Incipient speciation of Catostylus mosaicus (Scyphozoa, Rhizostomeae, Catostylidae), comparative phylogeography and biogeography in south-east Australia

Aim Phylogeography provides a framework to explain and integrate patterns of marine biodiversity at infra‐ and supra‐specific levels. As originally expounded, the phylogeographic hypotheses are generalities that have limited discriminatory power; the goal of this study is to generate and test specific instances of the hypotheses, thereby better elucidating both local patterns of evolution and the conditions under which the generalities do or do not apply. Location Coastal south‐east Australia (New South Wales, Tasmania and Victoria), and south‐west North America (California and Baja California). Methods Phylogeographic hypotheses specific to coastal south‐east Australia were generated a priori, principally from existing detailed distributional analyses of echinoderms and decapods. The hypotheses are tested using mitochondrial cytochrome c oxidase subunit I (COI) and nuclear internal transcribed spacer 1 (ITS1) DNA sequence data describing population variation in the jellyfish Catostylus mosaicus, integrated with comparable data from the literature. Results Mitochondrial COI distinguished two reciprocally monophyletic clades of C. mosaicus (mean ± SD: 3.61 ± 0.40% pairwise sequence divergence) that were also differentiated by ITS1 haplotype frequency differences; the boundary between the clades was geographically proximate to a provincial zoogeographic boundary in the vicinity of Bass Strait. There was also limited evidence of another genetic inhomogeneity, of considerably smaller magnitude, in close proximity to a second hypothesized zoogeographic discontinuity near Sydney. Other coastal marine species also show genetic divergences in the vicinity of Bass Strait, although they are not closely concordant with each other or with reported biogeographic discontinuities in the region, being up to several hundreds of kilometres apart. None of the species studied to date show a strong phylogeographic discontinuity across the biogeographic transition zone near Sydney. Main conclusions Patterns of evolution in the Bass Strait and coastal New South Wales regions differ fundamentally because of long‐term differences in extrinsic factors. Since the late Pliocene, periods of cold climate and low sea‐level segregated warm temperate organisms east or west of an emergent Bassian Isthmus resulting in population divergence and speciation; during subsequent periods of warmer and higher seas, sister taxa expanded into the Bass Strait region leading to weakly correlated phylogeographic and biogeographic patterns. The Sydney region, by contrast, has been more consistently favourable to shifts in species’ ranges and long‐distance movement, resulting in a lack of intra‐specific and species‐level diversification. Comparisons between the Sydney and Bass Strait regions and prior studies in North America suggest that vicariance plays a key role in generating coastal biodiversity and that dispersal explains many of the deviations from the phylogeographic hypotheses.     

Pliocene ostracods of Southwestern Europe

This paper analyzes the lithostratigraphic features and ostracod associations of the Pliocene deposits located in the western sector of the Guadalquivir basin (SW Spain). A regressive cycle is defined by the vertical distribution of five main facies (FA-1 to FA-5), which were deposited in upper bathyal to fluvial palaeoenvironments. The broad palaeontological record is utilized to draw a general outline of the food chain in each palaeoenvironment. A comparison with the Pliocene ostracod distribution of southeastern Spain, southwestern France and Portugal permits to define a common ostracod biozonation for southwestern Europe during this period. Four main marine biozones are distinguished: (a): Pontocythere elongata biozone (infralittoral); (b): Costa edwardsii biozone (shallow circalittoral); (c): Bosquetina carinella biozone (deep circalittoral); and (d): Henryhowella asperrima biozone (upper bathyal). Freshwater, brackish and lower bathyal/abyssal species are very scarce in this area during this period.     

Neogene stratigraphy,foraminifera, diatoms,and depositional history of Maria Madre Island,Mexico: Evidence of early Neogene marine conditions in the southern Gulf of California

