Ammonite Fauna Research Articles

Upper Frasnian Tornoceratidae (Ammonoidea) from the Sand Formation (Bergisch Gladbach-Paffrath Syncline, Rhenish Massif)

Excavations in the Sand district of Bergisch Gladbach (Rhenish Massif, Germany) yielded a rich ammonoid fauna of the upper Frasnian “Archoceras” varicosum Zone (Upper Devonian I-K, interval between the two Kellwasser levels). The previously unknown assemblages include six tornoceratid genera with 20 species, including seven new species (Aulatornoceras steinhauseni sp. nov., Aul. frenklerae sp. nov., Aul. ventrosulcatum sp. nov., Crassotornoceras nudum sp. nov., Cr. hetzeneggeri sp. nov., Retrotornoceras juxi sp. nov., Tornoceras aequilobum sp. nov.) and taxa described in open nomenclature. There are five associated gephuroceratid genera with nine species. The unexpectedly high genus- and species-level diversity at Sand, supported by statistical indices, is unprecedented compared to other contemporaneous ammonoid faunas. It highlights the currently fragmentary knowledge of top-Frasnian ammonoid faunas on a global scale. Phoenixites frechi, the dominant tornoceratid of hypoxic and organic-rich Kellwasser facies of Europe and North Africa, is completely missing at Sand. The local assemblage structure is analyzed statistically and interpreted in terms of palaeoecology. The occurrence of a new type of “Housean Pits”, probably caused by parasitism, is found in nine species of five genera, mostly in tornoceratids. The Sand fauna indicates that the species origination rate in tornoceratids remained high after the Lower Kellwasser Event.

The late Pliensbachian (Early Jurassic) ammonoidAmaltheusin Japan: systematics and biostratigraphic and paleobiogeographic significance

AbstractThe genusAmaltheus, one of the representative late Pliensbachian ammonoids, has biostratigraphic and paleobiogeographic significance in Japan. Four species,Amaltheus stokesi(Sowerby, 1818),A. margaritatusde Montfort, 1808,A. repressusDagis, 1976, andA. orientalisnew species, have been found in the Kuruma Group in central Japan;A. stokesiandA. margaritatusare also from the Toyora Group in southwest Japan. On the basis of taxonomic analysis of the genusAmaltheus, we distinguish two successive ammonoid biozones in the lower part of the Teradani Formation of the Kuruma Group: theAmaltheus stokesi–Amaltheus repressusand theAmaltheus margaritatusassemblage zones, in stratigraphic ascending order. This study also establishes the presence of theAmaltheus stokesiAssemblage Zone in the Higashinagano Formation of the Toyora Group. Thestokesi–repressusand thestokesiassemblage zones correspond biostratigraphically to theAmaltheus stokesiStandard Subzone of themargaritatusZone. ThemargaritatusAssemblage Zone is correlated with theAmaltheus subnodosusandAmaltheus gibbosusstandard subzones. The Japanese early–middle late Pliensbachian ammonoid faunas are composed almost entirely of pan-Boreal and Arctic species of the genusAmaltheus. This faunal composition has an affinity with that of the Northeast Russian region, and thus suggests a strong paleobiogeographic relationship between East Asian and Northeast Russian faunas throughout this time interval.UUID:http://zoobank.org/5F08121F-1DAF-4B24-BCBE-B08F7101CF29

New Advances in Biostratigraphy of the Lower/Middle Norian Transition: Conodonts of the Dov\u0161ko Section, Slovenia

This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dovško Section in Slovenia, which represents the eastern part of the Slovenian Basin. The age of the section ranges from the Lacian 1 to the Alaunian 1. The Lacian part of the succession is predominantly characterized by the representatives of the genus Ancyrogondolella. Transitional morphologies towards Alaunian faunas first appear in the Lacian 3 and become common during the Lacian-Alaunian transition. This evolutionary development coincides with a shift in microfacies from a dominantly radiolarian-bearing mudstone-wackestone-packstone to a filament- dominated wackestone-packstone, and the formation of small neptunian dykes, which may reflect environmental perturbations and/or a change in basin geometry. The proliferation of the genera Epigondolella and Mockina is observed in the Alaunian part of the section, though the genus Ancyrogondolella is still present in this interval. Systematic description of the conodont taxa is provided, and seven new species and two new subspecies are established. The new advances will be of great value in further biostratigraphic studies, especially in areas without ammonoid faunas, and in the reconstruction of the paleogeography of the Slovenian Basin.

