Ammonite succession at the Bajocian/Bathonian boundary in the Cabo Mondego region (Portugal)

The Cabo Mondego outcrops exposed along the cliffs, on the western margin of the Iberian Plate, show an expanded stratigraphic section of Lower Bathonian deposits containing abundant ammonoids. Upper Bajocian deposits correspond to similar facies, of muddy limestones alternating with marlstones, although ammonoids are scarce. A detailed succession of ammonites across the Bajocian/Bathonian boundary has been recognized at Cabo Mondego, which can form a useful bio‐ and chronostratigraphic standard for the Lusitanian Basin. The revision of previous collections from the classical section and new field samplings of two other separate sections allow the recognition through up to twenty metres of thickness, the highest zone of Bajocian (Parkinsoni Zone) and the lowest zone of Bathonian (Zigzag Zone). The Parkinsoni and the Zigzag zones established for NW European areas and belonging to the Northwest European Province, can be identified in the Lusitanian Basin, although the ammonite fossil assemblages are composed of Submediterranean taxa. However, a subdivision of the Parkinsoni Zone is not possible, due to the scarcity of well preserved ammonoids. The Zigzag Zone can be recognized and characterized as composed of two subunits (Parvum and Macrescens subzones) as represented in diverse European basins of the Submediterranean Province. Ammonite fossil assemblages of the Parvum Subzone may be grouped into two successive horizons, which are biochronostratigraphically equivalent to the subdivisions of the Convergens Subzone distinguished in the Digne‐Barrême area (SE France). New biochronostratigraphic data on the Bigotitinae, youngest members of Leptosphinctinae and oldest members of Zigzagiceratinae are relevant in understanding the evolution and faunal turnover of the West Tethyan Perisphinctidae during earliest Bathonian. The ammonite succession at the Bajocian/Bathonian boundary in the Cabo Mondego region (Portugal) represents one of the most complete biostratigraphic records so far recognized on the Iberian Plate.     

The Early Cretaceous of North-East Greenland: A crossroads of belemnite migration

Recent field work in Lower Cretaceous successions of Traill Ø and Wollaston Forland, North-East Greenland, have resulted in c. 2350 belemnite guards collected bed-by-bed from the upper Ryazanian – Hauterivian. The most common belemnite genera observed, Acroteuthis, Pachyteuthis, and Cylindroteuthis are of boreal-arctic affinities and closely related to NW European and Siberian faunas. Other taxa, including Hibolithes (common), Pseudobelus (relatively common) and Duvalia (rare), show faunal links to both NW European and Mediterranean faunas. This paper describes and discusses these findings in their taxonomic, biostratigraphic, palaeobiogeographic, palaeoecologic and palaeoceanographic context. In particular, the occurrence of Pseudobelus which is common in the circum Mediterranean area, is remarkable since it is the first observation of this Tethyan genus in the entire Boreal Realm. The palaeoecological interpretation of these observations result in the recognition of four different palaeobiogeographic belemnite assemblages for the Boreal Realm: 1) North-East Greenland, 2) Spitsbergen, 3) NW Europe and 4) Siberia. In contrast to the other assemblages, the belemnite faunas of North-East Greenland consist of a) Boreal-Arctic elements, b) Boreal-European taxa, c) endemic belemnites of Tethyan ancestry, and d) Tethyan species. These findings make North-East Greenland part of an immigration route from the Tethyan Realm via the north Atlantic to the high Boreal. This allowed Tethyan species, which are otherwise unknown from the Boreal Realm, to reach North-East Greenland. The occurrence of the Tethyan genus Pseudobelus in North-East Greenland also supports the interpretation of this taxon as a hemipelagic dweller, capable of crossing major distances. The belemnite patterns further suggest the existence of a proto Gulf-stream, documenting a south-to-north flow of warm surface waters as far north as Greenland already in the earliest Cretaceous (Valanginian). This has substantial implications for the interpretation of Early Cretaceous climate and oceanic current systems, as well as for the palaeobiology of belemnites.     

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.     

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.     

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.     

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.     

