born, 1778)

Figs 4C, 8A

*Murex lacerus* Born, 1778: 107–108. Type locality: unknown.

*Cymia lacera*. Bussarawit 1991: 32. Poutiers 1998b: 561, with in-text figs. Thach 2005: 123, pl. 36, fig. 1.

*Thais lacera*. Bosch et al. 1995: 123, fig. 491. Middlefart 1997: 369, pl. 4, fig. 4. Subba Rao and Dey 2000: 113. Tan 2000: 499. Swennen et al. 2001: 56, 127, fig. 422. Hylleberg and Kilburn 2003: 76–77. Robba et al. 2003: table 2. Robba et al. 2004: 102, pl. 13, fig. 6a, b. Dharma 2005: 170, pl. 60, fig. 12a-c; 338, pl. 134, fig. 15a-h. Dey 2006: 40–41, figs 45, 46. Ramakrishna et al. 2007: 11, 93, pl. 7, figs 79, 80. Robba et al. 2007: 92 (appendix). Nolf 2009: 9–10, figs 1–14. Kumar et al. 2017: 1101, fig. 1a, b.

*Cuma lacera*. Nabhitabhata 2009: 143. Yang et al. 2017: 78, fig. 324.

*Indothais lacera*. Sanpanich and Duangdee 2013: 63. BEDO 2017b: 305, with in-text fig. Kantharajan et al. 2017: table 1, fig. 3-11. Tudu et al. 2018: table 1. Wells et al. 2021: 114.

**Referred material.** CUF-NKNY-G08 (106 shells; Figs 4C, 8A).

**Habitat.** Mangrove forests (Kantharajan et al. 2017) and rocky bottom at a depth of 1–25 m (Thach 2005).

**Distribution.** South Africa to India; Indo-West Pacific, from Japan to New Caledonia (Poutiers 1998b; Robba et al. 2004; Kantharajan et al. 2017; Yang et al. 2017) as well as from western Mediterranean Sea (Nolf 2009). Records of
**Indothais Claremont et al., 2013**

**Indothais gradata (Jonas, 1846)**

Figs 4F, 7F

*Purpura gradata* Jonas, 1846: 14–15. Type locality: Indian Ocean, near Singapore.

*Thais gradata*. Bussarawit 1991: 33. Middelfart 1997: 367–368, pl. 4, fig. 1. Tan 2000: 499. Hylleberg and Kilburn 2003: 76. Dharma 2005: 170, pl. 60, fig. 11a, b; 340, pl. 135, fig. 1a–e. Printrakoon et al. 2008: table 1. Yang et al. 2017: 76, fig. 316.

*Stramonita gradata*. Wilson 1994: 47, pl. 4, fig. 5a, b. Thach 2005: 128, pl. 37, figs 33, 37.

*Indothais gradata*. Okutani 2017: 963, pl. 255, fig. 9. Wells et al. 2021: 114.

**Referred material.** CUF-NKNY-G29 (1 shell; Figs 4F, 7F).

**Habitat.** Rocky bottom at a depth from 1 to 5 m (Thach 2005; Okutani 2017).

**Distribution.** Indo-West Pacific, from Japan to Australia (Okutani 2017; Yang et al. 2017). Records of fossils from the Middle to Late Pliocene in Indonesia (Dharma 2005).

**Record in Thailand.** Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Middlefart (1997), specifically in having an erect and crenulate outer lip, which has a pronounced indentation in the subsutural ramp area, and an aperture with four denticles with proceeding lirae present inside.

**Indothais lacera (Born, 1778)**

Figs 4C, 8A

*Murex lacerus* Born, 1778: 107–108. Type locality: unknown.

*Cymia lacera*. Bussarawit 1991: 32. Poutiers 1998b: 561, with in-text figs. Thach 2005: 123, pl. 36, fig. 1.

*Thais lacera*. Bosch et al. 1995: 123, fig. 491. Middlefart 1997: 369, pl. 4, fig. 4. Subba Rao and Dey 2000: 113. Tan 2000: 499. Swennen et al. 2001: 56, 127, fig. 422. Hylleberg and Kilburn 2003: 76–77. Robba et al. 2003: table 2. Robba et al. 2004: 102, pl. 13, fig. 6a, b. Dharma 2005: 170, pl. 60, fig. 12a–c; 338, pl. 134, fig. 15a–h. Dey 2006: 40–41, figs 45, 46. Ramakrishna et al. 2007: 11, 93, pl. 7, figs 79, 80. Robba et al. 2007: 92 (appendix). Nolf 2009: 9–10, figs 1–14. Kumar et al. 2017: 1101, fig. 1a, b.

*Cuma lacera*. Nabhitabhata 2009: 143. Yang et al. 2017: 78, fig. 324.

*Indothais lacera*. Sanpanich and Duangdee 2013: 63. BEDO 2017b: 305, with in-text fig. Kantharajan et al. 2017: table 1, fig. 3-11. Tudu et al. 2018: table 1. Wells et al. 2021: 114.

**Referred material.** CUF-NKNY-G08 (106 shells; Figs 4C, 8A).

**Habitat.** Mangrove forests (Kantharajan et al. 2017) and rocky bottom at a depth of 1–25 m (Thach 2005).

**Distribution.** South Africa to India; Indo-West Pacific, from Japan to New Caledonia (Poutiers 1998b; Robba et al. 2004; Kantharajan et al. 2017; Yang et al. 2017) as well as from western Mediterranean Sea (Nolf 2009). Records of
<figure><img src="image_8.png" /><figcaption>**Figure 8.** Gastropods A Indothais lacera B Murex trapa C Turricula javana D Inquisitor vulpionis E Pristiterebra miranda F Granuliterebra bathyrhaphe.</figcaption></figure>

fossils from the Middle Miocene to Quaternary in Indonesia and from the Holocene in Thailand (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Middlefart (1997) and Poutiers (1998b), specifically in having a body whorl bearing one to two spiral ridges, in which the prominent one bears eight spines, and an elaborate crenulate outer lip with a strong incision where the spiral ridge(s) and the anal sulcus are positioned.
<figure><img src="image_9.png" /><figcaption>**Figure 8.** Gastropods A Indothais lacera B Murex trapa C Turricula javana D Inquisitor vulpionis E Pristiterebra miranda F Granuliterebra bathyrhaphe.</figcaption></figure>

fossils from the Middle Miocene to Quaternary in Indonesia and from the Holocene in Thailand (Robba et al. 2004; Dharma 2005).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Middlefart (1997) and Poutiers (1998b), specifically in having a body whorl bearing one to two spiral ridges, in which the prominent one bears eight spines, and an elaborate crenulate outer lip with a strong incision where the spiral ridge(s) and the anal sulcus are positioned.
**Murex Linnaeus, 1758**

**Murex trapa Röding, 1798**

Figs 4B, 8B

*Murex trapa* Röding, 1798: 145. Type locality: Tranquebar, India. Tantanasiri-wong 1978: 13, fig. 174. Nateewathana et al. 1981: 59. Way and Ponder 1981: 318. Ponder and Vokes 1988: 41–45, figs 17–19, 67g, h, 71b, c, 73d, 83g, h. Bussarawit 1991: 31. Middelfart 1997: 352, pl. 1, fig. 1. Poutiers 1998b: 565, with in-text figs. Subba Rao and Dey 2000: 102. Tan 2000: 503. Swennen et al. 2001: 55, 126, fig. 410. Hylleberg and Kilburn 2003: 72–73. Robba et al. 2003: table 5. Robba et al. 2004: 96–97, pl. 12, fig. 9a, b. Dharma 2005: 158, pl. 54, fig. 4a, b; 334, pl. 132, fig. 3a–c. Ramakrishna et al. 2007: 10, 85–86. Robba et al. 2007: 92 (appendix). Houart 2008: 136, pl. 636, fig. 2. Nabhitabhata 2009: 147. BEDO 2017b: 312, with in-text fig. Yang et al. 2017: 70, fig. 288. Surakiatchai et al. 2018: table 5, pl. 1, fig. 7a, b. Tudu et al. 2018: table 1. Wells et al. 2021: 116.

*Murex cf. trapa*. Aungtonya and Hylleberg 1998: 319.

*Murex (Murex) trapa*. Gemert 2003: 105. Thach 2005: 119, pl. 34, fig. 9. Merle et al. 2011: 59, text-fig. 27e; pl. 4, fig. 7; pl. 5, figs 8–10. Gopalakrishnan et al. 2012: 77. Sanpanich and Duangdee 2013: 63. Okutani 2017: 947, pl. 238, fig. 6.

**Referred material.** CUF-NKNY-G09 (33 shells; Figs 4B, 8B).

**Habitat.** Fine sand and muddy sand bottoms at a depth of 5–60 m (Swennen et al. 2001; Robba et al. 2004).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Fiji Islands (Dharma 2005; Okutani 2017). Records of fossils from the Middle Miocene to Holocene in Indonesia, Malaysia, the Philippines, Taiwan, and Thailand (Ponder and Vokes 1988; Robba et al. 2004; Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from other related species in having a higher spire, angulated whorls, and shorter spines (Ponder and Vokes 1988). See also comprehensive taxonomic remarks in Ponder and Vokes (1988).

**Superfamily Conoidea Fleming, 1822**

**Family Borsoniidae Bellardi, 1875**

**Maoritomella Powell, 1942**

**Maoritomella vallata (Gould, 1860)**

Figs 4S, 9A

*Drillia vallata* Gould, 1860: 336. Type locality: Hong Kong. Johnson 1964: 164, pl. 7, fig. 6.

*Asthenotoma vallata*. Yen 1944: 575, pl. 51, figs 6, 7.

*Maoritomella vallata*. Robba et al. 2003: table 5. Robba et al. 2004: 134–135, pl. 18, fig. 5a, b. Robba et al. 2007: 94 (appendix). Wells et al. 2021: 100.

