Ammonite Fauna Research Articles

The oppeliid, perisphinctid and aspidoceratid ammonite faunas of the ‘Corallian’ Beds (Upper Jurassic) in Cambridgeshire, England

The Upware Limestone Member comprises an enclave of Middle Oxfordian ‘Corallian’ facies limestone situated on the East Midlands Shelf within the more typical mudrock-dominated sequences of eastern England, and is assigned to the West Walton Formation. Recent deep excavations in the district have revealed the base of the Upware Limestone, not exposed since the last century, resting on a mudrock sequence, the Dimmock’s Cote Marl Member. The Upware Limestone and Dimmock’s Cote Marl have yielded an unusually common ammonite fauna, including both Boreal (Cardioceratidae) and Tethyan (Perisphinctinae) elements, and rare Tethyian oppeliids and aspidoceratids. Thirteen nominal species of Perisphinctes are described and figured, as are one species of Neocampylites and one of Euaspidoceras . Three distinct assemblages of Perisphinctes are recognized in the Upware succession. The faunas are correlated with existing zonations for the Middle Oxfordian of Sub-Boreal and Sub-Mediterranean regions, including sub-subzonal schemes (i.e. ‘biohorizons’). Such correlations aid the construction of correlative links between two distinct ammonite provinces and have great potential for resolving some of the outstanding questions of European Middle Oxfordian stratigraphy. The succession is also of great importance within Britain as it is the only known locality to yield faunas that are stratigraphically intermediate between the classic Corallian assemblages of Oxford and the later faunas of the Upper Calcareous Grit of Yorkshire.

Barremian–Albian (Early Cretaceous) ammonite faunas of the Katsuuragawa Basin, southwest Japan

The Lower Cretaceous ammonite fauna of Japan was influenced by the Tethyan, Boreal and North Pacific realms with their oceanic current patterns and ammonite distributions. The hypothesis of oceanic circulation can be utilized to interpret the existence of the “Bering Strait” and the changing position of the “Boreal front,” that is the contact region of warm and cold-water masses. To understand such a system fully, a comprehensive understanding of the geographical distribution of ammonite faunas is required. The occurrence of twenty-five ammonite species, belonging to twenty genera, is confirmed in the Barremian to Albian of Japan. Of these, 24 species are described in this paper, including Barremites macroumbilicus sp. nov. The fauna can be divided into three associations, lower, middle, and upper, indicating late Barremian, late Aptian, and late Albian of the European standard zonation. The faunal characters suggest that the habitats of these ammonite faunas may have changed during later Early Cretaceous, with faunas characterizing three different environments, i.e., nearshore, intermediate, and distal shelf to upper slope setting. Ammonites of the lower association (late Barremian) are related to those of the Tethys, Boreal European, and circum-Pacific regions, and suggest that the Early Cretaceous Katsuuragawa Basin was deposited under the influence of currents from both high latitude and equatorial areas. The occurrence of Crioceratites (Paracrioceras) suggests that the Boreal European elements, including Simbirskites and Crioceratites (Paracrioceras), transited between Northwest Europe and Japan through the Arctic Sea, indicating that the Pacific Ocean was connected with the Arctic Sea at that time. The second association (late Aptian) is composed of ammonites of the Tethyan and circum-Pacific regions. As European Boreal ammonite taxa are absent in this association, it is concluded that the Pacific Ocean probably was not connected with the Arctic Sea at the time. Consequently, the “Boreal Front,” marking the contact between warm and cold water masses, was located at mid-latitude in the “Bering Strait” region during Barremian and subsequently moved northward during Albian. The uppermost ammonite association (late Albian) also consists of Tethyan and circum-Pacific taxa. Desmoceras (Pseudouhligella) poronaicum expanded its range with northward and eastward circulation of oceanic currents, suggesting the current must have represented a warm water-mass from the equator. The species subsequently migrated from the southern Katsuuragawa Basin to the Hokkaido area during late to latest Albian.

