In this study, we report a cicada fossil from the Middle Pleistocene (Chibanian) of the Shiobara Group in Nasushiobara, Tochigi, Japan. The specimen, preserving 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.

In this paper, we described an ant fossil discovered in the Middle to Late Miocene Fuzawa Formation, Aizu region, Fukushima, Japan. This fossil was described as a new species of the Subfamily Myrmicinae Lepeletier de Saint-Fargeau, 1835, Paraphaenogaster tanemurai sp. nov., having long, straight third 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.

ZooBank registration: urn:lsid:zoobank.org:pub:A0A65E16-22FF-4D89-A088-8179063C8A25

For toothed whales, the Early Miocene was a time of transition between archaic and modern clades. In Japan, there are horizons that include whale fossils from the Early to early Middle Miocene, such as the Ichishi Group in Mie, the Mizunami and Iwamura groups in Gifu, the Morozaki Group in Aichi, and some formations in Akita, Iwate and Hokkaido. The Bihoku Group in Hiroshima has abundant baleen whale (Mysticeti) fossils, but only one possible toothed whale (Odontoceti) fossil exists. Here, we report the first unambiguous fossil record of Odontoceti from the Korematsu Formation of the Bihoku Group (latest Early to earliest Middle Miocene), a pair of fused middle parts of mandibles with two teeth. Although this specimen is fragmentary, it is evident that odontocetes lived in this region during the time of deposition of the Korematsu Formation. However, questions remain as to why there are so few odontocete specimens relative to mysticetes.

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 ~1.3 Ma to the present. Stilostomellidae and Pleurostomelidae also decreased gradually after ~1.3 Ma and disappeared at ~0.7 Ma, as taxa went extinct across the Mid-Pleistocene Transition. In contrast, Pseudoparrella obtusa, a possible phytodetritus species, increased intermittently after ~1.3 Ma. In the lower part of the core, Globocassidulina subglobosa–Globocassidulina ryukyuensis plexus were abundant before ~1.5 Ma, whereas Globocassidulina obtusa became common after ~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 ~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.

A new fossil sciarid species, Sciara katoi Aiba and Menzel sp. nov., is described based on 48 relatively well-preserved specimens from the Shiobara Group of the Middle Pleistocene (ca. 0.3 Ma) in Nasushiobara 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 Rübsaamen, 1894 and Sciara matsumurai Menzel and Aiba nom. nov.

ZooBank registration: urn:lsid:zoobank.org:pub:2F1F3444-71A7-460A-94A2-09B5D9466CDD

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.

ZooBank registration: urn:lsid:zoobank.org:act:CA1A427E-7EFE-438B-B1F9-D5E68F479395

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.

Well-preserved insect fossils in amber provide detailed morphological information. Mesozoic cockroach fossils are typically preserved as impressions, but many specimens have recently been discovered from the mid-Cretaceous Cenomanian Kachin amber (ca. 99–98 Ma). However, cockroach fossils from later in the Cretaceous are rare. Here, we report a new Coniacian (Late Cretaceous, ca. 87–86 Ma) cockroach, Ovaliblatta iwakiensis gen. et sp. nov., based on a fossil in amber from the Kohisagawa Member of the Tamayama Formation (Futaba Group) in Iwaki, Fukushima, Japan. Ovaliblatta iwakiensis gen. et sp. nov. is tentatively assigned as a member of Ectobiidae. The antennae, cerci, and tergum of Ovaliblatta iwakiensis gen. et sp. nov. have numerous trichoid sensilla, similar to those of extant nocturnal Ectobiidae. This suggests that Ovaliblatta iwakiensis gen. et sp. nov. represents an early example of the evolution of nocturnal behavior in cockroaches. This is the first record of a cockroach fossil preserved in amber from the late Coniacian and the first such record from Japan.