**Referred material.** CUF-NKNY-G30 (5 shells; Figs 4S, 9A).
**Murex Linnaeus, 1758**

**Murex trapa Röding, 1798**

Figs 4B, 8B

*Murex trapa* Röding, 1798: 145. Type locality: Tranquebar, India. Tantanasiri-wong 1978: 13, fig. 174. Nateewathana et al. 1981: 59. Way and Ponder 1981: 318. Ponder and Vokes 1988: 41–45, figs 17–19, 67g, h, 71b, c, 73d, 83g, h. Bussarawit 1991: 31. Middelfart 1997: 352, pl. 1, fig. 1. Poutiers 1998b: 565, with in-text figs. Subba Rao and Dey 2000: 102. Tan 2000: 503. Swennen et al. 2001: 55, 126, fig. 410. Hylleberg and Kilburn 2003: 72–73. Robba et al. 2003: table 5. Robba et al. 2004: 96–97, pl. 12, fig. 9a, b. Dharma 2005: 158, pl. 54, fig. 4a, b; 334, pl. 132, fig. 3a–c. Ramakrishna et al. 2007: 10, 85–86. Robba et al. 2007: 92 (appendix). Houart 2008: 136, pl. 636, fig. 2. Nabhitabhata 2009: 147. BEDO 2017b: 312, with in-text fig. Yang et al. 2017: 70, fig. 288. Surakiatchai et al. 2018: table 5, pl. 1, fig. 7a, b. Tudu et al. 2018: table 1. Wells et al. 2021: 116.

*Murex cf. trapa*. Aungtonya and Hylleberg 1998: 319.

*Murex (Murex) trapa*. Gemert 2003: 105. Thach 2005: 119, pl. 34, fig. 9. Merle et al. 2011: 59, text-fig. 27e; pl. 4, fig. 7; pl. 5, figs 8–10. Gopalakrishnan et al. 2012: 77. Sanpanich and Duangdee 2013: 63. Okutani 2017: 947, pl. 238, fig. 6.

**Referred material.** CUF-NKNY-G09 (33 shells; Figs 4B, 8B).

**Habitat.** Fine sand and muddy sand bottoms at a depth of 5–60 m (Swennen et al. 2001; Robba et al. 2004).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Fiji Islands (Dharma 2005; Okutani 2017). Records of fossils from the Middle Miocene to Holocene in Indonesia, Malaysia, the Philippines, Taiwan, and Thailand (Ponder and Vokes 1988; Robba et al. 2004; Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from other related species in having a higher spire, angulated whorls, and shorter spines (Ponder and Vokes 1988). See also comprehensive taxonomic remarks in Ponder and Vokes (1988).

**Superfamily Conoidea Fleming, 1822**

**Family Borsoniidae Bellardi, 1875**

**Maoritomella Powell, 1942**

**Maoritomella vallata (Gould, 1860)**

Figs 4S, 9A

*Drillia vallata* Gould, 1860: 336. Type locality: Hong Kong. Johnson 1964: 164, pl. 7, fig. 6.

*Asthenotoma vallata*. Yen 1944: 575, pl. 51, figs 6, 7.

*Maoritomella vallata*. Robba et al. 2003: table 5. Robba et al. 2004: 134–135, pl. 18, fig. 5a, b. Robba et al. 2007: 94 (appendix). Wells et al. 2021: 100.

**Referred material.** CUF-NKNY-G30 (5 shells; Figs 4S, 9A).
**Habitat.** Probably present in shallow sublittoral areas (Robba et al. 2004).

**Distribution.** Indo-West Pacific. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Yen (1944), Johnson (1964), and Robba et al. (2004), specifically in having a high-spired and claviform shell, with the sculpture of one rather strong and peripheral spiral cord, a weaker one abapical to the spiral cord, and one or two spiral threads on the shoulder slope, resulting in a total of 12–14 spirals occurring along the body whorl. This species is poorly known and has been assigned to *Maoritomella* due to a blunt, smooth, and paucispiral protoconch (1.5 whorls in this species), which is the diagnostic character of the genus (Powell 1942).

**Family Clathurellidae H. Adams & A. Adams, 1858**

*Pseudoetrema Oyama, 1953*

*Pseudoetrema fortilirata (Smith, 1879)*

Figs 4M, 9B

*Drillia fortilirata* Smith, 1879b: 194, pl. 19, fig. 22. Type locality: Station 14, east of Goto Islands, 32°48'N, 129°6'E; 47 fathoms, and station 21, between south-western extremity of Niphon and the island of Shikoku, 33°45'N, 132°30'E, 30 fathoms. Yokoyama 1927: 393, 410, pl. 46, fig. 20.

*Pseudoetrema fortilirata*. Oyama 1953: 154. Robba et al. 2004: 141, pl. 19, fig. 6. Robba et al. 2007: 94 (appendix). Okutani 2017: 1017, pl. 311, fig. 7. Wells et al. 2021: 101.

**Referred material.** CUF-NKNY-G38 (5 shells; Figs 4M, 9B).

**Habitat.** Sand and sandy mud in sublittoral areas to 50 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Japan and Thailand. Records of fossils from the Pliocene to Holocene in Japan, Taiwan, and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Smith (1879b), Yokoyama (1927), and Robba et al. (2004), specifically in having a high-spired, claviform shell with the sculpture of nine broad and low collabral ribs fading away shortly before the subsutural cord and overriding spirals, three closely set spiral cords: adapical, peripheral, and abapical cords, and a weaker more adapical one on the penultimate whorl, resulting in a total of 14 spirals occurring along the body whorl. This species is the type species of *Pseudoetrema* (Oyama 1953).

**Family Clavatulidae Gray, 1853**

*Turricula Schumacher, 1817*

*Turricula javana* (Linnaeus, 1767)

Figs 4I, 8C

*Murex javanus* Linnaeus, 1767: 1221. Type locality: Java.
**Habitat.** Probably present in shallow sublittoral areas (Robba et al. 2004).

**Distribution.** Indo-West Pacific. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Yen (1944), Johnson (1964), and Robba et al. (2004), specifically in having a high-spired and claviform shell, with the sculpture of one rather strong and peripheral spiral cord, a weaker one abapical to the spiral cord, and one or two spiral threads on the shoulder slope, resulting in a total of 12-14 spirals occurring along the body whorl. This species is poorly known and has been assigned to *Maoritomella* due to a blunt, smooth, and paucispiral protoconch (1.5 whorls in this species), which is the diagnostic character of the genus (Powell 1942).

**Family Clathurellidae H. Adams & A. Adams, 1858**

*Pseudoetrema Oyama, 1953*

*Pseudoetrema fortilirata (Smith, 1879)*

Figs 4M, 9B

*Drillia fortilirata* Smith, 1879b: 194, pl. 19, fig. 22. Type locality: Station 14, east of Goto Islands, 32°48'N, 129°6'E; 47 fathoms, and station 21, between south-western extremity of Niphon and the island of Shikoku, 33°45'N, 132°30'E, 30 fathoms. Yokoyama 1927: 393, 410, pl. 46, fig. 20.

*Pseudoetrema fortilirata*. Oyama 1953: 154. Robba et al. 2004: 141, pl. 19, fig. 6. Robba et al. 2007: 94 (appendix). Okutani 2017: 1017, pl. 311, fig. 7. Wells et al. 2021: 101.

**Referred material.** CUF-NKNY-G38 (5 shells; Figs 4M, 9B).

**Habitat.** Sand and sandy mud in sublittoral areas to 50 m depth (Robba et al. 2004; Okutani 2017).

**Distribution.** Japan and Thailand. Records of fossils from the Pliocene to Holocene in Japan, Taiwan, and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Smith (1879b), Yokoyama (1927), and Robba et al. (2004), specifically in having a high-spired, claviform shell with the sculpture of nine broad and low collabral ribs fading away shortly before the subsutural cord and overriding spirals, three closely set spiral cords: adapical, peripheral, and abapical cords, and a weaker more adapical one on the penultimate whorl, resulting in a total of 14 spirals occurring along the body whorl. This species is the type species of *Pseudoetrema* (Oyama 1953).

**Family Clavatulidae Gray, 1853**

*Turricula Schumacher, 1817*

*Turricula javana* (Linnaeus, 1767)

Figs 4I, 8C

*Murex javanus* Linnaeus, 1767: 1221. Type locality: Java.
<figure><img src="image_9.png" /><figcaption>**Figure 9.** Gastropods A Maoritomella vallata B Pseudoetrema fortilirata C Paradrillia melvilli D Comitas ilariae.</figcaption></figure>

*Turricula (Vulpecula) javana*. Tesch 1915: 48–49, pl. 80, fig. 104a, b.

*Turricula javana*. Powell 1969: 235–237, pl. 192, figs 10, 11; pl. 201, fig. 11. Tantana-siriwong 1978: 17. Nateewathana et al. 1981: 61. Way and Purchon 1981: 320. Poutiers 1998b: 630, with in-text figs. Swennen et al. 2001: 57, 133, fig. 463. Hyl-leberg and Kilburn 2003: 104. Robba et al. 2003: tables 3, 5. Robba et al. 2004: 136, pl. 18, fig. 8a, b. Dharma 2005: 130, pl. 40, fig. 8a, b. Thach 2005: 214, pl. 59,
<figure><img src="image_10.png" /><figcaption>**Figure 9.** Gastropods A Maoritomella vallata B Pseudoetrema fortilirata C Paradrillia melvilli D Comitas ilariae.</figcaption></figure>

*Turricula (Vulpecula) javana*. Tesch 1915: 48–49, pl. 80, fig. 104a, b.

*Turricula javana*. Powell 1969: 235–237, pl. 192, figs 10, 11; pl. 201, fig. 11. Tantana-siriwong 1978: 17. Nateewathana et al. 1981: 61. Way and Purchon 1981: 320. Poutiers 1998b: 630, with in-text figs. Swennen et al. 2001: 57, 133, fig. 463. Hyl-leberg and Kilburn 2003: 104. Robba et al. 2003: tables 3, 5. Robba et al. 2004: 136, pl. 18, fig. 8a, b. Dharma 2005: 130, pl. 40, fig. 8a, b. Thach 2005: 214, pl. 59,
fig. 16; pl. 60, fig. 24. Ramakrishna et al. 2007: 15, 133, 134. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 196. Sanpanich and Duangdee 2013: 60. BEDO 2017b: 354, with in-text fig. Yang et al. 2017: 114, fig. 472. Surakiatchai et al. 2018: table 5, pl. 1, fig. 11a, b. Tudu et al. 2018: table 1. Wells et al. 2021: 101.

