Metamicropora areolae
Creators
Description
Metamicropora areolae (Sakakura, 1935) (Figs 10–12, 13A)
Verminaria areolae Sakakura, 1935: 12, pl. 2, fig. 5, text-fig. 3; Hayami 1970: 324, pl. 36, fig. 4; Hayami 1975: 89 (only listed); Nishizawa and Sakagami 1986: 84, pl. 11, fig. 3; Arakawa 1995: 80 (only listed); Nishizawa 1997: 147, 152 (only listed).
Microporina areolae: Sakakura 1936: 264.
Microporina elongata (not of Hincks, 1880): Silén 1942: 65, pl. 3, fig. 12, text-figs 76–78; Hirose 2010: 45, pl. 78A–C. Micropora areolae: Arakawa 1999: 56.
Material examined. NMNS PA 16846 (two fragments, A, B), and SGBC-0105, Station 1748, Hakurei-Maru cruise GH80-2; NMNS PA 16845 (two colonies, A, B, the latter with ancestrula, on mollusc shell), 16847 (on mullusc shell), 16848 (on mullusc shell), 18158 (inner surface of frontal shield) and 18159, and SGBC-0002 (on mullusc shell), -0407 (on mullusc shell, not coated with metal), Jizodo Formation, Pleistocene, Nishiyatsu, Chiba Prefecture, Japan; NMNS PA 16849 and SGBC-0370 (on mullusc shell), Jizodo Formation, Pleistocene, Oi, Chiba Prefecture, Japan; NMNS PA 18157 (lateral and basal walls), Yabu Formation, Pleistocene, Neriki, Chiba Prefecture, Japan; SGBC-0410 (on mollusc shell, not coated with metal), Jizodo Formation, Pleistocene, Nagara Dam, Chiba Prefecture, Japan. See Table 1 for coordinates and depths of cruise samples.
Measurements (in milimetres). NMNS PA 16845, 16846, 16847, and 16848; SGBC-0002, -0105, -0370 and -0398. Autozooids (n =515, 10): ZL, 0.49–1.49 (0.780±0.124); ZW, 0.25–0.79 (0.396±0.0073; OrL, 0.06– 0.12 (0.082±0.010); OrW, 0.11–0.22 (0.162±0.020). Avicularia (n =184, 10): AvL, 0.07–0.18 (0.124±0.018); AvW, 0.05–0.12 (0.075±0.012).
Description. Colony encrusting, unilaminar, oπen becoming multilaminar; maximum size in largest dimension estimated to be more than 20 mm (SGBC-0407). Zooids irregularly hexagonal or rectangular. Frontal shield cryptocystal, flattened, finely granulated, with scattered frontal pores, surrounded by raised rim (Fig. 10A); frontal pores occluded, with three or more slit-like openings each (Fig. 10C). Six to nine pairs of circular opesiules present, closed by thin internal layer with radially arranged slits, or cribriform; distalmost pair generally larger than the others (Fig. 10A, C, D). Orifice semicircular, without oral spines. Operculum smooth (Fig. 10B). Paired tubercles lateral to orifice, derived from proximal gymnocyst of next-distal zooids (Fig. 11 A–D). Avicularium, when present, situated distal to orifice, interzooidal, directed distolaterally, with complete pivot bar; rostrum acute to frontal plane, mandibular opening semicircular to rounded triangular (Fig. 11A, B). Ancestrula similar to later zooids; rhomboidal or hexagonal, with one pair of large, irregularly shaped opesiules and a few additional smaller ones; ancestrula budding three daughter zooids, one distally and two distolaterally (Fig. 12A, B). Zooids interconnected by six or more basal uniporous septula in each lateral wall (Fig. 12C) and several basal septula (some of them pauciporous) in transverse wall (Fig. 12D). Ovicells absent.
Distribution. Sagami and Tokyo Bays (Sakakura 1935; Silén 1942; Nishizawa 1997; Hirose 2010) and the continental shelf east of the Boso Peninsula (station 1748, Hakurei- Maru cruise GH80-2). The recorded depth range is from 65 m (station 1748, this study) to more than 100 m (Silén 1942).
Fossils of this species have been collected from Miocene to Pliocene deposits in Hokkaido, Miyagi, and Ishikawa Prefectures (Hayami 1970, 1976; Nishizawa and Sakagami 1986), and from Pleistocene deposits in Chiba Prefecture (Sakakura 1935; Arakawa 1995; Nishizawa 1997). It is one of the predominant species among cheilostome bryozoans in the Pleistocene Jizodo Formation (Arakawa 1995).
Remarks. Silén (1942) advanced Sakakura’s (1936) discussion and concluded that Verminaria areolae is synonymous with Microporina elongata (Hincks, 1880) from southern Africa. However, Silén’s conclusion is incorrect, as it was based on Waters’ (1889) misinterpretation that Micropora variperforata is synonymous with M. elongata. Those two species are distinct, as Brown (1952: 128) discussed in detail. The opesiules of M. elongata are occluded with calcification lacking any small openings (Hincks 1880: pl. XVI, fig. 4).
