On the basis of rib morphology and other characters, Ostrea tissoti Peron and Thomas found in Egyptian Campanian sediments is placed in the genus Cameleolopha Vyalov, 1936 and the subgenus Hyotissocameleo n. subgen. This new subgenus is distinguished from Cameleolopha s. s. in having dichotomous to trichotomous round-crested radial ribs, chomata, a long triangular resilifer and a reniform to comma-shaped adductor muscle scar. The main part of the shell shows regularly foliated and in part cross-foliated structure. Neither chalky deposits nor chambers are recorded. Silicification of the original calcitic structure is recognized. Recrystallization and dolomitization resulting from diagenetic processes are observed.

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One of the virtues of molecular phylogeny for paleontology is that it can provide independent and often reliable sets of data from living relatives to test various evolutionary hypotheses inferred from fossil forms. In this study, we present results of a molecular phylogenetic analysis of 12 species of 7 genera belonging to the Laqueoidea, which is the most prolific of the brachiopod superfamilies in the seas around Japan. Onto a phylogenetic tree based on partial sequences (1218 bp) of the mitochondrial cox1 gene, we superimposed various external and internal morphologic characters of both juveniles and adults for the taxa examined. The resulting patterns indicated that several lineages experienced paedomorphic evolution in terms of the brachidial (loop) morphology, and that, contrary to some traditional views, certain adult features, such as the bilateral loop, possession of a cardinal process, and a rectimarginate commissure, had homoplasious distributions. Examination of the character distributions also revealed, however, that anterior nonbifurcation of the septal pillar at the axial phase is a synapomorphy for a major clade recognized in the molecular analysis. Those results suggest that early loop ontogeny, information about which is still fragmentary, would be useful in assessing relationships among laqueoid brachiopods, including certain Mesozoic genera.

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Stratigraphic and ontogenetic descriptions of three species of Hourcquia from the Cretaceous Yezo Supergroup of Hokkaido, Japan are given for the first time. H. ingens, H. hataii and H. kawashitai occur in the Inoceramus teshioensis Zone of the upper Turonian. Hourcquia evolved and radiated in not only the Tethyan and adjacent areas but also the Northwest Pacific region for a short period in the late Turonian.

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Permian ammonoids, Dzhulfoceras cf. furnishi, D. sp. and Stacheoceras? sp., are described from the Southern Kitakami Massif, Northeast Japan. The first two and the last were collected from the Lower and Middle Toyoman Series, respectively. The occurrence of Dzhulfoceras supports the previous correlation of the Lower Toyoman Series with the Wuchiapingian (Dzhulfian). This occurrence of Dzhulfoceras is the first record of the genus outside the Middle East and supports the conclusion that a close paleobiogeographic relationship existed between the Middle East and the Southern Kitakami in Late Permian time.

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A Middle Carboniferous (probable late Bashkirian) fauna of orthoconic cephalopods was collected from bioclastic rudstone/grainstone in the Omi Limestone Group, Central Japan. This fauna belongs to the Taishaku-Akiyoshi-South China Faunal Province. Recognized herein are the orthocerid nautiloid Bogoslovskya omiensis sp. nov., the bactritids Bactrites nagatoensis Niko, Nishida and Kyuma, 1991 and Bactrites sp., and an indeterminate body chamber. This is the first reliable documentation of orthoconic cephalopods from the Omi Limestone Group.

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The Middle Jurassic Mitarai Formation distributed in Shokawa Village, Gifu Prefecture, central Japan, is interpreted as deposits of wave-dominated shelf environments. The muddy shelf deposits yield abundant molluscs showing various modes of occurrence that can be divided into three fossil assemblages : (1) the autochthonous Modiolus maedae-Tetorimya carinata assemblage with commonly in-situ preserved semi-infauna and deep burrowers; (2) the Entolium inequivalve assemblage characterized by mixed autochthonous infauna and parautochthonous free-living elements; and (3) the allochthonous Inoceramus maedae assemblage. The Entolium inequivalve assemblage contains the chemosymbiotic bivalve Solemya and is associated with a low-diversity ichnofauna suggestive of low oxygen conditions.

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The physiological ecology of a spherical polycystine species, Diplosphaera hexagonalis collected from the surface water of the Kuroshio Current in the East China Sea off Sesoko Island, Okinawa, was observed in a culture dish for three days. The observed specimen demonstrated cyclic extension and contraction of axopodia by a regular interval of ca. 630 seconds. Each cycle was divided intro four phases based on the state of the axopodia and movement of axopodial vacuoles. Vertical migration in response to axopodial motility was also observed. The specimen began to rise accompanied with the axopodial extension, floated in the seawater and often moved horizontally when its axopodia were radiated symmetrically, and began to sink in correspondence with the axopodial contraction. The effect of thermal currents on this behavior is easily neglected on the ground of the definite coincidence with the rhythmic extension and contraction of axopodia. The rhythm appears to play important roles in the physiological ecology of this species, including food capture and possibly buoyancy. The taxonomic section presents a nearly complete synonym list of D. hexagonalis and summarizes that the genus Diplosphaera is a senior synonym of Astrosphaera, Drymosphaera and Leptosphaera. Thus, Diplosphaera hexagonalis is the only valid name for this species, according to ICZN Article 55.3. Diplosphaera is considered herein to belong not to the family Actinommidae but to the Astrosphaeridae, unlike in most previous paleontological and biological studies. The family Macrosphaeridae Hollande and Enjumet, 1960, to which the genus Diplosphaera was assigned, is treated as an invalid name because the type genus Macrosphaera has not been established yet.

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