Ammonite Species Research Articles

Macrofaunal communities in the Cenomanian-Turonian strata of Kasserine area (west central Tunisia, North Africa)

ABSTRACT The Cenomanian/Turonian strata of the Kasserine area: Tunisia exhibit a unique sedimentological and palaeontological pattern. Five lithological units have been identified: 1) lower unfossilferous black shale; 2) well-bedded marly unit with thin limestone interbeds; 3) marl unit, 4) same as 2, and 5) unfossilferous dolomitic thick-bedded limestone. The middle three units contain low diversity macrofaunal communities dominated mainly by oyster bivalves with few gastropods and echinoids. Fortunately, three marker ammonite species were identified and are used to subdivide the studied interval into three biozones, including 1) Calycoceras cenomanense, 2) Pseudaspidoceras pseudonodosoides and 3) Neoptychites Cephalotus. Based on constrained clustering and ordination techniques, three distinct macrofaunal associations were identified: 1) Ceratostreon flabellatum, 2) Ilymatogyra africana and 3) Tylostoma (Tylostoma) globosum. In general, the macrofaunal diversity decreases at the Cenomanian-Turonian boundary, which is interpreted to be a consequence of a global sea-level rise and the destruction of shallower habitats. Based on the life habits of the macrofaunal communities, a change from a high-energy (Ceratostreon and Ilymatogyra) to a low-energy (Tylostoma) shallow marine environment was indicated. The dominance of oysters in these nutrient-rich sediments was attributed to their ability to tolerate high turbidity water and to colonise soft-substrate sea bottoms.

Performance of machine-learning approaches in identifying ammonoid species based on conch properties

A recommendation of: Floe Foxon Ammonoid taxonomy with supervised and unsupervised machine learning algorithms https://doi.org/10.31233/osf.io/ewkx9

The concept of ‘heteromorph ammonoids’

‘Heteromorph ammonoids’ encompass all ammonoid species whose shapes do not conform to a closely coiled planispiral shell. The term is useful as a broad description for such ammonoids. However, as a concept, ‘heteromorph ammonoids’ no longer has any scientific value or explanatory power. Although such ammonoids have traditionally been considered aberrant forms, they represent instead an integral part of the evolutionary history of the Ammonoidea. ‘Heteromorph ammonoids’, as a whole, are a polyphyletic group, consisting of a heterogeneous mixture of taxa without any phylogenetic, morphological or ecological coherence. Their treatment as a single entity risks conflating convergences and phylogenetic affinities. It also vastly oversimplifies the stunning array of morphologies and ecological niches occupied by these animals. Investigation into the uncoiling (and recoiling) of ammonoids is a legitimate and worthwhile enterprise, especially in view of the realization that this phenomenon occurred several times in the history of the Ammonoidea. However, few insights can be gained by treating ‘heteromorph ammonoids’ as a single entity. Studies of such ammonoids should focus on monophyletic groups within a well-constrained phylogenetic and stratigraphical framework to yield meaningful results.

Record of the Middle Albian (Lower Cretaceous) ammonoids from the Cauvery Basin, southern India

ABSTRACT The two Middle Albian index ammonoid species Hamites (Hamites) attenuatus and Hamites (Hamites) rectus are recorded for the first time from the Karai Formation in the Ariyalur Sub-basin of the Cauvery Basin. The part of succession under the present endeavour has yielded eight ammonoid specimens from four ammonoid levels which are systematically described in the Cauvery Basin. Biostratigraphic evaluation of these ammonoids enables the authors to formulate Hamites (Hamites) attenuatus Zone which is broadly correlatable to the Hoplites dentatus Zone – Euhoplites lautus Zone interval of the standard ammonoid zonal scheme.

Ammonites from the Lias Group (Lower Jurassic, Sinemurian and Pliensbachian) of White Park Bay, Co. Antrim, Northern Ireland

Northern Ireland's Jurassic succession has received relatively little detailed investigation. Late Sinemurian and early Pliensbachian strata are present in parts of north Antrim but they are poorly exposed at outcrop and have been penetrated by just a single borehole, at Portmore, in which parts of the succession are missing. Collecting from White Park Bay over more than two decades, augmented by examination of museum material, has established the presence within the Rathlin (North Antrim) Basin of ammonite zones and subzones additional to those proven in the Portmore Borehole. This suggests that parts of the Sinemurian and Pliensbachian stages, from the Obtusum Zone through to the Davoei Zone, and possibly even higher, may be preserved in onshore or nearshore parts of the basin. Despite the generally poor exposure, the material recovered encompasses more than 40 ammonite species, including several taxa that are poorly represented elsewhere in the UK, of which two, Vicininodiceras dalriatense sp. nov. and Cheltonia howarthi sp. nov., are previously undescribed.