Upper Tithonian Himalayitidae Spath, 1925 (Perisphinctoidea, Ammonitina) from Le Chouet (Drôme, France): implications for the systematics

Abstract This contribution focuses on the late Tithonian ammonite faunas belonging to the Family Himalayitidae Spath in the key-section of Le Chouet (Drôme, France). The great majority of specimens from the Mediterranean Tethys, previously referred to Durangites Burckhardt, are now interpreted as juveniles and/or microconchs of the highly variable species Protacanthodiscus andreaei (Kilian). Moreover, comparison between specimens from France, Spain and Bulgaria formerly assigned to Durangites astillerensis Imlay and the type material of this species, supports the introduction of Boughdiriella chouetensis gen. nov. et sp. nov. Further, the revision of the type specimens of D. astillerensis and Durangites of the D. vulgaris group shows that the former species deserves a new generic status, for which Parrasiella gen. nov. is erected. Toucasiella, previously only known from Spain and Tunisia, is also reported for the first time from south east France. The revision of the “Mediterranean Durangites” supports the rejection of a Durangites spp. Zone as part of the standard zonation for the upper Tithonian, and its replacement by the P. andreaei Zone ( = D. vulgaris Zone sensu Sarti, 1988).

The ammonite fauna of the La Manga Formation (Late Callovian-Early Oxfordian) of Vega de la Veranada, Neuquén Basin, Argentina

The ammonite fauna of the La Manga Formation (Late Callovian-Early Oxfordian) of Vega de la Veranada, Neuquén Basin, Argentina

The Upper Jurassic ammonite Virgatopavlovia from NE Scotland: implications for palaeogeography and phylogeny

The upper part of the Helmsdale Boulder Beds Formation at Helmsdale, NE Scotland has yielded ammonites belonging to the genus Virgatopavlovia Cope, 1978. This genus is restricted to the youngest Bolonian Fittoni Zone that has hitherto not been recorded on the basis of its ammonite fauna outside of south Dorset. Palaeogeographical reconstructions suggest that these ammonites must have migrated (either northwards or southwards) through a narrow strait of probably shallow water in the English Midlands, although no record of the genus exists in that area. The Greenland ammonite genus Epipallasiceras Spath 1936 may be derived from Virgatopavlovia.

Lower Bajocian ammonites from the stratotype section of the Etropole Formation kept in the Historical Museum in Etropole (Bulgaria)

The area of the town of Etropole is famous for the well-preserved Lower Bajocian ammonites, which can be still often found in the nearly located exposures. These ammonites were the source of a number of species that enabled the recognition of the Bajocian in Bulgaria. The ammonite faunas and their host rocks were allocated to a series of stratigraphic horizons that composed the stratotype section designated as the reference standard for the definition and characterization of the Etropole Formation. The latter includes an ammonite spectrum which is composed of both Lower Bajocian species of Northwest European distribution and proper Bulgarian dispersal. It contains rare examples of the ammonite families Graphoceratidae and Sphaeroceratidae, frequent ammonites of the family Sonniniidae, and much more common members of the families Oppeliidae, Otoitidae and Stephanoceratidae that define a biostratigraphic interval from the Hyperlioceras discites to the Stephanoceras humphriesianum zones. This paper deals with the Lower Bajocian ammonite specimens hosted in the collection of the Historical Museum in Etropole (Bulgaria). The best preserved and the most valuable examples of this collection are described and figured. Although not purposefully collected, these ammonites give an excellent impression of the relative abundances of what is common and typical for stratotype section of the Etropole Formation. The study of this collection has triggered the rocks of the Etropole Formation (including the type-section) to be biostratigraphically reassessed, but this will be done elsewhere. Considering that both exposures and the fossil-bearing levels previously known from the Etropole area have now nearly disappeared, the ammonite collection of the Historical Museum in Etropole provides authentic specimens to be viewed. Besides, the collection forms an integral part of the overall heritage of the Etropole region and therefore offers both scientific and educational values.

