DOI: http://doi.org/10.18941/venus.75.1-4_99 Short Notes ©The Malacological Society of Japan99

A New Species of Pickworthiidae (Gastropoda, Caenogastropoda) from Easter Island, Southeastern Pacific

Tomoki Kase1* and Bret K. Raines2 1Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan; *[email protected] 2P. O. Box 1239, La Luz, NM 88337, USA

The family Pickworthiidae Iredale, 1917 consists one is a new species of the genus Microliotia and of microscopic, elongate rissoiform to planispiral the other is reallocated from Mareleptoptoma to gastropods with a characteristic circular rimmed Clatrosansonia. These two species are endemic to aperture and a deep sinusigeral notch in the Easter Island. variably tilted protoconch (Bouchet & Le Renard, Abbreviations: LACM – Natural History Museum 1998; Le Renard & Bouchet, 2003). A molecular of Los Angeles County Museum; MNHN – Muséum phylogenetic study has shown a close relationship national d’Histoire naturelle, Paris; NMNS – between Pickworthiidae and Cerithioidea (Takano & National Museum of Nature and Science, Tsukuba. Kano, 2014). During the last two decades shells of pickworthiids have been obtained through extensive Taxonomy collecting expeditions in the tropical Indo-West Pacific conducted mainly by the National Museum Family Pickworthiidae Iredale, 1917 of Natural History, Paris and the National Museum of Nature and Science, Japan (Kase, 1998a–c, Genus Microliotia Böttger, 1902 1999; Le Renard & Bouchet, 2003). Pickworthiids Type species: Microliotia brandenburgi Böttger, are a particularly large component of dead shell 1902, by monotypy. assemblages in tropical submarine caves and caverns Synonym: Latilabrum Kuroda & Habe, 1991; (e.g., Kase & Hayami, 1992; Kase, 1998a–c, type species Latilabrum mirabile Kuroda & Habe, 1999). The Pickworthiidae heretofore comprises 1991 by original designation. 14 genera, 65 Recent species and 12 fossil species (Le Renard & Bouchet, 2003; Janssen, 2004; Microliotia rehderi n. sp. Espinosa et al., 2006; Moolenbeek & Mussai, 2010; (Fig. 1A–C) Rolán, 2005; Moolenbeek, 2008; Santos & França, 2008; Moolenbeek & Hoenslaar, 2010; Kase & Microliotia corayi (Ladd, 1966) – Raines, 2002: Letourneux, 2013; Alhejoj et al., 2016). 19, fig. 14. Easter Island (Isla de Pascua) occupies an Type material: Holotype (Fig. 1A–C), LACM- easterly location in the South Pacific, and is 3378, from silty sand in a submarine cave, 15 m in traditionally regarded as the eastern border of the depth, off Hanga-Teo on northern coast of the island. Indo-West Pacific (IWP) faunal province. Located Six paratypes, LACM-3379, MNHN IM-2014-6874 at lat. 27°09´S, long. 109°26´W, 3,800 km off the and NMNS PMR 58 from the type locality. Chilean coast and separated by 2,200 km from Etymology: Named after Harold A. Rehder, Pitcairn Island, it is the most isolated island in the who greatly contributed to our knowledge of the IWP. Due to its remote geographic location, the molluscan fauna of Easter Island. marine fauna of Easter Island has been the subject of Distribution: Known only from the type locality. studies of latitudinal gradients of marine organisms Diagnosis: A rissoiform Microliotia characterized in the IWP faunal province (e.g., Briggs, 1974). A by highly elevated and constricted spire whorls, total of more than 200 mollusks have been identified three spiral cords on the penultimate whorl and a to species level from Easter Island, of which broad varix-like peristome. The last whorl is as high 37% are endemic (Rehder, 1980; Raines, 2002; as wide, with a rounded periphery. Raines & Huber, 2012). This paper redescribes two Description: Holotype (Fig. 1A–C). Shell small, pickworthiid species from Easter Island, of which 2.78 mm high and 1.88 mm wide, rissoiform, http://zoobank.org/urn:lsid:zoobank.org:pub:2B23068A-C4F2-4C27-94FB-71698BFB4DE6 100 VENUS 75 (1–4), 2017