UPPER KIMMERIDGIAN AND TITHONIAN AMMONITES FROM THE TUNISIAN "DORSALE" (NE TUNISIA): UPDATED BIOSTRATIGRAPHY FROM THE JEBEL OUST

In the context of updating biostratigraphic analysis in the Upper Kimmeridgian-lowermost Berriasian from the whole of the Tunisian Dorsale (NE Tunisia), new results obtained from the Jebel Oust reference section are presented. The bed-by-bed-sampling of a rather rich ammonite fauna gathered in the two most favourable profiles in the area allowed to propose, for the first time, a biozonation for Upper Kimmeridgian to Tithonian limestones. Calpionellids relayed or completed ammonite assemblages, and were also useful for biostratigraphy in beds close to the Jurassic-Cretaceous boundary. The composition of ammonite assemblages, as well as the known ranges for genera and species, is in accordance with the available information from epioceanic areas in West-Mediterranean Tethys. The recognized biozones fit the standard proposal given by Groupe Francais D'Etude du Jurassique in 1997. Age-interpretation for turbiditic horizons in the Jebel Oust is made for the first time. In spite of some limitations, the biostratigraphic results obtained in Jebel Oust sections provide a valuable tool for potential correlations with poorly known sections in northern Tunisia, as well as with other Tethyan areas.

Aptian (Lower Cretaceous) ammonite fauna of the Todai Formation, Nagano Prefecture, Japan

Twenty Aptian ammonite species including one new genus (Inaptychoceras) three new species (Hulenites kitamurai, Inaptychoceras koikei and Parahoplites inaensis) from the Todai Formation, central Japan, are described. The ammonite fauna of the Todai Formation can be divided into one horizon and two ammonite biostratigraphic zones (Aconeceras (A.) sp. Horizon, Epicheloniceras cf. claudii Zone and Diadochoceras nodosocostatiforme Zone, in ascending order), which are defined. This horizon and the two zones are correlated with the upper Aptian of the ammonite standard zonation in the west Mediterranean Province and the Tethyan Realm, and with the upper Aptian succession of England, Georgia and North Caucasus. The Diadochoceras nodosocostatiforme Zone of the Todai Formation corresponds to both Hypacanthoplites subcornuerianus and Diadochoceras nodosocostatiforme zones of the Miyako Group in Japan. The succession from the Aconeceras (A.) sp. Horizon to the Epicheloniceras cf. claudii Zone correlates with the succession beneath of the Hypacanthoplites subcornuerianus Zone of the Miyako Group. The ammonite fauna of the Todai Formation includes ornate planispiral forms, smooth or weakly ornate planispiral forms and heteromorph forms. There are almost an even ratio of morphotypes, and are similar to that of the Aketo Formation of the Miyako Group.

Cephalopods from the Cretaceous-Paleogene (K-Pg) Boundary Interval on the Brazos River, Texas, and Extinction of the Ammonites

We report on new collections of cephalopods (ammonites and nautilids) from the Cretaceous-Paleogene (K-Pg) successions of the Corsicana and Kincaid formations exposed along the Brazos River in Falls County, Texas. An abundant fauna of eight species comprising four genera of ammonites is described from the Corsicana Formation, including Discoscaphites mullinaxorum n. sp. The presence of abundant aptychi (probably lower jaws) of Discoscaphites and Eubaculites, as well as juvenile specimens, indicates a living population that experienced little postmortem drift. The lytoceratid genus Gaudryceras is also reported for the first time from the Brazos River area. Presence of the index taxon Discoscaphites iris (Conrad, 1858) indicates that the fauna belongs to the D. iris Range Zone, the highest ammonite range zone in North America. Correlation with new and existing microfossil data indicates that the fauna represents the uppermost Maastrichtian, and comparison with published records further suggests that this is the most diverse D. iris Zone fauna yet reported from the Gulf and Atlantic Coastal Plains of North America. Three ammonite genera are recorded from the basal units of the K-Pg event deposit at Brazos, which likely represents deposition in the immediate aftermath of the Chicxulub impact event. A single specimen of the nautilid Eutrephoceras is reported from the Danian Kincaid Formation, less than 300 kyr after the K-Pg boundary. These data provide new information on the differing fate of these cephalopod groups during the K-Pg mass extinction and add to the picture of diverse and abundant Maastrichtian ammonite faunas prior to the Chicxulub impact event.