New records of rare ammonite species from the Inferior Oolite Formation (Middle Jurassic, Aalenian and Lower Bajocian) of Dorset

Rare ammonite species are reported from the Inferior Oolite Formation of Dorset. In the Aalenian the ammonite Shahrudites is described from the Scissum Zone for the first time and Malladaites is recorded from the Murchisonae Zone. Tmetoceras regleyi occurs in the Scissum and Murchisonae zones and Tmetoceras henriquesae is described from the Concavum Zone. In the Lower Bajocian, specimens of Zurcheria are presented from the Discites Zone. A revised zonal scheme is used for the Aalenian Stage and two new biohorizons are introduced. The Leioceras subglabrum biohorizon is erected in the Opalinum Subzone and Leioceras evolutum in the Bifidatum Subzone.

New Findings of Latest Early Olenekian (Early Triassic) Fossils in South Primorye, Russian Far East, and Their Stratigraphical Significance

Information on latest early Olenekian (latest Smithian) ammonoids is available apparently from only seven regions of the world, including South Primorye. Latest Smithian evidences on this topic are recorded from the West SMID (abbreviation from the Russian name of the quarry: “Building Materials and Details”), East SMID and Golyj Cape areas in South Primorye. This provides additional information on systematic composition of latest Smithian ammonoid, as well as conodont and brachiopod assemblages from the recently identified Shimanskyites shimanskyi Zone, located between lower Olenekian Anasibirites nevolini Zone and upper Olenekian Tirolites subcassianus Zone. There are many common ammonoid species in the Shimanskyites shimanskyi Zone and the underlying Anasibirites nevolini Zone, e.g., Prosphingitoides sp., Arctoceras septentrionale (Diener), Churkites syskoi Zakharov et Shigeta, Submeekoceras? subhhydaspis (Kiparisova), Prionites markevichi Zakharov et Smyshlyaeva, ‘Anasibirites’ simanenkoi Zakharov et Smyshlyaeva, Xenoceltites? subvariocostatus Zakharov et Smyshlyaeva, and Mianwaliites zimini Zakharov et Smyshlyaeva. The base of the Shimanskyites shimanskyi Zone, marked by a negative δ13Corg excursion in the Kamenushka-2 Section by our previous study, coincides with the FO (first occurrence) of ammonoids Shimanskyites shimanskyi Zakharov et Smyshlyaeva and Glyptophiceras cf. sinuatum (Waagen) and conodont Hindeodella budurovi Buryi. This zone is characterized additionally by some fossils common for the overlying upper Olenekian Tirolites subcassianus Zone: ammonoids of the genus Kamenushkaites, brachiopods Bittnerihyris margaritovi (Bittner) and Lepismatina sp. and conodont ‘Neogondolella’ (=?Borinella) jubata Sweet. The latest Smithian ammonoids recorded from the Shimanskyites shimanskyi Zone totally consist of 30 taxa belonging to 11 families (Sageceratidae, Ussuiriidae, Aspenitidae, Paranannitidae, Arctoceratidae, Proptychitidae, ?Galfetitidae, Prionitidae, ?Kashmiritidae, Xenoceltitidae and Palaeophyllitidae). The problems of global correlation of uppermost Smithian strata are also discussed.

The Albian-Cenomanian transition in a shelf-basin transect: Biostratigraphy, sedimentology and paleontology of Jebel Mghila, Central Tunisia

Twenty-two ammonite species are identified in the upper Albian Mortoniceras (Subschloenbachia) rostratum, Mortoniceras (Subschloenbachia) perinflatum and Stoliczkaia (Shumarinaia) africana Zones, and in the lower Cenomanian Mantelliceras mantelli Zone. The species Placenticeras Saadensis Thomas and (Thomas and Peron, 1890, 1890 is revised, including Engonoceras Thomasi Pervinquière, 1907, and is placed within the genus Hypengonoceras Spath, 1922. This accurate biostratigraphic framework allowed to evidence, at the Albian-Cenomanian transition (S. (S.) africana Zone), a significant sea level drop, responsible for emergence and erosion to the SE, and for deposition of a Lowstand wedge to the NW, fed by erosional channels on the shelf slope. Plesiosaur remains found in the upper Albian series (base of M. (S.) rostratum Zone) represent one of the few elasmosaurids known worldwide in the Albian, and the first plesiosaurian reported from Tunisia.

