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We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al. 1973) Londeix et al. 2009, Spiniferites? rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes¸ 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail.

trains of a dinoflagellate from the Salton Sea, previously identified as Protoceratium reticulatum and yessotoxin producing, have been reexamined morphologically and genetically and Pentaplacodinium saltonense n. gen. et sp. is erected to accommodate this species. Pentaplacodinium saltonense differs from Protoceratium reticulatum (Claparède et Lachmann 1859) Bütschli 1885 in the number of precingular plates (five vs. six), cingular displacement (two widths vs. one), and distinct cyst morphology. Incubation experiments (excystment and encystment) show that the resting cyst of Pentaplacodinium saltonense is morphologically most similar to the cyst-defined species Operculodinium israelianum (Rossignol, 1962) Wall (1967) and O. psilatum Wall (1967). Collections of comparative material from around the globe (including Protoceratium reticulatum and the genus Ceratocorys) and single cell PCR were used to clarify molecular phylogenies. Variable regions in the LSU (three new sequences), SSU (12 new sequences) and intergenic ITS 1–2 (14 new sequences) were obtained. These show that Pentaplacodinium saltonense and Protoceratium reticulatum form two distinct clades. Pentaplacodinium saltonense forms a monophyletic clade with several unidentified strains from Malaysia. LSU and SSU rDNA sequences of three species of Ceratocorys (C. armata, C. gourreti, C. horrida) from the Mediterranean and several other unidentified strains from Malaysia form a well-supported sister clade. The unique phylogenetic position of an unidentified strain from Hawaii is also documented and requires further examination. In addition, based on the V9 SSU topology (bootstrap values >80%), specimens from Elands Bay (South Africa), originally described as Gonyaulax grindleyi by Reinecke (1967), cluster with Protoceratium reticulatum. The known range of Pentaplacodinium saltonense is tropical to subtropical, and its cyst is recorded as a fossil in upper Cenozoic sediments. Protoceratium reticulatum and Pentapl

Strains of a dinoflagellate from the Salton Sea, previously identified as Protoceratium reticulatum and yessotoxin producing, have been reexamined morphologically and genetically and Pentaplacodinium saltonense n. gen. et sp. is erected to accommodate this species. Pentaplacodinium saltonense differs from Protoceratium reticulatum (Claparède et Lachmann 1859) Bütschli 1885 in the number of precingular plates (five vs. six), cingular displacement (two widths vs. one), and distinct cyst morphology. Incubation experiments (excystment and encystment) show that the resting cyst of Pentaplacodinium saltonense is morphologically most similar to the cyst-defined species Operculodinium israelianum (Rossignol, 1962) Wall (1967) and O. psilatum Wall (1967). Collections of comparative material from around the globe (including Protoceratium reticulatum and the genus Ceratocorys) and single cell PCR were used to clarify molecular phylogenies. Variable regions in the LSU (three new sequences), SSU (12 new sequences) and intergenic ITS 1–2 (14 new sequences) were obtained. These show that Pentaplacodinium saltonense and Protoceratium reticulatum form two distinct clades. Pentaplacodinium saltonense forms a monophyletic clade with several unidentified strains from Malaysia. LSU and SSU rDNA sequences of three species of Ceratocorys (C. armata, C. gourreti, C. horrida) from the Mediterranean and several other unidentified strains from Malaysia form a well-supported sister clade. The unique phylogenetic position of an unidentified strain from Hawaii is also documented and requires further examination. In addition, based on the V9 SSU topology (bootstrap values >80%), specimens from Elands Bay (South Africa), originally described as Gonyaulax grindleyi by Reinecke (1967), cluster with Protoceratium reticulatum. The known range of Pentaplacodinium saltonense is tropical to subtropical, and its cyst is recorded as a fossil in upper Cenozoic sediments. Protoceratium reticulatum and

Dinoflagellate cysts (dinocysts) are widely used as tracers of sea surface conditions in late Quaternary marine records. However, paleoenvironmental reconstructions across the Pliocene–Pleistocene climatic transition and beyond are limited because the hydrologic conditions influencing assemblage compositions may not have a modern analogue, and the ecological optima of extinct dinocyst species are not well known. From a study of two cored sites in the central and eastern North Atlantic, we bypass these issues by statistically analyzing the variations in dinocyst assemblage composition and comparing the results directly to paleoecological parameters (δ18Obulloides, δ18Osalinity, and geochemical proxies for sea surface temperature [SST]) derived from the planktonic foraminifer Globigerina bulloides recovered from the same samples as the dinocysts. Through canonical correspondence analysis we demonstrate the co-variation of seasonality and dinocyst paleoproductivity. We show that Pyxidinopsis braboi is a cold tolerant species with an optimum SST between 12 and 14 °C. We extend the use of Nematosphaeropsis labyrinthus as an indicator of transitional climatic conditions to the Pliocene, we offer evidence for the correlation of Bitectatodinium tepikiense and Filisphaera microornata to high seasonality, and we reiterate an apparent link between Spiniferites mirabilis and eastern North Atlantic water masses. Finally, we confirm that Habibacysta tectata is cold-tolerant rather than a strictly cold-water indicator, that Operculodinium? eirikianum is a cold-intolerant species favoring outer neritic environments, and that Ataxiodinium confusum and Invertocysta lacrymosa are both warm-water species.