Foraminifera and diatoms have been analyzed from an upper Miocene through Pleistocene(?) sequence of marine sediments exposed on Maria Madre Island, largest of the Trés Marias Islands off the Pacific coast of Mexico. The Neogene stratigraphic sequence exposed on Maria Madre Island includes a mid-Miocene(?) non-marine and/or shallow marine sandstone unconformably overlain by a lower upper Miocene to uppermost Miocene upper to middle bathyal laminated and massive diatomite, mudstone, and siltstone unit. This unit is unconformably overlain by lower Pliocene middle to lower bathyal sandstones and siltstones which, in turn, are unconformably overlain by upper Pliocene through Pleistocene(?) upper bathyal to upper middle bathyal foraminiferal limestones and siltstones. These beds are unconformably capped by Pleistocene terrace deposits. Basement rocks on the island include Cretaceous granite and granodiorite, and Tertiary(?) andesites and rhyolites. The upper Miocene diatomaceous unit contains a low diversity foraminiferal fauna dominated by species of Bolivina indicating low oxygen conditions in the proto-Gulf Maria Madre basin. The diatomaceous unit grades into a mudstone that contains a latest Miocene upper to middle bathyal biofacies characterized by Baggina californica and Uvigerina hootsi along with displaced neritic taxa. An angular unconformity separates the upper Miocene middle bathyal sediments from overlying lower Pliocene siltstones and mudstones that contain a middle to lower bathyal biofacies and abundant planktonic species including Neogloboquadrina acostaensis and Pulleniatina primalis indicating an early Pliocene age. Significantly, this Pliocene unit contains common occurrences of benthic species restricted to Miocene sediments in California including Bulimina uvigerinaformis. Pliocene to Pleistocene(?) foraminiferal limestones and siltstones characterize submarine bank accumulations formed during uplift of the Trés Marias Island area, and include abundant planktonic foraminifera such as Pulleniatina obliquiloculata and Neogloboquadrina duterteri. Common benthic foraminifera in this unit are indicative of upper bathyal water depths. The Neogene depositional history recorded on Maria Madre Island involves an early late Miocene subsidence event marking formation of the Trés Marias Basin with relatively undiluted diatomaceous sediment deposited in a low oxygen setting. Subsidence and deepening of the basin continued into the early Pliocene along with rapid deposition of terrigenous clastics. Uplift of the basinal sequence began in late Pliocene time accompanied by deposition of upper Pliocene-Pleistocene foraminiferal limestones on a rising submarine bank. Continued episodic uplift of the Neogene deposits brought the island above sea level by late Pleistocene time.     

Historical demography and colonization pathways of the widespread intertidal seaweed Hormosira banksii (Phaeophyceae) in southeastern Australia

The palaeoceanography of southern Australia has been characterized by fluctuating sea levels during glacial periods, changing temperature regimes and modified boundary currents. Previous studies on genetic structuring of species in southeastern Australia have focused mainly on the differentiation of eastern and western populations while the potential role of Bass Strait as a region of overlap for three biogeographic provinces (Peronia, Maugea, and Flindersia) has been largely ignored. This study aimed to explore the likely roles of historic and contemporary factors in determining divergence patterns in the habitat‐forming intertidal seaweed Hormosira banksii in southeastern Australia with a special focus on postglacial dispersal into Bass Strait. We examined the genetic diversity of 475 Hormosira specimens collected from 19 sites around southern Australia using DNA sequence analysis of cytochrome oxidase 1. Three major haplotype groups were identified (western, centre and eastern) corresponding with the three existing biogeographical provinces in this region. Historic break points appeared to be retained and reinforced by modern day dispersal barriers. Phylogeographic grouping of Hormosira reflected a combination of historic and contemporary oceanography. As western and eastern group haplotypes were largely absent within Bass Strait, re‐colonization after the last glacial maximum appeared to have originated from refuges within or near present day Bass Strait. Patterns of genetic structure for Hormosira are consistent with other marine species in this region and highlight the importance of biogeographical barriers in contributing to modern genetic structure.     

Integrated analyses of litho- and biofacies in a Pliocene cyclothemic, alluvial to shallow marine succession (Tuscany, Italy)

Lithofacies analysis of the upper part of the Pliocene succession of the Valdelsa basin (central Italy) unravelled a number of depositional environments, ranging from alluvial plain to coastal, to marine. Strata are arranged in a hierarchy of elementary and composite unconformity-bounded units. A palaeoecological study of macro- (molluscs) and microfossils (pollen, dinocysts, foraminifera) allowed to finely reconstruct sub-environments within fine-grained terrestrial, coastal and marine deposits and thence to track the spatial and temporal change of physical conditions. The stacking pattern of sedimentary units highlights the lateral switching of onshore-offshore gradients and documents relative sea-level changes. These units are interpreted in a sequence stratigraphic framework. Elementary depositional sequences are arranged to form six composite depositional sequences, in turn encased within two major synthems. This hierarchy of unconformity-bounded sedimentary units suggests that sea-level variation has occurred at different time-frequencies. Glacio-eustasy and active tectonism are discussed as the main forcing factors regulating the different scales of sedimentary cyclicity.     