Nouvelles datations (Hauterivien supérieur–Barrémien inférieur) dans les « Couches rouges » continentales du Haut Atlas central marocain ; conséquences sur l’âge du magmatisme et des structurations mésozoïques de la chaîne Atlasique

In the Moroccan Central High Atlas, between the Bathonian and the Aptian, marine deposits are present in three continental formations. Known to be unfossiliferous for the main part, they are attributed to the Middle Jurassic or to the Lower Cretaceous, depending on the authors. Charophytes from the top of the second formation (Iouaridene Fm), and from the base of the third one (Jbel Sidal Formation), give an Upper Hauterivian–Lower Barremian age. Thanks to these biostratigraphical data, it has been possible to distinguish the different phases of the magmatic activity and the synsedimentary tectonic events, either linked to the closure of Tethyan Atlasic troughs during the Bathonian or associated with the development of the new basins, diachronous in the Atlasic Belt, during the Lower Cretaceous.     

西藏北部安多地区中侏罗统(巴通阶-卡洛夫阶)菊石

最近从藏北安多地区中侏罗统发现较丰富的菊石类化石,巴通期的菊石有OxyceritesoppeliElmi,Ho moeoplanulitescf. homoeomorphus(Buckman),H. cf. acuticosta(Roemer), Choffatiacf. vicentiMangold, Siemiradzkiacf. matisconensis(Lissajous), Proceritessp., Neuquenicerascf. yokoyamaiKobayashiandFukada和Indosphinctessp.。卡洛夫期的菊石有Oxyceritescf. subcotarius(Oppel), Macrocephalites? sp., Homoeoplanulitescf. furculus(Neumayr),Indospinctes(Elatmites) cf. reveliMangold和Reineckeitessp.。其中Indosphinctes,Indospinctes(Elatmites),Neu queniceras,Siemiradzkia和Procerites等属(或亚属)在西藏北部地区为首次报道。安多地区中—晚巴通期和早卡洛夫期菊石动物群凸现较强的地方性色彩; 晚巴通期ORBIS菊石带和早卡洛夫期KOENIGI菊石带是藏北地区菊石动物群扩散的重要时期。     

New species of Franchia and Protozigzagiceras (Ammonoidea,Middle Jurassic): the phyletic origin of Zigzagiceratinae

Three genera and seven species belonging to the subfamily Zigzagiceratinae (family Perisphinctidae) are described from the Lower Bathonian of France and Saudi Arabia. Intraspecific dimorphism is recognized. A revision of the genus Franchia proposed by Sturani (1967), based on the syntypes and new specimens from south‐east France, is presented. Franchia arkelli Sturani, Franchia subalpina sp. nov., Protozigzagiceras torrensi (Sturani), Protozigzagiceras tethycum sp. nov., Protozigzagiceras flexum sp. nov. and Protozigzagiceras densum sp. nov. are described from the Digne–Castellane region of south‐east France. Megazigzagiceras subarabicum, gen. et sp. nov. is described from the Dharma region of Saudi Arabia. The successive Early Bathonian species of Franchia and Protozigzagiceras herein identified in West Tethyan areas, as members of the Mediterranean–Caucasian Subrealm, formed lasting separate peramorphoclines characterized by increasing hydrodynamic coiling of the shell. In contrast, rapid proterogenesis originated and diversified the earliest Bathonian zigzagiceratin lineages, giving paedomorphic members, commonly neotenic and more scarcely progenetic. Procerites–Siemiradzkia seems to be the oldest zigzagiceratin member in the French Subalpine, Iberian and Lusitanian basins, branched off by paedomorphosis from leptosphinctins at the Bajocian–Bathonian transition. The Mediterranean–Caucasian genera Franchia, Zigzagiceras, Zigzagites and Wagnericeras branched from successive species of Protozigzagiceras, in turn, a direct derivative of Procerites. The oldest lineages of the clade Zigzagiceratinae evolved by iterative, rapid, paedomorphic changes and additional, lasting, peramorphic modifications during the Early Bathonian.     

Tithonian-Berriasian foraminiferal faunas from the Torinosu-type calcareous blocks of the southern Kanto Mountains, Japan: their implications for post-accretionary tectonics of Jurassic to Cretaceous terranes

The Torinosu-type limestones, having many lithologic characters showing their original deposition on shallow shelves, are widely distributed in the Jurassic to Cretaceous terranes of Japan. The foraminiferal faunas from the Jurassic to the lowermost Cretaceous of Japan were first revealed in the calcareous blocks of the southern Kanto Mountains. Distinguished microfaunas consist of 39 species including many marker species of the Upper Jurassic to Lower Cretaceous in Europe, West Asia, and North Africa such as Melathrokerion spirialis, Charentia evoluta, Freixialina planispiralis, Nautiloculina oolithica, Everticyclammina cf. virguliana, Haplophragmium lutzei and Pseudocyclammina lituus. These faunas suggest a Tithonian to Berriasian age of Torinosu-type limestones. They are contained in four tectonostratigraphic units (Kamiyozawa, Hikawa and Gozenyama Formations; Ogouchi Group) continuously accreted from Middle Jurassic to Late Cretaceous. The younger deposition age of Torinosu-type limestones than the accretion age (Bajocian to Bathonian) in the Kamiyozawa Formation and their older age than the accretion age of the Ogouchi Group (late Albian to middle Maastrichtian) are important to date the post-accretionary tectonics of Jurassic to Cretaceous terranes of Japan and to explain the emplacement process of Torinosu-type limestones.     

