Two New Gastropods from the Late Pliocene Omma-Manganji Fauna In
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Two New Gastropods from the Late Pliocene Omma-Manganji Fauna in the Japan Sea Borderland of Honshu, Japan Author: Kazutaka Amano Source: Paleontological Research, 23(2) : 85-94 Published By: Palaeontological Society of Japan URL: https://doi.org/10.2517/2018PR011 BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Complete website, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/terms-of-use. Usage of BioOne Complete content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Downloaded From: https://bioone.org/journals/Paleontological-Research on 10 Apr 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by The Palaeontological Society of Japan Paleontological Research, vol. 23, no. Gastropods2, pp. 85–94, Aprilfrom 1, late 2019 Pliocene Omma-Manganji fauna 85 © by the Palaeontological Society of Japan doi:10.2517/2018PR011 Two new gastropods from the late Pliocene Omma- Manganji fauna in the Japan Sea borderland of Honshu, Japan KAZUTAKA AMANO Department of Geoscience, Joetsu University of Education, Joetsu, Niigata 943-8512, Japan (e-mail: [email protected]) Received February 26, 2018; Revised manuscript accepted June 2, 2018 Abstract. A new genus and species of the gastropod family Capulidae, Vermeijia japonica, is described from the upper Pliocene Kuwae Formation in Niigata Prefecture and the lowermost part of the Sasaoka Formation in Akita Prefecture, Japan. This genus is similar to the boreal genus Ariadnaria although it was collected in association with several warm-water species. In another gastropod family, Nassariidae, Cyllene satoi is a new species from the upper Pliocene Tentokuji Formation in Akita Prefecture. Nine warm-water taxa in the Omma- Manganji fauna, including Cyllene, no longer live in the Japan Sea, except for its westernmost part. They suggest that the Tsushima Current had a higher SST during the late Pliocene than at present. Vermeijia is the fourth extinct genus of the Omma-Manganji fauna, but it disappeared in the Japan Sea by Datum A (2.75 Ma), earlier than the other three genera, which became extinct by the end of the early Pleistocene. Key words: Gastropoda, Japan Sea, late Pliocene, Omma-Manganji fauna, paleotemperature Introduction ermost part of the Sasaoka Formation. One of them is the capulid Vermeijia japonica gen. and sp. nov. and the During the early Pliocene to early Pleistocene, many other is Cyllene satoi sp. nov. Both genera were collected endemic species of mollusks originated in the semi- from assemblages that included warm-water species. closed Japan Sea (Chinzei, 1978). The fauna is known Among them, Cyllene is now widely distributed in the as the Omma-Manganji fauna (Otuka, 1939) and the tax- Indo-Pacific region, but is confined to the westernmost onomy of its mollusks has been studied by many authors part of the Japan Sea (Higo et al., 1999). In this paper, I (Kaseno and Matsuura, 1965; Ogasawara, 1977, 1986; describe these gastropods and discuss their biogeographi- Kitamura and Kondo, 1990; Amano, 2001, 2004, 2007). cal significance. The Omma-Manganji fauna mainly consists of shallow cold-water species as well as endemic extinct species. Material and methods However, it contains some warm-water species, indicat- ing inflow of the Tsushima warm current (e.g. Ogasawara, One specimen of Vermeijia japonica gen. and sp. nov. 1986). During the late Pliocene, many kinds of shallow was recovered from Loc. 2 by Amano et al. (2000a) (Loc. warm-water taxa were recovered from the upper Pliocene 3 in Figure 1) in the upper Pliocene Kuwae Formation deposits along the Japan Sea, from the Tentokuji Forma- in Niigata Prefecture and another one from Loc. TH1 by tion and the lowermost part of the Sasaoka Formation Amano et al. (2011) (Loc. 1 in Figure 1) in the upper in Akita Prefecture, the Kuwae and Shitoka formations Pliocene part of the Sasaoka Formation in Akita Pre- in Niigata Prefecture, and the Mita and Zuwaka forma- fecture. Based on the associated molluscan fossils, both tions in Toyama Prefecture (Amano et al., 2000a, b, 2008, formations were deposited in lower sublittoral depths. 2009, 2011, 2012). Thus, in the late Pliocene, the warm However, in the case of the Kuwae Formation, the fossils Tsushima current flowed into the Japan Sea and reached reveal that the occurrence is allochthonous, in contrast as far north as Akita Prefecture, northern Honshu. with their autochthonous occurrence in the Sasaoka For- Two new gastropods have been collected from the mation (see Amano et al., 2000a, 2011). The new genus Tentokuji Formation, the Kuwae Formation and the low- possibly lived in water shallower than the lower sublit- Downloaded From: https://bioone.org/journals/Paleontological-Research on 10 Apr 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by The Palaeontological Society of Japan 86 Kazutaka Amano the new taxa are stored at the University Museum of the University of Tokyo. Abbreviations of institutions: IGPS, Institute of Geology and Paleontology, Faculty of Sci- ence, Tohoku University; JUE, Joetsu University of Edu- cation; NMNS, National Museum of Nature and Science, Tsukuba; UMUT, University Museum of the University of Tokyo. Systematic descriptions Family Capulidae Fleming, 1822 Genus Vermeijia gen. nov. Etymology.