Messinian Lago-Mare deposits near the Strait of Gibraltar (Malaga Basin,S Spain)

A new stratigraphic unit (named LM unit) located at the base of the Pliocene marine succession in the eastern sector of the Malaga Basin has been distinguished. This unit is composed of two fining-upward sequences bounded by a discontinuity related to synsedimentary tectonic activity. Both sequences are made up of basal alluvial deposits overlain by subaquatic deposits. The lower sequence contains rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin, and non-marine gastropods, typical of oligo-low mesohaline shallow waters, and low diversified ostracod faunas of Paratethyan origin (Loxocorniculina djafarovi, Tyrrhenocythere pontica, Euxinocythere (Maeotocythere) praebaquana and Amnicythere propinqua) typical of low mesohaline waters. Alternances of monospecific ostracod assemblages made of Cyprideis agrigentina or oligotypic assemblages made of C. agrigentina and Loxoconcha spp. and richer assemblages made of L. djafarovi accompanied by several Amnicythere spp. and Camptocypria sp.1 characterize the upper sequence, pointing to more unstable environment affected by salinity and depth changes. Some samples collected from this upper sequence yielded rare, planktonic and benthic foraminifera, which could suggest the sporadic establishment of quasi-normal marine conditions in the westernmost Mediterranean during the deposition of this sequence. The palaeontological data and the palaeomagnetic results obtained in both the LM unit and the overlying Pliocene marine sediments restrict the age of the former to the post-evaporitic late Messinian. The age and the environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the quick and widespread marine flooding of the Mediterranean at the beginning of the Pliocene.     

Évolution du trait de côte à l’Holocène supérieur dans la Sebkha El-Guettiate de Skhira (Golfe de Gabès, Tunisie) à travers sa faune d’ostracodes et de foraminifères

A 122 cm-long core was taken in the El-Guettiate Sebkha of Skhira (southeastern part of Tunisia) in order to investigate the recent palaeoenvironmental evolution of this region. The quantitative and qualitative analysis of ostracod and benthic foraminifera assemblages coupled with a correspondence analysis allows the reconstruction of palaeoenvironmental changes during the Holocene in this area. Four typical associations of ostracods (open marine, coastal marine, lagoonal and estuarine brackish) and two associations of benthic foraminifera (coastal and lagoonal) were distinguished. The onset of restricted lagoonal environments linked to the building-up of sand spit led to the onset of restricted lagoon and brackish environment at cal. 5408 years BP. The Shannon and equitability index of diversity were used to decipher the structural variations of the populations of ostracods and benthic foraminifera along the sampled core. We note a reduction in the Shannon index from the bottom to the top, which indicates a progressive isolation of the biotope. The open lagoonal episode is characterized by high values of diversity. During restricted lagoonal episodes the Shannon and equitability index are reduced. The correspondence analysis reveals an environmental gradient related to the marine influence. It shows an antagonism between the widely opened estuarian lagoonal species and those of restricted lagoon. The less opened estuarian lagoonal taxa occupy an intermediate position. Based on these evidences, microfauna carried out in the El-Guettiate Sebkha allows us to recognize four phases beginning with a widely opened estuarian lagoon (ca. cal. 7460 years PB), followed by a restricted lagoon (ca. cal. 5408 years BP) and finally a brackish lagoon evolving towards the present-day sebkha environment. The opened estuarine lagoon is characterized by high values of species richness and diversity indices.     

Lack of stasis in late Cenozoic marine faunas and communities, central California

Pliocene strata in the Kettleman Hills of west-central California were deposited in the broad San Joaquin embayment as a cyclic succession of parasequences during approximately three million years. Depositional environments within each cycle ranged from relatively open marine to brackish and non-marine. Although the strata were deposited in similar, recurrent environments, the fauna changed gradually rather than during brief intervals separating periods of stasis. Although environmental gradients and community structure in the Pliocene San Joaquin Embayment and in the present-day San Francisco Bay are similar, species compositions of the faunas and of parallel communities at the two sites are markedly different. In addition, times of origination and extinction of species in the Pliocene strata of the Kettleman Hills and in San Francisco Bay do not document coordinated stasis within the Late Cenozoic. In contrast, Silurian and Devonian faunas and communities of the Appalachian Basin persisted with little change in ecological-evolutionary units that lasted for up to eight million years. Relatively brief intervals of great biotic change separate these intervals of stasis. One intriguing explanation of this pattern of coordinated stasis within an ecologic-evolutionary unit is ecological locking, in which interaction between species within the community is sufficiently strong that only major changes in the environment are able to change community and faunal composition. Probably the late Cenozoic fauna underwent rapid evolution as a result of rapidly changing environmental conditions within a complex and changing shallow, inshore marine paleogeography. In contrast, coordinated stasis in the lower Paleozoic probably resulted from negligible evolution during long periods of stable to gradually changing environments in an outer shelf setting, punctuated by brief episodes of abrupt environmental change and large-scale turnover. The independent assortment of species in late Cenozoic parallel communities indicates that ecological locking did not exist.     

