Comparison of carbonate C and O stable isotope records across the Jurassic/Cretaceous boundary in the Tethyan and Boreal Realms

Carbon and oxygen stable isotope records were compared for Jurassic/Cretaceous (J/K) boundary sections located in the Tethyan Realm (Brodno, Western Slovakia, and Puerto Escaño, Southern Spain; bulk limestones), and the Boreal Realm (Nordvik Peninsula, Northern Siberia, belemnites). Since a detailed biostratigraphic correlation of these Tethyan and Boreal sections is impossible due to different faunal assemblages, correlation of the isotope records was based on paleomagnetic data. This novel approach can improve our understanding of the synchroneity of individual isotope excursions in sections where detailed biostratigraphic correlation is impossible. No significant excursions in either the carbon or oxygen isotope records to be used for future Boreal/Tethyan correlations were found around the J/K boundary (the upper Tithonian and lower Berriasian; magnetozones M20n to M18n) in the studied sections. At the Nordvik section, where a much longer section (middle Oxfordian–basal Boreal Berriasian) was documented, the transition from the middle Oxfordian to the Kimmeridgian and further to the Volgian is characterized by a decrease in belemnite δ¹⁸O values (from δ¹⁸O values up to + 1.6‰ vs. V-PDB in the Oxfordian to values between + 0.3 and ? 0.8‰ in the late Volgian and earliest Boreal Berriasian). This trend, which has previously been reported from the Russian Platform and Tethyan Realm sections, corresponds either to gradual warming or a decrease in seawater δ¹⁸O. Supposing that the oxygen isotope compositions of seawater in the Arctic/Boreal and Tethyan Realms were similar, then the differences between oxygen isotope datasets for these records indicate differences in temperature. The Boreal/Tethyan temperature difference of 7–9 °C in the middle and late Oxfordian decreases towards the J/K boundary, indicating a significant decrease in latitudinal climatic gradients during the Late Jurassic. Two positive carbon isotope excursions recorded for the middle Oxfordian and upper Kimmeridgian in the Nordvik section can be correlated with a similar excursion described earlier for the Russian Platform. Minor influence of biofractionation at the carbon isotopes, and the influence of migration of belemnites to deeper, slightly cooler water at the oxygen isotopes, cannot be excluded for the obtained belemnite data.     

Un faux polymorphitiné: Dubariceras, nouveau genre d'Ammonitina du Carixien mésogéen

Most of the Tethyan species usually attributed to the genera Platypleuroceras, Uptonia and Dayiceras (Polymorphitidae) are in reality forms phylogenetically related to Metaderoceras, but which show convergence in their morphology. Their originality justifies the creation of a new genus, Dubariceras and two new species, D. dubari and D. freboldi.The palaeobiogeographic implications of this phylogenetic interpretation confirm the profound differences between Tethyan and Boreal faunas in the Carixian. The platycone Polymorphitidae (Platypleuroceras, Uptonia and Dayiceras) are almost completely restricted to the Boreal Realm, whereas the faunas of the Tethyan Realm largely comprise the Acanthopleuroceratidae (Tropidoceras), Metaderoceras and its allied genus Dubariceras.     

Palaeobiogeography of late cretaceous belemnites of Europe

A North Temperate Realm, characterized by Belemnitellidae Pavlov, and a South Temperate Realm, characterized by Dimitobelidae WHITEHOUSE, existed throughout the Late Cretaceous, while Tethyan belemnites belonging to Belemnopseidae Naef existed only in the Cenomanian and disappeared afterwards. The North Temperate Realm may be subdivided into North European and North American Provinces. The latter province includes Greenland, Canada, the Western Interior Region of North America, and the Atlantic and Gulf coasts of North America. The belemnites from the North American Province, consisting of populations of the generaActinocamax Miller andBelemnitella d’Orbigny, are closely related to the belemnites of the North European Province and appear to have migrated from this province to North America via Greenland and Arctic Canada. The North European Province extends from Ireland to the Ural Mountains. Belemnites from this province belong to the following genera:Neohibolites Stolley,Parahibolites Stolley,Belemnocamax Crick,Actinocamax Miller,Belemnellocamax Naidin,Gonioteuthis Bayle,Belemnitella d’Orbigny,Belemnella Nowak, andFusiteuthis Kongiel. Two subprovinces within the North European Province have been recognized: the Central European and Central Russian Subprovinces. These subprovinces are well-defined in the late Coniacian-Early Campanian and are characterized by theGonioteuthis stock andBelemnitella stock, respectively. The two subprovinces are less distinct in other periods of the Late Cretaceous and may disappear completely.     