**Referred material.** CUF-NKNY-G15, G20 (53 shells; Figs 4I, 8C).

**Habitat.** Intertidal sand and rocks and muddy bottoms at a depth from 20 to 80 m (Robba et al. 2004; Thach 2005).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Yang et al. 2017). Records of fossils from the Late Miocene to Holocene in India, Indonesia, and Thailand (Robba et al. 2004; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Powell (1969) and Robba et al. (2004), specifically in having an elongate-fusiform shell with the sculpture of oblique nodes on the peripheral angulation and finer spiral cords over the shoulder slope as well as a twin cord forming a weak subsutural margin. See also comprehensive taxonomic remarks in Powell (1969).

**Family Horaiclavidae Bouchet et al., 2011**

**Paradrillia Makiyama, 1940**

**Paradrillia melvilli Powell, 1969**

Figs 4N, 9C

*Paradrillia melvilli* Powell, 1969: 314–315, pl. 242, fig. 2; pl. 245, figs 1, 2. Type locality: Persian Gulf. Robba et al. 2004: 137, 139, pl. 19, fig. 2. Robba et al. 2007: 95 (appendix). Wells et al. 2021: 107.

**Referred material.** CUF-NKNY-G52 (7 shells; Figs 4N, 9C).

**Habitat.** Sublittoral and upper bathyal zones (Robba et al. 2004).

**Distribution.** Persian Gulf and Indian Ocean; Gulf of Thailand. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Powell (1969) and Robba et al. (2004), specifically in having a light built claviform shell with a medially situated blunt peripheral keel bearing rather weak cog-like axial nodes, approximately 18 or 19 per whorl.

**Family Pseudomelatomidae Morrison, 1966**

**Inquisitor Hedley, 1918**

**Inquisitor vulpionis Kuroda & Oyama, 1971**

Figs 4H, 8D

*Inquisitor vulpionis* Kuroda & Oyama in Kuroda et al., 1971: 215, pl. 56, fig. 4; pl. 110, fig. 15. Type locality: Sagami Bay, Japan. Robba et al. 2004: 133, pl. 18, fig. 2a-c. Robba et al. 2007: 93 (appendix). Wells et al. 2021: 108.
fig. 16; pl. 60, fig. 24. Ramakrishna et al. 2007: 15, 133, 134. Robba et al. 2007: 93 (appendix). Nabhitabhata 2009: 196. Sanpanich and Duangdee 2013: 60. BEDO 2017b: 354, with in-text fig. Yang et al. 2017: 114, fig. 472. Surakiatchai et al. 2018: table 5, pl. 1, fig. 11a, b. Tudu et al. 2018: table 1. Wells et al. 2021: 101.

**Referred material.** CUF-NKNY-G15, G20 (53 shells; Figs 4I, 8C).

**Habitat.** Intertidal sand and rocks and muddy bottoms at a depth from 20 to 80 m (Robba et al. 2004; Thach 2005).

**Distribution.** Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Yang et al. 2017). Records of fossils from the Late Miocene to Holocene in India, Indonesia, and Thailand (Robba et al. 2004; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Powell (1969) and Robba et al. (2004), specifically in having an elongate-fusiform shell with the sculpture of oblique nodes on the peripheral angulation and finer spiral cords over the shoulder slope as well as a twin cord forming a weak subsutural margin. See also comprehensive taxonomic remarks in Powell (1969).

**Family Horaiclavidae Bouchet et al., 2011**

**Paradrillia Makiyama, 1940**

**Paradrillia melvilli Powell, 1969**

Figs 4N, 9C

*Paradrillia melvilli* Powell, 1969: 314–315, pl. 242, fig. 2; pl. 245, figs 1, 2. Type locality: Persian Gulf. Robba et al. 2004: 137, 139, pl. 19, fig. 2. Robba et al. 2007: 95 (appendix). Wells et al. 2021: 107.

**Referred material.** CUF-NKNY-G52 (7 shells; Figs 4N, 9C).

**Habitat.** Sublittoral and upper bathyal zones (Robba et al. 2004).

**Distribution.** Persian Gulf and Indian Ocean; Gulf of Thailand. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Powell (1969) and Robba et al. (2004), specifically in having a light built claviform shell with a medially situated blunt peripheral keel bearing rather weak cog-like axial nodes, approximately 18 or 19 per whorl.

**Family Pseudomelatomidae Morrison, 1966**

**Inquisitor Hedley, 1918**

**Inquisitor vulpionis Kuroda & Oyama, 1971**

Figs 4H, 8D

*Inquisitor vulpionis* Kuroda & Oyama in Kuroda et al., 1971: 215, pl. 56, fig. 4; pl. 110, fig. 15. Type locality: Sagami Bay, Japan. Robba et al. 2004: 133, pl. 18, fig. 2a-c. Robba et al. 2007: 93 (appendix). Wells et al. 2021: 108.
**Referred material.** CUF-NKNY-G28 (1 shell; Figs 4H, 8D).

**Habitat.** Sandy bottoms at a depth from 10 to 100 m (Robba et al. 2004).

**Distribution.** Japan and the Philippines. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2004), specifically in having a claviform shell with the sculpture of nine collabral ribs resulting in a nodose appearance at the periphery and gradually fading away on the shoulder slope as well as the very faint spiral sculpture all over the shell except for the base where more prominent cords are developed.

**Comitas Finlay, 1926**

**Comitas ilariae Bozzetti, 1991**

Figs 4Q, 9D

*Comitas ilariae* Bozzetti, 1991: 26–28, figs 1–3. Type locality: island of Bohol, central Philippines. Olivera and Sysoev 2008: 786, pl. 688, figs 9, 10.

**Referred material.** CUF-NKNY-G55 (1 shell; Figs 4Q, 9D).

**Habitat.** Sandy bottoms at a depth from 100 to 150 m (Bozzetti 1991).

**Distribution.** Known only from the type locality (Bozzetti 1991).

**Record in Thailand.** New record in Thailand from this study.

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bozzetti (1991) and Olivera and Sysoev (2008), specifically in having a slight, fusiform, and high-spired shell with the axial sculpture made of 7–9 very pronounced, long, and thick tubercles positioned obliquely on each whorl as well as numerous dense spiral cords.

**Family Terebridae Mörch, 1852**

**Duplicaria Dall, 1908**

**Duplicaria tricincta (Smith, 1877)**

Figs 4O, 10A

*Terebra tricincta* Smith, 1877: 225. Type locality: Persian Gulf. Bratcher and Cer-nohorsky 1987: 76, pl. 17, fig. 58a, b. Wilson 1994: 229, with in-text fig. Hyl-leberg and Kilburn 2003: 106. Robba et al. 2004: 157, pl. 21, fig. 8. Robba et al. 2007: 95 (appendix).

*Granuliterebra tricincta*. BEDO 2017b: 360, with in-text fig. Okutani 2017: 1050, pl. 339, fig. 14. Tudu et al. 2018: table 1. Wells et al. 2021: 109.

*Duplicaria tricincta*. Fedosov et al. 2019: 365, fig. 3b. Aubry et al. 2021: pl. 36. Bibi et al. 2021: 51, pl. 1, figs 9–11.

**Referred material.** CUF-NKNY-G33 (5 shells; Figs 4O, 10A).

**Habitat.** Sandy mud bottoms at a depth from 10 to 50 m (Robba et al. 2004; Okutani 2017).
**Referred material.** CUF-NKNY-G28 (1 shell; Figs 4H, 8D).

**Habitat.** Sandy bottoms at a depth from 10 to 100 m (Robba et al. 2004).

**Distribution.** Japan and the Philippines. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2004), specifically in having a claviform shell with the sculpture of nine collabral ribs resulting in a nodose appearance at the periphery and gradually fading away on the shoulder slope as well as the very faint spiral sculpture all over the shell except for the base where more prominent cords are developed.

**Comitas Finlay, 1926**

**Comitas ilariae Bozzetti, 1991**

Figs 4Q, 9D

*Comitas ilariae* Bozzetti, 1991: 26–28, figs 1–3. Type locality: island of Bohol, central Philippines. Olivera and Sysoev 2008: 786, pl. 688, figs 9, 10.

**Referred material.** CUF-NKNY-G55 (1 shell; Figs 4Q, 9D).

**Habitat.** Sandy bottoms at a depth from 100 to 150 m (Bozzetti 1991).

**Distribution.** Known only from the type locality (Bozzetti 1991).

**Record in Thailand.** New record in Thailand from this study.

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bozzetti (1991) and Olivera and Sysoev (2008), specifically in having a slight, fusiform, and high-spired shell with the axial sculpture made of 7–9 very pronounced, long, and thick tubercles positioned obliquely on each whorl as well as numerous dense spiral cords.

**Family Terebridae Mörch, 1852**

**Duplicaria Dall, 1908**

**Duplicaria tricincta (Smith, 1877)**

Figs 4O, 10A

*Terebra tricincta* Smith, 1877: 225. Type locality: Persian Gulf. Bratcher and Cer-nohorsky 1987: 76, pl. 17, fig. 58a, b. Wilson 1994: 229, with in-text fig. Hyl-leberg and Kilburn 2003: 106. Robba et al. 2004: 157, pl. 21, fig. 8. Robba et al. 2007: 95 (appendix).

*Granuliterebra tricincta*. BEDO 2017b: 360, with in-text fig. Okutani 2017: 1050, pl. 339, fig. 14. Tudu et al. 2018: table 1. Wells et al. 2021: 109.

*Duplicaria tricincta*. Fedosov et al. 2019: 365, fig. 3b. Aubry et al. 2021: pl. 36. Bibi et al. 2021: 51, pl. 1, figs 9–11.

**Referred material.** CUF-NKNY-G33 (5 shells; Figs 4O, 10A).

**Habitat.** Sandy mud bottoms at a depth from 10 to 50 m (Robba et al. 2004; Okutani 2017).
**Distribution.** Persian Gulf; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), and differs from its similar species, *Granuliterebra bathyrhaphe* (Smith, 1875), in having a smaller shell and two additional minutely beaded spiral cords abapical to the subsutural margin and on the lower base.