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.

Reappraisal of the latest Albian (Mortoniceras fallax Zone) cephalopod fauna from the classical Salazac locality (Gard, southeastern France)

The Salazac locality (Gard, southeastern France) is renowned for the richness of its cephalopod fauna (especially ammonites) from the Mortoniceras fallax Zone (uppermost Albian, Lower Cretaceous). However, most ammonite species have paradoxically been scarcely illustrated up to now. Furthermore, the rare assessments of ammonite taxonomic diversity are presumably inaccurate, as they either result from a drastic typological approach or could not benefit from the most recent advances in modern concepts of ammonoid intraspecific and ontogenetic variations. In this work, we document an original cephalopod assemblage from Salazac represented by abundant, well-preserved specimens (564 studied ammonites, including ca. 50% of heteromorphs) constituting a high diversity. The sample size and quality of this new material allowed some extensive morphological and biometric analyses whenever possible (i.e., for subdatasets in which a significant number of measurements is available) and to thoroughly assess intraspecific and ontogenetic variations for a few species. This led to determine the diagnostic value of various shell characters commonly used to characterize both well-documented and poorly-defined species. In particular, we show that a significant part of the variation in the number of ribs per whorl within the heteromorphic genera Mariella and Turrilitoides is directly related to shell size and that the strength of tubercles covaries negatively with the number of ribs in Mariella, therefore challenging the diagnostic value of these characters. We further suggest that rib density covaries with whorl shape in Mariella, following Buckman’s first rule of covariation. In total, one species of nautilid and 38 taxa (25 genera) of ammonites are described, among which five species are documented from Salazac for the first time. In turn, this study provides valuable data for future phylogenetic, biostratigraphical, biogeographical and broad-scale diversity studies.

The First Occurrence of Ptychodus latissimus from the Codell Sandstone Member of the Carlile Shale in Kansas

Three teeth of the late Cretaceous shark Ptychodus latissimus (Agassiz) are described from the upper Middle Turonian Codell Sandstone Member of the Carlile Shale. These teeth are significant because they are the first documented occurrence of the species in Kansas, extending the paleobiogeographic range of species and adding a new paleoecological component to the Codell Sandstone fauna. Its association with various ammonite species living in different trophic levels with other ptychodontid sharks may be indicative of niche partitioning.

Large Scaphitid Ammonites (Hoploscaphites) from the Upper Cretaceous (Upper Campanian–Lower Maastrichtian) of North America: Endless Variation on a Single Theme

We describe three species of large scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (upper Campanian–lower Maastrichtian) of the Western Interior of North America. Each species occurs as two dimorphs, referred to as macroconch and microconch. All three species share a similar pattern of ornamentation consisting of long, thin, nonbifurcating ribs on the adoral part of the phragmocone, suggesting that they constitute a single monophyletic clade. Macroconchs of Hoploscaphites crassus (Coryell and Salmon, 1934) are characterized by a globose whorl section, with closely spaced ventrolateral tubercles on the body chamber, usually persisting to the aperture. Macroconchs of Hoploscaphites plenus (Meek and Hayden, 1860) differ from those of H. crassus in having a more subquadrate whorl section with flatter flanks, and fewer, larger, and more widely spaced ventrolateral tubercles. Macroconchs of Hoploscaphites peterseni, n. sp., closely resemble those of H. crassus, but differ in being nearly circular in side view with a more compressed whorl section. All three species lived at approximately the same time in the same general area and depositional environment. They are abundant in the Baculites baculus Zone but also occasionally occur in the B. eliasi Zone and possibly lower part of the B. grandis Zone. They are present in the Pierre Shale of east-central Montana and east-central Wyoming, the Lewis Shale of south-central Wyoming, and the Bearpaw Shale of northeast Montana. It is possible that these three species represent subspecies within a single species or a “flock” of very closely related species, similar to the “species flocks” observed in modern cichlid fishes.