Jurassic evolution of Southern Hemisphere marine palaeobiogeographic units based on benthonic bivalves

The distribution of benthonic Jurassic bivalve genera in the Southern Hemisphere is analysed here. For this region, palaeobiogeographic units (biochoremas) are quantitatively characterized according to their biologic contents (mainly levels of endemism). Their evolution through time is followed from the latest Triassic to the earliest Cretaceous. The Tethyan Realm is undoubtedly the most mature and persistent through time, with three subordinate units: an Australian unit restricted to the Late Triassic, a North Andean unit, which appears sporadically as an endemic centre, and an East African unit which is recognisable from Bajocian times onwards. From Late Triassic times, a South Pacific Realm has been recognised, with a Maorian Province mostly based on the distribution of monotoid genera. A South Andean unit is also recognisable through most of the Jurassic, and its reference either to the South Pacific unit or to the Tethyan Realm is a matter of debate. Being a transitional biogeographic setting between Tethyan and South Pacific first-order units, it is included in the South Pacific unit due to the common presence of antitropical (didemic) genera. The East African unit is included within the Tethyan Realm during the Jurassic, but during Early Cretaceous times, it splits into two units, one of which was regarded as part of the “South Temperate Realm” by Kauffman. The rank of all these units changed with time. Throughout the Jurassic, the ecotone between South Pacific and Tethyan palaeobiogeographic units fluctuated in position with time. The approximate latitudinal location of the ecotonal boundary area and its shift through time are recognised on the basis of faunal composition along the Andean region.     

An early Bathonian Tethyan ammonite fauna from Argentina

Evidence for the Lower Bathonian Substage in most of the Pacific area has been lacking or controversial because index ammonoids of the Tethyan Subrealm in southern Europe and North Africa were unknown. During the Bathonian, the East Pacific margin belonged to either the Boreal Realm or the East-Pacific Subrealm of the Tethyan Realm, each with faunas distinctly different from the Eurafrican Tethyan faunas that form the basis for the chronostratigraphical standard. The first representatives of Morphoceras from South America, M. gulisanoi sp. nov., here described from a single locality in southern Mendoza Province, clearly document the Lower Bathonian Substage, probably the Zigzag Zone. Associated ammonoids are the perisphinctoidean Procerites cf. schloenbachi de Grossouvre and the oppeliid Oxycerites ( O. ) cf. aspidoides (Oppel), also typical Tethyan elements but less useful for dating.     

Biodiversity and biogeography of middle–late liassic ammonoids: implications for the early Toarcian mass extinction

In Western Tethyan areas, the Toarcian stage begins with two important evolutionary events in ammonite faunas: (1) the disruption of Tethyan–Boreal provinciality; (2) a biological crisis linked with the oceanic anoxic event OAE. The analysis of these events has been addressed by constructing curves of ammonoid diversity (species richness, origination and extinction rates) in the Late Pliensbachian (= Domerian)–Early Toarcian interval in selected localities. Two diversity drops are recognized. The first one is recorded at the end of the Dactylioceras mirabile subzone and reflects the disruption of Tethyan–Boreal provinciality, through the progressive extinction of the Boreal endemic family Amaltheidae that occupied the north-western European seas during the whole Pliensbachian on the one hand, and the extinction of Late Domerian Ammonitina endemic to the Mediterranean areas on the other hand. The Early Toarcian homogeneization of Mediterranean and north-western European ammonoid faunas was reached via elimination of both Boreal and Mediterranean endemics with differential rates of extinction in the two palaeogeographic domains and the subsequent geographical expansion of Tethyan-derived ammonoids. The second, dramatic drop in ammonite diversity in the upper part of the Dactylioceras semicelatum subzone coincided with the onset of OAE. It also affected epioceanic ammonoid clades like Phyllocerataceae and Lytocerataceae. These two drops are interpreted as two distinct extinctions and not as episodes of a single, stepwise event. Complex relations between ammonoid diversity and sea-level changes are suggested by trends in endemism, which may be reversed during either a single transgression or a single regression.     