**Granuliterebra Oyama, 1961**

**Granuliterebra bathyrhaphe (Smith, 1875)**

Figs 4P, 8F

*Terebra* (*Myurella*) *bathyrhaphe* Smith, 1875: 415. Type locality: Gulf of Yedo [Edo Bay, Honshu, Japan].

*Terebra* sp. Dheeradilok et al. 1984: pl. 3, fig. 11.

*Terebra bathyrhaphe*. Bratcher and Cernohorsky 1987: 75, pl. 17, fig. 57a-e. Wilson 1994: 223, with in-text fig. Bosch et al. 1995: 171, fig. 765. Robba et al. 2004: 155, pl. 21, fig. 5. Robba et al. 2007: 95 (appendix).

*Granuliterebra bathyrhaphe*. Okutani 2017: 1049–1050, pl. 339, fig. 13. Fedosov et al. 2019: 379, fig. 10a. Aubry et al. 2021: pl. 73. Bibi et al. 2021: 50, pl. 1, figs 14–17. Wells et al. 2021: 109.

**Referred material.** CUF-NKNY-G66 (1 shell; Figs 4P, 8F).

**Habitat.** Muddy and sandy bottoms from intertidal zones to 200 m depth (Robba et al. 2004; Aubry et al. 2021).

**Distribution.** Persian Gulf and Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017; Aubry et al. 2021). Records of fossils from the Quaternary in Japan and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), and differs from its similar species, *Duplicaria tricincta* (Smith, 1877), by lacking the band anterior to the subsutural band and by having the other two bands that are connected by well-developed ribs rather than by thin cords.

**Pristiterebra Oyama, 1961**

**Pristiterebra miranda (Smith, 1873)**

Figs 4D, 8E

*Myurella miranda* Smith, 1873: 267–268. Type locality: Malacca.

*Terebra miranda*. Bratcher and Cernohorsky 1987: 78, pl. 18, fig. 63a, b; colour pl. D, fig. 13. Swennen et al. 2001: 57, 134, fig. 471. Robba et al. 2004: 155–156, pl. 21, fig. 6a, b. Dharma 2005: 114, pl. 32, fig. 5a, b. Robba et al. 2007: 95 (appendix).

*Pristiterebra miranda*. Aubry et al. 2021: pl. 296. Wells et al. 2021: 109.
**Distribution.** Persian Gulf; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), and differs from its similar species, *Granuliterebra bathyrhaphe* (Smith, 1875), in having a smaller shell and two additional minutely beaded spiral cords abapical to the subsutural margin and on the lower base.

**Granuliterebra Oyama, 1961**

**Granuliterebra bathyrhaphe (Smith, 1875)**

Figs 4P, 8F

*Terebra* (*Myurella*) *bathyrhaphe* Smith, 1875: 415. Type locality: Gulf of Yedo
[Edo Bay, Honshu, Japan].

*Terebra* sp. Dheeradilok et al. 1984: pl. 3, fig. 11.

*Terebra bathyrhaphe*. Bratcher and Cernohorsky 1987: 75, pl. 17, fig. 57a-e.
Wilson 1994: 223, with in-text fig. Bosch et al. 1995: 171, fig. 765. Robba et
al. 2004: 155, pl. 21, fig. 5. Robba et al. 2007: 95 (appendix).

*Granuliterebra bathyrhaphe*. Okutani 2017: 1049–1050, pl. 339, fig. 13. Fedosov et al. 2019: 379, fig. 10a. Aubry et al. 2021: pl. 73. Bibi et al. 2021: 50, pl. 1, figs 14–17. Wells et al. 2021: 109.

**Referred material.** CUF-NKNY-G66 (1 shell; Figs 4P, 8F).

**Habitat.** Muddy and sandy bottoms from intertidal zones to 200 m depth (Robba et al. 2004; Aubry et al. 2021).

**Distribution.** Persian Gulf and Indian Ocean; Indo-West Pacific, from Japan to Australia (Robba et al. 2004; Okutani 2017; Aubry et al. 2021). Records of fossils from the Quaternary in Japan and Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), and differs from its similar species, *Duplicaria tricincta* (Smith, 1877), by lacking the band anterior to the subsutural band and by having the other two bands that are connected by well-developed ribs rather than by thin cords.

**Pristiterebra Oyama, 1961**

**Pristiterebra miranda (Smith, 1873)**

Figs 4D, 8E

*Myurella miranda* Smith, 1873: 267–268. Type locality: Malacca.

*Terebra miranda*. Bratcher and Cernohorsky 1987: 78, pl. 18, fig. 63a, b; colour pl. D, fig. 13. Swennen et al. 2001: 57, 134, fig. 471. Robba et al. 2004: 155–156, pl. 21, fig. 6a, b. Dharma 2005: 114, pl. 32, fig. 5a, b. Robba et al. 2007: 95 (appendix).

*Pristiterebra miranda*. Aubry et al. 2021: pl. 296. Wells et al. 2021: 109.
<figure><img src="image_10.png" /><figcaption>**Figure 10.** Gastropods and bivalves. A *Duplicaria tricincta* B *Cylichna modesta* C *Jupiteria puellata* D *Saccella mauritiana*.</figcaption></figure>

**Referred material.** CUF-NKNY-G23 (17 shells; Figs 4D, 8E).

**Habitat.** At sea depth of 6–10 m (Bratcher and Cernohorsky 1987; Robba et al. 2004).

**Distribution.** Indo-West Pacific, from Thailand to Indonesia (Bratcher and Cernohorsky 1987; Robba et al. 2004). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), specifically in having a turreted and slightly cyrtoconoid shell with the sculpture completely cancellate throughout and with numerous and unevenly spaced axial cords crossed by ~ 6 spiral cords forming small bead-like nodes at intersections.
<figure><img src="image_11.png" /><figcaption>**Figure 10.** Gastropods and bivalves. A *Duplicaria tricincta* B *Cylichna modesta* C *Jupiteria puellata* D *Saccella mauritiana*.</figcaption></figure>

**Referred material.** CUF-NKNY-G23 (17 shells; Figs 4D, 8E).

**Habitat.** At sea depth of 6–10 m (Bratcher and Cernohorsky 1987; Robba et al. 2004).

**Distribution.** Indo-West Pacific, from Thailand to Indonesia (Bratcher and Cernohorsky 1987; Robba et al. 2004). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Bratcher and Cernohorsky (1987) and Aubry et al. (2021), specifically in having a turreted and slightly cyrtoconoid shell with the sculpture completely cancellate throughout and with numerous and unevenly spaced axial cords crossed by ~ 6 spiral cords forming small bead-like nodes at intersections.
**Subclass Heterobranchia Burmeister, 1837**

**Grade "Lower Heterobranchia"**

**Superfamily Architectonicaidea Gray, 1850**

**Family Architectonicidae Gray, 1850**

**Architectonica Röding, 1798**

**Architectonica perdix** (Hinds, 1844)

Figs 4J, 11A

**Solarium perdix** Hinds, 1844: 22–23. Type locality: Ceylon; north-west coast of Australia.

**Architectonica perdix**. Bieler 1993: 48–52, figs 35–38. Swennen et al. 2001: 57, 135, fig. 477. Hylleberg and Kilburn 2003: 113. Robba et al. 2004: 158, pl. 21, fig. 10a, b. Dharma 2005: 204, pl. 77, fig. 2a, b; 358, pl. 144, fig. 7a, b. Thach 2005: 224. Robba et al. 2007: 95 (appendix). Nabhitabhata 2009: 200. BEDO 2017b: 73, with in-text fig. Yang et al. 2017: 118, 120, fig. 493. Surakiatchai et al. 2018: table 5, pl. 1, fig. 12a, b. Tudu and Balakrishnan 2018: 199–200, fig. 1a–f. Wells et al. 2021: 131.

**Referred material.** CUF-NKNY-G02, G31 (155 shells; Figs 4J, 11A).

**Habitat.** Sandy and muddy bottoms at a depth from 10 to 60 m (Bieler 1993; Thach 2005; Yang et al. 2017).

**Distribution.** Indian Ocean; Indo-West to Central Pacific, from China to Australia and Polynesia (Robba et al. 2004; Tudu and Balakrishnan 2018). Records of fossils from the Middle Pliocene in Indonesia and from the Holocene in Thailand (Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Adelphotectonica reevei* (Hanley, 1862), by having a much smaller protoconch and a much higher upper point of attachment of the whorls (Bieler 1993). See also comprehensive taxonomic remarks in Bieler (1993).

**Cohort Tectipleura Schrödl et al., 2011**

**Subcohort Euopisthobranchia Jörger et al., 2010**

**Order Cephalaspidea Fischer, 1883**

**Superfamily Cylichnoidea H. Adams & A. Adams, 1854**

**Family Cylichnidae H. Adams & A. Adams, 1854**

**Cylichna Lovén, 1846**

**Cylichna modesta Thiele, 1925**

Figs 4R, 10B

**Cylichna modesta** Thiele, 1925: 241–242 [275–276], pl. 44 [32], fig. 7. Type locality: "Neu-Amsterdam", Station 167 (37° 47' südl. Br., 77° 33.7' östl. L., 496 m). Swennen et al. 2001: 137, fig. 497. Wells et al. 2021: 144.

**Adamnestia modesta**. Robba et al. 2004: 230, pl. 34, fig. 5a, b. Robba et al. 2007: 97 (appendix). Negri et al. 2014: table 3.