ZooBank registration: urn:lsid:zoobank.org:pub:AF30CED2-6F01-48EE-9D44-A61EE910378A

Well-preserved external molds of an articulated brittle star from the upper lower Maastrichtian (Upper Cretaceous) strata of the Futakawa Formation (Sotoizumi Group) of Wakayama, southwestern Japan, are described as a new ophiosphalmid genus and species, Enakosphalma nagashimai. It differs from other members of the Ophiosphalmidae in having lateral arm plates with a smooth outer surface stereom, a beveled outer proximal edge, very small spine articulations grouped ventrally in a shallow depression, small dorsal and ventral contact surfaces with the opposite lateral arm plates, oval radial shields, small disc scales, a large oval plate in the ventral interradius, small and rounded pentagonal oral shields, and tentacle pores developed as between-plate openings until the sixth arm segment. The new species is morphologically intermediate between Enakomusium from the Jurassic of Europe and the extant Ophiosphalma. It therefore contributes to a better understanding of the fossil record and evolutionary history of the important deep-sea family Ophiosphalmidae. It furthermore demonstrates that the Ophiosphalmidae have inhabited deep-sea environments since at least the Late Cretaceous.

ZooBank registration: urn:lsid:zoobank.org:pub:58D441C1-ACCA-464C-BABF-A766BFE2096D

Iguanodontia is a diverse clade of ornithopod dinosaurs known from Upper Jurassic to Upper Cretaceous deposits worldwide, including Japan. In 1999, an isolated sternal element tentatively attributed to a hadrosauroid was collected from the marine Ashizawa Formation of the Upper Cretaceous Futaba Group in Fukushima, northeastern Japan. Our description of this specimen reveals that it is a hatchet-shaped (unfused) sternal plate with an undeveloped caudomedial process, a concave lateral margin, and a relatively short (unflattened) caudolateral process. This element is assignable to an indeterminate styracosternan (Iguanodontia), likely a hadrosauroid. The size of the sternal plate suggests that it is from an individual with a body length of about 3 m. Given that all iguanodontian specimens previously recovered from Upper Cretaceous marine strata in Japan appear to belong to larger (over 3 m in body length) animals, our findings suggest that smaller individuals also inhabited coastal settings in the region.

Taphonomy plays a crucial role in shaping the fossil record and thereby influencing broader interpretations of evolution, biodiversity and palaeoecology. However, its effects on echinoderm taxonomy are seldom considered. Here, we report new fossil loveniid echinoids from the Late Miocene of Taiwan, represented by both external and internal moulds that exhibit markedly different morphologies. The external moulds display the typical diagnostic features of the genus Breynia, whereas the internal moulds lack the inner fasciole and possess pore pairs fully developed to the apical system, making them resemble Spatangomorpha, a fossil genus currently treated as in need of re-description. However, by comparing the fossil internal moulds with the internal surface of skeletons of modern Breynia species, we found that their morphologies closely resemble each other, indicating that the fossils are indeed Breynia species but reflect the preservation of the internal surface of the skeletons. Our results demonstrated that taxonomically important traits of echinoids such as fascioles and pore pairs may be different in internal mould preservation. This case study highlights that relying solely on preserved internal moulds or steinkerns can lead to taxonomic misidentification of fossil echinoids, which may be generally applicable to other biomineralised fossils.

A new species of mountain avens, Dryas nukabiraensis sp. nov., is described based on well-preserved leaf fossils from the Late Miocene lacustrine mudstone of the Tokachihoroka Formation distributed in Lake Nukabira area, eastern central Hokkaido, Japan. Based on the preservation of the new leaf fossils, which is consistent with predopositional transport, and the mixed physiognomic signals of the co-occurring leaf fossils, as well as the modern climate range of extant Dryas, D. nukabiraensis may have inhabited in an open, boreal to cold-temperate highland environment. The present discovery is important as this species is the earliest fossil record of the genus Dryas, extending its range to the Late Miocene. It also represents the southernmost fossil record of the genus in the Northern Hemisphere. We hypothesize that the genus first appeared at mid-latitude areas of East Asia under boreal to cold-temperate climatic conditions, and subsequently spread to Arctic/Subarctic habitats during the Pliocene and Pleistocene.

