A jaw fragment of a large mosasaurine (Squamata, Mosasauridae) was discovered from the uppermost Cretaceous Izumi Group in Sennan City, Osaka Prefecture, Southwest Japan as a concretionary float. While the specimen is fragmentary, three complete and one partial alveoli are preserved, the anteriormost one being largest. The third alveolus contains a replacement tooth crown, whose lingual surface was prepared and exposed. The relatively straight crown possesses a smooth enamel surface and two well developed carinae that are oriented in a fore-and-aft position. A deep, columnar root supports such a crown and, when combined with the crown features, suggests that the specimen has the closest taxonomic affinity with a deep-jawed, non-durophagous mosasaurine, Prognathodon. Beginning in the latest Campanian-early Maastrichtian, Prognathodon increased their body size and subsequently became globally distributed during the Maastrichtian, involving the invasion of the Pacific in as early as the late early Maastrichtian. Combined with a minimally estimated mandible length of 119.6 cm, the occurrence of the new specimen in the northwest Pacific suggests its Maastrichtian age, which is congruent with the age assignment to the Izumi Group along the Izumi Mountains on the basis of various macroinvertebrate correlations and magnetostratigraphic studies.

The Early Permian organic-rich black coloured limestone from Mugi County, Gifu Prefecture, central Japan, was sampled for ostracods. Eleven species belonging to six genera were identifıed This ostracod assemblage is the first report of Palaeozoic species from central Japan. Nine species are new: Amphissites gifuensis Tanaka and Yuan sp. nov., Aurikirkbya miyakei Tanaka and Ono sp. nov., Glyptopleura mugiensis Tanaka and Yuan sp. nov., Bairdia fujisan Tanaka and Maeda sp. nov., Bairdia ikeyai Tanaka sp. nov., Bairdia spindlica Tanaka and Yuan sp. nov., Bairdia minoensis Tanaka and Ono sp. nov., Microcheilinella subovata Tanaka and Maeda sp. nov., and Microcheilinella tsubogawensis Tanaka and Ichida sp. nov.

The Indo-West Pacific (IWP) benthos, which shows the highest diversity of marine organisms worldwide, is thought to have originated from the Tethys Ocean. Little is known about Miocene ostracodes in the IWP, that is, subsequent to the closure of the Tethys Ocean. To understand the paleobiogeography of Miocene ostracodes in the IWP, we examined ostracodes from the Middle Miocene—Lower Pliocene Osaki Formation, Kukinaga Group, at Tanegashima, Southwest Japan, revealing the presence of Neocytheromorpha, an IWP taxon that originated from South Australia. Neocytheromorpha occurs abundantly with Trachyleberis in Middle Miocene sublittoral deposits. This finding indicates that Neocytheromorpha migrated northward from South Australia, along the Australian coast, and settled in coastal areas of the West Pacific during the Oligocene—Middle Miocene. Because the migration coincided with diversification in the West Pacific and the invasion of corals and molluscs, it was synchronous with changes in the populations of the IWP biota. Two new species are systematically described: Acanthocythereis inouei sp. nov. and Neocytheromorpha priscipacifica sp. nov.

This paper presents the litho- and biostratigraphy of the Permian-Triassic boundary (PTB) siliceous rocks that accumulated on the lower flank of a seamount in a mid-oceanic realm of the Panthalassa Ocean. The study section correlates with the upper part of the Lower Permian to Lower Triassic Hashikadani Formation of the Mino terrane in the Mt. Funabuseyama area, central Japan.

The lithologic succession comprises a lower unit (ca. 6.2 m thick) dominated by gray chert with small amounts of black chert and black claystone, middle unit (ca. 0.7 m) of black chert with subordinate black claystone and gray chert including pyrite nodules near the top, and upper unit (ca. 0.9 m) characterized by black claystone with thin black chert beds. The lithologic change from the middle unit to the upper unit is sharp and abrupt.

The lower and middle units correlate to the upper Wuchiapingian to Changhsingian (Neoalbaillella ornithoformis to N. optima zones). The upper unit includes the lower Induan, as the black chert bed in its middle part yields Hindeodus parvus. These beds also yield Triassospongocyrtis? sp., a primitive Mesozoic-type Nassellaria, with several types of the sphaeroid spumellarians.

The Permian radiolarians exhibit a marked loss in diversity across the lithologic boundary between the middle and upper units. We hypothesize that this lithologic boundary marks the main extinction horizon of the Permian radiolarians. Also a profound faunal turnover of radiolarians occurred at this level.

On the basis of the Global Boundary Stratotype Section and Point (GSSP) designation, it is reasonable to position the PTB at the bottom of the H. parvus-yielding chert bed in the upper unit. Nevertheless placing the PTB at this level remains tentative, because age-diagnostic fossils are absent from the lower part of the upper unit. Alternatively, with the emphasis upon correlation with the recently reported PTB section of the Hashikadani Formation, the PTB of the study section is preferably positioned at the sharp lithologic boundary between the middle and upper units. Given this alternative, the PTB corresponds to the main extinction event of Permian radiolarians, which, in turn, is thought to correspond to significant environmental changes.

The genus Nuttallia can be distinguished from other psammobiids by having a wide hinge plate, a subumbonal pit and the lower limb of the pallial sinus detached from the pallial line. It consists of the Nuttallia petri and N. nuttallii groups, based on the outline and size of shell. Among the large-sized N. petri group, Nuttallia commoda can be separated from the extant species N. petri by having a thin-walled shell, a compressed right valve, a gently sloping dorsal margin, and a lower shell. Moreover, it has been elucidated that N. commoda is one of the characteristic species of the Omma-Manganji fauna, which was confined to the Pliocene and lower Pleistocene deposits in the Japan Sea borderland. From the fossil records, the N. petri group appeared earlier than the N. nuttallii group geologically. Probably it evolved from the Eocene Soletellina, which spread northward taking advantage of the warm climate during the Eocene and adapted to the cooler temperature of the Oligocene in the northwestern Pacific. On the other hand, the N. nuttallii group flourished in the northeastern Pacific during the Miocene to Pliocene and migrated to the northwestern Pacific by the Pliocene.

The sand button of the psammocoral (vendobiont) Spatangopsis costata from the Early Cambrian Mickwitzia Sandstone of Sweden possessed radial rays on its uppermost surface that extended outward, in the living organism, farther than previously recognized. With intact rays, the button reached a diameter three or more times larger than its normally preserved central portion. The rays were likely housed in softtissue slots in close proximity to the external environment, and may have become directly exposed and easily broken off if the soft tissues contracted during storm-induced transportation, thus producing the normally observed short rays.

A large individual, exceptionally preserved in situ, shows the true length of rays, as well as a major portion of a circular, radially ribbed mechanical impression of a soft-tissue surface underneath the button. Back-filling of this impression suggests a slight, active upwards movement to counter sedimentation. Small individuals are more commonly preserved with complete rays.

A reconstruction of the S. costata organism as a solitary polyp appears unlikely, since the above evidence leaves insufficient space for an actinian-like gut above the sand button. More likely alternatives are a colonial organism in which a large, central polyp/zooid was specialized as a sand-weighted anchor and supported a number of smaller feeding individuals, or a solitary or colonial descendant of frond-bearing Ediacaran vendobionts that replaced the basal holdfast with a weighted anchor, as an evolutionary response to the Early Paleozoic decrease in biomats suitable for the disc type of attachment, and probably carried multiple fronds. Fragmentary impressions of suitable candidates for these fronds are preserved in the same sediments.