Fig. 1. A–C. Microliotia rehderi n. sp., holotype, LACM-3378, apertural and lateral views, and protoconch. D–G. Clatrosansonia circumserrata (Raines, 2002); LACM-180379b, protoconch, and apertural, basal and lateral views. colorless, consisting of 6.25 whorls. Spire elevated, whorls, constricted between whorls. Suture linear conical, occupying about 55% of shell height. at bottom of sutural furrow. First teleoconch whorls Pleural angle 65°. Protoconch colorless, of two angulate at middle with appearance of spiral cord, whorls (Fig. 1C); protoconch I, apparently smooth sculptured by about 17 opisthocline axial ribs, due to erosion, consisting of one swollen whorl, ribs tuberculate at intersection with spiral cord; and protoconch II of one whorl sculptured with spiral cord gradually shifting downward to edge two thick spiral cords and several fine, beaded of sutural furrow in second to third whorls, adding spiral threads; sinusigeral notch with raised lip second cord at adapical edge of upper sutural and long abapical projection. Teleoconch of 4.25 furrow in third teleoconch whorl and third one Short Notes 101 at middle of whorl in fourth teleoconch whorl; Letourneux, 2013), among which Microliotia axial ribs changing inclination from opisthocline hawaiensis Kase, 1998b most closely resembles to more or less prosocline through growth, almost this new species but differs in having a more juxtaposed on successive whorls, and prominently elongate shell form with thicker axial ribs and in tuberculate at intersection with spiral cords. Last lacking thick spiral cords on the shell surface. The whorl as high as wide, weakly convex above basal protoconch morphology clearly differs between the periphery, continuously sloping into inclined and two species: M. rehderi n. sp. has a protoconch of very weakly convex base sculptured with three two whorls, while M. hawaiensis has a protoconch thick and tuberculate spiral cords, most abaxial of 1.25 whorls. one smooth. Umbilicus closed. Aperture circular, surrounded by raised rim, further surrounded by Genus Clatrosansonia Sabelli & Taviani smooth peristome. Outer lip thickened and broad, in Le Renard & Bouchet, 2003 and sculptured with five radial ribs extending from Type species: Mecoliotia philippina Bandel & last whorl surface and weak interstitial radial cord Kowalke, 1997, by original designation. between major cords. Dimensions: Clatrosansonia circumserrata (Raines, 2002) Shell Shell (Fig. 1D–G) length width (mm) (mm) Mareleptopoma circumserrata Raines, 2002: 18, LACM-3378 Holotype 2.78 1.88 fig. 13. LACM-3379a Paratype 2.28 1.61 Type material: Holotype, LACM-2938, from LACM-3379b Paratype 1.97 1.38 silty sand in a submarine cave, 15 m in depth, off LACM-3379c Paratype 1.97 1.45 Hanga-Teo on northern coast of the island. LACM-3379d Paratype 1.72 1.27 Material examined: Five specimens, LACM- MNHN IM-2014-6873 Paratype 2.08 1.43 180379a–c, MNHN IM-2014-6874, NMNS PMR 59 NMNS PMR 58 Paratype 1.63 1.22 from the type locality. Remarks: This species exhibits a wide range of Distribution: Known only from the type locality. variation in shell size: the largest specimen is 2.78 Diagnosis: A species of Clatrosansonia with a