**Referred material.** CUF-NKNY-G39 (11 shells; Figs 4R, 10B).

**Habitat.** Sublittoral in muddy or fine sandy bottoms (Robba et al. 2004).
**Subclass Heterobranchia Burmeister, 1837**

**Grade "Lower Heterobranchia"**

**Superfamily Architectonicaidea Gray, 1850**

**Family Architectonicidae Gray, 1850**

**Architectonica Röding, 1798**

**Architectonica perdix** (Hinds, 1844)

Figs 4J, 11A

**Solarium perdix** Hinds, 1844: 22–23. Type locality: Ceylon; north-west coast of Australia.

**Architectonica perdix**. Bieler 1993: 48–52, figs 35–38. Swennen et al. 2001: 57, 135, fig. 477. Hylleberg and Kilburn 2003: 113. Robba et al. 2004: 158, pl. 21, fig. 10a, b. Dharma 2005: 204, pl. 77, fig. 2a, b; 358, pl. 144, fig. 7a, b. Thach 2005: 224. Robba et al. 2007: 95 (appendix). Nabhitabhata 2009: 200. BEDO 2017b: 73, with in-text fig. Yang et al. 2017: 118, 120, fig. 493. Surakiatchai et al. 2018: table 5, pl. 1, fig. 12a, b. Tudu and Balakrishnan 2018: 199–200, fig. 1a–f. Wells et al. 2021: 131.

**Referred material.** CUF-NKNY-G02, G31 (155 shells; Figs 4J, 11A).

**Habitat.** Sandy and muddy bottoms at a depth from 10 to 60 m (Bieler 1993; Thach 2005; Yang et al. 2017).

**Distribution.** Indian Ocean; Indo-West to Central Pacific, from China to Australia and Polynesia (Robba et al. 2004; Tudu and Balakrishnan 2018). Records of fossils from the Middle Pliocene in Indonesia and from the Holocene in Thailand (Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Adelphotectonica reevei* (Hanley, 1862), by having a much smaller protoconch and a much higher upper point of attachment of the whorls (Bieler 1993). See also comprehensive taxonomic remarks in Bieler (1993).

**Cohort Tectipleura Schrödl et al., 2011**

**Subcohort Euopisthobranchia Jörger et al., 2010**

**Order Cephalaspidea Fischer, 1883**

**Superfamily Cylichnoidea H. Adams & A. Adams, 1854**

**Family Cylichnidae H. Adams & A. Adams, 1854**

**Cylichna Lovén, 1846**

**Cylichna modesta Thiele, 1925**

Figs 4R, 10B

**Cylichna modesta** Thiele, 1925: 241–242 [275–276], pl. 44 [32], fig. 7. Type locality: "Neu-Amsterdam", Station 167 (37° 47' südl. Br., 77° 33.7' östl. L., 496 m). Swennen et al. 2001: 137, fig. 497. Wells et al. 2021: 144.

**Adamnestia modesta**. Robba et al. 2004: 230, pl. 34, fig. 5a, b. Robba et al. 2007: 97 (appendix). Negri et al. 2014: table 3.

**Referred material.** CUF-NKNY-G39 (11 shells; Figs 4R, 10B).

**Habitat.** Sublittoral in muddy or fine sandy bottoms (Robba et al. 2004).
**Distribution.** Southwest Pacific. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Cylichna sibogae* Schepman, 1913, by having a less slender shell and an adapical umbilicus unbounded by sharp angulation (Robba et al. 2004). The generic assignment to either *Adamnestia* Iredale, 1936 or *Cylichna* requires further investigation.

**Subcohort Panpulmonata Jörger et al., 2010**

**Superorder Eupulmonata Haszprunar & Huber, 1990**

**Order Ellobiida Van Mol, 1967**

**Superfamily Ellobioidea Pfeiffer, 1854**

**Family Ellobiidae Pfeiffer, 1854**

**Ellobium Röding, 1798**

*Ellobium aurisjudae* (Linnaeus, 1758)

Figs 4G, 11B

*Bulla aurisjudae* Linnaeus, 1758: 728. Type locality: unknown.

*Ellobium aurisjudae*. Cernohorsky 1972: 211, pl. 60, fig. 7. Brandt 1974: 227–228, pl. 16, fig. 94. Tantanasiriwong 1978: 20, fig. 256. Nateewathana et al. 1981: 62. Way and Purchon 1981: 321. Bosch et al. 1995: 183, fig. 852. Nateewathana 1995: 100, with in-text fig. Poutiers 1998b: 643, with in-text figs. Subba Rao and Dey 2000: 187. Swennen et al. 2001: 60, 143, fig. 524. Gemert 2003: 107, with in-text fig. Hylleberg and Kilburn 2003: 133. Robba et al. 2003: tables 1, 2. Robba et al. 2004: 241–242, pl. 35, fig. 5. Sri-aroon et al. 2004: table 1. Dharma 2005: 206, pl. 78, fig. 18; 360, pl. 145, fig. 11. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Thach 2005: 232, pl. 71, figs 11, 14. Dey 2006: 56, figs 75, 76. Raven and Vermeulen 2007: 37, 39, pl. 2, figs 10–13. Robba et al. 2007: 98 (appendix). Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 227. Groh 2010: 446, pl. 914, figs 8, 9. Hamli et al. 2013: tables 2, 3, fig. 2t. Hylleberg and Aungtonya 2013: 97. Sanpanich and Duangdee 2013: 64. Dechruksa et al. 2014: fig. 3e. BEDO 2017b: 81, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 146.

*Ellobium* (*Ellobium*) cf. *aurisjudae*. Matsubara and Komori 2007: 326–328, fig. 2a–d.

*Ellobium* (*Ellobium*) *aurisjudae*. Matsubara and Komori 2007: fig. 2e–h.

**Referred material.** CUF-NKNY-G65 (25 shells; Figs 4G, 11B).

**Habitat.** In estuaries, mangrove and coastal forests, on salt marshes above the normal high tide line in or under rotting wood, and on sandy soil bordering a sandy beach (Raven and Vermeulen 2007).

**Distribution.** Arabian Gulf and Indian Ocean; Indo-West Pacific, from South China Sea to Australia (Poutiers 1998b; Robba et al. 2004). Records of fossils from the Early Miocene to Holocene in Indonesia, Japan, Malaysia, and Thailand (Robba et al. 2004; Dharma 2005; Matsubara and Komori 2007; Raven and Vermeulen 2007).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).
**Distribution.** Southwest Pacific. Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Cylichna sibogae* Schepman, 1913, by having a less slender shell and an adapical umbilicus unbounded by sharp angulation (Robba et al. 2004). The generic assignment to either *Adamnestia* Iredale, 1936 or *Cylichna* requires further investigation.

**Subcohort Panpulmonata Jörger et al., 2010**

**Superorder Eupulmonata Haszprunar & Huber, 1990**

**Order Ellobiida Van Mol, 1967**

**Superfamily Ellobioidea Pfeiffer, 1854**

**Family Ellobiidae Pfeiffer, 1854**

**Ellobium Röding, 1798**

*Ellobium aurisjudae* (Linnaeus, 1758)

Figs 4G, 11B

*Bulla aurisjudae* Linnaeus, 1758: 728. Type locality: unknown.

*Ellobium aurisjudae*. Cernohorsky 1972: 211, pl. 60, fig. 7. Brandt 1974: 227–228, pl. 16, fig. 94. Tantanasiriwong 1978: 20, fig. 256. Nateewathana et al. 1981: 62. Way and Purchon 1981: 321. Bosch et al. 1995: 183, fig. 852. Nateewathana 1995: 100, with in-text fig. Poutiers 1998b: 643, with in-text figs. Subba Rao and Dey 2000: 187. Swennen et al. 2001: 60, 143, fig. 524. Gemert 2003: 107, with in-text fig. Hylleberg and Kilburn 2003: 133. Robba et al. 2003: tables 1, 2. Robba et al. 2004: 241–242, pl. 35, fig. 5. Sri-aroon et al. 2004: table 1. Dharma 2005: 206, pl. 78, fig. 18; 360, pl. 145, fig. 11. Sri-aroon et al. 2005: tables 2, 3, 5, 6. Thach 2005: 232, pl. 71, figs 11, 14. Dey 2006: 56, figs 75, 76. Raven and Vermeulen 2007: 37, 39, pl. 2, figs 10–13. Robba et al. 2007: 98 (appendix). Printrakoon et al. 2008: table 1. Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 227. Groh 2010: 446, pl. 914, figs 8, 9. Hamli et al. 2013: tables 2, 3, fig. 2t. Hylleberg and Aungtonya 2013: 97. Sanpanich and Duangdee 2013: 64. Dechruksa et al. 2014: fig. 3e. BEDO 2017b: 81, with in-text fig. Tudu et al. 2018: table 1. Wells et al. 2021: 146.

*Ellobium* (*Ellobium*) cf. *aurisjudae*. Matsubara and Komori 2007: 326–328, fig. 2a–d.

*Ellobium* (*Ellobium*) *aurisjudae*. Matsubara and Komori 2007: fig. 2e–h.

**Referred material.** CUF-NKNY-G65 (25 shells; Figs 4G, 11B).

**Habitat.** In estuaries, mangrove and coastal forests, on salt marshes above the normal high tide line in or under rotting wood, and on sandy soil bordering a sandy beach (Raven and Vermeulen 2007).

**Distribution.** Arabian Gulf and Indian Ocean; Indo-West Pacific, from South China Sea to Australia (Poutiers 1998b; Robba et al. 2004). Records of fossils from the Early Miocene to Holocene in Indonesia, Japan, Malaysia, and Thailand (Robba et al. 2004; Dharma 2005; Matsubara and Komori 2007; Raven and Vermeulen 2007).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).
<figure><img src="image_11.png" /><figcaption>**Figure 11.** Gastropods and bivalves **A Architectonica perdix** **B Ellobium aurisjudae** **C Cassidula nucleus** **D Anadara inaequi-valvis** **E Anadara indica** **F Tegillarca granosa**.</figcaption></figure>

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Brandt (1974), Poutiers (1998b), and Robba et al. (2004), specifically in having an elongate-oval and unshouldered shell with the sculpture of numerous axial grooves and fine spiral lines.

**Cassidula Férussac, 1821**

**Cassidula nucleus** (Gmelin, 1791)

Figs 4L, 11C

*Helix nucleus* Gmelin, 1791: 3193. Type locality: “Tahiti” [Cooktown, Queensland, Australia].
<figure><img src="image_12.png" /><figcaption>**Figure 11.** Gastropods and bivalves **A Architectonica perdix** **B Ellobium aurisjudae** **C Cassidula nucleus** **D Anadara inaequivalvis** **E Anadara indica** **F Tegillarca granosa**.</figcaption></figure>

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Brandt (1974), Poutiers (1998b), and Robba et al. (2004), specifically in having an elongate-oval and unshouldered shell with the sculpture of numerous axial grooves and fine spiral lines.