Paleobiogeography of Mesozoic brachiopod faunas from Andean–Patagonian areas in a global context

During the Mesozoic, the Andean region has played a hinging role between high- and low-latitude faunas, which are, respectively, characterized by stocks that display long-term fidelity. This paper is aimed at providing an updated review of Late Triassic to Late Cretaceous South American articulated brachiopods in the light of previous knowledge at worldwide scale. Late Triassic brachiopods from the Argentine–Chilean Andes show unmistakable Maorian (or Notal) faunal elements alongside some more cosmopolitan genera, with certain influence of Eastern Pacific taxa. By Early Jurassic times, differentiation of Tethyan and Boreal Realms became progressively evident in Europe. In South America, Hettangian–Sinemurian brachiopod faunules from the Argentinian Andes are somewhat impoverished, with mostly cosmopolitan genera showing certain affinities to Maorian species, and with the addition of some endemics later. Increasingly, diverse Pliensbachian Andean brachiopods denote close relationships to Celto-Swabian taxa, then by Domerian times, a certain degree of endemism was developed, though somewhat delayed Tethyan influences, and persistent links with New Zealand are subordinately recognizable, too; most Toarcian assemblages reveal basically Celto-Swabian and Iberian affinities as well. East-west austral links across the Pacific may have been favored by migratory routes fringing the Gondwana margin, whereas faunal exchange with the western end of the Tethys appears to reflect an intermittent shallow-marine connection through the Hispanic Corridor. During the Middle Jurassic, distinction of Tethyan and Boreal Realms was maintained in the northern Hemisphere, and the differentiation of an Ethiopian or Southern Tethyan fauna became better characterized. Aalenian and Bajocian brachiopods of the Andes display generic affinities mainly with those from western Europe, with some minor endemic developments; brachiopods recorded from the Bathonian–Callovian of Argentina (and Chile) also occur along the northern Tethyan margin, yet with some genera extending into Indo-Ethiopian areas. During the Late Jurassic, Boreal faunas from high-latitudes became even more strongly differentiated from low-latitude, Tethyan ones. Oxfordian and Tithonian brachiopods from the Andes apparently belong to genera of cosmopolitan or northern Tethyan affiliation, yet there are few elements in common with other eastern Pacific areas, such as Mexico. Early Cretaceous brachiopods, in addition to Andean basins of Chile and western Argentina, are known also from Patagonia and Tierra del Fuego. They belong mostly to widely distributed, mainly Tethyan genera, with some quasi-cosmopolitan and circum-Pacific components (some shared with Antarctica become noticeable). Late Cretaceous brachiopods from northern Patagonia show significant affinities to Maastrichtian ones of northwest Europe and central Asia, which calls for further assessing the potential role that may have played the trans-Saharan passageway in such dispersal. Broad aspects of Mesozoic brachiopod paleobiogeography are fairly well understood, yet details of ranking and naming of certain units are still in need of more agreement.     

Multiple deep-water sources and trophic regimes in the latest Cretaceous deep sea: evidence from benthic foraminifera

Benthic foraminifera from 24 DSDP/ODP sites were investigated to assess their global horizontal and vertical distribution in the deep-sea environment at the end of the Cretaceous period. The samples analyzed are from the late Maastrichtian and within the planktic forammiferal Abathomphalus mayaroensis Zone from a wide range of oceans and paleolatitudes, including the low-latitude Sites 10 and 384 (Atlantic Ocean), 47, 171, 305, and 465 (Pacific Ocean), the mid-latitude Sites 20, 111, 356, 363, 516, 525, 527, 548, and 605 (Atlantic Ocean), 216, 217, and 758 (Indian Ocean), and the high-latitude Sites 208 (Pacific Ocean), 689, 698, 700, 738 and 750 (Southern Ocean).Correspondence analysis, based on the 75 most common taxa, shows a clear biogeographic trend along the first correspondence axis by arranging the sites in paleolatitudinal order. The assemblages from the Tethyan Realm (i.e., low latitudes) are marked by abundant heavily calcified buliminids (such as Bulimina incisa B. trinitatensis B. velascoensis, and Reussella szajnochae) and Aragonia spp., whereas high-latitude faunas are characterized by abundant Alabamina creta, Gyroidinoides quadratus, and Pullenia coryelli.The results indicate that the faunas at low and high latitudes, respectively, were influenced by quite different environmental conditions. This is based on the much higher abundance of infaunal morphotypes at low and mid latitudes compared to high latitudes, suggesting that the biogeographic trend found in the data set coincides with the trophic regime at the various sites. The results also provide support for the hypothesis that postulates two simultaneous sources and mechanisms for deep-water formation during the Late Cretaceous, including warm, saline deep water produced by evaporation at low (equatorial) latitudes in contrast to the formation of cold deep waters at high (southern) latitudes.     

