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Paleozoic scaphopods are among the most poorly known mollusks because of their featureless tubular shell morphology and fragmentary preservation. An apical orifice at the posterior end of a conch is a diagnostic character of Scaphopoda that distinguishes them from other groups of animals that produce similar calcareous tubes, but this structure is rarely preserved. A rich molluscan fauna from the Permian Akasaka Limestone in central Japan includes scaphopod shells, and past studies have reported four species, all of which were based on fragmentary specimens. This study recognizes six species in the Akasaka Limestone mainly on the basis of museum/institution collections, and a new genus (Minodentalium) and three species (Prodentalium onoi, M. hayasakai, and M. okumurai) are described, two known species (P. akasakensis and P. neornatum) are redescribed in more detail, and one species (Prodentalium sp.) is described under open nomenclature. The following eight known species are allocated to the new genus Minodentalium: Plagioglypta furcataWaterhouse, 1980; Pl. girtyiKnight, 1940; Pl. subannulataEaston, 1962; Dentalium ingensDe Koninck, 1843; D. meekianumGeinitz, 1866; Pl. prosseriMorningstar, 1922; Dentalium priscum Münster in Goldfuss, 1842; and D. herculeum De Koninck, 1863. All the species, except for M. hayasakai, are gigantic, reaching 200 mm or more in length. The species richness is the greatest known from a single locality/formation worldwide.

The region with the highest marine biodiversity on our planet is known as the Coral Triangle or Indo-Australian Archipelago (IAA) 1 , 2 . Its enormous biodiversity has long attracted the interest of biologists; however, the detailed evolutionary history of the IAA biodiversity hotspot remains poorly understood 3 . Here we present a high-resolution reconstruction of the Cenozoic diversity history of the IAA by inferring speciation–extinction dynamics using a comprehensive fossil dataset. We found that the IAA has exhibited a unidirectional diversification trend since about 25 million years ago, following a roughly logistic increase until a diversity plateau beginning about 2.6 million years ago. The growth of diversity was primarily controlled by diversity dependency and habitat size, and also facilitated by the alleviation of thermal stress after 13.9 million years ago. Distinct net diversification peaks were recorded at about 25, 20, 16, 12 and 5 million years ago, which were probably related to major tectonic events in addition to climate transitions. Key biogeographic processes had far-reaching effects on the IAA diversity as shown by the long-term waning of the Tethyan descendants versus the waxing of cosmopolitan and IAA taxa. Finally, it seems that the absence of major extinctions and the Cenozoic cooling have been essential in making the IAA the richest marine biodiversity hotspot on Earth. A reconstruction of Cenozoic marine biodiversity in the Indo-Australian Archipelago reveals decreasing rates of net diversification and identifies the factors that have established it as the richest marine biodiversity hotspot.

Predation pressure occurs as a result of predation frequency and prey vulnerability. Although quantifying these factors individually is essential to precisely understand predation effects on evolution, they have been generally less accessible. Here, using a modified form of Poisson function, we quantified the frequencies and vulnerabilities, as well as the resulting predation pressures, concerning the shell drillers versus prey interactions from the Eocene and Miocene periods. Our analysis quantitatively revealed that low-spired shells tend to show increased vulnerability except for two planispiral species that exhibit an unexpectedly low vulnerability. We then identified septal structures within the two species that resemble those in nautiloids and ammonoids but which provided a defensive role against the predators, enhancing the mean lifetime by approximately 20%. The current approach enables us to quantitatively trace how predation frequency and prey vulnerability have interacted, been transformed spatio-temporally, and been a driving force of evolution at geological time scales.

Neogene diversity history in the world center of biodiversity known as the Indo-Australian Archipelago (IAA) or the Coral Triangle remains poorly understood. Of particular interest is the recently reported Pliocene diversity jump that is considered to have established the present-day biodiversity level of the region needs rigorous inspections. We investigated Neogene fossil marine ostracods from Java, Indonesia and evaluate and test the Pliocene Diversity Jump hypothesis. We found a significant diversity increase from the late Miocene to the Pliocene, supporting the hypothesis. At the same time, there are considerable differences in depositional environments between the Miocene and Pliocene samples. Although it is unlikely that the main reason of the diversity increase is due to this paleoenvironmental difference, further samples and data from the IAA hotspot region are needed for more rigorous inspections. Our comparison between species-level and genus-level data indicated that species-level data are better to detect detailed macroevolutionary diversity histories, and genus level data are more useful for paleoenvironmental and paleoceanographic reconstructions.

A well-supported phylogeny of the Neritopsina, a gastropod superorder archaic in origin, radiated ecologically and diverse in morphology, is reconstructed based on partial 28S rRNA sequences. The result (Neritopsidae (Hydrocenidae (Helicinidae + Neritiliidae) (Neritidae + Phenacolepadidae))) is highly congruent with the fossil records and the character distribution of reproductive tracts in extant taxa. We suggest that the Neritopsina originated in subtidal shallow waters, invaded the land and became fully terrestrial at least three times in different clades, by the extinct Dawsonellidae in the Late Palaeozoic and by the Helicinidae and Hydrocenidae in the Mesozoic. Invasion of fresh- and brackish waters is prevalent among the Neritopsina as the Jurassic and freshwater ancestory is most probable for helicinids. The Phenacolepadidae, a group exclusively inhabiting dysoxic environments, colonized deep-sea hydrothermal vents and seeps in the Late Cretaceous or Early Cenozoic. Submarine caves have served as refuges for the archaic Neritopsidae since the Early to Middle Cenozoic, and the marine neritopsine slug Titiscania represents a highly specialized but relatively recent offshoot of this family. The Neritiliidae is another clade to be found utilizing submarine caves as shelter by the Oligocene; once adapted to the completely dark environment, but some neritiliids have immigrated to surface freshwater habitats.

