Ammonite Shells Research Articles

Large Fe-Mn oncoids from Early Jurassic Ammonitico Rosso Facies (eastern Sakarya Zone, NE Turkey): new insight into palaeogeographic conditions of Tethys Ocean

ABSTRACT Oncoids, significant sedimentary structures within the Jurassic strata of the Mediterranean Region, serve as valuable indicators of paleoenvironmental conditions during their formation. One of the important examples of oncoids has been discovered in the Pliensbachian (Early Jurassic) Ammonitico Rosso Facies (ARF) of the eastern Sakarya Zone (Eastern Pontides, NE Turkey). This study presents the first comprehensive sedimentological and petrographic (textural and compositional characteristics) examination, as well as geochemical analyses (trace and rare earth elements) of these Fe-Mn oncoids. The oncoids consist of nuclei coated with irregular laminae and exhibit a range of sizes, from 10 to over 45 mm, displaying various colours such as brown, reddish, and metallic-looking. They mostly have a discoidal shape, although some are spherical. The nuclei consist of bioclastic wackestones, containing remnants of ammonoid shells. Some oncoids, especially the discoidal forms, have multiple nuclei. The cortex of the oncoid predominantly consists of wrinkled bands displaying micritic laminae, with an abundance of filamentous bodies and the local presence of encrusting microfossils. In the cortex of the oncoids, iron predominates over manganese, and there are compositional variations within the cortex, especially enriched in Si, Fe, and Ca. They predominantly fall within the region associated with hydrothermal Fe and Mn sediments, as indicated by discrimination diagrams involving Ni, Co, Zn, and plots of Ce/Ce* vs Y/HoN and Nd contents, suggesting a hydrothermal origin. Furthermore, their rare earth elements (REE) chemistry displays distinct Y/Ho, Sm/Yb, Ce/Ce, and Nd values, indicating the presence of seawater mixing with hydrothermal fluids. However, they show relatively low Sm/Yb, Y/Ho, Eu/Sm, Nd/YbN, and La/Yb values, suggesting a limited contribution from hydrothermal sources to the surrounding seawater. Nevertheless, the cortex of the oncoids exhibits a complex and variable mineralogy that changes over short distances, implying the dynamic nature of the depositional environment, characterized by fluctuating hydrological regimes, varying oxygen levels, elemental supply, and the saturation of specific elements in seawater. The increased presence of specific trace elements, including Fe, and REE during this period, is likely linked to hydrothermal fluid input into marine environments, coinciding with intensified syn-sedimentary tectonic activity, where ongoing extensional tectonic movements occasionally influenced paleoenvironmental conditions. In these conditions, the formation of oncoids is influenced by various sedimentary factors, including the availability of metal sources, specific paleoenvironmental conditions, and the presence of microbial organisms, thereby enriching our understanding of palaeogeography during the Early Jurassic period. Additionally, the studied oncoids, with their comparable stratigraphic position and petrographic characteristics to those in both the eastern and western parts of the Tethyan basin, underscore their significance in palaeogeography and stratigraphy.

“Searching for order at all levels”. Antonio Lima-de-Faria (July 4, 1921 – December 27, 2023)

“Searching for order at all levels”. Antonio Lima-de-Faria (July 4, 1921 – December 27, 2023)

Bite traces of a large, mosasaur-type(?) vertebrate predator in the lower Turonian ammonite Mammites nodosoides (Schlüter, 1871) from the Czech Republic

A specimen of the acanthoceratid ammonite Mammites nodosoides from the lower Turonian of the Bohemian Cretaceous Basin shows signs of having been preyed upon by a reptile, probably with a mosasaur-like dentition. Based on these traces, a new ichnotaxon, Nihilichnus quadripertitus Mikuláš, isp. nov., is erected. Several bite traces are arranged into two convergent, straight rows, which would rule out sauropterygian reptiles or fishes as agents. Jaw margins appear to contour the ammonite aperture, suggesting an attack directed at the apertural part with the head and arm crown. The lethal nature of the bite(s) inflicted is supported by the crushed anterior, albeit not anteriormost, portion of the body chamber. Spacing, size and angle of these traces, as well as the angle of convergence between both rows would suggest that the agent was a medium-sized (up to 6 m) member of the marine lizard family Mosasauridae, and more specifically, of the subfamily Tethysaurinae. However, a representative of another closely related subfamily, the Yaguarasaurinae (which includes the genus Romeosaurus), cannot be ruled out. The bite marks on the present ammonite shell contribute to a palaeoecological evaluation of tethysaurines (in particular with regard to food adaptations) and to a better picture of the palaeogeographical distribution of early Turonian mosasauroids across central European shelves.

