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Pteropods are a group of planktonic gastropods that are widely regarded as biological indicators for assessing the impacts of ocean acidification. Their aragonitic shells are highly sensitive to acute changes in ocean chemistry. However, to gain insight into their potential to adapt to current climate change, we need to accurately reconstruct their evolutionary history and assess their responses to past changes in the Earth's carbon cycle. Here, we resolve the phylogeny and timing of pteropod evolution with a phylogenomic dataset (2,654 genes) incorporating new data for 21 pteropod species and revised fossil evidence. In agreement with traditional taxonomy, we recovered molecular support for a division between "sea butterflies" (Thecosomata; mucus-web feeders) and "sea angels" (Gymnosomata; active predators). Molecular dating demonstrated that these two lineages diverged in the early Cretaceous, and that all main pteropod clades, including shelled, partially-shelled, and unshelled groups, diverged in the mid- to late Cretaceous. Hence, these clades originated prior to and subsequently survived major global change events, including the Paleocene-Eocene Thermal Maximum (PETM), the closest analog to modern-day ocean acidification and warming. Our findings indicate that planktonic aragonitic calcifiers have shown resilience to perturbations in the Earth's carbon cycle over evolutionary timescales. [ABSTRACT FROM AUTHOR]

Three pteropod species are recorded from late Waitakian–Otaian (Aquitanian–early Burdigalian) rocks of the Taumarunui Formation (Mahoenui Group) outcropping southwest of Taumarunui, King Country, New Zealand. Two of these, Limacinidae sp. andClio sp. have been recorded in open nomenclature due to poor preservation. The third,Clio triplicataAudenino, 1899, was previously known only from Miocene deposits in Europe and offers possibilities for long-distance correlation. [ABSTRACT FROM AUTHOR]

Shelled pteropods (Gastropoda, Thecosomata, Euthecosomata) are a group of holoplanktonic gastropods that occur predominantly in the surface layers of the world's oceans. Accurate species identifications are essential for tracking changes in species assemblages of planktonic gastropods, because different species are expected to have different sensitivities to ocean changes. The genus Cuvierina has a worldwide warm water distribution pattern between ~36°N and ~39°S. Based on an integrative taxonomic approach combining morphometric, genetic, and biogeographic information, the two subgenera of Cuvierina, Cuvierina s. str. and Urceolarica, are rejected. A new species is introduced: Cuvierina tsudai sp. n., which has to date been considered the same species as Cuvierina pacifica. Cuvierina tsudai sp. n. is endemic to the Pacific Ocean and is characterised by a shell height of 7.2-8.0 mm, a moderately cylindrical shell shape, the absence of micro-ornamentation and a triangular aperture. Cuvierina pacifica is restricted to the centre of the oligotrophic southern Pacific gyre, has a shell height of 6.6-8.5 mm, a more cylindrical shell shape, no micro-ornamentation and a less triangular aperture than C. tsudai sp. n. [ABSTRACT FROM AUTHOR]

Distinguishing the various Recent taxa of the pteropod genus Creseis, especially the nominal species Creseis acicula (Rang, 1828), C. clava (Rang, 1828), C. virgula ( Rang, 1828) and C. conica Eschscholtz, 1829, has long been problematic. Based on misinterpretations of the shell morphology, some of these were deemed to represent subspecies or forms, or were synonymized with other species in this group. Shell-morphological and nomenclatural evidence has recently been provided demonstrating that C. clava and C. acicula in fact represent a single species, for which the name C. clava is valid. Both C. conica and C. virgula represent independent species, and the same is true for C. chierchiae (Boas, 1886). This study recapitulates the background to the taxonomic problem, presents a summary of previously published morphological characters to identify species, provides diagnoses of these species and analyses new and previously published sequences from the cytochrome oxidase I barcoding gene, thus showing the utility of this gene to identify species. The data demonstrate that four Recent species should be recognized: C. clava, C. conica, C. virgula and C. chierchiae, but the last of these and its f. constricta, although clearly differing by shell-morphological characteristics, should be studied further by molecular techniques. Hyalocylis striata (Rang, 1828) and Styliola subula (Quoy & Gaimard, 1827), traditionally included in the Creseidae, are easily recognized on shell characteristics. A key to the identification of members of this family is provided. [ABSTRACT FROM AUTHOR]