**Cassidula Férussac, 1821**

**Cassidula nucleus** (Gmelin, 1791)
Figs 4L, 11C

*Helix nucleus* Gmelin, 1791: 3193. Type locality: “Tahiti” [Cooktown, Queensland, Australia].
*Auricula mustelina* Deshayes, 1830: 92. Type locality: "New Zealand".

*Cassidula nucleus*. Cernohorsky 1972: 212, pl. 60, fig. 8. Bosch et al. 1995: 183, fig. 851. Subba Rao and Dey 2000: 188. Swennen et al. 2001: 60, 143, fig. 526. Hylleberg and Kilburn 2003: 133. Robba et al. 2004: 242–243, pl. 35, fig. 6. Dharma 2005: 208, pl. 79, fig. 1a, b. Thach 2005: 233, pl. 72, fig. 8. Dey 2006: 55–56, figs 73, 74. Raven and Vermeulen 2007: 50–51, pl. 4, figs 35, 36. Robba et al. 2007: 98 (appendix). Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 227. Groh 2010: 448, pl. 915, figs 9–11. Zvonareva and Kantor 2016: 429–430, fig. 8s, t. BEDO 2017b: 80, with in-text fig. Kantarajan et al. 2017: table 1, fig. 4-32. Yang et al. 2017: 134, fig. 545. Tudu et al. 2018: table 1. Wells et al. 2021: 145.

*Cassidula mustelina*. Brandt 1974: 221, pl. 16, fig. 88. Tantanasiriwong 1978: 20, fig. 259. Nateewathana et al. 1981: 62. Way and Purchon 1981: 321. Hylleberg and Kilburn 2003: 133. Sri-aroon et al. 2004: table 1, fig. 2-9. Sri-aroon et al. 2005: tables 2–6. Dechruksa et al. 2014: fig. 3c. BEDO 2017b: 80, with in-text fig. Okutani 2017: 1128, pl. 427, fig. 4.

**Referred material.** CUF-NKNY-G63 (1 shell; Figs 4L, 11C).

**Habitat.** On mud in shaded areas and on tree trunks in mangrove and nipa palm forests, sometimes present in salt marsh or on muddy tidal flats (Brandt 1974; Raven and Vermeulen 2007; Zvonareva and Kantor 2016).

**Distribution.** Arabian Gulf and Indian Ocean; Indo-West Pacific, from Japan to Australia (Brandt 1974; Bosch et al. 1995; Subba Rao and Dey 2000; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Brandt 1974; Swennen et al. 2001; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Cassidula aurisfelis* (Bruguière, 1789), by having a normal and non-bifurcated columellar fold, a less rounded outline with a less convex shoulder, a straighter aperture, and a thinner palatal ridge (Raven and Vermeulen 2007). See also comprehensive taxonomic remarks in Raven and Vermeulen (2007).

**Class Bivalvia Linnaeus, 1758**

**Subclass Protobranchia Pelseneer, 1889**

**Order Nuculanida Carter et al., 2000**

**Superfamily Nuculanoidea H. Adams & A. Adams, 1858**

**Family Nuculanidae H. Adams & A. Adams, 1858**

**Jupiteria Bellardi, 1875**

**Jupiteria puellata** (Hinds, 1843)

Figs 10C, 120

*Nucula puellata* Hinds, 1843: 100. Type locality: Malacca; from 10 to 17 fathoms, coarse sand.

*Nuculana puellata*. Lynge 1909: 105. Hylleberg and Kilburn 2003: 139.

*Nuculana* (*Jupiteria*) *puellata*. Robba et al. 2002: 53, pl. 1, fig. 4a, b. Robba et al. 2003: tables 1, 2, 4–5. Robba et al. 2007: 83 (appendix). Nabhitabhata 2009: 279. Negri et al. 2014: table 3. Huber 2015: C666.

*Jupiteria puellata*. Wells et al. 2021: 50.
*Auricula mustelina* Deshayes, 1830: 92. Type locality: "New Zealand".

*Cassidula nucleus*. Cernohorsky 1972: 212, pl. 60, fig. 8. Bosch et al. 1995: 183, fig. 851. Subba Rao and Dey 2000: 188. Swennen et al. 2001: 60, 143, fig. 526. Hylleberg and Kilburn 2003: 133. Robba et al. 2004: 242–243, pl. 35, fig. 6. Dharma 2005: 208, pl. 79, fig. 1a, b. Thach 2005: 233, pl. 72, fig. 8. Dey 2006: 55–56, figs 73, 74. Raven and Vermeulen 2007: 50–51, pl. 4, figs 35, 36. Robba et al. 2007: 98 (appendix). Kesavan et al. 2009: 382, with in-text fig. Nabhitabhata 2009: 227. Groh 2010: 448, pl. 915, figs 9–11. Zvonareva and Kantor 2016: 429–430, fig. 8s, t. BEDO 2017b: 80, with in-text fig. Kantarajan et al. 2017: table 1, fig. 4-32. Yang et al. 2017: 134, fig. 545. Tudu et al. 2018: table 1. Wells et al. 2021: 145.

*Cassidula mustelina*. Brandt 1974: 221, pl. 16, fig. 88. Tantanasiriwong 1978: 20, fig. 259. Nateewathana et al. 1981: 62. Way and Purchon 1981: 321. Hylleberg and Kilburn 2003: 133. Sri-aroon et al. 2004: table 1, fig. 2-9. Sri-aroon et al. 2005: tables 2–6. Dechruksa et al. 2014: fig. 3c. BEDO 2017b: 80, with in-text fig. Okutani 2017: 1128, pl. 427, fig. 4.

**Referred material.** CUF-NKNY-G63 (1 shell; Figs 4L, 11C).

**Habitat.** On mud in shaded areas and on tree trunks in mangrove and nipa palm forests, sometimes present in salt marsh or on muddy tidal flats (Brandt 1974; Raven and Vermeulen 2007; Zvonareva and Kantor 2016).

**Distribution.** Arabian Gulf and Indian Ocean; Indo-West Pacific, from Japan to Australia (Brandt 1974; Bosch et al. 1995; Subba Rao and Dey 2000; Okutani 2017). Records of fossils from the Holocene in Thailand (Robba et al. 2004).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Brandt 1974; Swennen et al. 2001; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Cassidula aurisfelis* (Bruguière, 1789), by having a normal and non-bifurcated columellar fold, a less rounded outline with a less convex shoulder, a straighter aperture, and a thinner palatal ridge (Raven and Vermeulen 2007). See also comprehensive taxonomic remarks in Raven and Vermeulen (2007).

**Class Bivalvia Linnaeus, 1758**

**Subclass Protobranchia Pelseneer, 1889**

**Order Nuculanida Carter et al., 2000**

**Superfamily Nuculanoidea H. Adams & A. Adams, 1858**

**Family Nuculanidae H. Adams & A. Adams, 1858**

**Jupiteria Bellardi, 1875**

**Jupiteria puellata** (Hinds, 1843)

Figs 10C, 120

*Nucula puellata* Hinds, 1843: 100. Type locality: Malacca; from 10 to 17 fathoms, coarse sand.

*Nuculana puellata*. Lynge 1909: 105. Hylleberg and Kilburn 2003: 139.

*Nuculana* (*Jupiteria*) *puellata*. Robba et al. 2002: 53, pl. 1, fig. 4a, b. Robba et al. 2003: tables 1, 2, 4–5. Robba et al. 2007: 83 (appendix). Nabhitabhata 2009: 279. Negri et al. 2014: table 3. Huber 2015: C666.

*Jupiteria puellata*. Wells et al. 2021: 50.
<figure><img src="image_12.png" /><figcaption>**Figure 12.** Size comparison of bivalves, scaphopod and other invertebrates found in this study. **A** *Tegillarca nodifera* **B** *Volachlamys singaporina* **C** *Tegillarca granosa* **D** *Noetiella pectunculiformis* **E** *Magallana* cf. gigas **F** *Estellacar olivacea* **G** *Anadara indica* **H** *Dentalium variabile* **I** *Siliqua minima* **J** *Corbula fortisulcata* **K** *Fistulobalanus kondakovi* **L** *Placamen lamellatum* **M** *Martesia striata* **N** *Potamocorbula* sp. **O** *Jupiteria puellata* **P** *Saccella mauritiana* **Q** *Paratapes undulatus* **R** *Dosinia dilecta* **S** *Joannisiella oblonga* **T** *Temnotrema siamense* **U** *Pholas orientalis*.</figcaption></figure>

**Referred material.** CUF-NKNY-B25 (37 shells; Figs 10C, 120).

**Habitat.** Subtidal on coarse sand, soft clay, and mud bottoms at a depth from 5 to 40 m (Huber 2015).

**Distribution.** Indo-West Pacific, from southern China to New Guinea (Huber 2015). Records of fossils from the Holocene in Thailand (Robba et al. 2002).
<figure><img src="image_13.png" /><figcaption>**Figure 12.** Size comparison of bivalves, scaphopod and other invertebrates found in this study. **A** *Tegillarca nodifera* **B** *Volachlamys singaporina* **C** *Tegillarca granosa* **D** *Noetiella pectunculiformis* **E** *Magallana* cf. gigas **F** *Estellacar olivacea* **G** *Anadara indica* **H** *Dentalium variabile* **I** *Siliqua minima* **J** *Corbula fortisulcata* **K** *Fistulobalanus kondakovi* **L** *Placamen lamellatum* **M** *Martesia striata* **N** *Potamocorbula* sp. **O** *Jupiteria puellata* **P** *Saccella mauritiana* **Q** *Paratapes undulatus* **R** *Dosinia dilecta* **S** *Joannisiella oblonga* **T** *Temnotrema siamense* **U** *Pholas orientalis*.</figcaption></figure>

**Referred material.** CUF-NKNY-B25 (37 shells; Figs 10C, 120).

**Habitat.** Subtidal on coarse sand, soft clay, and mud bottoms at a depth from 5 to 40 m (Huber 2015).

**Distribution.** Indo-West Pacific, from southern China to New Guinea (Huber 2015). Records of fossils from the Holocene in Thailand (Robba et al. 2002).
**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2002), specifically in having an unsculptured surface bearing only faint growth markings.