Bathymetric distribution of fossil foraminifera within marine sediment cores from the eastern part of Lützow-Holm Bay, East Antarctica, and its paleoceanographic implications

Faunal analysis of fossil foraminifera from marine gravity and piston cores collected by the Japanese Antarctic Research Expeditions (1981 and 1992) is used to estimate the impact of the latest Quaternary paleoceanography on coastal environments of the eastern part of Lützow-Holm Bay, East Antarctica.Accelerator Mass Spectrometry (AMS) carbon-14 ages produced from sedimentary organic carbon were less than 16 ka (non-corrected). Detailed correlation among submarine cores and Holocene elevated marine deposits exposed on the eastern shore of the embayment is difficult due to the indefinite reservoir correction value for marine organic matter and to upward-increasing abnormal ages for some cores.A local carbonate dissolution level can be delineated around the present depth of 300–400 m or shallower in the eastern part of Lützow-Holm Bay during the Holocene, based on distributional trends of arenaceous, calcareous benthic, and planktonic foraminifera recognized within a depth less than 600 m. Downcore recovery of calcareous foraminifera containing Bulimina aculeata from two cores obtained in a drowned glacial trough deeper than 600 m situated far beyond the dissolution depth of CaCO₃ indicates the incursion of warm, high-nutrient, and CaCO₃-saturated Circumpolar Deep Water (CDW) from the offshore area along the trough toward the southeastern coast of Lützow-Holm Bay during the Holocene. The intrusion of CDW impacted on the marine environments of the southeastern coast, thereby contributing to peripheral retreat of the ice sheet as well as increasing calcareous benthic foraminiferal productivity along the southeastern coast of Lützow-Holm Bay.     

Palaeoenvironmental interpretation of the Pliocene fan-delta system of the Vera Basin (SE Spain): Fossil assemblages,ichnology and taphonomy

The marine fossil assemblages of the Pliocene of south Spain constitute the record of the marine fauna that colonised the western part of the Mediterranean after the Messinian Salinity Crisis. This work focuses on the analysis of lithofacies and fossil assemblages including trace fossils, invertebrates, and vertebrates with special attention to taphonomic features, for interpreting palaeoenvironmental conditions in the Vera Basin (SE Spain). The sedimentary sequences of the northern region of the Vera Basin display diverse stratigraphical, sedimentological, and palaeontological features that correspond to the evolution of a fan-delta in a narrow basin. The Vera Basin was characterised by shallow-marine shelf conditions during the early-mid Pliocene (Cuevas Formation). The basin emergence with the development of Gilbert-type fan deltas (Vera Member), and a protected, partially-enclosed marine embayment (Almanzora Member) occurred during the mid-late Pliocene due to regional uplift and movements of the Palomares strike-slip Fault along the eastern basin margin. The progradation of the central fan-delta lobes and the interaction with marginal fan-delta resulted in the partitioning of the basin that formed a small sub-basin with restricted stagnant conditions that favoured a Konservat Fossil-Lagerstätte. The high input of siliciclasts due to the uplift context of the margins of the basin favoured a high sedimentation rate and the fast burial of vertebrate remains. Fossil marine mammals occurs from shallow shelf deposits (Cuevas Formation) to bottomset (Cuevas Formation-Vera Member transition) and lower part of the clinoforms in the foreset (Vera Member). Cetacean remains are usually recorded not only in the relatively deep-water silty marls and sandy marls of the outer shelf and distal facies of the fan-delta (Espiritu Santo Formation), but also in the shallower coarse sands and conglomerates (Cuevas Formation and Espiritu Santo Formation). Sirenian remains, in contrast, are only recorded in coarse sand facies (Cuevas Formation and Espiritu Santo Formation) associated to charcoal wood fragments deposited in shallow waters near the shoreline. This narrow and relatively protected basin is interpreted as an area of reproduction and nursery of juveniles on the basis of the presence of cetaceans.     