A summary of the Jurassic System in North and East-Central Iran

The rocks of the Jurassic System in North and Central Iran are represented by very thick sedimentary successions reflecting the deposition during two tectono-stratigraphic megacycles, bounded by three important unconformities. The older (Early to early Middle Jurassic) cycle starts, after the Late Triassic closure of the Palaeotethys and the collision of the Iran Plate with the southern margin of Eurasia (Turan Plate), with an abrupt uplift of the Cimmerian Mountains around the Triassic–Jurassic boundary (Main-Cimmerian Event) and is terminated by the Mid-Cimmerian Tectonic Event in the mid-Bajocian. The predominantly siliciclastic sediments of this tectono-stratigraphic cycle are accommodated in the Ab-e-Haji Subgroup of the (upper) Shemshak Group. The Ab-e-Haji Subgroup consists of thick and widespread, partly coal-bearing siliciclastic strata and also records some important marine ingressions, especially in the Toarcian and Aalenian. The younger tectono-stratigraphic cycle starts with an extensive marine transgression in the Late Bajocian and ends around the Jurassic-Cretaceous boundary with the Late Cimmerian Tectonic Event. In the aftermath of the Mid-Cimmerian Tectonic Event, the Iran Plate was dissected into several structural units, the geological histories of which differed and so did their facies patterns. Thus, in North Iran two main sedimentary areas developed, namely the Alborz and Koppeh Dagh basins, which show moderate diffe-rences in lithology and thicknesses. However, the differentiation is much more pronounced on the Central-East Iranian Microcontinent, which comprises three N–S-oriented and independent structural units, i.e., from east to west the Lut, Tabas and Yazd blocks. During the Jurassic Period, the sea mostly covered the Tabas and Lut blocks, whereas the Yazd Block remained largely emergent. The lithologically diverse and numerous formations of the area are combined in the Magu and Bidou groups. Early to Early Middle Jurassic ammonite fau-nas of North and Central Iran are palaeobiogeographically closely related to Northwest European (Subboreal) ammonite faunas, allowing a similar biozonation. Concurrent with the Late Bajocian transgression, there is an abrupt change in faunal composition and the Middle and Late Jurassic ammonite faunas of North and Central Iran are much more similar to those of epicontinental seas bordering the nort-hern margin of the western Tethys and occupy an intermediate position between the Mediterranean and the Submediterranean Province. The results of the studies on ammonoid palaeobiogeography are in line with Early Jurassic palaeogeographic reconstructions that place the Iran Plate at fairly high palaeo-latitudes of about 45°N, followed by a rapid southward shift throughout the Middle and Late Jurassic to a position of about 30°N.

Callovian and Kimmeridgian fossils and stratigraphy of the Blue Nile Basin (central western Ethiopia)

A refined, stratigraphic and biostratigraphic framework for Ethiopia has a strong bearing on the Jurassic sedimentary evolution, not only for the Horn of Africa, but also for the North African region. The present contribution provides an updated Callovian–Kimmeridgian stratigraphy and biostratigraphy, on the basis of the occurrences of age-diagnostic ammonites from Dejen (Blue Nile Basin; central western Ethiopia). Here, the late Callovian (Lamberti Zone) ammonite Pachyceras cf. lalandeanum (d’Orbigny) is associated with the nautiloid Paracenoceras cf. giganteum (d’Orbigny). The early Kimmeridgian Orthosphinctes aff. tiziani (Oppel) is associated with the nautiloids Paracenoceras cf. kumagunense (Waagen) and P. cf. ennianus (Dacqué) and a large gastropod Purpuroidea gigas (Étallon). The previously recorded middle Callovian ammonite Erymnoceras cf. coronatum (Bruguière) is associated with the now recorded P. gigas (Étallon). Additionally, the age of the Antalo Limestone Fm is also reassessed on the basis of the ammonite records from the three basins – Ogaden, Blue Nile and Mekele. The Ogaden Basin strata span from the late Callovian to the late Tithonian (from ammonite records), the Blue Nile Basin from the early Callovian to the late Tithonian (calcareous nannofossils) and the Mekele Basin from the uppermost middle Oxfordian to the early Kimmeridgian (ammonite records). However, the upper age assignments should be considered tentative, as much of the previously recorded Oxfordian–Kimmeridgian ammonite fauna needs taxonomic re-evaluation and precise resampling. Contextually, it should be mentioned that in all the three sedimentary basins, the top part of the Antalo Limestone Fm did not yield any ammonites.