New data from Oman indicate benthic high biomass productivity coupled with low taxonomic diversity in the aftermath of the Permian–Triassic Boundary mass extinction

A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daffah conglomerate in eastern Oman (Batain), which provides new insights into the ecology and diversity during the early aftermath of the Permian–Triassic Boundary mass extinction. Based on conodont quantitative biochronology, we assign a middle Griesbachian age to the upper part of this boulder. It was derived from an offshore seamount and yielded both nektonic and benthic faunas, including conodonts, ammonoids, gastropods and crinoid ossicles in mass abundance. This demonstrates that despite the stratigraphically near extinction at the Permian–Triassic Boundary, Crinoidea produced enough biomass to form crinoidal limestone as early as middle Griesbachian time. Baudicrinus, previously placed in Dadocrinidae, is now placed in Holocrinidae; therefore, Dadocrinidae are absent in the Early Triassic, and Holocrinidae remains the most basal crown‐group articulates, originating during the middle Griesbachian in the Tethyan Realm. Abundant gastropods assigned to Naticopsis reached a shell size larger than 20 mm and provide another example against any generalized Lilliput effect during the Griesbachian. Whereas the benthic biomass was as high as to allow the resumption of small carbonate factories, the taxonomic diversity of the benthos remained low compared to post‐Early Triassic times. This slow benthic taxonomic recovery is here attributed to low competition within impoverished post‐extinction faunas.     

The two Early Toarcian (Early Jurassic) extinction events in ammonoids

The Early Toarcian (Early Jurassic) biological crisis was one of the ‘minor’ mass extinctions. It is linked with an oceanic anoxic event. Fossil data from sections located in northwestern European (epicontinental platforms and basins) and Tethyan (distal, epioceanic) areas indicate that Late Pliensbachian–Early Toarcian ammonoids experienced two extinction events during the Early Toarcian. The older one is linked with disruption of the Tethyan–Boreal provinciality, whereas the younger event correlates with the onset of anoxia and corresponds with the Early Toarcian mass‐extinction event. These two extinctions cannot be interpreted as episodes of a single, stepwise, event. Values of the net diversification, more than the number of extinctions, allow the two extinction events to be clearly recognized and distinguished. Values of regional net diversification for northwestern European and Tethyan faunas point to greater evolutionary dynamics in the epioceanic areas. The inclusion of Mediterranean faunas in the database proves that the ammonite turnover at the Early Toarcian mass‐extinction event was more important than previously thought. Progenitor (evolute Neolioceratoides), survivor (Dactylioceras, Polyplectus pluricostatus) and Lazarus (Procliviceras) taxa have been recognized. Different selectivity patterns are shown for the two events. The first one, linked to the disruption of the Tethyan–Boreal provinciality, has mainly affected ammonites adapted to epicontinental platforms. In the mass‐extinction event, no selectivity is recognized, because also Phylloceratina and Lytoceratina were deeply affected at species level, although their wide biogeographical distribution at clade level was a significant buffer against extinction. In contrast to Palaeozoic mass extinctions, ammonoid survivors and Lazarus taxa are characterized by complex sutures: Phylloceratina (long‐ranging ammonoids) and Polyplectus (relatively long‐ranging compared to other Ammonitina).     

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.     