The western edge of the Mediterranean Pelagian Platform: A Messinian mixed siliciclastic–carbonate ramp in northern Tunisia

The marine Messinian deposits of Tunisia cover a narrow littoral strip some 300 km long between the northern Bizerte and Cap Bon areas and the central–eastern Sahel region. Litho- and biofacies analysis of six stratigraphic sections reveals the distinctive features of these deposits.The lower Messinian deposits are characterized by ubiquitous siliciclastics and abundant oolitic/bioclastic limestones organized in an eastward facing ramp. Westward (landward), this ramp changes into coastal lagoons, sometimes containing evaporites. Eastward, the ramp passes to the reefal Pelagian Platform extending as far as Lampedusa.Two main sedimentary cycles are distinguished: 1) an early Messinian siliciclastic retrogradational then oolitic/bioclastic progradational cycle (Beni Khiar Formation and lower Oued bel Khedim Formation); 2) a late Messinian brackish to continental cycle that probably accumulated in rapidly subsiding lagoons (Oued el Bir Formation and upper Oued bel Khedim Formation). The Tunisian early Messinian cycle is partly eustatically controlled, but the late Messinian cycle cannot be confidently correlated to other well-known Messinian series because of tectonic movements.The lower Messinian deposits of Tunisia are also characterized by abundant suspension-feeding organisms (molluscs and bryozoans) and rare corals, calcareous algae, echinoids, and larger benthic foraminifers. The proposed palaeoenvironmental model shows that the lower Messinian ramp of Tunisia was located on a current-protected margin and subjected to continent-derived sediment and nutrient supply. Eastward, nutrient influx diminished and a shallow-water isolated carbonate platform with coralgal facies developed between the western and the eastern Mediterranean basins. The main hydrological connection between these two basins occurred through a narrow seaway situated to the northeast of the Pelagian Platform, south of Sicily and Malta.     

Late Oligocene to Early Miocene foraminifers and ostracods from Karben (Wetterau,Hesse State,Germany): stratigraphic occurrence and palaeoecological implications

Foraminiferal and ostracod assemblages from two upper Oligocene to lower Miocene sections located in the Wetterau region (NE Frankfurt a. M.) were analysed. The lithologie units investigated encompass Cyrenenmergel, Glimmersand, Vilbeler Kies, Cerithiensand, Cerithienkalk andCorbicula-Schichten. Hemicyprideis basiliensis, H. helvetica andCypridopsis? cyclocypriformae are characteristic of Cyrenenmergel deposits, representing the last marine influence around the Rupelian/Chattian boundary. The ostracod assemblages from the Cerithiensand are characterized by variousHemicyprideis species, of whichH. rhenana is the most frequent. The microfossil assemblages of the Cerithiensand indicate normal marine conditions for the basal and upper portions of the unit and slightly brackish to normal marine conditions for the middle portion. Very low salinities are indicated for some levels close to the base (around levels of emergence above sealevel) and for the clay layer around sample 30 in the lower part of the Cerithiensand. The Cerithienkalk represents a transitional facies from normal marine to brackish/freshwater conditions as indicated by successive higher contents of stress tolerant foraminifera and freshwater ostracods. TheCorbicula-Schichten are characterized by largeEucypris-moulds and various proportions ofCypridopsis spp. (freshwater indicators). When foraminifera (Bolivina spp.) are present, the fauna indicates slightly higher but still low salinities for a few levels of theCorbicula-Schichten. Oxygenation levels were generally high (presence of large ostracods and epifaunal foraminifera) and vary from suboxic to high oxic. As in the Mainz Basin, the last occurrence ofHemicyprideis rhenana marks the upper boundary of the Cerithienschichten.Protelphidium nonioninoides can be used to identify the Cyrenenmergel when it occurs in high numbers. Cerithiensand-samples show the highest diversities and contain high portions ofUvigerinella michelsi. Overall, highest diversities and normal marine salinities are reached during deposition of the basal and upper parts of the Cerithiensand, which may correspond to global sealevel rises at the end of the Chattian.     