The Kimmeridgian of the south-western margin of the Holy Cross Mts., central Poland: stratigraphy and facies development. Part I. From deep-neritic sponge megafacies to shallow water carbonates

The stratigraphical interval of the Kimmeridgian between the Bimammatum and the Hypselocylum zones in the SW margin of the Holy Cross Mts. shows a transition from the open shelf deep-neritic sponge megafacies to the shallow-water carbonate platform, including its development and decline. The uniform progradation of the shallow-water carbonate platform occurred at the end of the Planula Chron. Development of the shallow-water carbonate platform was controlled by climatic and tectonic factors. The former induced by orbital cyclicity resulted in changes of sea-level, revealed i.a. by the incoming of open-marine ammonite faunas, the latter were related to the synsedimentary activity of faults which resulted in contrasted facies changes. The episodically occurring strong influx of siliciclastic material was at least partly controlled by the tectonic activity. The newly elaborated formal lithostratigraphic subdivision takes into account the facies development of the succession in relation to climatically and tectonically induced changes. Such is e.g. the Małogoszcz Oolite Formation, corresponding to a single 100-kyr eccentricity cycle from the late Platynota Chron to the earliest Hypselocyclum Chron, bordered from the base and top by two transgressive climatically-controlled levels. The final stage of the shallow-water platform development at the end of the Hypselocyclum Chron was marked by the successive limitation of restricted environments, and the appearance of more open-marine conditions related to tectonic subsidence of the area of study. Comparison between the carbonate platform development of the Holy Cross Mts. in central Poland, and the coeval shallow-water carbonates of the Jura Mts. in northern Switzerland and south-eastern France provides an opportunity to consider similarities in the successions which can be attributed to the climatically-controlled sedimentary cyclicity and/or the wide-ranged tectonic phenomena. The palaeontological part of the study gives comments on the classification and phylogeny of ammonites of the families Ataxioceratidae and Aulacostephanidae.

Bilinguites — a cosmopolitan Late Carboniferous ammonoid genus

The Bashkirian (Late Carboniferous) ammonoid genus Bilinguites has a nearly global distribution in the tropical and subtropical zones and 25 species have been described up till now. Most of them are considered endemic, but some may have a wide geographic distribution. Our study on new and previously collected materials from North China (Gansu and Ningxia) shows that the stratigraphically youngest species of Bilinguites in North China and Western Europe are morphologically very similar, possibly indicating correspondence of the ammonoid faunas. Bilinguites scalpratus is revised and established as a stratigraphically important species of the genus in North China; it co-occurs with the first gastrioceratid species Cancelloceras pachygyrum. This occurrence can be correlated with the Western European co-occurrence of Cancelloceras cancellatum and Bilinguites superbilinguis at the base of the G1 Zone.

Lower Cretaceous heteromorph ammonites (Ancyloceratina) from Leše near Prevalje (North Karavanke Mts. NE Slovenia)

The paper deals with newly discovered Valanginian-Hauterivian fauna of heteromorphic ammonites (Ancyloceratina) from locality south of the village of Leše above the Meža River valley (North Karavanke Mountains). Fossils were recovered from the pelagic limestone. Among the studied heteromorphic ammonites are Lower Cretacaoeus species Himantoceras trinodosum (Upper Valanginian) and Crioceratites cf. nolani (Hauterivian). Based on the accompanied ammonites (Ammonitina) from the outcrop, we biostratigraficaly confirm the presence of Lower Cretaceous ammonites fauna in the Northern Karavanke Mountains. This is also the first report on heteromorphic ammonites in Slovenia.