Holoplanktonic Mollusca collected from c. 60 localities in Cenozoic (Eocene-Ypresian to Miocene-Serravallian) rocks of the Aquitaine Basin (southwest France) are represented by 75 taxa: five supposed Heteropoda (Pterotracheoidea) and 70 Pteropoda (69 Thecosomata, one Gymnosomata). All Heteropoda and 19 species of the Pteropoda had to be included in open nomenclature or with a query. Twelve species of pteropods are described as new to science: Heliconoides daguini sp. nov., H. merlei sp. nov., H. pyrenaica sp. nov. and Limacina? vegrandis sp. nov. from the Ypresian; Creseis antoni sp. nov. and Vaginella gaasensis sp. nov. from the Rupelian; Clio lozoueti sp. nov. and Clio vasconiensis sp. nov. from the Chattian; Diacrolinia cluzaudi sp. nov., from the Aquitanian; Creseis roesti sp. nov. from the Aquitanian/Burdigalian; and Heliconoides mermuysi sp. nov. and Creseis tugurii sp. nov. from the Early Burdigalian. Neotypes are designated for Diacrolinia aquensis, D. orbignyi and Vaginella depressa. The Aquitaine Basin assemblages are correlated with the existing holoplanktonic mollusc zonation for the North Sea Basin. Zones 9 (Ypresian), 10 (Lutetian) and 11/12 (Priabonian) could be recognised in the Aquitaine Basin Eocene, zones 15a (Rupelian) and 16b (Chattian) in the Oligocene, and zones 17 (Aquitanian-Burdigalian), 18 (Late Burdigalian), 18a (Langhian) and 19 (Serravallian) in the Miocene. Zone 17 could be subdivided on the basis of occurrences observed in the Aquitaine Basin, into three subzones, 17a (Aquitanian), 17b (earliest Burdigalian) and 17c (middle Burdigalian). [ABSTRACT FROM AUTHOR]

Eleven randomly chosen outcrops in the Miocene Pakhna Formation of Cyprus were sampled for holoplanktonic Mollusca. Four species of Heteropoda were found, and 24 of Pteropoda, a substantial increase from the two species recorded until now from the Miocene of Cyprus. One pteropod species, Peracle charlotteae sp. nov. (Gastropoda, Pseudothecosomata), is introduced. Age assignments based on holoplanktonic molluscs for the 11 localities are as follows: Langhian (Alassa 1-4), (Serravallian?) Tortonian to Messinian (Episkopi 1), Tortonian (Agios Tychon, Tokhni and the Maroni Marlstone of Khirokitia 1-2) and Tortonian to Early Messinian (Episkopi 2). These age determinations in some cases are at odds with those from previous publications based on calcareous nannofossils and Foraminifera. The sediments underlying the Amathus Channel outcrop yielded insufficient fauna for definitive dating, but we suggest are younger than Late Serravallian. At some localities, particularly in the Alassa area, pteropod assemblages are strongly variable on a bed-by-bed basis, and this offers possibilities for future refined biostratigraphical interpretations. This is the first substantial holoplanktonic mollusc fauna described from the eastern Mediterranean basin and allows correlation with assemblages in the central Mediterranean and elsewhere. [ABSTRACT FROM AUTHOR]

A borehole was drilled at Rotterdam in 1955 as a demonstration during the E55 exhibition. Holoplanktonic molluscs (pteropods) were found to be present in the interval 504.5-655.0 m below rotary table (= RT). The upper sample of Middle Eocene (Lutetian) age yielded just a few unidentifiable limacinids. The section between 507.5-607.0 m, of Early Eocene (Ypresian) age, yielded poorly preserved pteropods and demonstrated that the complete interval belongs to pteropod zone 9. Apart from the most abundant species, Camptoceratops priscus, which is the index taxon of pteropod zone 9, the section yielded Heliconoides mercinensis and Limacina taylori, which are known to accompany the index species. Two further limacinid species are described as new to science, viz. Limacina erasmiana sp. nov. and L. guersi sp. nov., to date not known from elsewhere in the North Sea Basin. The occurrence of L. pygmaea in a restricted interval (569.0-574.0 m-RT) is remarkable; it is generally considered to be of Lutetian age, but also is found in the Ypresian of Gan, southwest France. Its occurrence in the E55 section is explained as a 'sea-level related molluscan plankton event', allowing species of oceanic distribution to enter the basin during sea level high stands, as was recently also demonstrated for several Oligocene pteropods. [ABSTRACT FROM AUTHOR]

