Carbonate concretions occur in sedimentary rocks of widely varying geological ages throughout the world. Many of these concretions are isolated spheres, centered on fossils. The formation of such concretions has been variously explained by diffusion of inorganic carbon and organic matter in buried marine sediments. However, details of the syn-depositional chemical processes by which the isolated spherical shape developed and the associated carbon sources are little known. Here we present evidence that spherical carbonate concretions (diameters φ : 14 ~ 37 mm) around tusk-shells (Fissidentalium spp.) were formed within weeks or months following death of the organism by the seepage of fatty acid from decaying soft body tissues. Characteristic concentrations of carbonate around the mouth of a tusk-shell reveal very rapid formation during the decay of organic matter from the tusk-shell. Available observations and geochemical evidence have enabled us to construct a ‘Diffusion-growth rate cross-plot’ that can be used to estimate the growth rate of all kinds of isolated spherical carbonate concretions identified in marine formations. Results shown here suggest that isolated spherical concretions that are not associated with fossils might also be formed from carbon sourced in the decaying soft body tissues of non-skeletal organisms with otherwise low preservation potential.

Lanternfishes (Myctophidae) are one of the most common groups of fishes in the mesopelagic zone of the world ocean, and their otoliths have been dominant in pelagic sediments since at least Miocene times. Many species have a wide geographic distribution, with several being circumglobal. This wide distribution makes myctophid otoliths potentially useful for supraregional stratigraphic purposes. The Sea of Japan and the Northwest Pacific is an important region for investigations into the diversity and evolution of the Myctophidae. Here, we describe a large collection of myctophid otoliths from the late early to early middle Miocene (late Burdigalian to early Langhian) from six localities on western and central Honshu, which were under warm water influence during that time. A total of 22 species are recognized, of which eight are new. In the order in which they are described, the new species are Bolinichthys higashibesshoensissp. nov., Ceratoscopelus brevissp. nov., Lampadena eximasp. nov., Lampanyctus lenticularissp. nov., Lampanyctus tsuyamaensissp. nov., Stenobrachius ohashiisp. nov., Diaphus epipedussp. nov., and Diaphus watatsumisp. nov. At least nine species are also known from coeval sediments outside of Japan, most notably New Zealand and Europe. This distribution reflects the extraordinary geographic spread of myctophid species already in the early Miocene and indicates the potential for their future use for biostratigraphic purposes. The paleoecological and paleobiogeographical implications of the studied myctophid otolith assemblages are discussed. Furthermore, the stratigraphic ranges of the observed species are discussed and compared with data from other regions of the world in an attempt to outline the potential future application of myctophid otoliths for supraregional biostratigraphic purposes.

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Twenty-four species of pteropods are described from the Pliocene Miyazaki Group in the Tsuma-Takanabe district, Miyazaki Prefecture, southwest Japan. Five are new: Clio shibatai new species, Cuvierina miyazakiensis new species, Cavolinia floridana japonica new subspecies, C. itoigawai new species, and C. vendryesiana hyugaensis new subspecies.The pteropod fauna of the two lower members of the Miyazaki Group consists largely of extinct species. Whereas more than one-half of the species of the two upper members are extant.Twelve species, Limacina sp., Clio hataii (Noda, 1972), C. shibatai new species, Cuvierina miyazakiensis new species, Bowdenatheca? sp., Diacria digitata subsp. indet., Cavolinia floridana japonica new subspecies, C. cf. C. gypsorum (Bellardi, 1873), C. itoigawai new species, C. mexicana (Collins, 1934), C. rattonei Simonelli, 1896, and C. vendryesiana hyugaensis new subspecies seem to serve as good index fossils for the Pliocene.

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