Cenomanian (early Late Cretaceous) ammonoid faunas of western Europe. Part I: Biochronology (unitary associations) and diachronism of datums

Biochronological data of Cenomanian ammonoid faunas of Western Europe are analyzed for three well-documented basins: the Vocontian Basin in southeastern France, the Mnster Basin in Germany, and the Anglo-Paris Basin. A taxonomically standardized data set is constructed for these three basins and includes more than one hundred species and is analyzed with the deterministic Unitary Association Method. Data for each basin are first processed separately, thus yielding three regional biochronological zonations. Then, the three regional sequences are processed together as a three- section data set for the construction of the inter-basin sequence. The latter comprises 24 unitary associations grouped in eight zones for the Cenomanian Stage. These results take into account species that co-occur in time and space (real coexistence), those that only co-occur in time (virtual coexistence), and those that do not co-occur in space nor in time (exclusion of chronological significance). At the paleogeographical scale of Western Europe, this new zonation is in good agreement with the widely used standard zonation, but its resolution is three times higher. This demonstrates the benefits of applying the Unitary Association Method, even to a taxonomic group which is traditionally acknowledged as one of the leading group in dating Mesozoic marine rocks. It also highlights the variable completeness and resolution of the faunal record through space and time, and reveals that a substantial number of the taxa (47%, inclusive of some indexes) have a diachronous distribution across these three Cenomanian basins. However, even with such an enhanced time resolution, no preferred orientation of the diachronous taxa emerges, suggesting that none of these basins seemed to have functioned as a paleobiogeographical source or sink. The absence of any preferred direction of the diachronism of the datums is most likely explained by two, non-mutually exclusive causes: either a random distribution of the incompleteness of the faunal record and/or a common paleobiogeographical history of the faunas in the three basins.

Late Triassic to Early Jurassic radiolarian, conodont and ammonite assemblages from the Tavuscayiri block, Mersin Mélange, southern Turkey: Time constraints for the T/J boundary and sedimentary evolution of the southern margin of the northern Neotethys

The Mersin Mélange (northwest of Mersin city) includes a variety of large sedimentary blocks/tectonic slices of Palaeozoic and Mesozoic origins. Of these, the latter represents facial and tectonostratigraphic counterparts of the Beysehir-Hoyran Nappes (remnants of the northern Neotethys). The Tavuscayiri Block, located at the center of the mélange and close to the Orbuklukeli hill, is one of such Mesozoic occurrences, with a continuous pelagic sequence from the Upper Triassic to Lower Jurassic. At the Orbuklukeli hill, a succession of middle Norian to Toarcian age has been precisely dated, which starts with conodont assemblages for the Norian and Rhaetian and includes radiolarians for the upper Rhaetian. An acidic tuff layer corresponds to the T-J boundary, which passes above to an increasingly dominating chert-bearing limestone series, marking a gradually deepening-upward of the sequence. The early Hettangian radiolarians are poorly represented, but diverse and well-preserved radiolarians have been retrieved from the middle Hettangian to the Pliensbachian. A total of eighty-five taxa, including fourteen new species, have been determined. In addition to these, one new genus (Praeudalia Tekin, n. gen.) has been described from the Rhaetian part of the section. The top of the section is represented by nodular limestones in Ammonitico rosso facies, including a diverse Toarcian ammonite fauna. All lithologies of the Orbuklukeli section along the Tavuscayiri Block can be correlated with the previously described lithologies of the Kayabasi Group/Formation in the Bozkir Unit, and Gülbahar/Gümüslü units in the Lycian Nappes.

Early Asselian (Earliest Permian) Ammonoids from the Taishaku Limestone, Akiyoshi Belt, Southwest Japan: An Asselian Ammonoid Fauna of the Mid-Panthalassan Realm

An early Asselian ammonoid fauna comprising nine species belonging to nine genera (Agathiceras, Neoglaphyrites, Somoholites, Shumardites, Vidrioceras, Almites, Eoasianites?, Boesites and Metapronorites) and one indeterminable Adrianitidae is described from the Uyamanoro Formation of the Taishaku Limestone at Miharanoro in the Akiyoshi Belt (late Permian accretionary belt), Southwest Japan. The fauna includes four new species: Shumardites umbilicatus, Vidrioceras ellipticum, Almites hayasakai and Boesites biconcavus. The age of the fauna is determined to be early Asselian based on the fusulinoidean biostratigraphy. In addition to the previously known late Asselian taxa, the number of Taishaku Asselian ammonoid genera is now ten genera. This is the only known Asselian ammonoid fauna from the mid-Panthalassa Ocean. The ammonoid faunal composition of this region, the Mid-Panthalassa Realm, is closely related to those of Paleotethyan (Pamirs and South China), Uralian and American (eastern Panthalassa) realms.