**Saccella Woodring, 1925**

**Saccella mauritiana (Sowerby I, 1833)**

Figs 10D, 12P

*Nucula mauritiana* Sowerby I, 1833: 15, fig. 7. Type locality: Mauritius.

*Nuculana mauritiana*. Lynge 1909: 105. Swennen et al. 2001: 43, 62, fig. 4. Gopalakrishnan et al. 2012: 61.

*Nuculana* (Scaeoleda) caspidata [non Gould]. Robba et al. 2002: 53, pl. 1, fig. 3a, b.

*Nuculana* (Scaeoleda) mauritiana. Robba et al. 2003: tables 1, 3, 5. Robba et al. 2004: 245. Robba et al. 2007: 83 (appendix). Negri et al. 2014: table 3.

*Saccella mauritiana* [sic]. Nabhitabhata 2009: 278.

*Nuculana* (Saccella) mauritiana. Huber 2010: 97, with in-text fig. Huber 2015: C612.

*Saccella mauritiana*. Wells et al. 2021: 50.

**Referred material.** CUF-NKNY-B24 (20 shells; Figs 10D, 12P).

**Habitat.** Sublittoral on mainly mud and clay with sand and shells at a depth from 11 to 92 m (Huber 2015).

**Distribution.** Indian Ocean; Indo-West Pacific, from China to Indonesia (Huber 2015). Records of fossils from the Holocene in Thailand (Robba et al. 2002).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Swennen et al. 2001; Nabhitabhata 2009; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2002) and Huber (2010), specifically in having strong commarginal ridges in the umbonal area then changing into flat and somewhat imbricate low rugae which are more raised on crossing the postero-dorsal keel. This species often co-occurs with *Jupiteria puellata*, which has an unsculptured shell (Robba et al. 2002).

**Superorder Pteriomorphia Beurlen, 1944**

**Order Arcida Stoliczka, 1871**

**Superfamily Arcoidea Lamarck, 1809**

**Family Arcidae Lamarck, 1809**

**Anadara Gray, 1847**

**Anadara inaequivalvis (Bruguière, 1789)**

Figs 11D, 13D

*Arca inaequivalvis* Bruguière, 1789: 106–107. Type locality: East India. Reeve 1844: Arca, pl. 8, sp. 54.

*Scapharca inaequivalvis*. Tantanasiriwong 1979: 4. Morris and Purchon 1981: 322. Nateewathana et al. 1981: 63. Poutiers 1998a: 152, with in-text
**Record in Thailand.** Gulf of Thailand (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2002), specifically in having an unsculptured surface bearing only faint growth markings.

**Saccella Woodring, 1925**

**Saccella mauritiana (Sowerby I, 1833)**

Figs 10D, 12P

*Nucula mauritiana* Sowerby I, 1833: 15, fig. 7. Type locality: Mauritius.

*Nuculana mauritiana*. Lynge 1909: 105. Swennen et al. 2001: 43, 62, fig. 4. Gopalakrishnan et al. 2012: 61.

*Nuculana* (Scaeoleda) caspidata [non Gould]. Robba et al. 2002: 53, pl. 1, fig. 3a, b.

*Nuculana* (Scaeoleda) *mauritiana*. Robba et al. 2003: tables 1, 3, 5. Robba et al. 2004: 245. Robba et al. 2007: 83 (appendix). Negri et al. 2014: table 3.

*Saccella mauritiana* [sic]. Nabhitabhata 2009: 278.

*Nuculana* (Saccella) *mauritiana*. Huber 2010: 97, with in-text fig. Huber 2015: C612.

*Saccella mauritiana*. Wells et al. 2021: 50.

**Referred material.** CUF-NKNY-B24 (20 shells; Figs 10D, 12P).

**Habitat.** Sublittoral on mainly mud and clay with sand and shells at a depth from 11 to 92 m (Huber 2015).

**Distribution.** Indian Ocean; Indo-West Pacific, from China to Indonesia (Huber 2015). Records of fossils from the Holocene in Thailand (Robba et al. 2002).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Swennen et al. 2001; Nabhitabhata 2009; Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Robba et al. (2002) and Huber (2010), specifically in having strong commarginal ridges in the umbonal area then changing into flat and somewhat imbricate low rugae which are more raised on crossing the postero-dorsal keel. This species often co-occurs with *Jupiteria puellata*, which has an unsculptured shell (Robba et al. 2002).

**Superorder Pteriomorphia Beurlen, 1944**

**Order Arcida Stoliczka, 1871**

**Superfamily Arcoidea Lamarck, 1809**

**Family Arcidae Lamarck, 1809**

**Anadara Gray, 1847**

**Anadara inaequivalvis (Bruguière, 1789)**

Figs 11D, 13D

*Arca inaequivalvis* Bruguière, 1789: 106–107. Type locality: East India. Reeve 1844: Arca, pl. 8, sp. 54.

*Scapharca inaequivalvis*. Tantanasiriwong 1979: 4. Morris and Purchon 1981: 322. Nateewathana et al. 1981: 63. Poutiers 1998a: 152, with in-text
figs. Subba Rao and Dey 2000: 205. Robba et al. 2002: 58–59, pl. 2, fig. 8. Robba et al. 2003: tables 4, 5. Robba et al. 2007: 83 (appendix). Nabhitabhata 2009: 294. Negri et al. 2014: table 3. Okutani 2017: 1168, pl. 468, fig. 3. Yang et al. 2017: 148, fig. 580.

*Anadara (Scapharca) inaequivalvis*. Vongpanich 1996: 182, figs 21–23. Aungtonya et al. 1999: 372. Dharma 2005: 242, pl. 96, fig. 10. Dey and Ramakrishna 2007: 151, 174. Huber 2010: 137, with in-text fig. Huber 2015: C3218.

*Anadara cf. inaequivalvis*. Swennen et al. 2001: 44, 65–66, fig. 29.

*Anadara inaequivalvis*. Hylleberg and Kilburn 2003: 148. Poppe 2010a: 474, pl. 928, figs 5, 6. Sanpanich 2011: table 2. Gopalakrishnan et al. 2012: 59. Surakiatchai et al. 2018: table 6, pl. 3, fig. 1a, b. Tudu et al. 2018: table 1. Tudu et al. 2019: 38–40, fig. 3c–e. Wells et al. 2021: 52.

**Referred material.** CUF-NKNY-B03, B21 (21L+30R shells; Figs 11D, 13D).

**Habitat.** Sandy and muddy bottoms in intertidal and upper sublittoral zones (Robba et al. 2002; Huber 2015).

**Distribution.** Red Sea to India Ocean; Indo-West Pacific, from Japan to Australia as well as from Mediterranean and Black Sea (Robba et al. 2002; Tudu et al. 2019). Records of fossils from the Late Miocene and Pliocene in Indonesia and from the Holocene in Thailand (Robba et al. 2002; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Poutiers (1998a) and Tudu et al. (2019), specifically in having an inflated, inequilateral, and roughly quadrate shell shape with 30–37 radial ribs.

### *Anadara indica* (Gmelin, 1791)

Figs 11E, 12G

*Arca indica* Gmelin, 1791: 3312. Type locality: the Indian Ocean. Reeve 1844: *Arca*, pl. 9, sp. 56.

*Anadara (Scapharca) indica*. Lynde 1909: 126–127, pl. 2, figs 5–12.

*Scapharca indica*. Morris and Purchon 1981: 322. Bosch et al. 1995: 211, fig. 928. Poutiers 1998a: 153, with in-text figs. Robba et al. 2002: 59, pl. 2, fig. 9. Gemert 2003: 107. Robba et al. 2003: tables 1–5. Thach 2005: 243, pl. 75, fig. 17. Robba et al. 2007: 83 (appendix). Nabhitabhata 2009: 294. Yang et al. 2017: 148, fig. 581. Surakiatchai et al. 2018: pl. 3, fig. 3a, b.

*Anadara indica*. Vongpanich 1996: 183, figs 26, 27. Aungtonya et al. 1999: 372. Tudu et al. 2018: table 1. Wells et al. 2021: 52.

*Anadara (Anadara) indica*. Huber 2010: 136, with in-text fig. Huber 2015: C3220.

**Referred material.** CUF-NKNY-B06 (16L+24R shells; Figs 11E, 12G).

**Habitat.** In soft sand or sandy mud bottoms at bays, river mouths, and intertidal zones down to 15 m depth (Huber 2015).

**Distribution.** Persian Gulf to India Ocean; Indo-West Pacific, from Japan to Australia (Poutiers 1998a; Robba et al. 2002). Records of fossils from the Holocene in Thailand (Robba et al. 2002; Surakiatchai et al. 2018).
figs. Subba Rao and Dey 2000: 205. Robba et al. 2002: 58–59, pl. 2, fig. 8.
Robba et al. 2003: tables 4, 5. Robba et al. 2007: 83 (appendix). Nabhitabha-
ta 2009: 294. Negri et al. 2014: table 3. Okutani 2017: 1168, pl. 468, fig. 3.
Yang et al. 2017: 148, fig. 580.

*Anadara (Scapharca) inaequivalvis*. Vongpanich 1996: 182, figs 21–23. Aung-
tonya et al. 1999: 372. Dharma 2005: 242, pl. 96, fig. 10. Dey and Ramakrish-
na 2007: 151, 174. Huber 2010: 137, with in-text fig. Huber 2015: C3218.

*Anadara cf. inaequivalvis*. Swennen et al. 2001: 44, 65–66, fig. 29.

*Anadara inaequivalvis*. Hylleberg and Kilburn 2003: 148. Poppe 2010a: 474, pl. 928, figs 5, 6. Sanpanich 2011: table 2. Gopalakrishnan et al. 2012: 59. Surakiatchai et al. 2018: table 6, pl. 3, fig. 1a, b. Tudu et al. 2018: table 1. Tudu et al. 2019: 38–40, fig. 3c–e. Wells et al. 2021: 52.