Corrélation des successions de l'Albien par les ammonites entre la Province Nord-Pacifique et les Provinces européenne et arctique du Domaine boréal : zonation, eustatisme et paléobiogéographie

The vertical distribution of Albian ammonites of the North Pacific Province is described on the basis of several sections located in Northern California. Nine Albian ammonite assemblages are identified, compared to the 4 previously described by Murphy in 1956. Owing to several gaps of observation possibly more assemblages could exist. In the North California Albian history, the first results show a succession of confinement periods - with numerous endemic faunas - followed by periods of open communications with other faunal provinces. As an example, the base of the Middle Albian is marked by exotic ammonites coming from the Tethyan realm (Oxytropidoceras, Lyelliceras) and from the Arctic Province of the Boreal realm (Gastroplites, Pseudopulchellia). These ammonites - except Oxytropidoceras - were not known in that area and are described relatively to their palaeobiogeographical interest. Although rare these migrant faunas give valuable elements to correlate these various provinces. Planktonic foraminifera confirm the existence of open sea communications during the uppermost Albian.With such faunal links, a comparison is proposed between the Albian ammonite zonation of Northern California and the standard and phyletic ones of Europe. This attempt suggests that the major connections between the three faunal provinces are established at second order peak transgressions in the Early and Middle Albian, and during the sea-level high of the Late Albian transgressive period. So, it seems that the vertical distribution of Albian non-endemic ammonites of North California and Europe is largely controlled by global eustatic events. Two palaeobiogeographic maps for Early and Middle Albian and one map for the late Late Albian show the migration outer of these exotic ammonites.     

Embryonic shell structure of Early–Middle Jurassic belemnites,and its significance for belemnite expansion and diversification in the Jurassic

Early Jurassic belemnites are of particular interest to the study of the evolution of skeletal morphology in Lower Carboniferous to the uppermost Cretaceous belemnoids, because they signal the beginning of a global Jurassic–Cretaceous expansion and diversification of belemnitids. We investigated potentially relevant, to this evolutionary pattern, shell features of Sinemurian–Bajocian Nannobelus, Parapassaloteuthis, Holcobelus and Pachybelemnopsis from the Paris Basin. Our analysis of morphological, ultrastructural and chemical traits of the earliest ontogenetic stages of the shell suggests that modified embryonic shell structure of Early–Middle Jurassic belemnites was a factor in their expansion and colonization of the pelagic zone and resulted in remarkable diversification of belemnites. Innovative traits of the embryonic shell of Sinemurian–Bajocian belemnites include: (1) an inorganic–organic primordial rostrum encapsulating the protoconch and the phragmocone, its non‐biomineralized component, possibly chitin, is herein detected for the first time; (2) an organic rich closing membrane which was under formation. It was yet perforated and possessed a foramen; and (3) an organic rich pro‐ostracum earlier documented in an embryonic shell of Pliensbachian Passaloteuthis. The inorganic–organic primordial rostrum tightly coating the protoconch and phragmocone supposedly enhanced protection, without increase in shell weight, of the Early Jurassic belemnites against explosion in deep‐water environment. This may have increased the depth and temperature ranges of hatching eggs, accelerated the adaptation of hatchlings to a nektonic mode of life and promoted increasing diversity of belemnoids. This study supports the hypothesis that belemnite hatchlings were ‘a miniature of the adults’.     

Reconstructing the palaeoenvironment of the Middle Russian Sea during the Middle–Late Jurassic transition using stable isotope ratios of cephalopod shells and variations in faunal assemblages