The semimammatum and semiarmatum ammonite biohorizons (Late Oxfordian, Hypselum Zone) in the Upper Jurassic of Southwestern Germany

The Late Oxfordian ammonite faunas of the semimammatum and semiarmatum biohorizons are described, mostly based on material from the Impressamergel Formation of the Plettenberg Quarry near Dotternhausen (western Swabian Alb). 21 ammonite are recorded, including some previously undescribed from the Upper Jurassic of SW Germany. Previously, the semimammatum Biohorizon has been studied in Franconia, Western France and central Poland and the semiarmatum Biohorizon only in Western France, respectively. Compared to the semimammatum Biohorizon, the semiarmatum Biohorizon is characterized by a significant increase of Submediterranean and Tethyan taxa and a total decline of Subboreal ones. This phenomenon is interpreted as the result of a seawater warming trend towards the above following bimammatum Biohorizon, which correlates with the recently suggested Oxfordian/Kimmeridgian stage boundary. This article summarizes the current state of knowledge of the Hypselum Zone in SW Germany. A lectotype is designated for Richeiceras lochense (Oppel, 1863).

Upper Albian, Cenomanian and Upper Turonian ammonite faunas from the Fahdène Formation of Central Tunisia and correlatives in northern Algeria

Over 130 species are documented from the Upper Albian, Cenomanian and Upper Turonian Fahdène Formation and correlatives in Central Tunisia and northern Algeria, based on material described by Henri Coquand (1852, 1854, 1862, 1880), Léon Pervinquière (1907, 1910), Georges Dubourdieu (1953), Jacques Sornay (1955), and new collections. The material consists predominantly of limonitic nuclei, together with adults of micromorphs. There is no continuous record, and a series of faunas are recognised that can be correlated with the zonation developed in Western Europe. These are the Upper Albian Ostlingoceras puzosianum fauna, Lower Cenomanian Neostlingoceras carcitanense and Mariella (Mariella) harchaensis faunas, the upper Lower to lower Middle Cenomanian Turrilites scheuchzerianus fauna, Middle Cenomanian Calycoceras (Newboldiceras) asiaticum fauna, Upper Cenomanian Eucalycoceras pentagonum fauna, and the Upper Turonian Subprionocyclus neptuni fauna. Two new micromorph genera are described, Coquandiceras of the Mantelliceratinae and Cryptoturrilites of the Turrilitinae. Most of the taxa present have a cosmopolitan distribution, with a minority of Boreal, North American and endemic taxa.

New middle and late Smithian ammonoid faunas from the Utah/Arizona border: New evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin

New Smithian (Early Triassic) ammonoid assemblages were sampled near the Utah/Arizona border. They provide several spatiotemporal constraints on the regional Sinbad Formation showing that the extent of the Smithian sea in the southwestern-most part of the western USA basin is larger than previously expected, reaching northern Arizona and an area just east of Kanab in Kane County, Utah. This southwestern-most excursion of the sea in the western USA basin is part of the third order Smithian transgression-regression cycle, which is well-documented worldwide. These new spatiotemporal constraints also indicate that the Sinbad Formation spans the late middle to early late Smithian time interval in the studied area. The observed transgressive trend corresponds to the warm temperatures of the middle-early late Smithian and the regressive trend to the cooling phase spanning the Smithian-Spathian transition. Thus, the Sinbad Formation and its marine deposits are the direct result of global climatic fluctuations and related sea-level changes that occurred from the late middle Smithian to the Smithian-Spathian transition. This highlights the importance of the Sinbad Formation in untangling local and global changes occurring around the late Smithian, and thus in overcoming a major obstacle to the understanding of the biotic recovery after the Permian/Triassic boundary mass extinction. This also indirectly confirms that the western USA basin is a key area containing essential information for the understanding of the Early Triassic events. The taxonomic richness of late middle Smithian assemblages is much lower in the studied area than in the more northern localities. However, the occurring taxa confirm the known regional to global distribution of Smithian ammonoids, witnessing the major global environmental changes from the middle Smithian to the early Spathian.