A possible link between the Carnian Pluvial Event, global carbon-cycle perturbation, and volcanism: New data from the Qinghai-Tibet Plateau

Abstract The Carnian Pluvial Event (CPE) is recorded widely across the Tethys region. Here we present high-resolution carbonate (δ13Ccarb) and organic (δ13Corg) carbon-isotope records and mineral data from the Boli La to lower Bagong formations in the Quemo Co area of the Qiangtang Basin, Qinghai-Tibet Plateau. In this studied section, a calcareous fine-grained sandstone bed that yields a detrital zircon maximum depositional age of 232.5 ± 3.3 Ma, together with ammonoid species and bivalves, allows identification of the Carnian Stage. An intensification of siliciclastic supply and a large drop in calcite and illite is recorded in the Carnian section, suggesting a palaeoclimatic shift from arid to warm and humid during the CPE. A negative carbon-isotope excursion (CIE) in both δ13Corg and δ13Ccarb is also reported, which could be explained by a global perturbation of the carbon cycle and the release of CO2 enriched in 12C. The magnitude of the negative CIE in the Quemo Co area displays a significant shift towards lighter values compared to other reported carbonate carbon-isotope values across the onset of the CPE. A combination of both volcanic emissions from the synchronous Wrangellia large igneous province and release of methane clathrate hydrate is the most likely explanation for the significant negative excursion in δ13C.

Cenomanian Cephalopods of Bellezma-Aures mountains, NE Algeria: Taxonomy and biostratigraphy

The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria is well exposed and rich in macroinvertebrates, including cephalopods. Twenty-five ammonite species and two nautiloid species from the Thénièt El Manchar, Djebel Metrassi and Djebel Bouarif sections are described and seven assemblage zones proposed as provisional working units: Mantelliceras mantelli–Sharpeiceras laticlavium Assemblage Zone (lower Cenomanian), Mantelliceras dixoni Assemblage Zone (uppermost lower Cenomanian), Cunningtoniceras inerme Assemblage Zone (lower middle Cenomanian), Acanthoceras rhotomagense and Acanthoceras cf. rhotomagense Assemblage Zone (middle middle Cenomanian), Acanthoceras amphibolum Assemblage Zone (upper middle Cenomanian), Acanthoceras jukesbrownei Assemblage Zone (uppermost middle Cenomanian), and Neolobites vibrayeanus Assemblage Zone (lower upper Cenomanian). The lower Cenomanian Mantelliceras mantelli–Sharpeiceras laticlavium Zone is subdivided into the Submantelliceras aumalense, Sharpeiceras schlueteri and Mantelliceras saxbii subzones. The base of the middle Cenomanian is marked by the disappearance of species of Mantelliceras and the appearance of the scleractinian coral Aspidiscus cristatus (Lamarck, 1801), associated with Cunningtoniceras inerme (Pervinquière, 1907). The middle Cenomanian contains abundant A. cristatus and species of Acanthoceras, i.e., A. cf. rhotomagense (Defrance in Brongniart, 1822), A. jukesbrownei (Spath, 1926) and A. amphibolum Morrow, 1935. An ammonite zonal scheme is then applied to the Cenomanian exposed in the Bellezma-Aures mountains located on the southern Tethys margin in Algeria.

Affinities between the Lower Cretaceous Ammonoidea Ammonites crassicostatus d'Orbigny, 1841 and Ammonites gargasensis d'Orbigny, 1841

The present contribution provides a taxonomic reassessment of the Lower Cretaceous ammonite species Ammonites crassicostatus d'Orbigny (type species of Colombiceras Spath) and Ammonites gargasensis d'Orbigny (type species of Gargasiceras Casey) from the Aptian-type area (Apt, Vaucluse, southeastern France). Those nominal species represent two ornamental poles of a single population, here referred to C. crassicostatum. The genus Gargasiceras is, therefore, synonymised with Colombiceras. Implications on the taxonomy at the specific, generic, and supra-generic levels are discussed.