Tithonian and Lower Berriasian calpionellid against ammonite biostratigraphy of the Dvuyakornaya Formation in eastern Crimea

The Dvuyakornaya Formation in eastern Crimea of late Kimmeridgian to Berriasian age represents a thick flysch-like succession of clays, marls and less common limestones. The ammonite zonation includes incomplete record from the Beckeri Zone in the uppermost Kimmeridgian up to the Jacobi Zone in the Lower Berriasian. Two main sections have been micropalaeontologically studied – the Dvuyakornaya Buhta and the Cape Svyatogo Ili’i. Eighteen calpionellid species of the genera Longicollaria, Chitinoidella, Daciella, Dobeniella, Popiella, Praetintinnopsella, Tintinnopsella, Crassicollaria and Calpionella have been found. The calpionellid zones Chitinoidella (with Dobeni and Boneti subzones), Crassicollaria and Calpionella (with Alpina and Elliptica subzones) are described and directly correlated to the existing ammonite biostratigraphy. The Dobeni Subzone corresponds to a part of the barren interval between the ammonite Hybonotum and Microcanthum zones, the Boneti Subzone – to the Microcanthum Zone, and the Crassicollaria Zone – to the Durangites Zone p.p. and Jacobi Subzone p.p. The boundary between the Crassicollaria and Calpionella zones is within the Jacobi Subzone. In the Berriasian, the Alpina Subzone has been correlated to the Jacobi and Grandis subzones, and the Elliptica Subzone – to upper part of the Grandis Subzone that was characterized in the Dvuyakornaya Formation by diverse ammonite faunas of the “Feodosiya Marlstones”. Chitinoidellids of the Dobeni Subzone for the first time determine late Early Tithonian age in the area. Calpionellid to ammonite correlation of the Dvuyakornaya Formation is discussed in the light of previous direct correlations between macro- and microfossil biostratigraphy of the Tithonian and the Lower Berriasian in the Tethyan Realm.

Record of Juraphyllites ex gr. libertus (Gemmellaro 1884) from the Ururoan Stage (Early Jurassic, New Zealand) and observations on the paleoenvironmental dynamics of the Ururoan ammonite fauna

Juraphyllites libertus is a common member of Tethyan Juraphyllitid assemblages of Pliensbachian age in Central and Southern Europe and the eastern Mediterranean. Judging from these occurrences, the age of J. ex gr. libertus in New Zealand probably ranges from the Jamesoni Zone to the Margaritatus Zone, i.e. from the lowermost zone of the Lower Pliensbachian to the middle zone of the Upper Pliensbachian. The presence in New Zealand of J. ex gr. libertus, together with other ammonite taxa previously recorded from the Ururoan (Harpoceras, Zugodactylites and Catacoeloceras), all with strong Tethyan affinities, is discussed. The paleoenvironmental factors that enabled them to migrate to the southwest Pacific, on the southern margin of Gondwana are considered. Their migration was probably facilitated by a combination of the following factors: 1. dispersal ability of taxa; 2. global sea levels; 3. availability of migration routes; 4. local seawater temperatures; and 5. local facies conditions.

The Carnian/Norian boundary succession at Berlin-Ichthyosaur State Park (Upper Triassic, central Nevada, USA)