Preliminary environmental reconstructions from late Quaternary pollen and mollusc assemblages at Egg Lagoon,King Island,Bass Strait

Abstract A late Quaternary environmental record is currently being developed from Egg Lagoon, King Island, Bass Strait, a site which is geographically well situated to contribute towards a history of the Bass Strait region. Environmental reconstructions are based on a stratigraphic survey and pollen, charcoal and mollusc analyses of sediment core samples. The recorded stratigraphy includes five sedimentary units representing estuarine-marine, freshwater lake and swamp depositional environments. Amino-acid racemization analyses of marine shells indicate a greater than last interglacial age for the basal estuarine-marine unit, while radiocarbon analyses of organic muds and wood suggest that a substantial section of the overlying freshwater lake and swamp facies is beyond the conventional limit for this technique. Local pollen assemblages represent freshwater lake and swamp plant communities that have varied presumably according to water level changes at the site. Regional pollen assemblages represent terrestrial herbaceous communities, believed to have existed under cooler and drier climates than today, and Eucalyptus- and Phyllocladus-dom'maied forests and woodlands from periods with greater effective precipitation than at present. A sustained increase in charcoal representation dating from at least 39 000 years before the present may indicate an anthro-pogenically induced change in the fire regime, consistent with the earliest dates for human occupation in mainland Tasmania.     

Did the Mediterranean marine reflooding precede the Mio–Pliocene boundary? Paleontological and geochemical evidence from upper Messinian sequences of Tuscany,Italy

The events related to the Messinian salinity crisis are among the most deeply investigated of Earth's history. According to the current hypothesis of Neogene paleogeographic evolution, approximately 5.5 Ma ago, after evaporitic sedimentation and before the Mio–Pliocene boundary, the Mediterranean was characterized by the widespread development of non-marine environments inhabited by molluscs and ostracods of brackish affinity. The Messinian post-evaporitic deposits that testify such a dramatic environmental change are commonly referred to as ‘Lago-mare’ and have been reported from several outcrops and boreholes throughout the entire Mediterranean basin. The origin of ‘Lago-mare’ conditions is commonly interpreted as the result of the synergistic effect of both the humid climatic conditions and change of the drainage patterns at the Mediterranean scale, with the capture of Paratethyan brackish waters. A few recent studies, however, suggest that such a scenario probably represents an oversimplification of the original context, from both a paleogeographical and paleoenvironmental point of view. Unfortunately, the results of these studies have never been commonly accepted and the proposed evidences have been considered questionable. In this paper we describe the fish assemblages from the ‘Lago-mare’ deposits of two localities, Cava Serredi and Podere Torricella, located in the Neogene hinterland basins of Tuscany, central Italy. These assemblages consists of a mixture of marine euryhaline and stenohaline taxa suggesting that the depositional environments were characterized by permanently open connections with a marine basin filled with normal marine waters. In order to better define the paleontological significance of these upper Messinian fish assemblages, the oxygen, carbon and strontium isotopic composition of fish otoliths and other fossils has been measured. These isotopic compositions are strongly indicative of the presence of normal marine conditions close to the depositional environments testified by the sedimentary sequences, thereby implying that the interpretation of the geochemical results are consistent with those derived from the paleoecological analyses of the fish assemblages. Based on the integrated paleoichthyological–geochemical approach discussed in this paper it is possible to unambiguously demonstrate that normal marine rather than fresh- or brackish waters were present in the Mediterranean at least during the upper part of the ‘Lago-mare’ event, providing an unquestionable evidence that the marine refilling of the basin preceded the Mio–Pliocene boundary.     

Late Silurian plant microfossil assemblage from Guangyuan,Sichuan, China

A dispersed plant microfossil assemblage is described from Late Silurian deposits from Guangyuan, Sichuan, China. These strata are interpreted as nearshore, shallow marine deposits, and brachiopods suggest a late Ludlow–early Pridoli age. The palynomorph assemblage is dominated by terrestrial forms, including cryptospores and trilete spores, tubular structures and cuticle-like sheets, although rare marine acritarchs are also present. This microfossil assemblage is comparable to coeval assemblages from around the world (South and Southwest Wales; Libya; Canada; Southeastern Turkey; Northwest Spain; and Jiangsu, China). The sporomorphs from this assemblage indicate the existence of early land plants during the late Ludlow–early Pridoli in Guangyuan, Sichuan, China; and suggests that floras of this age were cosmopolitan and exhibited little palaeogeographical differentiation.     