A 5000-year fossil series of minute submarine cave bivalves was studied using morphometric and evolutionary analyses. The obtained results indicate that the shapes of larval shells of studied species were labile, whereas the size of the larval shell was stable in each species studied. This result is different than that previously reported in most other studies in which size change is more common than shape change. This unique evolutionary pattern of these bivalves might be attributed to their refugial lifestyle.

The enigmatic fossil Moniopterus japonicusHatai et al., 1974 from the early Middle Miocene Moniwa Formation of northern Japan has been described as the only known example of fossil sea-snake eggs and also as fossilized pupal chambers of a coleopteran insect. A reexamination of the holotype provides no evidence in support of these previous interpretations. Scanning electronic microscopy and computed tomography observations on the holotype reveal that the calcareous lining, previously interpreted as eggshell, is instead composed of irregular spherulitic prisms, thin in the middle and becoming thicker toward both ends. In addition to the elongate oval shape and the presence of an opening at the more pointed end, these observations strongly suggest that M. japonicus is a boring of the mytilid boring bivalve Lithophaga isolated from the host rock. This reinterpretation is further supported by the occurrence of similar isolated and in situ borings with Lithophaga shells within the type and a nearby locality. Regarding this fossil as an ichnofossil makes the generic name Moniopterus a junior synonym of GastrochaenolitesLeymerie, 1842 and the species name japonicus is a senior synonym of Gastrochaenolites torpedoKelly and Bromley, 1984. G. torpedo should thus be replaced with Gastrochaenolites japonicus (Hatai et al., 1974).

Then as now for El Niño Coarse resolution palaeoclimate proxy evidence has suggested that the Pliocene warm period (PWP) between 3 million and 5 million years ago was characterized by permanent El Niño conditions in which the equatorial Pacific was uniformly warm, instead of having the modern-day 'cold tongue' extending westward from South America. New high-resolution climate proxy data from fossil corals raise doubts over this assertion. Well-preserved PWP-era fossil corals with clear skeletal annual bands, discovered in the Philippines, show that ocean conditions in the western Pacific during the PWP were characterized by El Niño variations that are similar to those we see today. Coarse-resolution palaeoclimate proxy evidence has suggested that the Pliocene warm period (∼3–5 million years ago) was characterized by permanent El Niño conditions in which the equatorial Pacific was uniformly warm, instead of having the modern-day 'cold tongue' extending westward from South America. This study uses high-resolution climate proxy information from fossil corals to challenge this assertion and shows that ocean conditions in the western Pacific during the Pliocene warm period were characterized by El Niño variations similar to modern-day variations. The El Niño/Southern Oscillation (ENSO) system during the Pliocene warm period (PWP; 3–5 million years ago) may have existed in a permanent El Niño state with a sharply reduced zonal sea surface temperature (SST) gradient in the equatorial Pacific Ocean 1 . This suggests that during the PWP, when global mean temperatures and atmospheric carbon dioxide concentrations were similar to those projected for near-term climate change 2 , ENSO variability—and related global climate teleconnections—could have been radically different from that today. Yet, owing to a lack of observational evidence on seasonal and interannual SST variability from crucial low-latitude sites, this fundamental climate characteristic of the PWP remains controversial 1 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 . Here we show that permanent El Niño conditions did not exist during the PWP. Our spectral analysis of the δ 18 O SST and salinity proxy, extracted from two 35-year, monthly resolved PWP Porites corals in the Philippines, reveals variability that is similar to present ENSO variation. Although our fossil corals cannot be directly compared with modern ENSO records, two lines of evidence suggest that Philippine corals are appropriate ENSO proxies. First, δ 18 O anomalies from a nearby live Porites coral are correlated with modern records of ENSO variability. Second, negative-δ 18 O events in the fossil corals closely resemble the decreases in δ 18 O seen in the live coral during El Niño events. Prior research advocating a permanent El Niño state may have been limited by the coarse resolution of many SST proxies, whereas our coral-based analysis identifies climate variability at the temporal scale required to resolve ENSO structure firmly.

Aim: Cenozoic dynamics of large-scale species diversity patterns remain poorly understood, especially for the Western Pacific, in part, because of the paucity of well-dated fossil records from the tropics. This article aims to reveal the spatiotemporal dynamics of species diversity in the Western Pacific through the Cenozoic, focusing on the tropical Indo-Australian Archipelago (IAA) biodiversity hotspot. Location: Tropical and north-western Pacific Ocean. Methods: We analysed well-preserved fossil ostracodes from the tropical Western Pacific and combined their diversity data with other published data from the region to reconstruct Cenozoic dynamics of species diversity in the tropical and north-western Pacific Ocean. We fitted generalized additive models to test for differences in richness over time and across geographical regions while accounting for sample-size variation among samples. Results: Low-, mid- and high-latitude regions all show a similar diversity trajectory: diversity is low in the Eocene and Oligocène, increases from the Early Miocene to the Plio-Pleistocene but then declines to the present day. Present-day high biodiversity in these regions was established during the Pliocene with a remarkable diversity increase at that time. Latitudinal diversity patterns are relatively flat and never show a simple decline from the tropics to higher latitudes. Main conclusions: Western Pacific Cenozoic ostracodes exhibit a spatiotemporal pattern of species diversity that is inconsistent with the commonly reported and persistent pattern of declining diversity from the tropics to the extratropics. While this inconsistency could be interpreted as evidence that ostracodes are a contrarian clade, Atlantic ostracodes display a standard latitudinal species diversity gradient. Contrasting patterns between oceans suggest an important role for regional factors (e.g. plate tectonics and temporal geomorphological dynamics) in shaping the biodiversity of the Western Pacific.