On the other hand, Silén (1942) correctly described that the tubercles lateral to the orifice in this species are derived from the next-distal zooids. Similar structures are evident in Verminaria oblonga (Busk, 1859), Calpensia rebeshovensis Zágoršek, 2010 and Micropora finisterrae, although the tubercles in these species are situated distal to the orifice of the proximal zooid (Bishop 1987; Zágoršek 2010; Moyano 1994b). The occurrence of such tubercles thus seems to be polyphyletic.
Notes
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Linked records
Additional details
Identifiers
Biodiversity
- Collection code
- NMNS
- Family
- Microporidae
- Genus
- Metamicropora
- Kingdom
- Animalia
- Material sample ID
- PA 16846, PA 16845, PA 16849, PA 18157
- Order
- Cheilostomatida
- Phylum
- Bryozoa
- Scientific name authorship
- Sakakura
- Species
- areolae
- Taxon rank
- species
- Taxonomic concept label
- Metamicropora areolae (Sakakura, 1935) sec. Arakawa, 2016
References
- Sakakura, K. 1935. Pliocene and Pleistocene Bryozoa from the Boso Peninsula (I). Journal of the Faculty of Science of the Imperial University of Tokyo (Sec. II) 4: 1 - 48.
- Hayami, T. 1970. Miocene Bryozoa from northwest Hokkaido, Japan. Transactions and Proceedings of the Palaeontological Society of Japan (New Series) 79: 316 - 336.
- Hayami, T. 1975. Neogene Bryozoa from northern Japan. Science Reports of the Tohoku University, 2 nd Series (Geology) 45: 83 - 126.
- Nishizawa, Y. and Sakagami, S. 1986. Bryozoa. Pp. 78 - 95. In: Fuji, N. (Ed.) Paleontological Study of the Nanao Calcareous Sandstone in Noto. Board of Education, Nanao City, Ishikawa Prefecture, Japan. [In Japanese]
- Arakawa, S. 1995. Bryozoan fauna in the Jizodo Formation (Pleistocene), Boso Peninsula, Honshu, Japan. Natural History Research 3: 75 - 110.
- Nishizawa, Y. 1997. The Pleistocene cheilostome bryozoans from the Boso Peninsula in comparison with Recent cheilostomes in Aburatsubo Bay and off Jogashima Island. Pp. 143 - 155. In: Arakawa, S. (Ed.) Professor Sumio Sakagami Memorial Volume. Association for the Publication of Professor Sumio Sakagami Memorial Volume, Kashima. [In Japanese]
- Sakakura, K. 1936. On Microporina articulata (Fabricius), a cheilostomatous Bryozoa. Journal of Geology 43: 259 - 267. [In Japanese with English description]
- Hincks, T. 1880. Contributions towards a general history of the marine Polyzoa. II. Foreign Membraniporina (continued). Annals and Magazine of Natural History (Series 5) 6: 376 - 381.
- Silen, L. 1942. Cheilostomata Anasca (Bryozoa) collected by Prof. Dr. Sixten Bock's expedition to Japan and the Bonin Islands 1914. Arkifv for Zoologi 33 A: 1 - 130, pls 1 - 9.
- Hirose, M. 2010. Cheilostomatous Bryozoa (Gymnolaemata) from Sagami Bay, with notes on bryozoan diversity and faunal changes over past 130 years. PhD Dissertation, Department of Natural History Science, Hokkaido University, Sapporo, Japan, 177 pp., 18 tabs., 20 figs.
- Arakawa, S. 1999. A preliminary report on cheilostomatous bryozoans from the coast and the eastern continental shelf of the Boso Peninsula. Bulletin of Seishin-Gakuen 14: 43 - 107. [In Japanese]
- Hayami, T. 1976. Cheilostomatous Bryozoa from the Moniwa Formation. Saito Ho-on Kai Museum Resaerch Bulletin 44: 39 - 51.
- Brown, D. A. 1952. The Tertiary Cheilostomatous Polyzoa of New Zealand. Trustees of the British Museum (Natural History), London, xii + 405 pp.
- Zagorsek, K. 2010. Bryozoa from the Langhian (Miocene) of Czech Republic. Part I: Geology of the studies sections, systematic description of the Order Cyclostomata, Ctenostomata, and " Anascan " Cheilostomata (Suborders Malacostega Levinsen, 1902 and Flustrina Smitt, 1868). Acta Musei Nationalis Pragae, Series B, Historia Naturalis 66: 3 - 136.
- Bishop, J. D. D. 1987. Type and figured material from the ' Pliocene Bryozoa of the Low Countries' (Lagaaij, 1952) in the collection of the Royal Belgian Institute of Natural Science. Institute Royal des Science Naturelles de Belgique, Documents de Travail 37: 1 - 36.
- Moyano G., H. I. 1994 b. Micropora finisterrae sp. n. a new bryozoan species from the Magellan Strait, Chile. Boletin de la Sociedad de biologia de Concepcion 65: 187 - 190.