Ihering's hypothesis in the light of foraminiferological data

The presence of several typically northern hemisphere foraminiferal species in the upper Miocene and Recent deposits of the Río de la Plata, Paraná river and adjacent areas, and their absence along the Brazilian coast strongly suggests that in the late Miocene the Caribbean and the Southern Atlantic were linked by a marine connection. This connection was first envisioned by H. von Ihering, who called it the 'Arm of the Tethys'. It was represented by a very broad strait which ran meridionally across the South American continent. In the Pliocene it shrank considerably and its salinity was lowered by Andean river runoff. At the end of the Pliocene - beginning of the Pleistocene it gave rise to the Paraná river, a series of brackish water lakes and lagoons, and the Río de la Plata. □ Foraminifera, arm of the Tethys, South America.     

Paratethyan Ostracod immigrants in Italy during the Late Miocene

In this paper the ostracod assemblages recovered from several brackish Late Miocene Italian deposits have been analysed from a palaeobiogeographical perspective. During late Tortonian-early Messinian it is possible to recognize in Italy rich ostracod assemblages characterized by a wide contingent of taxa with central European or Mediterranean affinity, while only few brackish and freshwater ostracods show Paratethyan affinity. The recognized composition of the ostracod assemblages matches the palaeogeographic setting of the palaeo-Mediterranean/Paratethys at that moment. In fact during late Tortonian-early Messinian the palaeo-Mediterranean and Paratethysian domains were divided and, even if the connection via the present Marmara Sea-Strimon Basin was still open, the different salinity between them represented an ecological barrier, preventing faunal exchanges. Since normal aquatic migration was impossible, it must be assumed that the Paratethyan-like taxa entered the palaeo-Mediterranean area via passive dispersal by aquatic birds. On the contrary, the ostracod assemblages from the Italian Lago-Mare deposits show the absolute predominance of Paratethyan taxa, which, according to the known palaeogeographic setting during the late Messinian Lago-Mare event, could actively migrate from the Paratethys domain, colonizing the palaeo-Mediterranean, whose endemic fauna was severely impoverished by the Messinian salinity crisis and the following water dilution.     

La microflore de diatomées au passage mio-pliocène en Corse

The “Aleria formation”, described in northeastern Corsica, consists of siliciclastic deposits referred to a deltaic environment and comprises diatomitic lenses exposed at Casabianda. The Aleria formation fills a depression of the Messinian erosional surface and is overlain by Early Pliocene sediments in several places. This suggests a late Messinian-earliest Pliocene age. Diatom microflora is well-preserved and contains 59 species. Pennates indicate a very large diversity with 54 species, while Centrics are represented only by five species. Diatom assemblages show a relative constant composition along the studied interval. The species Aulacoseiragranulata is the dominant taxon with about 90% in all samples. Taxa are of different salinity classes and different modes of life (planktic, tychoplanktic, benthic, epiphytic…), suggesting multiple environmental factor interactions. The environmental model suggested by sedimentological and biological data led as to assume a pond-like coastal receptacle common in deltaic system. This receptacle was slightly influenced by the close marine waters and was supplied by permanent freshwaters from continental run-off and alluvial sheet. This model based on diatom assemblages provides new data for palaeoenvironmental and chronological interpretations of the so-called Messinian Lago-Mare deposits.     

Could coastal plants in western Amazonia be relicts of past marine incursions?

The rainforests of Amazonia comprise some of the most biologically diverse ecosystems on Earth. Despite this high biodiversity, little is known about how landscape changes that took place in deep history have affected the assembly of its species, and whether the impact of such changes on biodiversity can still be observed. Here, we present a hypothesis to explain our observation that plants typical of Neotropical coastal habitats also occur in western Amazonia, in some cases thousands of kilometres away from the coast. Evidence on their current distribution, dispersal biology and divergence times estimated from molecular phylogenies suggest that these plants may be the legacy of the large marine‐influenced embayment that dominated the area for millions of years in the Neogene. We hypothesize that coastal plants dispersed along the shores of this embayment and persisted as inland relicts after the marine incursion(s) retreated, probably with the aid of changes in soil conditions caused by the deposition of marine sediments. This dispersal corridor may also have facilitated the colonization of coastal environments by Amazonian lineages. These scenarios could imply an unexpected coastal source that has contributed to Amazonia's high floristic diversity and led to disjunct distributions across the Neotropics. We highlight the need for future studies and additional evidence to validate and shed further light on this potentially important pattern.