The Upper Carnian-Lower Norian (Upper Triassic) Luning Formation at Berlin-Ichthyosaur State Park (BISP) in central NV (USA) has been sampled using for the first time the bed-by-bed approach for ammonoids, pelagic bivalves, and conodonts, more than 60 years after its first description by Silberling (U.S. Geological Survey Professional Paper 322: 1–63, 1959). BISP is historically important for the definition of the uppermost Carnian of the North American Triassic chronostratigraphic scale and is known worldwide as one of the most important ichthyosaur Fossil-Lagerstätte because of its extraordinary record of 37 articulated, large-sized specimens of Shonisaurus popularis. Nearly 190 ammonoids were collected from two stratigraphic sections, documenting all the latest Carnian to Early Norian ammonoid faunas previously described by Silberling. Halobiids were collected from five levels, and the first report of conodonts from BISP includes faunas from 13 levels. The ~340-m thick Brick Pile section, the most complete in the study area, includes the uppermost Carnian Macrolobatus Zone, which provides conodont faunas of the lower primitia zone and Halobia septentrionalis. The 200-m thick lowermost Norian Kerri Zone, which begins 52 m above the Macrolobatus Zone, yields conodonts of the upper primitia zone in its lower part, together with H. cf. beyrichi and H. cf. selwyni. The ichthyosaur-bearing interval, whose stratigraphic position has been interpreted quite differently by previous authors, is documented in the uppermost Carnian Macrolobatus Zone and is characterized by rich Tropites-dominated ammonoid faunas and by the onset of Halobia. All models proposed by various workers to explain the unusual ichthyosaur record are discussed and an additional explanation for the main ichthyosaur-bearing bed is proposed. The new hypothesis is that a harmful algal bloom (HAB) may have been the trigger for the mass mortality recorded in this level. Although the C/N boundary in the Brick Pile section lies within a 52 m interval that presently lacks paleontologic data, this succession is included in a small group of sections that are expected to contribute to the definition of the GSSP of the Norian stage. Correlation of the Brick Pile section with the best Carnian/Norian sections in northeastern British Columbia is discussed. Compared to the British Columbia Juvavites Cove and the GSSP candidate Black Bear Ridge sections, the Brick Pile section exhibits an ammonoid and Halobia record that is slightly more similar to that of the Tethyan sections. Correlation of the Brick Pile section with the second GSSP candidate Pizzo Mondello (Sicily, Italy) well demonstrates the significant problems encountered in calibration of the Tethyan and North American scales.

Upper Devonian (Famennian) and Lower Carboniferous (Tournaisian) ammonoids from western Junggar, Xinjiang, northwestern China—stratigraphy, taxonomy and palaeobiogeography

Seven ammonoid levels/assemblages are recognised in the Devonian (Famennian) and Carboniferous (Tournaisian) of the northwestern Junggar Basin, Xinjiang, northwestern China. Eleven genera and 20 species, including six new species (Becanites sp. nov., Protactoclymenia junggarensis sp. nov., Prot. magna sp. nov., Cyrtoclymenia? parallela sp. nov., Sporadoceras impressum sp. nov. and “Mimimitoceras” transiens sp. nov.) are described from the Hongguleleng and Heishantou formations in the Bulongguoer, Hebukehe, Emuha and Hashatu sections. The first assemblage is characterised by Platyclymenia subnautilina (Sandberger), Prionoceras frechi (Wedekind) and Sp. impressum sp. nov. It is assigned to the basal upper Famennian Pl. annulata Zone (UD IV-A) and indicates that the global, transgressive Annulata Event enabled the first spread of ammonoids to the region. The second assemblage is characterised by large-sized Cyrtoclymeniaceae (Protactoclymenia and Cyrtoclymenia?) and Sporadoceras aff. muensteri (Munster) and correlates with the orbiculare Zone (UD IV-C) of North Africa, which also contains very large clymeniids and goniatites. The third regional assemblage consists of rare Gonioclymenia sp. and a related, more evolute form. The fourth assemblage is a peculiar Cymaclymenia “Mimimitoceras” fauna, including C. striata (Munster) s.l., C. cf. involvens Lange, Sporadoceras sp., “Mimimitoceras” cf. geminum Korn, “M.” transiens sp. nov. and M. cf. rotersi Korn, most of which are discovered for the first time in the vast Junggar and adjacent areas. Based on conodont (associated Protognathodus fauna) and palynomorph data (LN Zone), this assemblage corresponds to the lower Hangenberg Event Interval (UD VI-E). Rare records from a fifth level suggest that cymaclymeniids survived regionally into the conodont Pr. kockeli Zone, as in other regions. The sixth level consists of a single Lower Tournaisian Acutimitoceras (Stockumites)?. The seventh level also has a low diversity and includes Weyerella angularia (Liang and Wang) and Becanites sp. nov. in the Emuha section. It falls in the Middle Tournaisian, as do Weyerella faunas that were previously reported from the region. The endemic species and the distinctive lack of otherwise widespread genera provide a strong regional signature of the overall ammonoid fauna.