**Referred material.** CUF-NKNY-B03, B21 (21L+30R shells; Figs 11D, 13D).

**Habitat.** Sandy and muddy bottoms in intertidal and upper sublittoral zones (Robba et al. 2002; Huber 2015).

**Distribution.** Red Sea to India Ocean; Indo-West Pacific, from Japan to Aus-
tralia as well as from Mediterranean and Black Sea (Robba et al. 2002; Tudu et
al. 2019). Records of fossils from the Late Miocene and Pliocene in Indonesia
and from the Holocene in Thailand (Robba et al. 2002; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Poutiers (1998a) and Tudu et al. (2019), specifically in having an inflated, inequilateral, and roughly quadrate shell shape with 30–37 radial ribs.

**Anadara indica (Gmelin, 1791)**

Figs 11E, 12G

*Arca indica* Gmelin, 1791: 3312. Type locality: the Indian Ocean. Reeve 1844: *Arca*, pl. 9, sp. 56.

*Anadara (Scapharca) indica*. Lynde 1909: 126–127, pl. 2, figs 5–12.

*Scapharca indica*. Morris and Purchon 1981: 322. Bosch et al. 1995: 211, fig. 928. Poutiers 1998a: 153, with in-text figs. Robba et al. 2002: 59, pl. 2, fig. 9. Gemert 2003: 107. Robba et al. 2003: tables 1–5. Thach 2005: 243, pl. 75, fig. 17. Robba et al. 2007: 83 (appendix). Nabhitabhata 2009: 294. Yang et al. 2017: 148, fig. 581. Surakiatchai et al. 2018: pl. 3, fig. 3a, b.

*Anadara indica*. Vongpanich 1996: 183, figs 26, 27. Aungtonya et al. 1999: 372. Tudu et al. 2018: table 1. Wells et al. 2021: 52.

*Anadara (Anadara) indica*. Huber 2010: 136, with in-text fig. Huber 2015: C3220.

**Referred material.** CUF-NKNY-B06 (16L+24R shells; Figs 11E, 12G).

**Habitat.** In soft sand or sandy mud bottoms at bays, river mouths, and inter-
tidal zones down to 15 m depth (Huber 2015).

**Distribution.** Persian Gulf to India Ocean; Indo-West Pacific, from Japan to Australia (Poutiers 1998a; Robba et al. 2002). Records of fossils from the Holocene in Thailand (Robba et al. 2002; Surakiatchai et al. 2018).
**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Poutiers (1998a), Robba et al. (2002), and Huber (2010), specifically in having an inequilateral, laterally compressed, and sub-rectangular shell shape with 30–36 flat radial ribs.

**Tegillarca Iredale, 1939**

**Tegillarca granosa (Linnaeus, 1758)**

Figs 11F, 12C

*Arca granosa* Linnaeus, 1758: 694. Type locality: southern European ocean. Reeve 1844: *Arca*, pl. 3, sp. 15. Yokoyama 1927: 403. Lutaenko 2015: 135–136, pl. 1, fig. a–d.

*Arca (Anadara) granosa*. Lynge 1909: 118. Tesch 1920: 92–93, pl. 137, figs 248a, b, 249a–c.

*Anadara granosa*. Tantanasiriwong 1979: 4. Morris and Purchon 1981: 322. Nateewathana et al. 1981: 63. Nateewathana 1995: 101, with in-text fig. Poutiers 1998a: 147, with in-text figs. Aungtonya et al. 1999: 372. Subba Rao and Dey 2000: 204. Hylleberg and Kilburn 2003: 148, pl. 1, fig. 3. Robba et al. 2002: 57–58, pl. 2, fig. 4. Robba et al. 2003: tables 1–5. Dey 2006: 61, figs 86, 87. Dey and Ramakrishna 2007: 151, 172. Robba et al. 2007: 83 (appendix). Printrakoon et al. 2008: table 1. Nabhitabhata 2009: 284. Sanpanich 2011: table 2. Hylleberg and Aungtonya 2013: 94. Negri et al. 2014: table 3. Surakiatchai et al. 2018: table 6, pl. 2, fig. 7a, b.

*Anadara (Tegillarca) granosa*. Vongpanich 1996: 187, 189, figs 47–50. Dharma 2005: 242, pl. 96, fig. 9; 362, pl. 146, fig. 10. Lutaenko et al. 2019: 174, pl. 3, fig. c, d.

*Tegillarca granosa*. Swennen et al. 2001: 44, 66, fig. 35. Gemert 2003: 107. Thach 2005: 244, pl. 75, fig. 8. Huber 2010: 141, with in-text fig. Poppe 2010a: 486, pl. 934, figs 9, 10. Huber 2015: C3352. BEDO 2017a: 27, with in-text fig. Kantharajan et al. 2017: table 1, fig. 2-10. Okutani 2017: 1168, pl. 468, fig. 9. Yang et al. 2017: 150, fig. 586. Tudu et al. 2018: table 1. Tudu et al. 2019: 42–44, fig. 5c, d. Wells et al. 2021: 54.

**Referred material.** CUF-NKNY-B20 (15L+15R shells; Figs 11F, 12C).

**Habitat.** Mud down to 10 m depth in mangrove forests and muddy estuaries (Swennen et al. 2001; Thach 2005; Kantharajan et al. 2017).

**Distribution.** East Africa to India; Indo-West Pacific, from Japan to Australia and Polynesia (Poutiers 1998a; Kantharajan et al. 2017; Tudu et al. 2019). Records of fossils from the Late Miocene to Holocene in Indonesia, Japan, the Philippines, Taiwan, and Thailand (Robba et al. 2002; Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Tegillarca nodifera*, by having a less elongated shell with a lower number of ribs (15–21) and a lower number of nodules on ribs (Tudu et al. 2019).
**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species is recognised based on the descriptions and figures in Poutiers (1998a), Robba et al. (2002), and Huber (2010), specifically in having an inequilateral, laterally compressed, and sub-rectangular shell shape with 30–36 flat radial ribs.

**Tegillarca Iredale, 1939**

**Tegillarca granosa (Linnaeus, 1758)**

Figs 11F, 12C

*Arca granosa* Linnaeus, 1758: 694. Type locality: southern European ocean. Reeve 1844: *Arca*, pl. 3, sp. 15. Yokoyama 1927: 403. Lutaenko 2015: 135–136, pl. 1, fig. a–d.

*Arca (Anadara) granosa*. Lynge 1909: 118. Tesch 1920: 92–93, pl. 137, figs 248a, b, 249a–c.

*Anadara granosa*. Tantanasiriwong 1979: 4. Morris and Purchon 1981: 322. Nateewathana et al. 1981: 63. Nateewathana 1995: 101, with in-text fig. Poutiers 1998a: 147, with in-text figs. Aungtonya et al. 1999: 372. Subba Rao and Dey 2000: 204. Hylleberg and Kilburn 2003: 148, pl. 1, fig. 3. Robba et al. 2002: 57–58, pl. 2, fig. 4. Robba et al. 2003: tables 1–5. Dey 2006: 61, figs 86, 87. Dey and Ramakrishna 2007: 151, 172. Robba et al. 2007: 83 (appendix). Printrakoon et al. 2008: table 1. Nabhitabhata 2009: 284. Sanpanich 2011: table 2. Hylleberg and Aungtonya 2013: 94. Negri et al. 2014: table 3. Surakiatchai et al. 2018: table 6, pl. 2, fig. 7a, b.

*Anadara (Tegillarca) granosa*. Vongpanich 1996: 187, 189, figs 47–50. Dharma 2005: 242, pl. 96, fig. 9; 362, pl. 146, fig. 10. Lutaenko et al. 2019: 174, pl. 3, fig. c, d.

*Tegillarca granosa*. Swennen et al. 2001: 44, 66, fig. 35. Gemert 2003: 107. Thach 2005: 244, pl. 75, fig. 8. Huber 2010: 141, with in-text fig. Poppe 2010a: 486, pl. 934, figs 9, 10. Huber 2015: C3352. BEDO 2017a: 27, with in-text fig. Kantharajan et al. 2017: table 1, fig. 2-10. Okutani 2017: 1168, pl. 468, fig. 9. Yang et al. 2017: 150, fig. 586. Tudu et al. 2018: table 1. Tudu et al. 2019: 42–44, fig. 5c, d. Wells et al. 2021: 54.

**Referred material.** CUF-NKNY-B20 (15L+15R shells; Figs 11F, 12C).

**Habitat.** Mud down to 10 m depth in mangrove forests and muddy estuaries (Swennen et al. 2001; Thach 2005; Kantharajan et al. 2017).

**Distribution.** East Africa to India; Indo-West Pacific, from Japan to Australia and Polynesia (Poutiers 1998a; Kantharajan et al. 2017; Tudu et al. 2019). Records of fossils from the Late Miocene to Holocene in Indonesia, Japan, the Philippines, Taiwan, and Thailand (Robba et al. 2002; Dharma 2005; Surakiatchai et al. 2018).

**Record in Thailand.** Gulf of Thailand and Andaman Sea (Wells et al. 2021).

**Taxonomic remarks and comparisons.** This species differs from its similar species, *Tegillarca nodifera*, by having a less elongated shell with a lower number of ribs (15–21) and a lower number of nodules on ribs (Tudu et al. 2019).
<figure><img src="image_13.png" /><figcaption>**Figure 13.** Size comparison of bivalves and other invertebrates found in this study. **A Placuna placenta** **B Standella pellu-cida** **C Geloina bengalensis** **D Anadara inaequivalvis** **E Pegophysema bialata** **F Megabalanus** cf. tintinnabulum **G Cultellus maximus** **H Lutraria complanata** **I Thalassina** sp. **J Tellinides conspicuus**.</figcaption></figure>
<figure><img src="image_14.png" /><figcaption>**Figure 13.** Size comparison of bivalves and other invertebrates found in this study. **A Placuna placenta** **B Standella pellu-cida** **C Geloina bengalensis** **D Anadara inaequivalvis** **E Pegophysema bialata** **F Megabalanus** cf. tintinnabulum **G Cultellus maximus** **H Lutraria complanata** **I Thalassina** sp. **J Tellinides conspicuus**.</figcaption></figure>