Répartition stratigraphique et biozones des kystes de dinoflagellés au passage Jurassique moyen–Jurassique supérieur (Bathonien supérieur–Oxfordien inférieur) dans le Bassin de Guercif,Maroc nord-oriental

Despite the stratigraphical significance of dinoflagellate cysts as reliable markers for correlating and dating Jurassic–Cretaceous strata, investigations into this palynomorph group in the southern Tethyan Realm, specifically northwest Africa, are sparse and somewhat parochial. Most research on Jurassic dinoflagellate cysts is focussed on European depocentres in the Boreal and Sub-Boreal realms. This study is on biostratigraphical data from two petroleum boreholes (MSD1 and KDH1) drilled during 1985 in the Guercif Basin, northeast Morocco by ONAREP (Office National de Recherche et d’Exploitation Pétrolier), now ONHYM (Office National des Hydrocarbures et des Mines). These boreholes penetrated a thick siliciclastic succession, attributed to the Middle and Upper Jurassic, below Miocene marls. Over sixty dinoflagellate cyst taxa were identified. Four dinoflagellate cyst biozones, named GI to GIV, are established for the late Bathonian to early Oxfordian interval. These biozones are defined on the basis of the first appearance datum (FAD) and/or the last appearance datum (LAD) of some biomarker taxa which have wide geographical distributions. These are: Ctenidodinium combazii and Ctenidodinium sellwoodii for the GI Biozone (late Bathonian–early Callovian); Ctenidodinium continuum and Meiourogonyaulax caytonensis for the GII Biozone (middle Callovian); Gonyaulacysta centriconnata and Wanaea thysanota for the GIII Biozone (late Callovian–earliest Oxfordian); and Liesbergia liesbergensis and Systematophora penicillata for the GIV Biozone (early Oxfordian). These biozones are correlated to those already established for the respective intervals in other palaeogeographic regions, such as the Boreal, Sub-boreal and Tethyan realms.     

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.     

Les Pachyerymnoceras (Pachyceratidés,Périsphinctacés,Ammonites) du Callovien moyen et supérieur de la région de Saida (Algérie occidentale). Origine phylétique et biogéographie des Pachyceratidés

The genus Pachyerymnoceras, with four new species,is described for the first time in Western Algeria. The genus first appears in the Middle Callovia (Coronatum Zone) as in Saudi Arabia. It is represented in the Saida region by uncommon P. praecox nov. sp. followed during the Upper Callovian (Athleta Zone) by specimens belonging to P. flamandi sp. nov., P. kmerense nov. sp. and P. saidense nov. sp. Every species is represented by a dimorphic pair.Pachyceratidae are put into Perisphinctaceae. If Pachyerymnoceras arises from Erymnoceras, a genus suddenly appearing during the Middle Callovian on northern and southern Tethyan borders, the origin of Erymnoceras is still unknown. Three phylogenetic hypothesis are considered here. Erymnoceras may have evolved during Lower Callovian: 1) from serpenticonic Tethyan Pseudoperisphinctinae like Choffatia (Subgrossouvria); 2) from Tulitids via ellipticoncic Bullatimorphites (Kheraiceras); 3) through a double lineage arisen in Subboreal and Tethyan platyconic Proplanulitids.Pachyceratids have a wide paleobiogeographic distribution in NW Europe and on the Tethyan margins. The genus Pachyerymnoceras evolves in Ethiopian Province of the Tethyan Realm. Some species migrate into Indo-Malagasian Province and others, through the south Tethyan border came to Europe were they are found restricted to Upper Callovian (Athleta and Lamberti Zones). Therefore this migration has a duration of two or even three zones.     

Ostracods of the genus Palaeocytheridea Mandelstam in the Middle and Upper Jurassic of Europe: 3. Stratigraphy and paleobiogeography

The analysis of distribution of endemic and cosmopolitan ostracods of the genus Palaeocytheridea shows that, in the Bajocian and Bathonian, the Tethyan and Boreal-Atlantic regions of Western and Eastern Europe developed in partial isolation, while beginning from the middle of the Lower Callovian, these parts of the European paleobasin were connected. For the Middle Jurassic of Western and Eastern Europe and, in particular, for Ukraine, the ostracod zones are recognized based on stratigraphic distribution of species of the genus Palaeocytheridea.     

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.     

A new tribe of dictyoclostid brachiopods from the Lower Permian of the Tarim Basin,north-west China

Several finely capillated brachiopod genera are re-examined based on new material obtained from the Lower Permian of the Tarim Basin, north-western China and previously published information. A new genus, Tarimoplecta, is proposed. Comparison with other related genera reveals that Liraplecta Jin and Sun and Tarimoplecta gen. nov. represent a new tribe, Liraplectini, of the Dictyoclostidinae Stehli. The stratigraphical and geographical distributions of both LiraplectaTarimoplecta indicate that they are restricted to the Sakmarian to Kungurian (Lower Permian) of the Tethyan Realm. Four species are described herein: Liraplectapaojianggouensis sp. nov., L. richthofeni (Chao), L. apsera (Wang), and Tarimoplecta tarimensis gen. et sp. nov.     

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.