A new genus and species of the family Turrilitidae, Heterocarinella japonica gen. et sp. nov., is described from the Santonian (Upper Cretaceous) of the Haboro and Kotanbetsu areas in Hokkaido, northern Japan. This taxon is characterized by a persistently turriconic shell, a siphuncle positioned near the upper edge of the flank, and a vertically asymmetrical keel at or below the middle flank of the whorls. Notably, the keel differentiates Heterocarinella japonica gen. et sp. nov. from all other genera belonging to the Turrilitidae. The family Turrilitidae has previously been considered to range from the middle Albian to the late Cenomanian. However, the occurrence of Heterocarinella japonica gen. et sp. nov. demonstrates that this family survived until at least the Santonian. In addition, Tridenticeras from the Turonian to Coniacian of Europe, which is often assigned to the Nostoceratidae, is here re-evaluated as more appropriately belonging to the Turrilitidae. The previous misclassification likely resulted from limited knowledge of the position of the siphuncle, an internal structure, and from the tendency to prioritise stratigraphic consistency over morphological characters in taxonomic assignments. The discovery of Heterocarinella japonica gen. et sp. nov. suggests that the Turrilitidae survived the Cenomanian–Turonian Oceanic Anoxic Event 2 (OAE-2) while progressively narrowing their palaeogeographic range, ultimately contracting only in the northwestern Pacific realm.

ZooBank registration: urn:lsid:zoobank.org:pub:7980761E-A428-4B6D-842B-82CD1F83BABB

The Izu Peninsula of central Japan is a volcanic block that originated far to the south and was transported to its current location by the northward migration of the Philippine Sea Plate. Several small limestone bodies within the upper Lower to lower Middle Miocene volcaniclastic Yugashima Group on the Izu Peninsula contain a molluscan fossil assemblage associated with coral reefs. This assemblage provides insights into the shallow-water diversity of tropical oceanic islands on the eastern margin of the Philippine Sea Plate during the Miocene. Here, a new species of patellid limpet, Scutellastra kadotai sp. nov., is described based on specimens from the Makinoko Limestone in the Shuzenji area of the Izu Peninsula. This new species is distinct from Scutellastra mizunamiensis and Scutellastra itoigawai from contemporaneous strata in the Mizunami and Chichibu basins on the Honshu Arc of mainland Japan. The molluscan assemblage of the upper Lower to lower Middle Miocene limestone bodies on the Izu Peninsula differs in species composition from those of the nearly contemporaneous Kadonosawa/Moniwa faunas of the Honshu Arc. The discovery of a new Scutellastra species provides additional evidence that the late Early to early Middle Miocene fauna of the Izu Peninsula was distinct from those of the Honshu Arc. We propose the new faunal name “Yugashima Fauna” for the molluscan assemblage found within the limestone bodies of the Yugashima Group and discuss its paleobiogeographic significance.

ZooBank registration: urn:lsid:zoobank.org:pub:F6DEB4AA-87AE-4E86-B32A-B146DD60DB7F

A taxonomic re-evaluation of the genus Canadoceras Spath (Ammonoida, Pachydiscidae) was conducted based on a large sample collected from the Orannai Formation in the Soya area, northern Hokkaido, Japan. Morphometric analyses of 37 specimens from the middle Campanian (Upper Cretaceous) utilizing X-ray computed tomography and statistical tests revealed that four species described from the Sphenoceramus schmidti Zone in Hokkaido can be reduced to three valid taxa: C. yokoyamai (Jimbo), C. kossmati Matsumoto, and C. mysticum Matsumoto. Statistical analysis of relative umbilical size and relative whorl thickness identifies three distinct ontogenetic trajectories corresponding to these species. Notably, Canadoceras minimum Matsumoto and Miyauchi is herein regarded as a junior synonym of C. mysticum, as its holotype represents a juvenile stage within the variation range of the latter. The unique ontogenetic growth patterns observed in each species are established at very early stages, driven by an interplay between modifications in the whorl expansion rate and the underlying geometric constraints of shell construction. This suggests that modifications in these early growth modes were a primary factor in the diversification of the genus. These findings refine paleobiodiversity estimates for the Northwestern Pacific and provide a clearer framework for understanding the phylogenetic and paleobiogeographic history of the genus Canadoceras.