Fifteen samples taken from interbedded sandstone, siltstone and claystone of Pliocene age, underlying the Bolinao Limestone, at the localities Anda, Roxas and Tiep (Pangasinan, Luzon, Philippines), were analysed for holoplanktonic gastropods; they have yielded 50 species (16 Heteropoda, one Janthinidae, and 33 Pteropoda, the latter consisting of 30 Euthecosomata, two Pseudothecosomata and one Gymnosomata). Faunal diversity between the localities sampled is restricted and explained by differences in sample size and/or preservation. The time interval represented by all samples taken together is postulated to have been brief. Fifteen new taxa (= 30% of the total number of encountered holoplanktonic molluscan species) are erected; Atlanta lingayanensis sp. nov., A. richteri sp. nov., A. seapyi sp. nov., Heliconoides sondaari sp. nov., Striolimacina andaensis sp. nov., Hyalocylis marginata sp. nov., Cavolinia baniensis sp. nov., C. perparvula sp. nov., C. shibatai sp. nov., Diacavolinia pristina sp. nov., Diacria italica Grecchi, 1982 f. fissicostata f. nov., D. microstriata sp. nov., D. paeninsula sp. nov., D. philippinensis sp. nov. and Sphaerocina convolvula sp. nov. Calibration with vertical ranges of holoplanktonic molluscan species as now known enables an age assignment for the Pangasinan assemblages of Pliocene (Piacenzian). A number of species, in particular Atlantidae (Heteropoda), were so far known only from Quaternary or extant assemblages. Comparisons with published data for Japan allow the conclusion that the Philippine assemblages are coeval with the Takanabe Member (Miyazaki Group) in Miyazaki Prefecture (southwest Japan), a unit which incidentally has yielded far fewer species. The absence of bathypelagic holoplanktonics, as well as littoral benthic species indicate an epi- to upper mesopelagic setting, with depth ranges extending to a maximal depth of c. 200 to 300 m. [ABSTRACT FROM AUTHOR]

Background: The aragonite shelled, planktonic gastropod family Atlantidae (shelled heteropods) is likely to be one of the first groups to be impacted by imminent ocean changes, including ocean warming and ocean acidification. With a fossil record spanning at least 100 Ma, atlantids have experienced and survived global-scale ocean changes and extinction events in the past. However, the diversification patterns and tempo of evolution in this family are largely unknown. Results: Based on a concatenated maximum likelihood phylogeny of three genes (cytochrome c oxidase subunit 1 mitochondrial DNA, 28S and 18S ribosomal rRNA) we show that the three extant genera of the family Atlantidae, Atlanta, Protatlanta and Oxygyrus, form monophyletic groups. The genus Atlanta is split into two groups, one exhibiting smaller, well ornamented shells, and the other having larger, less ornamented shells. The fossil record, in combination with a fossil-calibrated phylogeny, suggests that large scale atlantid extinction was accompanied by considerable and rapid diversification over the last 25 Ma, potentially driven by vicariance events. Conclusions: Now confronted with a rapidly changing modern ocean, the ability of atlantids to survive past global change crises gives some optimism that they may be able to persist through the Anthropocene. [ABSTRACT FROM AUTHOR]

Pteropods are a widespread group of holoplanktonic gastropod molluscs and are uniquely suitable for study of long-term evolutionary processes in the open ocean because they are the only living metazoan plankton with a good fossil record. Pteropods have been proposed as bioindicators to monitor the impacts of ocean acidification and in consequence have attracted considerable research interest, however, a robust evolutionary framework for the group is still lacking. Here we reconstruct their phylogenetic relationships and examine the evolutionary history of pteropods based on combined analyses of Cytochrome Oxidase I, 28S, and 18S ribosomal rRNA sequences and a molecular clock calibrated using fossils and the estimated timing of the formation of the Isthmus of Panama. Euthecosomes with uncoiled shells were monophyletic with Creseis as the earliest diverging lineage, estimated at 41–38 million years ago (mya). The coiled euthecosomes (Limacina, Heliconoides, Thielea) were not monophyletic contrary to the accepted morphology-based taxonomy; however, due to their high rate heterogeneity no firm conclusions can be drawn. We found strong support for monophyly of most euthecosome genera, but Clio appeared as a polyphyletic group, and Diacavolinia grouped within Cavolinia, making the latter genus paraphyletic. The highest evolutionary rates were observed in Heliconoides inflatus and Limacina bulimoides for both 28S and 18S partitions. Using a fossil-calibrated phylogeny that sets the first occurrence of coiled euthecosomes at 79–66 mya, we estimate that uncoiled euthecosomes evolved 51–42 mya and that most extant uncoiled genera originated 40–15 mya. These findings are congruent with a molecular clock analysis using the Isthmus of Panama formation as an independent calibration. Although not all phylogenetic relationships could be resolved based on three molecular markers, this study provides a useful resource to study pteropod diversity and provides general insight into the processes that generate and maintain their diversity in the open ocean. [ABSTRACT FROM AUTHOR]