Sediments deposited after the peak of the Messinian Salinity Crisis (MSC) in the Apennine foredeep of Italy embody a topic debated on both chronostratigraphic and palaeoenvironmental grounds. We performed micropalaeontological (calcareous nannofossil and dinoflagellate cyst) analyses on four stratigraphic sections (Monticino, Civitella del Tronto, Fonte dei Pulcini, Fonte la Casa) and reused those previously published from Maccarone. All sections belong to the p-ev2 Fm. that includes the Colombacci deposits, usually considered emblematic of the Lago Mare in the area. Marine microfossils recorded in previous studies have often been neglected or considered reworked and hence discarded. We propose the occurrence of at least four marine inflows between 5.36 and 5.33 Ma, the first of which is reflected in the Apennine foredeep by marine dinoflagellates that are then replaced by Paratethyan (brackish) ones. Paratethyan species occupied favourable environments during intervals separating marine inflows while the marine species survived elsewhere. From this perspective, the Apennine foredeep was an isolated perched basin during most of the peak of the MSC (5.60–5.36 Ma), and was progressively and repeatedly invaded by marine waters overflowing a palaeo-sill before the beginning of the Zanclean (5.33 Ma) which itself reflects a continuing eustatic rise. The Gargano Peninsula and, offshore, the present-day Pelagosa sill may be regarded as the remnants of this Messinian sill. This interpretation provides new possibilities for ecostratigraphically correlating the sections with Lago Mare biofacies, the deposition of which unquestionably started prior to the deposition of Colombacci sediments and continued into the earliest Zanclean. The results of this study show that the Lago Mare facies cannot be restricted to a single brackish palaeoenvironment but included competing marine and brackish waters controlled by geographic and chronological factors. Deposits overlying the unconfor

A range of published arguments against formalizing the Anthropocene as a geological time unit have variously suggested that it is a misleading term of non-stratigraphic origin and usage, is based on insignificant temporal and material stratigraphic content unlike that used to define older geological time units, is focused on observation of human history or speculation about the future rather than geologically significant events, and is driven more by politics than science. In response, we contend that the Anthropocene is a functional term that has firm geological grounding in a well-characterized stratigraphic record. This record, although often lithologically thin, is laterally extensive, rich in detail and already reflects substantial elapsed (and in part irreversible) change to the Earth System that is comparable to or greater in magnitude than that of previous epoch-scale transitions. The Anthropocene differs from previously defined epochs in reflecting contemporary geological change, which in turn also leads to the term's use over a wide range of social and political discourse. Nevertheless, that use remains entirely distinct from its demonstrable stratigraphic underpinning. Here we respond to the arguments opposing the geological validity and utility of the Anthropocene, and submit that a strong case may be made for the Anthropocene to be treated as a formal chronostratigraphic unit and added to the Geological Time Scale.

Two separate taxonomic traditions have arisen in dinoflagellates at the generic level and below: one centred on the living motile cell but potentially incorporating all aspects of the biology, and the other based exclusively on resting cyst morphology including the fossil record. Where a cyst has been described and named as a fossil and subsequently shown through life-cycle observations to be equivalent to a named living species, the cyst morphotype may then bear two names. This dual nomenclature is supported for all algae (diatoms excepted) by the International Code of Nomenclature for Algae, Fungi and Plants (ICN) through Articles 1.2, 11.1, and 11.7 (Head, M.J. et al., 2016, Taxon 65: 902– 903). The ICN acknowledges that a fossil-taxon (having a fossil as its type) is conceptually distinct from its living (non-fossil) counterpart, and that equivalency need not mean synonymy. This distinction reflects the different species concepts involved, based on different stages of the same life cycle, and acknowledges that cyst morphology alone retrieves only limited genetic information from the fossil record. While cyst-based taxonomy strives to reflect evolution, there is a long observed mismatch between fossil-defined genera and the genera of living equivalents. Molecular phylogenies from living material now expose these discrepancies and others with new clarity. This requires the reassessment of our current taxonomic schemes if they are to be more reflective of evolution, although any major nomenclatural changes should be balanced against the value of stability in connecting living dinoflagellates to their fossil lineages.