Oxygen and carbon isotope data of well-preserved belemnite rostra and ammonite shells are presented from the Callovian–Oxfordian boundary (uppermost Lamberti to lowermost Cordatum zones) of the Dubki section near Saratov in the Russian Platform. Palaeotemperatures calculated for nektobenthic belemnites (averages of 5 °C and 8 °C for cylindroteuthids and belemnopseids, respectively) show the presence of cold bottom waters in the central part of the Middle Russian Sea during the studied interval. Palaeotemperatures calculated for ammonites, which are assumed to have lived in near-surface waters, are considerably higher (average 13 °C). The presented data show a vertical thermal gradient in the Middle Russian Sea. The belemnite oxygen isotope record and the relative abundances of ammonite families in the Dubki section do not correlate with each other probably as a result of different depth habitats of ammonites and belemnites. A review of literature isotope data shows the climatic zonation in European seas at the Middle–Late Jurassic transition. Despite the flux of cold polar waters to the Middle Russian Sea and the area of Scotland there is no evidence for glaciation at the Middle–Late Jurassic transition. Changes in water circulation during a sea-level highstand were likely a source of spreads of cold bottom waters and cardioceratid ammonite fauna in this time period.The belemnite isotope record of the Callovian–Oxfordian boundary in the Russian Platform is characterized by significant scatter of δ¹³C values. No temporal carbon isotope trend is observed. The δ¹³C values of Russian belemnite rostra average 2.6‰ VPDB being 1 to 2‰ higher than the values of coeval Lower Oxfordian belemnites from the area of the Submediterranean ammonite province. Higher (than Submediterranean) δ¹³C values of Russian belemnite rostra are likely related to high biologic productivity and/or high organic matter burial in semi-isolated Boreal–Subboreal marine basins.     

Early Cretaceous calcareous nannofossils from high latitudes: implications for palaeobiogeography and palaeoclimate

In order to better understand the palaeoceanography and palaeoclimate of the Early Cretaceous, nannofossil data have been obtained from high-latitudinal sites from offshore mid-Norway and from the Barents Sea. No consistent nannofossil data are yet available for Early Cretaceous high latitudes, which should more clearly reflect possible palaeoclimatic changes, as recorded in fluctuations of diversity and abundance. Existing data from France, Italy, Romania, Poland and NW Europe (Germany, North Sea, England) have been complemented by material from higher latitudes. In order to record the Arctic–Boreal nannofossil assemblages, 400 samples from the Norwegian Shelf and the Barents Sea have been analysed. Sixty samples, covering the Berriasian–Barremian interval, yielded calcareous nannofossils. These are derived from cores between 63 and 73°N of present-day latitudes. The nannofossil assemblages recorded are generally of a low diversity and characterized by abundant Watznaueria barnesae and Crucibiscutum salebrosum, whereas Biscutum constans is less common. C. salebrosum, rare or absent at low latitudes, is extremely common in the Norwegian samples. It shows a bipolar distribution especially during Valanginian–Hauterivian times. In the early Valanginian, a distinctive latitudinal gradient in the abundance of C. salebrosum, impoverished in low latitudes and abundant in high latitudes, possibly reflects latitudinal differences in temperature. Restricted palaeoceanographic settings, caused by a sea-level lowstand, may have amplified these thermal gradients. Palaeoclimatically this implies the existence of climatic belts throughout parts of the Early Cretaceous (early Valanginian, Hauterivian), resulting from considerable temperature gradients from north to south. The palaeobiogeographic patterns discussed resulted in the formation of distinctive latitudinally bound nannofossil zones, which, to a certain extent, are similar to those of modern oceans. The palaeobiogeographic patterns described support the idea of an ice-house phase for the early Valanginian and disagree with the suggestion of a globally warm equable climate during that time.     

Palaeobiogeography of Early Cretaceous (Berriasian–Barremian) calcareous nannoplankton

In order to assess Early Cretaceous nannoplankton biogeography, we studied a series of sites which provide a north–south transect across the Atlantic Ocean, supplemented by sections from the North Sea Basin, Barents Sea, Falkland Plateau, Weddell Sea (Antarctica), Argo Abyssal Plain (NW of Australia) and Neuquén Basin (Argentina). Quantitative assemblage data were gathered from each site for seven time-slices within the Berriasian to Barremian interval, each horizon being determined by a nannofossil datum. Trends in species relative abundance and measures of diversity, evenness and richness provide revealing biogeographic information. A broad, low- to mid-palaeolatitude zone (50°N–50°S) is flanked in both Northern and Southern Hemispheres by distinct high-palaeolatitude zones. Major changes in assemblage abundance and composition occur across a sharp biogeographic ‘front’ at around 50°N and S palaeolatitude. High-palaeolatitude assemblages are lower in species richness and diversity and characterised by the presence of abundant, typically bipolar, taxa (e.g. Crucibiscutum salebrosum). A less distinct biogeographic boundary at 40°N is distinguished by the presence/absence of rarer, but biogeographically significant, taxa, many of which have previously been assigned to Boreal or Tethyan provinces. Continental shelf sites are characterised by lower-diversity assemblages with common to dominant diagnostic taxa, which vary with palaeolatitude: Nannoconus and Micrantholithus at low palaeolatitudes, and Biscutum constans and Zeugrhabdotus spp. at higher palaeolatitudes. The latter two taxa are considered to be indicative of elevated surface-water fertility and the former two may have been similarly adapted. The genus Watznoueria is ubiquitously dominant, giving the populations an unevenness, which appears to be a common feature throughout coccolithophore history.     