The atlantid heteropods are regularly encountered, but rarely studied marine planktonic gastropods. Relying on a small (<14 mm), delicate aragonite shell and living in the upper ocean means that, in common with pteropods, atlantids are likely to be affected by imminent ocean changes. Variable shell morphology and widespread distributions indicate that the family is more diverse than the 23 currently known species. Uncovering this diversity is fundamental to determining the distribution of atlantids and to understanding their environmental tolerances. Here we present phylogenetic analyses of all described species of the family Atlantidae using 437 new and 52 previously published cytochrome c oxidase subunit 1 mitochondrial DNA (mtCO1) sequences. Specimens and published sequences were gathered from 32 Atlantic Ocean stations, 14 Indian Ocean stations and 21 Pacific Ocean stations between 35°N and 43°S. DNA barcoding and Automatic Barcode Gap Discovery (ABGD) proved to be valuable tools for the identification of described atlantid species, and also revealed ten additional distinct clades, suggesting that the diversity within this family has been underestimated. Only two of these clades displayed obvious morphological characteristics, demonstrating that much of the newly discovered diversity is hidden from morphology-based identification techniques. Investigation of six large atlantid collections demonstrated that 61% of previously described (morpho) species have a circumglobal distribution. Of the remaining 39%, two species were restricted to the Atlantic Ocean, five occurred in the Indian and Pacific oceans, one species was only found in the northeast Pacific Ocean, and one occurred only in the Southern Subtropical Convergence Zone. Molecular analysis showed that seven of the species with wide distributions were comprised of two or more clades that occupied distinct oceanographic regions. These distributions may suggest narrower environmental tolerances than the described morphospecies. Results provide an updated biogeography and mtCO1 reference dataset of the Atlantidae that may be used to identify atlantid species and provide a first step in understanding their evolutionary history and accurate distribution, encouraging the inclusion of this family in future plankton research. [ABSTRACT FROM AUTHOR]

Fewer than 1% of marine gastropod species live a holoplanktic life. Of these, the shelled heteropods of the family Atlantidae are among the most poorly understood. The atlantids potentially make up an important part of the ocean zooplankton, composing up to 69% of shelled holoplanktic gastropods in the Late Pleistocene to Recent fossil record. They are also likely to be at high risk from current and future global changes, including anthropogenic ocean acidification. However, due to their small size (>12 mm), difficulty of sampling and complicated morphology, we still lack key information about atlantid taxonomy and ecology. This makes it difficult to understand how important they are in the ocean foodweb and how they will be affected by environmental change. Although many studies have been carried out on the atlantids, these have generally been broad and unconnected. Here, we draw together this previous research, summarizing what is currently known about atlantid taxonomy, palaeontology, ecology and biogeography, and aiming to provide a foundation for future research on this group. The data indicate complex behaviours involving seasonal and vertical migration, and demonstrate extended geographical ranges, with implications for understanding the role of atlantids in the ocean foodweb and their sensitivity to environmental changes. This review highlights the urgent need for further taxonomic research on the atlantids, including molecular analysis, and for improved sampling techniques. [ABSTRACT FROM AUTHOR]

ossils of a single pteropod species were found in an isolated carbonate deposit within middle Eocene deep-water strata of the Humptulips Formation in western Washington State, U.S.A. The carbonate formed at a cold seep where fluids containing high concentrations of hydrocarbons, principally methane, emanated from the seafloor. Anaerobic oxidation of the methane by prokaryotes caused localized and rapid precipitation of calcium carbonate that encased biogenic detritus including wood fragments and mollusk shells; in this case even the minute and delicate aragonitic shells of the pteropod Heliconoides nitens (Lea, 1833), the first certain record of this taxon for the Pacific Basin. The presence of H. nitens in the Humptulips Formation allows us to recalibrate the age of the formation as late Lutetian or early Bartonian, up to 8 million years younger than previously thought. Heliconoides nitens has been found in temporally equivalent strata elsewhere in the world, and this is another example of some fossil pteropods having utility for long distance biostratigraphic correlations. Pteropod shells rapidly dissolve in deep-water environments, thus cold seep deposits may be a source of pteropod fossils in deep-water strata where they otherwise would not occur. [ABSTRACT FROM AUTHOR]

Fossils of a single pteropod species were found in an isolated carbonate deposit within middle Eocene deep-water strata of the Humptulips Formation in western Washington State, U.S.A. The carbonate formed at a cold seep where fluids containing high concentrations of hydrocarbons, principally methane, emanated from the seafloor. Anaerobic oxidation of the methane by prokaryotes caused localized and rapid precipitation of calcium carbonate that encased biogenic detritus including wood fragments and mollusk shells; in this case even the minute and delicate aragonitic shells of the pteropod Heliconoides nitens (Lea, 1833), the first certain record of this taxon for the Pacific Basin. The presence of H. nitens in the Humptulips Formation allows us to recalibrate the age of the formation as late Lutetian or early Bartonian, up to 8 million years younger than previously thought. Heliconoides nitens has been found in temporally equivalent strata elsewhere in the world, and this is another example of some fossil pteropods having utility for long distance biostratigraphic correlations. Pteropod shells rapidly dissolve in deep-water environments, thus cold seep deposits may be a source of pteropod fossils in deep-water strata where they otherwise would not occur. [ABSTRACT FROM AUTHOR]