mm high (holotype), whereas the smallest one with shell that is slightly wider than high, a deep and a well-developed peristome measures about 3/5 of wide umbilicus, an angulate basal periphery, flush- the largest one. To the best of our knowledge, such sided penultimate and last whorls, a mesh-like shell size variation is uncommon among specimens sculpture on the upper whorl surface and about nine collected from the same site in the Pickworthiidae. regularly spaced spiral cords on the base. The largest specimen is more elongate than the Description (Fig. 1D–G): Shell very small, 1.13 smaller specimens, but we consider them to belong mm high and 1.19 mm wide, slightly depressed to the same species because the other shell characters trochiform, of five whorls. Spire low conical, are the same. comprising half of shell height. Pleural angle about Raines (2002) referred this species to Alvania 80°. Protoconch light orange in color, composed of (Taramellelia) corayi Ladd, 1966, thought to be a two whorls; protoconch I of one smooth whorl, and Recent form that was described from a drillhole protoconch II of 1.5 whorls sculptured with two on Eniwetok atoll in the Marshall Islands, but he major and some minor spiral cords and microscopic reallocated its generic position to Microliotia. Le granules not spirally arranged; sinusigeral notch Renard & Bouchet (2003) assigned A. (T.) corayi deep with reflected lip. First teleoconch whorl with to the genus Clatrosansonia Sabelli & Taviani in spiral cord at middle crossed by axial cords; spiral Le Renard & Bouchet, 2003. Although the generic cord quickly descending to abapical edge of whorl. position of A. (T.) corayi needs to be reviewed in Penultimate whorl and upper whorl surface of last any rigorous revision of the Pickworthiidae, it differs whorl almost flat, covered with mesh-like sculpture from our new species in having a slightly lower composed of three and five rather irregularly spaced spire, a more angulate basal periphery in the last spiral cords and thin prosocline axial ribs, granulate whorl, and a larger number of finer axial ribs. at their intersections, about 25 in number per whorl. To date, the genus Microliotia comprises 11 Last whorl angulate at periphery with serrated species (Le Renard & Bouchet, 2003; Kase & thick spiral cord crossed by axial ribs. Base more 102 VENUS 75 (1–4), 2017 convex than upper whorl surface, covered with nine Bandel, K. & Kowalke, T. 1997. Systematic value of spiral cords crossed by obscure axial ribs that are the larval shell of fossil and modern Vanikoridae, extensions of those on upper whorl surface near Pickworthiidae and the genus Fossarus aperture. Umbilicus broad and deep, surrounded by (Caenogastropoda, Mollusca). Berliner geowissenschaftliche Abhandlungen, Series E robust rim, sculptured internally with revolving and 25: 3–29. obscure cords. Aperture circular with well elevated Böttger, O. 1902. Zur Kenntnis der Fauna der rim, further surrounded by peristome with rough mittelmiocänen Schichten von Kostej im surface. Outer lip rather thin, disc-like, covered Krassó-Szörényer Komitat. Verhandlungen und with spiral cords that are extensions of those on Mittheilungen des Siebenbürgischen Vereins für last whorl. Naturwissenschaften zu Hermannstadt 51: Dimensions: 1–200. Shell length Shell width Bouchet, P. & Le Renard, J. 1998. Family Pickworthiidae: 739–741. In: Beesley, P. L., (mm) (mm) Ross, G. J. B. & Wells, F. (eds.), Mollusca, The LACM-0003 1.20 1.33 Southern Synthesis, Part B, Fauna of Australia LACM-0004 1.13 1.19 Volume 5, pp. 739–741. CSIRO Publishing, LACM-0005 0.88 0.96 Melbourne. NMNS PM0002 ca. 1.2 1.34 Briggs, J. C. 1974. Marine Zoogeography. 