A new ammonoid fauna from the Carnian (Upper Triassic) Kasimlar Formation of the Taurus Mountains (Anatolia,Turkey)

We describe a new ammonoid fauna from the Taurus Mountains of southern Turkey. The Carnian ammonoid fauna from A?a?iyaylabel is presented for the first time. Ammonoids were obtained from limestone to marl beds of an approximately 35‐m‐thick section, which presents the rare opportunity to investigate ammonoid faunas across the Lower–Upper Carnian boundary. Intense sampling near the village of A?a?iyaylabel led to the recognition of a new Lower Carnian (Julian 2) to Upper Carnian (Tuvalian 1) ammonoid fauna from the Kasimlar Formation. The genus Kasimlarceltites gen. nov. is reported for the first time from the Taurus Mountains, which represents the main faunal element and occurs as huge mass occurrence (n ? 1 million). Kasimlarceltites krystyni gen. et sp. nov., Klipsteinia disciformis sp. nov. and Anasirenites crassicrenulatus sp. nov. occur within the Lower Carnian Carbonate member (Units A–B) of the Kasimlar Formation from the Taurus Platform Units. Ammonoids described from the marls of the Tuvalian Marlstone member were deposited during a major, Tethyan‐wide climate crisis – the so‐called Carnian crisis – characterized by a demise of carbonate platforms. Based on the biostratigraphic relevance of certain ammonoid taxa described herein, the age of the analysed parts of the Kasimlar Formation is Julian 2 to Tuvalian 1. The discovery of the new ammonoid assemblages from A?a?iyaylabel substantiates the significance of Upper Triassic faunas within the Taurus Mountains and facilitates the correlation with faunal assemblages from other regions in the Tethyan Realm. The ammonoid fauna and facies indicate a general deepening from open‐platform margins, over deeper shelf settings down to an open marine‐influenced basinal environment. The tentative habitat for Kasimlarceltites gen. nov. is a shallow platform environment to upper mid‐ramp.     

Provenance analysis of Cenozoic conglomerates: Insights from Lower Cretaceous radiolarians in chert clasts from the Xigaze area,southern Tibet

Conglomerates, exposed on either side of the Yarlung Tsangpo suture zone (YTSZ) in southern Tibet, have attracted wide attention in elucidating uplift and erosion histories of the Himalayan-Tibetan orogen. However, the provenance of these conglomerates remains controversial. Although radiolarian-bearing chert clasts within these conglomerates have received little focus, identification of the radiolarian assemblages they contain could shed light on the provenance of these sedimentary units. We present the first report of Upper Jurassic to Lower Cretaceous (upper Kimmeridgian–lower Barremian) radiolarian assemblages recovered from chert clasts within the Liuqu and Gangrinboche conglomerates in the Xigaze area. To extract radiolarian fossils from independent clasts in the conglomerates, a detailed and efficient experimental process is illustrated. The assemblages are well correlated to those in the YTSZ and Tethyan Himalaya, showing typical Tethyan characteristics. The lithology of chert clasts and ages of constituent radiolarian faunas suggest that the chert clasts in Liuqu and Gangrinboche conglomerates were derived from the Bainang terrane. This interpretation implies that Early Cretaceous accretionary complexes in the YTSZ had been exposed and eroded before deposited as clasts in the Cenozoic Liuqu and Gangrinboche conglomerates.     

Cenomanian belemnites from the teutoburger Wald,NW Germany

A small fauna of belemnites collected recently from the Cenomanian deposits of the Teutoburger Wald, NW Germany, is described. It includes the belemnopseidNeohibolites ultimus (d’Orbigny) and the belemnitellidsBelemnocamax boweri Crick,Actinocamax primus Arkhangelsky, andA. plenus (Blainville). The Teutoburger Wald is thus one of the few regions in NW Europe, where these four species occur. The Cenomanian belemnite events, theultimus eustato-event, theprimus eco-event, andme plenus eustato-event, are discussed.     