Lower Toarcian (Jurassic) ammonites of the South Riffian ridges (Morocco): systematics and biostratigraphy

A rich ammonite fauna from the Lower Toarcian (Lower Jurassic) of the South Riffian ridges (northern Morocco), collected bed-by-bed from 14 new outcrops, is described. The fauna is nearly exclusively composed of already-known taxa, allowing correlation from the chronozone down to the zonule level. Fourteen species are described, among them the new species Dactylioceras (Dactylioceras) laticostatum sp. nov. The stratigraphical interval studied spans the first chronozone of the Toarcian, the Polymorphum Chronozone, but it remains unclear whether the Toarcian Oceanic Anoxic Event is represented in the studied succession. The Early Toarcian is mainly characterized by representatives of the family Dactylioceratidae, which are abundant but commonly crushed or deformed. Two new descriptors are proposed to describe the shell shape of crushed or incomplete specimens and have been used together with the classical ones for the taxonomic treatment of this group. A hypothesis about dimorphism in Dactylioceras (Orthodactylites) semicelatum (Simpson, 1843) and Dactylioceras (Dactylioceras) laticostatum sp. nov. is proposed.http://zoobank.org/urn:lsid:zoobank.org:pub:E7934E4A-942C-4C73-9831-22A8C0B0B89A

Late Albian ammonites from the Aitamir Formation (Koppeh Dagh, northeast Iran)

Late Albian ammonite faunas from the Aitamir Formation of the Koppeh Dagh Basin in northeast Iran are described and illustrated. These comprise 14 taxa, several of which are recorded from Iran for the first time, namely Anahoplites planus (formerly recorded from central Iran in open nomenclature only), Semenoviceras solidus, Epihoplites (Metaclavites) iphitus, Hysteroceras orbignyi and Pseudhelicoceras robertianum. New records of Placenticeras grossouvrei extend the stratigraphic range of this species downwards into the Late Albian; previously it was known from the Early and Middle Cenomanian only. The record of the rare E. (M.) iphitus fills a palaeobiogeographic gap between Crimea and Tajikistan, and the holotype of Spath is re-illustrated here. Additionally, Epihoplites trapezoidalis, from the Late Albian of Tajikistan, is relegated into the synonymy of Spath's species. A large number of taxa typical of the Late Albian (upper part of the Gault Clay Formation) of northwest Europe indicate close palaeobiogeographic affinities with the Koppeh Dagh Basin and faunal exchange across the Russian Platform and Transcaspia. The stratigraphic succession of the ammonite faunas is used for a biostratigraphic subdivision of the upper Aitamir Formation.

Phylloceratoidea du Jurassique moyen et supérieur du Nord-Est de l’Iran (Monts Binalud)

Phylloceratidae are often the most frequent taxa within the Middle and Late Jurassic ammonite faunas of North Iran but so far they have not been noticed much within the existing literature and have been described only sporadically. In this study, the Phylloceratidae of north Iran are treated systematically and described comprehensively. These include 16 taxa, most of them being previously unpublished for Iran.