475 pp. MNHNxxxx2 1.10 1.23 McGraw-Hill, New York. Remarks: Raines (2002) was aware that this Espinosa, J., Ortea, J., Caballer, M. & Moro, L. 2006. Moluscos marinos de la peninsula de species probably did not belong to Mareleptopoma Guanahacabibes, Pinar del Río, Cuba, con la Moolenbeek & Faber, 1984 and therefore this descripción de nuevos taxones. Avicennia 18: assignment was tentative. This species is safely 1–83. referable to Clatrosansonia Sabelli & Taviani in Le Janssen, R. 2004. The family Pickworthiidae in the Renard & Bouchet, 2003, because it shares many Middle Miocene of the Paratethys (Gastropoda: shell characters with the type species of the genus, Caenogastropoda: Littorinoidea?). Courier C. philippina (Bandel & Kowalke, 1997). Compared Forschungsinstitut Senckenberg 246: 169–186. with C. philippina, C. circumserrata has finer and Kase, T. 1998a. The family Pickworthiidae (Gastropoda: Caenogastropoda) from tropical more numerous spiral cords on the last whorl (four Pacific submarine caves: four new species of or five above and nine below the basal periphery, Sansonia. Venus (Japanese Journal of compared with two and five in C. philippina), Malacology) 57: 161–172. weaker granules at the intersections of the axial Kase, T. 1998b. The family Pickworthiidae ribs and spiral cords, no clear axial rib on the base, (Gastropoda: Caenogastropoda) from tropical and a slightly wider umbilicus. Clatrosansonia Pacific submarine caves: seven new species of circumserrata also resembles Clatrosansonia Microliotia. Venus (Japanese Journal of troendlei Le Renard & Bouchet, 2003 from the Malacology) 57: 173–190. Kase, T. 1998c. The family Pickworthiidae Society Islands and New Caledonia but is easily (Gastropoda: Caenogastropoda) from tropical distinguished in having a less convex upper whorl Pacific submarine caves: five new species of surface, more angulate basal periphery and less Reynellona. Venus (Japanese Journal of prominent granulation at the intersection of the axial Malacology) 57: 245–257. ribs and spiral cords. Kase, T. 1999. The family Pickworthiidae (Gastropoda: Caenogastropoda) from tropical Acknowledgements: We wish to thank anonymous Pacific submarine caves: Ampullosansonia n. gen. and n. gen. ( reviewers for comments and suggestions. Tinianella Venus Japanese Journal of Malacology) 58: 91–100. Kase, T. & Hayami, I. 1992. Unique submarine cave References fauna: composition, origin and adaptation. Journal of Molluscan Studies 58: 446–449. Alhejoj, I., Bandel, K. & Al-Najjar, T. 2016. Kase, T. & Letourneux, J. 2013. Microliotia Pickworthiidae and Aqabarellidae new family wargnieri, a new species of the family (Caenogastropoda, Mollusca) of Aqaba, Jordan: Pickworthiidae (Gastropoda: Caenogastropoda) their larval shells and remarks about their from Tahiti, French Polynesia. Venus 71: 220– evolution and relation. Natural Science 8: 222. 403–430. Kuroda, T. & Habe, T. 1991. Two new genera and Short Notes 103