The Upper Jurassic Faïdja Formation (Northwestern Algeria): Sedimentology, biostratigraphy and ichnology

The Faïdja Formation displays mixed siliciclastic-carbonate deposits distributed in three members, which are organised from bottom to top as follows: the Clayey Sandstone Faïdja Member; the Clayey Limestone Bel Aoura Member and the Sandy Claystone Douaouda Member. Sedimentological data indicate the evolution of a subsiding marine environment from the shelf edge to the lower shoreface, sporadically dominated by storms. New age based on recently collected ammonite fauna allowed us to update the age of the Faïdja Formation as Early-Late Kimmeridgian. Ichnological analysis reveals the occurrence of abundant and diverse invertebrate trace fossils, grouped in four ichnoassociations. Ichnoassociation -A- coincides with the lowermost part of the Clayey Sandstone Faïdja Member; it is distinguished by a combination of pre-graphoglyptids and post-depositional traces, ascribed to the distal Cruziana ichnofacies transitional to the Nereites ichnofacies, which indicates a lower offshore zone to shelf edge environment characterised by a low-oxygenated period (anoxic event), frequent storm events and nutrient frequency. Ichnoassociation -B- occupies the middle and upper parts of the Clayey Sandstone Faïdja Member, it is characterised by an abundance of post-depositional traces, corresponding to the archetypal Cruziana ichnofacies that indicates a lower to transitional offshore environment with short phases of low hydrodynamic energy. Ichnoassociation -C- corresponds to the Clayey Limestone Bel Aoura Member that coincides with a drastic facial change and depositional conditions; this association documents a proximal Cruziana ichnofacies, and indicates an upper to transitional offshore zone as a depositional environment. Finally, ichnoassociation -D- coincides with the Sandy Claystone Douaouda Member; it is ascribed to the proximal Cruziana ichnofacies, indicating a lower shoreface environment. The combined sedimentological and ichnological data indicates a relatively subsiding platform with shallowing upwards corresponding to distal, archetypal and proximal Cruziana ichnofacies, respectively.

Smithian (Early Triassic) ammonoid faunas from Timor: taxonomy and biochronology

Two extensive collections retrieved from West Timor have yielded several astonishingly well-preserved and highly diversified Smithian (Early Triassic) ammonoid faunas (Kashmirites fauna, Owenites fauna, Anasibirites fauna). A population approach on this material, with an emphasis on ontogeny and covariation of morphological characters, led to the unprecedented assessment of intraspecific variation for many species. Based on this, their synonymy is thoroughly discussed whenever possible. One new genus (Roopnarinites) and five new species (Paraspidites bicarinatus, Flemingites lidakensis, Subflemingites bihatiense, Baidites obesus and Churkites warei) are described. These results have a direct impact on the resolution and accuracy of biochronological correlations, as well as on the accuracy of diversity counts at the species level, which is important for potential future broad-scale diversity analyses. This material also provides highly valuable data for comprehensive biogeographical and phylogenetic studies hopefully to come. Finally, these new Timor data strengthen the singularly uniform biogeographical distribution of the Smithian ammonoid faunas within the Tethys. Keywords: Ammonoids; Early Triassic; Smithian; Timor

REMARKS ON THE SCYTHIAN-ANISIAN BOUNDARY

Different definitions of the Scythian—Anisian boundary are discussed. Based on taxa and sequence of Keyserlingites faunas at 19 Boreal localities and 6 Tethyan localities, Keyserlingites faunas are considered to be Late Sparhian in the Boreal province and Early Anisian in the Tethyan province. Keyserislingites not appropriate for cosmopolitan zoning. The base of Lenotropites—Japonites zone of Central Qinghai, China appears to indicate base Middle Triassic: it has abundant earliest Anisian ammonite faunas of mixed Boreal—Tethyan character (ecotone) providing direct correlation between these provinces.
 Correlations of Anisian (Aegean), Spathian and the Anisian—Scythian boundary are made between different localities, particularly between the Tethyan and Boreal provinces and between basin and platform facies. Olenikites zone is coeval to Subcolumbites zone; Lenotropites caurus zone to Lenotropites—Japonites zone; Columbites zone to Tirolites cassianus zone;and Subcolumbites zone to Tirolites carniolicus zone.
 Scythian—Anisian mixed faunas and stratigraphic condensation are also discussed.