Roadian (earliest Guadalupian, Middle Permian) Radiolarians from the Guadalupe Mountains,West Texas, USA Part I: Albaillellaria and Entactinaria

Roadian radiolarians are described from strata exposed in a small quarry (Quarry section) on U.S. Highway 62/180 located 3 km northeast of its junction with Texas Highway 54, Culberson County, Guadalupe Mountains, West Texas. These strata were long considered as Bone Spring Limestone of Leonardian (Early Permian) in age, but in recent years have been assigned to the Williams Ranch Member of the Cutoff Formation of the Roadian Stage (Guadalupian, middle Permian) based on the presence of the ammonoid species Paraceltites elegans. Radiolarians are of excellent preservation and the fauna is very diverse with 29 species of 11 genera described belonging to orders Albaillellaria and Entactinaria.Among them, 15 new species and one new genus, Apachevella, have been described, and five species emended. New species are Campanulithus cutoffi, Albaillella exilis, Pseudoalbaillella pseudoscalprata, P. japonica, P. laevis, Entactinia siciformis, E. longiacus, E. rezedae, Trilonche belli, Entactinosphaera texana, Polyedroentactinia macilenta, P. cancellata, P. porosa, P. bifida, and Kashiwara roadensis. Emended species are Pseudoalbaillella cona Cornell and Simpson, Entactinia parapycnoclada Nazarov and Ormiston, Trilonche tyrrelli (Nazarov and Ormiston), Apachevella capitanensis (Nestell and Nestell), and Wuyia endocarpa (Nazarov and Ormiston). Conodonts are represented by Jinogondolella nankingensis (Jin) with its three subspecies, J. nankingensis nankingensis (Jin), J. nankingensis behnkeni Wardlaw and Nestell and J. nankingensis tenuis Wardlaw, and elements of Sweetina and Hindeodus wordensis Wardlaw.

The polyphasic ontogeny of the discoidal Late Devonian ammonoid Acrimeroceras

The Late Devonian ammonoid species Acrimeroceras falcisulcatum and A. stella have similar-shaped discoidal adult conchs. Their conch morphology and its ontogenetic development are described and analysed. Despite great similarities in their adult conch morphology, they can be clearly distinguished by differences in the shape of their juvenile whorl profile and by the growth trajectories of their cardinal conch parameters: conch width index, umbilical width index and whorl expansion rate. Quantification of ontogenetic change in the two species demonstrates that the stratigraphically younger species A. falcisulcatum possesses the less complex ontogeny compared to the stratigraphically older A. stella. The closely related genus Paratornoceras (early Famennian) and the unrelated Late Visean Calygirtyoceras show juvenile conch morphology and ontogenetic trajectories very similar to Acrimeroceras stella. This similarity can be seen as iterative independent unfolding of homoplastic characters, possibly linked to size-dependence of the functional morphology of the conchs.

First record of bioeroding barnacles (Cirripedia: Acrothoracica) on ammonite shells

Oval, elongated and radially orientated pits were found on specimens of a Kimmeridgian (Upper Jurassic) aspidoceratid ammonite species from Páskom Hill (Bakony Mountains, Transdanubian Range, Hungary). These trace fossils most probably represent acrothoracica (burrowing barnacles) borings, which have never been documented on ammonites before, and are described here as Paskomella acanthicola nov. igen. et nov. isp. The tiny barnacles were living together with the cephalopods; therefore, these trace fossils represent a new type of commensalism between the ammonites and the boring, host-specific, acrothoracid cirriped.

Rare representatives of new Late Devonian ammonoids from the Rhenish Mountains and the Montagne Noire

The new genera and species of the early late Famennian (Late Devonian) ammonoids Hoevelia schindewolfi n. gen. n. sp. and Beulia wunderlichi n. gen. n. sp. are described from material collected in the Rhenish Mountains and attributed to the new family Hoeveliidae. The genus Falciclymenia Schindewolf, 1923 is revised with the description of the proposed new type species Falciclymenia cabrierensis n. sp. from the Montagne Noire.

Taxonomy and stratigraphic distribution of the ammonite Schloenbachia Neumayr, 1875 from the Bohemian Cretaceous Basin

Abstract Only two specimens of the ammonite genus Schloenbachia have hitherto been recorded from the Bohemian Cretaceous Basin (BCB). While the first specimen was originally described by Dr. J. Soukup in the 1970s, the other one was discovered in an older collection of the Faculty of Science, Charles University in Prague in 2018. Recently, both specimens were systematically investigated and interpreted as Schloenbachia lymensis, a new ammonite species for the BCB. The stratigraphic distribution of S. lymensis as well as the palaeobiogeography of this taxon are discussed in this paper.