species of gastropods from Tokunoshima in 南東太平洋・イースター島の Amami Islands, south of Kyushu, Japan. Venus (Japanese Journal of Malacology) 50: 175– 海底洞窟から採取された 178. ソビエツブ科 1 新種 Ladd, H. S. 1966. Chitons and gastropods (Haliotidae through Adeorbidae) from the Western Pacific Islands. United States 加瀬友喜・Bret K. Raines Geological Survey Professional Paper 531: 1–98, pls. 1–16. Le Renard, J. & Bouchet, P. 2003. New species and 要 約 genera of the family Pickworthiidae (Mollusca, Caenogastropoda). Zoosystema 25: 569–591. イースター島はインド・西太平洋生物地理区の lredale, T. 1917. On some new species of marine Mollusca from Christmas Island, Indian Ocean. 東端に位置し，最も近いピトケーン島から 2,200 Proceedings of the Malacological Society of km も離れた南東太平洋の孤島である。この島から London 12: 331–334, pl. 13. は 200 種を超える貝類の報告があり，そのうちの Moolenbeek, R. G. 2008. A new genus for Manzania 37 (Taramellia) minuta Hornung & Mermod, 1927 ％の種が固有種である。本報告では，同島の水 (Gastropoda: Pickworthiidae). Miscellanea 深 15 m の海底洞窟から採取されたソビエツブ科ク Malacologica 3: 9–11. チビロガイ属 1 新種を記載し，またアミメクチビ Moolenbeek, R. G. & Faber, M. J. 1984. Studies of ロガイ属（新称）の 1 既知種を再記載した。これ Western Indian marine Mollusca. A new gastropod genus and species from Bonaire, らの 2 種もイースター島の固有種と考えられる。 Netherlands Antilles. Studies on the Fauna of Curaçao and Other Caribbean Islands 206: Microliotia rehderi n. sp. モアイクチビロガイ（新 98–103. 種・新称） Moolenbeek, R. G. & Hoenslaar, H. J. 2010. A new genus and species, Kaseilla sanciae, from the 殻高は最大で 2.28 mm，リソツボ形，白色。螺 Moluccas, Indonesia. Micellanea Malacologica 層は 6 階を超え，螺管側面はほぼ平で，螺塔高は 4: 17–19. 殻高の 55％を占める。胎殻は平滑で約 1 階の胎殻 Moolenbeek, R. G. & Mussai, P. 2010. A new from Mauritius (Gastropoda: Ⅰと顆粒状の螺脈で覆われる胎殻Ⅱからなり， Chrystella 1 Pickworthiidae). Miscellanea Malacologica 4: sinusigera notch は深く湾入する。後生層は 4 /4 階， 5–7. 縫合付近で括れるが，縫合は線状を呈し，次体層 Raines, B. K. . Contributions to the knowledge 2002 では 3 本の螺肋が 17 本前後の縦肋と交叉し，疣列 of Easter Island Mollusca. La Conchiglia 304: 11–40. となる。体層は螺層上部でやや膨らみ，殻底周辺 Raines, B. K. & Huber, M. 2012. Biodiversity 部は角張らず，殻底には 3 本のやや強い螺肋があ Quadrupled – Revision of Easter Island and る。臍孔は閉じる。殻口は真円形で明瞭な縁取り Salas y Gómez Bivalves. Zootaxa 3217: 1–106. があり，周辺部は肥厚して広く拡がり，やや翼状 Rehder, H. A. 1980. The marine mollusks of Easter Island (Isla de Pascua) and Sala y Gómez. になる。殻高 2.78 mm，殻幅 1.88 mm（ホロタイ Smithsonian Contributions to Zoology 289: プ）． 1–167. 模式産地：イースター島 Hanga-Teo 沖の海底洞 Rolán, E. 2005. A new species of Mareloptopoma (Mollusca, Pickworthiidae) from the Cape 窟，水深 15 m。 Verde archipelago. Gloria Maris 44: 1–9. 分布：イースター島。 Santos, F. N. & França, M. C. 2008. A new species of 既知のクチビロガイ属 11 種の中で，本種は Chrystella (Caenogastropoda: Pickworthiidae) ハワイ産のアラボリクチビロガイ（Microliotia from northwestern Brazil. Strombus 15: 26–29. Takano, T. & Kano, Y. 2014. Molecular phylogenetic hawaiensis Kase, 1998b）に最も近似する。後者とは investigations of the relationships of the 殻形がより細長いこと，強い螺脈を持つこと，ま echinoderm-parasite family Eulimidae within た 2 階の胎殻（後者は 1.25 階）を持つことで区別 Hypsogastropoda (Mollusca). Molecular Raines 2002 Phylogenetics and Evolution 79: 258–269. される。 （ ）は本種をエニウェトク環 礁から知られる Alvania（Taramellelia）corayi Ladd, (Accepted September 22, 2017) 1966 に同定するとともに，属位をクチビロガイ 属に変更している。一方，Le Renard & Bouchet 104 VENUS 75 (1–4), 2017

（2003）は A.（T.）corayi をアミメクチビロガイ属 は太い螺肋で縁取られる。殻口はほぼ真円形で縁 に帰属させており，この種の属位は今後検討の余 取りがある。外唇は板状で体層から伸びる螺肋に 地がある。M. corayi は本種よりも螺塔が低く，殻 覆われる。 底周辺部が角張ること，羅肋と縦肋がより細かい 模式産地：イースター島 Hanga-Teo 沖の海底洞 など，区別が容易である。 窟，水深 15 m。 分布：イースター島。 Clatrosansonia circumserrata（Raines, 2002）イー 本種は Reines（2002）によりイースター島から スターアミメクチビロガイ（新称） Mareleptozoma 属の新種として報告されたが，その 殻は微小で，殻高は最大で 1.2 mm，エビスガイ 属位に関しては暫定的なもので，更なる検討が必 形を呈し，螺塔は低い。螺管は約 5 階，縫合はや 要であることが指摘されていた。本種の殻形態はア や深い。胎殻は薄いオレンジ色，約 1 階で滑らか ミメクチビロガイ属の属模式である Clatrosansonia な胎殻Ⅰと螺脈を持つ 1.5 階の胎殻Ⅱからなり， philippina（Bandel & Kowalke, 1997）と多くの点で sinusigera notch は深く湾入する。次体層と体層上 共通しており，この属に位置づけられる。本種は 部表面は平で螺肋と縦肋が交叉して編み目状を呈 属模式種と比べて弱い縦肋と螺肋を持つこと，体 し，角張った肩部には太い螺肋があり，縦肋と交 層上の螺肋の数が多いこと，明瞭は縦肋が発達し わるところはやや棘状となる。殻底は若干膨らみ， ないこと，臍孔がより広いことなどで区別される。 約 9 本の螺脈で覆われる。臍孔は広く開き，周辺