We examined biostratigraphic age inferences based on planktonic foraminifera and calcareous nannoplankton and documented the faunal associations of benthic foraminifera during the Quaternary in core PC311 taken from the top of a seamount (1,370 m water depth) in the Magellan Seamounts (western Pacific Ocean). Six and five biostratigraphic datums were recognized by planktonic foraminifera and calcareous nannofossils, respectively. In the lower part of the core, a planktonic foraminiferal datum occurred at the depth corresponding to 2.332 Ma, whereas the two datums of calcareous nannofossils were observed at 2.76 Ma and 2.78 Ma. As a result, we propose two age models. The diversity measures of benthic foraminifera declined gradually from similar to 1.3 Ma to the present. Stilostomellidae and Pleurostomelidae also decreased gradually after similar to 1.3 Ma and disappeared at similar to 0.7 Ma, as taxa went extinct across the Mid-Pleistocene Transition. In contrast, Pseudoparrella obtusa, a possible phytodetritus species, increased intermittently after similar to 1.3 Ma. In the lower part of the core, Globocassidulina subglobosa-Globocassidulina ryukyuensis plexus were abundant before similar to 1.5 Ma, whereas Globocassidulina obtusa became common after similar to 1.4 Ma. The faunal transition in core PC311 from the seamount top in the western Pacific Ocean appears to be related to the enhanced zonal gradient of sea surface temperature between the eastern and western Equatorial Pacific Ocean at similar to 1.3 Ma as well as the changes in global deep-water circulation including the persistent North Pacific Deep Water and/or the Upper Circumpolar Deep Water from the Southern Ocean-originated deep water.
The Hauterivian coral fauna of Oshima Island (Miyagi, Japan) is taxonomically revised on the basis of the type and additional materials. The fossil localities are no longer accessible. Sixteen species from 13 genera and seven families are described. Not all originally described species could be revised either because the type material could not be found or owing to the poor state of preservation of the corals. The coral fauna from Oshima shares most species with the species-rich Hauterivian coral fauna of the Paris Basin (France). Four genera undergo a range extension: Calamophylliopsis, ?Eohydnophora, Siderohelia and Palaeosiderofungia.
A new smelt fish, Spirinchus izumoensis sp. nov., is described from the Lower to Middle Miocene Kawai Formation in Shimane, southwestern Japan. The new species differs from its congeners in possessing the unique combination of the following characteristics: enlarged and thickened anal fin rays and enlarged anterior proximal pterygiophores; non-parallel anterior half proximal pterygiophores and parallel posterior proximal pterygiophores of the anal fin; short proximal pterygiophores at the middle part of the anal fin, almost as short as or shorter than their associated haemal spines; and total of 48 vertebrae. The new species was found along bedding planes with well-developed lamination, suggesting that it was deposited under low-oxygen bottom-water conditions. It is inferred that a brackish estuarine environment influenced by both freshwater and marine conditions prevailed during the deposition of mudstone in the Kawai Formation.
A new fossil sciarid species, Sciara katoi Aiba and Menzel sp. nov., is described based on 48 relatively well-preserved specimens from the City, Tochigi Prefecture, Japan. With an average body length of 11 mm, this female fossil is the largest species in the genus Sciara Meigen, 1803 ever found and also the first sciarid species described from the Pleistocene. For a solid comparison with other representatives of the genus, all original descriptions of extant and fossil Sciara (Lycoria) species were reviewed. The extensive literature study revealed that the name Sciara thoracica is in use for three different Sciara species. For this reason, two homonyms are replaced as follows: Sciara matsumurai Menzel and Aiba nom. nov. for Sciara thoracica Matsumura, 1916; and Sciara statzi Menzel and Aiba nom. nov. for Sciara thoracica (Statz, 1944) (both preoccupied, not Sciara thoracica Macquart, 1838). Following these nomenclatural corrections, the fossil Sciara katoi Aiba and Menzel sp. nov. is morphologically compared with the two extant species Sciara rotunda R & uuml;bsaamen, 1894 and Sciara matsumurai Menzel and Aiba nom. nov.
In this paper, we described an ant fossil discovered in the Middle to Late described as a new species of the Subfamily Myrmicinae Lepeletier de Saintthird cubital vein reaching apical margin, and long hindfemur. The genus Paraphaenogaster is extinct, with 22 species reported worldwide, but its distribution is centered in Europe. In Asia, only four species are known from China and one from Japan. This study adds a second new species from Japan, suggesting that this genus also exhibited diversity in East Asia. This is the first discovery of insect fossil from the Fuzawa Formation and the second report of a new ant fossil from Japan.
In this study, we report a cicada fossil from the Middle Pleistocene (Chibanian) serving both wings and the body, represents a large individual with an estimated total length of 62 mm (head to forewing apex). Its body size, operculum morphology, and wing venation most closely resemble the extant Auritibicen flammatus (Distant, 1892). However, it differs from that species in its elongated wings and absence of forewing infuscation. Therefore, we tentatively identified the fossil as Auritibicen cf. flammatus (Distant, 1892). Morphological differences between a fossil and extant species may indicate that the fossil represents either an extinct species or an ancestral form of the extant species. Cicada fossils are extremely rare, with only 45 species described to date, all from the Cenozoic. Most are fragments of wings, with few specimens preserving the entire body. The specimen reported here is relatively well-preserved among cicada fossils and is the largest known specimen with the entire body intact. A detailed description of this fossil provides important insights into cicada evolution and speciation. Being from the Middle Pleistocene, it is also the youngest occurrence of a fossil cicada.
The lower jaws of two pachydiscid ammonites, Menuites japonicus (Matsumoto) and Eupachydiscus sp., are described based on two specimens from the Coniacian to Santonian (Upper Cretaceous) strata of the Haboro and Mikasa areas in Hokkaido, Japan. They are preserved in situ in the body chamber and exhibit features intermediate between the lower jaws of anaptychus and aptychus types, specifically, a broadly open outer lamella composed of inner "chitinous" and outer calcareous layers, a flat rostrum, and a median furrow along the hood ridge of the inner layer. These characteristics have also been documented in the lower jaws of other previously described pachydiscid species, suggesting they are diagnostic of the family. The unusually large, shovel-shaped lower jaws with flat rostral margins may have evolved in relation to a microphagous feeding strategy. Additionally, the ventral outline of the lower jaw roughly matches the cross-sectional outline of shell aperture, although the former is smaller than the latter. As previously supposed in some Jurassic ammonoids, Late Cretaceous pachydiscids were presumably able to withdraw their soft parts deep into the body chamber, thereby avoiding being eaten by predators. Under such circumstances, their widely open lower jaws could have an operculum-like role to protect the retracted soft body from predator's attack.
Here, we report the first discovery of Mesozoic insect fossils from the Late Cretaceous of Kyushu Island, Japan. The specimens include an isolated abdomen (Insecta, fam., gen. et sp. indet.) from the Santonian Hinoshima Formation in Kumamoto, and an isolated elytron (Coleoptera, fam., gen. et sp. indet.) from the Campanian Mitsuse Formation in Nagasaki. Although the preservation of fossils does not allow for species-level identification, these finds represent a crucial initial step toward understanding insect diversity and the composition of terrestrial ecosystems in the eastern margin of East Asia during the Late Cretaceous.