Albian ammonites from northern Pakistan

Abstract The occurrence of rich Albian ammonite faunas in what is now northern Pakistan has been known for more than 80 years, but there has been no comprehensive account of the assemblages present. A total of 36 taxa are described below. The middle part of the Lumshiwal Formation yields Upper Aptian ammonites south of the Samana Range. Elsewhere, it yields Douvilleiceras leightonense Casey, 1962, of the lower Lower Albian Leymeriella regularis Zone and the Sonneratia perinflata and S. kitchini Subzones of the Sonneratia chalensis Zone of the northwest European sequence. The top one to two metres of the Lumshiwal yields an abundant fauna of rolled and phosphatised ammonites that includes elements from much of the Albian. Of these, Prolyelliceras gevreyi (Jacob, 1907) first appears in the lower Lower Albian Leymeriella tardefurcata Zone. The commonest ammonite is Douvilleiceras mammillatum (Schlotheim, 1813) sensu lato, which ranges from the perinflata Subzone of the chalensis Zone to the Otohoplites bulliensis Subzone of the O. auritiformis Zone of the Lower Albian. The presence of Lyelliceras pseudolyelli (Parona and Bonarelli, 1897) indicates the uppermost, pseudolyelli Subzone of the auritiformis Zone. The presence of Lyelliceras lyelli (d’Orbigny, 1841) indicates the basal Middle Albian lyelli Subzone of the Hoplites dentatus Zone. There is no evidence for the higher parts of the Middle Albian. Dipoloceras (Rhytidoceras ) sp. indicates the presence of lower Upper Albian, possibly the pricei Zone. There is evidence, in the form of specifically indeterminate Mortoniceras (Mortoniceras) sp., of a level within the inflatum to fallax Zone inteval from a single locality, but no evidence of the succeeding parts of the upper Upper Albian. The base of the Kawagarth Formation that succeeds the Lumshiwal yields lower Upper Albian Mortoniceras (M.) geometricum Spath, 1932 of the Mortoniceras pricei Zone, northwest of Darmasand in the Samana range.

ORGANISM-ENVIRONMENT INTERACTIONS DURING THE PERMIAN-TRIASSIC MASS EXTINCTION AND ITS AFTERMATH

ORGANISM-ENVIRONMENT INTERACTIONS DURING THE PERMIAN-TRIASSIC MASS EXTINCTION AND ITS AFTERMATH

Recovery of brachiopod and ammonoid faunas following the End-Permian crisis: Additional evidence from the lower Triassic of the Russian Far East and Kazakhstan

After the End-Permian mass extinction, ammonoids reached levels of taxonomic diversity higher than in the Changhsingian by the Dienerian Substage of the Induan. However, brachiopods exhibit a prolonged delay in recovery, and their taxonomic diversity had not recovered to Late Permian levels even by the Olenekian. The differential patterns of recovery between these two clades may reflect fundamental differences in physiology and behavior. Brachiopods were benthic organisms that were dependent on specific trophic sources, and their general reduction in size during the Early Triassic may have been a response to a relative paucity of food resources. In contrast, ammonoids were sluggishnektic organisms that utilized a wider range of trophic sources and that suffered no comparable size decrease during the Early Triassic. Brachiopods may have been at a disadvantage also due to vulnerabilities associated with their larval stage, during which they had to locate a suitable substrate for settlement. In contrast, ammonoids had no larval stage and juveniles may have been dispersed widely into favorable habitats. These factors may account for differences in the relative success of ammonoids and brachiopods at high-latitude regions following the End-Permian mass extinction: ammonoids successfully recolonized the Boreal region during the Early Triassic whereas brachiopods did not.