—The present new genus is named for Geerat J. Vermeij (University of California at Davis) who has contributed extensively to the taxonomy of gastro- pods. Type species.—Vermeijia japonica sp. nov. Diagnosis.—Shell moderate-sized, rather thin, glo- bose; spire very low; surface of spire whorls cancellate with a few spiral cords and fine axial ribs; surface of last whorl sculptured with spiral costae; aperture very wide, Figure 1. Localities of the fossils herein treated. posterior end located above deep suture between last and penultimate whorls; inner lip covered by callus with one weak fold in its anterior part; outer lip thin; umbilicus toral zone. narrow, with weak fasciole; anterior canal very short and Six specimens of Cyllene satoi sp. nov. were collected narrow. from Loc. 21 by Amano et al. (2000b) (Loc. 2 in Figure 1) Included species.—Other than the type species, Trichot- in the upper Pliocene Tentokuji Formation in Akita Pre- ropis planicostata Yokoyama, 1920 is included in this fecture. The occurrence at this locality is allochthonous. genus. Trichotropis planicostata was originally described Many shallow-water gastropods were carried down to by Yokoyama (1920) from the lower Pleistocene Koshiba upper bathyal or lower sublittoral depths (Amano et al., Formation in Kanagawa Prefecture, based on one young 2000b). specimen. Baba (1990) described and illustrated the adult For proposing these new taxa, the following speci- specimen having a rapidly expanding last whorl from the mens were also examined; Trichotropis planicostata lower Pleistocene Umegase Formation in Chiba Prefec- Yokoyama, UMUT CM 20192 (holotype; Loc. Koshiba, ture (Figure 2.3). Nemoto and O’Hara (2005) illustrated Kanagawa Prefecture; the lower Pleistocene Koshiba one specimen which has a rapidly expanding last whorl Formation), NMNS PM25264 (Loc. Kamataki, Kimitsu as T. insignis (Middendorff) from the lower Pleistocene City, Chiba Prefecture; the middle Pleistocene Ichijuku Tomioka Formation in Fukushima Prefecture. Adding Formation), NMNS PM28601 (collected by Baba, 1990 one specimen (Figure 2.4) from the middle Pleistocene from Higashi-Hikasa, Kimitsu City, Chiba Prefecture; the Ichijuku Formation in Chiba Prefecture and stored at the lower Pleistocene Kiwada Formation); Cyllene pulchella National Museum of Nature and Science, Tsukuba, this Adams and Reeve, IGPS no. 55136 (Loc. Ananai, Kochi species has been recorded from lower to middle Pleisto- Prefecture; the lowest Pleistocene Ananai Formation); cene deposits on the Pacific side of central Honshu. Cyllene lugubris Adams and Reeve, IGPS nos. 53912, Remarks.—The present genus has a unique and enig- 53913, 53914, 53915, 53916, 53917, 53918, 53919 (the matic form. However, despite lacking the protoconch, lower Pleistocene Byoritsu Beds in Taiwan); Cyllene the close similarity to species of Ariadnaria Habe, 1961, rubulolineata Sowerby, JUE no. 16068 (Loc. off Minabe, Neoiphinoe Habe, 1978, and Trichotropis Broderip and Wakayama Prefecture, 80–100 m in depth). Sowerby, 1829 demonstrates that it should be classified I measured and counted the following characters of the in Capulidae Fleming, 1822. fossils: shell height, height of the spire, maximum diam- Ariadnaria is the most similar to Vermeijia gen. nov. It eter, and the number of axial ribs and spiral cords on the is similar in having a low spire, a large last whorl, distinct penultimate and last whorls. All specimens representing cancellate sculpture which is observed in the early whorls Downloaded From: https://bioone.org/journals/Paleontological-Research on 10 Apr 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by The Palaeontological Society of Japan Gastropods from late Pliocene Omma-Manganji fauna 87 Figure 2. Vermeijia japonica gen. et sp. nov. and V. planicostata (Yokoyama, 1920). 1, 2, Vermeijia japonica gen. et sp. nov.; 1a, b, paratype, UMUT CM 32796; 1a, internal mold; 1b, outer cast (silicone rubber), Loc. 1; 2a–e, holotype, UMUT CM 32795; 2a, apertural view; 2b, apical view; 2c, enlargement of apical view; 2d, enlargement of early whorls from abapertural side; 2e, abapertural view, Loc. 3; 3, 4, Ver- meijia planicostata (Yokoyama, 1920); 3, NMNS PM28601 abapertural view; 4, NMNS PM25264, apertural view. All scale bars show 5 mm.