Jung, K. K. (1988). Morphology and taxonomy of late Cenozoic uvigerine foraminifera from Japan. The science reports of the Tohoku University. Second series, Geology. 59: 99-175.

148244

Jung, K. K.

1988

59: 99-175

Publication

http://hdl.handle.net/10097/00105183

Available for editors  

Japanese Miocene to Recent uvigerine foraminifera are studied taxonomically. For developing meaningful taxonomy, several morphological features are examined by means of optical and electron microscopes, and soft X-radiography : apertural apparatus including toothplate, coiling mode, wall structure, pores, ornaments, test size, prolocular size and length and breadth developments through ontogeny (growth pathway). Their biogeographic distributions are also inspected. Two types of toothplates are recognized : euuvigerine and neouvigerine types. The euuvigerine toothplate is simple, straight, and attached to the lip of the preceding foramen. The neouvigerine toothplate is straight or trough-like, and attached to the outer margin of the preceding apertural neck. Three forms are discriminated among the neouvigrine type : a toothplate folded and concave to the side of the preceding foramen, a toothplate convex and folded away from the preceding foramen, and a straight one, each of which is represented by N. setosa, n. sp., N. proboscidea, and N. interrupta, respectively. The toothplate has stable characteristics, though its shape alters a little with the change of coiling mode through ontogeny. The adhesion patterns of the toothplate to the preceding foramen, however, are consistent, and do not change with coiling mode. Ontogenetic coiling alterations pose a practical problem with classifying juvenile individuals, though they provide a significant clue not only for morphological taxonomy but also for biological consideration. The test wall consists of two morphologically different layers. A fibrous calcitic layer is covered with inner and outer veneers of granular nature. Through ontogeny, the wall thickens and surface configuration changes as the formation of the subsequent lamellae which are principally monolamellar. The distribution of pores is more or less restricted. An imperforate area develops at the apertural apparatus including toothplates, and is closely related to the nature of veneers. The size and density of pores are changeable with environments, and similar among coexisting congeners. Therefore, pore patterns are a potential tool for the recognition of ecophenotypes rather than species. Intraspecific variations in test size are mainly ascribed to those in chamber size. Uvigerine tests grow up by tri- to uniserial chamber adding. Among adult individuals the number of chambers is quite uniform within the same reproductive generation of a species. The frequency distribution of prolocular size is discrete, and bimodal within a given population--dimorphism corresponds to the number of chambers. Microspheric specimens have more chambers than in megalospheric ones. Test size, however, does not show any relation with prolocular dimorphism. Coexisting congeners are well assorted into clouds in their test size, probably implying resource partitioning. The pattern of surface ornaments changes generally with water depth, though certain ornaments occupy different depth ranges in different bioprovinces. Shallow faunas are composed of a costate form which is replaced by a spinose-costate form with increasing water depth, and finally a spinose form occupies deep habitats. From these morphological and biogeographical studies, 29 uvigerine morphotypes are distinguished : 19 come under Euuvigerina (s. s.), three E. (Hopkinsina) and seven Neouvigerina. They include eight new species or subspecies : E. akitaensis grandis, E. akitaensis pumila, E. introrsa, E. kiyoshiasanoi, E. lobulata, E. nipponica, N. setosa, and N. takayanagii. uvigerine foraminifera Miocene to Recent taxonomy surface ornaments toothplate test wall test size pore distribution

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