Late Jurassic decapod crustaceans from northeast Japan

Abstract: Astacidean and thalassinidean macrurans (Glyphea sp., ?Eryma sp. and Protaxius sp.) and a new longodromitid crab, Planoprosopon kashimaensis, are recorded from the Upper Jurassic (upper Kimmeridgian to lower Tithonian) of Fukushima Prefecture, northeast Japan. Material was collected from the Tatenosawa Sandstone Member of the Nakanosawa Formation, Somanakamura Group, from which abundant Tethyan‐type marine invertebrates are known. Planoprosopon kashimaensis sp. nov. closely resembles P. heydeni (von Meyer), a common form in the Upper Jurassic of the Tethyan realm in Europe, and represents the oldest record of a brachyuran from the circum‐Pacific region. Similarities to contemporaneous decapod assemblages in southern Germany indicate that closely comparable, parallel decapod faunas in the Tethyan realm, inclusive of brachyurans, had already been established in the western circum‐Pacific region by the Late Jurassic.     

Berriasian ammonites of supposed Tethyan origin from the type ‘Ryazanian’, Russia: a systematic re-interpretation

For more than a century, a number of ammonite taxa of supposed Tethyan origin or affinity have been reported from the Berriasian condensed deposits of Russia (referred to as ‘Ryazanian’). These occurrences have been used to constrain long-distance correlation and palaeobiogeographic interpretation of the Russian Platform during the earliest Cretaceous. We revise these taxa herein. To accommodate the systematic issues, we introduce a new ammonite genus: Mittaites n. gen. (type species: Mazenoticeras ceccai). We also provide re-assessment for the genera Tauricoceras (= Subriasanites), Riasanella, Riasanites, Prorjasanites, and Karasyazites. Considering the strong affinities between these genera (except for Karasyazites), resctricted palaeobiogeographic distribution and a problematic phyletic origin, we erect a new family Riasanitidae n. fam. Our re-examination suggests that the occurrence of western Tethyan migrants in the type ‘Ryazanian’ should be ruled out. Pending new investigation, correlation of the ammonites of the type ‘Ryazanian’ beds with the Berriasian part of the Standard Mediterranean Ammonite Scale (SMAS) should be treated with caution.     

Les ammonites boréales des formationsnéocomiennes du Sud-Est français (province subméditerranéenne)

The boreal Ammonites (and the more or lessphylogenetically related ones) of the southeast France (Tethyan Realm) are described and figured. 24 forms are refered to, or compared with, previously identified species. 3 are left under open nomenclature, and 7 are new ones. Two new subgenus: Julianites (Paquiericeras) and Lemurostephanus (Olcostephanus) are also introduced.Their biostratigraphic position in the Frenchzonal scheme is detailed. Their contribution to the establishment of correlation between the Boreal and Tethyan provinces is stressed.The most interesting feature is the identification of a Prodichotomites horizon just below the Verrucosum zone, allowing comparison of the definition of the Lower-Upper Valanginian boundary in these two paleobiogeographic realms.     

Oligocene and Early Miocene gastropods from Kutch (NW India) document an early biogeographic switch from Western Tethys to Indo-Pacific

Shallow marine gastropod assemblages from Chattian, Aquitanian and Burdigalian sections in the Indian Kutch Basin are described. They provide insight into the composition and biogeographic relations of the gastropod assemblages at this junction between the Western Tethys and Proto-Indo-Pacific Ocean. For the first time, an improved biostratigraphy allows a clear separation of the assemblages, especially for the hitherto undifferentiated Early Miocene faunas. Throughout the Oligocene, about one-third of the species are also frequently found in the Western Tethys, documenting a passable Tethyan Seaway for nearshore molluscs. A considerable provincialism is evident as well. The expected turnover during the Early Miocene, due to the closing of the Tethyan Seaway, is reflected in the Miocene assemblages. Surprisingly, however, the cut appears very early, i.e. already during the Aquitanian, when the West–East interrelation drops to zero despite the passage having been open during this interval. In contrast, the Burdigalian assemblages witness a minor re-appearance of Western Tethys taxa, suggesting the re-establishment of rather ineffective migration pathways prior to the final closure of the Tethyan Seaway. Cerithium bermotiense and Lyria (Indolyria) maniyaraensis are introduced as new species.