Depositional sequences and ammonoid assemblages in the upper Cenomanianlower Santonian of the Iberi

A clear relationship exists between eustatic sea-level rises and falls recorded as cyclical depositional sequences and ammonite faunas during the Cenomanian-Santonian in the Iberian and West Portuguese basins. Most of the faunal turnovers correlate with stratigraphic intervals related to marine transgressions, maximum flooding of the shelf (locally associated to anoxic events), and marine regressions. Specifically, within each depositional sequence, three distinct and identical events of morphological change occur, involving ammonoids belonging to different groups. Transgressive sediments are characterized by moderately ornamented, inflated and evolute morphologies, which are replaced by smooth, involute and compressed oxycones (the most hydrodynamic shells) during maximum flooding (and to a lesser extent at the early highstand) of the sequences. The latter morphologies in turn are replaced by coarsely ornamented and evolute shells during late highstands. We conclude that ammonoid faunal analysis can be used to trace sea-level changes and provides an additional tool for sequence stratigraphy.

Early Permian (Asselian) Ammonoids from the Taishaku Limestone, Akiyoshi Belt, Southwest Japan

Abstract. An ammonoid fauna comprising eight species belonging to seven genera (Agathiceras, Neoglaphyrites, Emilites, Somoholites, Marathonites, Eoasianites and Metapronorites) is described from the Uyamano Formation (Taishaku Limestone) at Miharanoro in the Akiyoshi Belt, Southwest Japan. The fauna includes two new species: Neoglaphyrites discoidalis and Somoholites miharanoroensis. The genera Emilites, Somoholites, Marathonites, and Metapronorites are described from Japan for the first time. From the coexisting interval of these seven genera, the age of the Miharanoro fauna is between the Kasimovian and Asselian, being very probably Asselian because some species show close resemblance to those known from Asselian strata. This is the most diverse early Permian ammonoid fauna ever known from Japan.

Upper Albian and Cenomanian (Cretaceous) ammonites from the Debarsu Formation (Yazd Block, Central Iran)

ABSTRACT Wilmsen, M., Storm, M., Fürsich, F.T. and Majidifard, M.R. 2013. Upper Albian and Cenomanian (Cretaceous) ammonites from the Debarsu Formation (Yazd Block, Central Iran). Acta Geologica Polonica, 63 (4), 489-513. Warszawa. New ammonite faunas consisting of 13 taxa provide the first reliable biostratigraphic dating of the Debarsu Formation of the Yazd Block, west-central Iran, indicating several levels in the Upper Albian and Lower Cenomanian, while a foraminiferal assemblage places the top of the Formation in the Middle Turonian. Among the identified ammonite taxa, Acompsoceras renevieri (Sharpe, 1857) is recorded from Iran for the first time. The upper part of the lower Upper Albian is proved by the occurrences of mortoniceratines of the Mortoniceras (M.) inflatum Zone in the lowermost part of the Debarsu Formation. For the upper Upper Albian (traditional Stoliczkaia dispar Zone), the M. (Subschloenbachia ) rostratum and M. (S.) perinflatum zones are proved by their index taxa. However, there is no evidence of the terminal Arrhaphoceras (Praeschloenbachia) briacensis Zone. The upper part of the lower Lower Cenomanian Mantelliceras mantelli Zone (M. saxbii Subzone) is proved by M. saxbii and M. cf. mantelli. Below, there is an ammonite- barren interval of ca. 100 m in thickness between M. (S.) perinflatum zonal strata and the M. saxbii Subzone. The upper Lower Cenomanian is documented by the presence of typically M. dixoni zonal ammonites such as Acompsoceras renevieri. Upper Cenomanian and Turonian ammonites have not been found in the upper part of the Debarsu Formation, but micro-biostratigraphic evidence (planktonic foraminifers) from the uppermost part of the formation indicate that the formation ranges into the Turonian. For the development of the major tectonic unconformity at the base of the overlying Haftoman Formation (which yielded Lower Coniacian inoceramids near its base), only 2-3 myr remain, stressing the geodynamic activity of Central Iran during mid-Cretaceous times.

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

AbstractWe describe a new ammonoid fauna from the Taurus Mountains of southern Turkey. The Carnian ammonoid fauna from Aşağiyaylabel 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 Aşağiyaylabel 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 Aşağiyaylabel 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.