Death by ammonite: fatal ingestion of an ammonoid shell by an Early Jurassic bony fish

AbstractA remarkable specimen of the actinopterygian fish Pachycormus macropterus from the Early Jurassic (Toarcian) Posidonienschiefer Formation of Germany exceptionally preserves an unusually large ammonite inside its gut. The ammonite was swallowed by the fish, likely by accident, and represents the first direct evidence for an actinopterygian fish consuming an ammonoid. Exceptional aragonite preservation of the conch retaining partial nacreous lustre, combined with only minor acid etching of the shell, strongly indicates that the ammonite was ingested immediately prior to and was directly responsible for the fish’s death. The fish’s stomach provided a microenvironment protecting the aragonite from chemical dissolution.

A nautiloid with ventral bitemarks from the Charmouth Mudstone Formation (Lower Jurassic) near Lyme Regis, Dorset, UK

Locally within the Charmouth Mudstone Formation (Sinemurian, Lower Jurassic) of the Dorset coast fatally bitten ammonites with ventral bite marks are common. Ventral bite marks occur at the rear of the body-chamber. The predator probably severed attachment muscles, thus removing its prey more easily. We report the first ventrally bitten fossil nautiloid, which is unusual in that the large bite mark is entirely within the phragmocone. The nautiloid is juvenile with a very short body-chamber extending 46° back from the apparently undamaged aperture. The whorl cross-section is nearly circular, giving the predator little to grip when biting. Nautiloid shells are also thicker than ammonite shells. Despite these difficulties, the predator bit repeatedly and damaged both the shell and septa. Five rounded bites occur on the left side, separated by sharp points. This suggests the predator was probably another cephalopod with suckered arms and powerful jaws. The centre of the bite is 160.5° back from the aperture, close to the mean value for ammonites (184.5°), suggesting the predator located the position of the first bite opposite the victim's aperture. Thus, we think the predator attacked an incomplete nautiloid shell which explains why the damage affects only the phragmocone.

Pore-canal network (“wrinkles”) in ammonoid shell wall (Cephalopoda)

ABSTRACT The shell wall in ammonoids contains a pore-canal network similar to that detected recently in the shell wall of the Ordovician nautiloid Orthoceras. In the Jurassic monomorphic ammonoids Quenstedtoceras, Cosmoceras, Lissoceras and the Cretaceous heteromorphic ammonoid Ptychoceras investigated in this study vertical canals arranged in parallel rows, are partially preserved, although no horizontal canals are preserved as in Orthoceras. In Quenstedtoceras and Ptychoceras the vertical canals extend not only through the inner prismatic layer, as in Orthoceras, but also through the nacreous layer. Therefore both layers were secreted on the body-shell attachment band behind the apertural margin. In the juvenile shells, only the very thin outer prismatic layer formed the apertural margin. As in Orthoceras, the canals had walls of calcified organic fibres that were partially or entirely dissolved during diagenesis. The pore-canal network in the shell wall of Quenstedtoceras and Ptychoceras contributed to achieving neutral buoyancy. As indicated by the high numbers of mini-pores in the connecting rings, the siphuncle was employed for adjusting buoyancy during vertical migrations. The “wrinkles”, “furrows”, “pits”, “dots”, “ridges”, “Ritzsteifen” and “Runselschicht” in the “wrinkle layer”, previously described in the ammonoid shell walls, are remnants of the pore-canal network.

Upper Oxfordian (Upper Jurassic) radiolarians from Rybaki Section, Moscow Region, Central Russia

A well-preserved radiolarian assemblage was recovered from the Upper Jurassic section near the Rybaki village, Moscow Region, Central Russia. The radiolarians were found within the Amoeboceras serratum ammonite zone (upper Oxfordian), in phosphatized body chambers of ammonite shells. The radiolarian assemblage is represented by 23 species of 11 genera and displays Boreal affinity. It is characterized by abundance of Praeparvicingula: P. blackhorsensis (Pessagno and Whalen), P. donnae Bragin, P. elementaria (Carter), P. enormis (Yang) and by presence of the characteristic boreal family Echinocampidae (genera Echinocampe and Nordvikella). Five new species are described.

Experience in studying natural fractals

We investigate the fractal characteristics of diverse natural objects and discuss their possible applications. Fractal dimensions of the suture lines of ammonite shells, granite textures, the portions of the river network in the Onega and the Ladoga lakes basin and the multi-fractal spectra of varved clay sedimentation in these lakes were calculated. It is shown that the fractal dimensions of the suture lines of shells can be used to identify ammonites. Fractal textures of granites can be applied to improve their aesthetic perception. The fractal parameters of the river network and the sedimentation regimes in the lakes may be related to tectonics.

Sheltered preservation of cyrtocrinid crinoids from the Lower Cretaceous of Madagascar and their palaeogeographic significance

Sheltered preservation, in which organisms are trapped within shells of cephalopods, is a well-known phenomenon. This preservational style constitutes an important source of paleontological data. Here, we report the first crinoid preserved inside the early Albian ammonite Cleoniceras besairiei Collignon from Madagascar. This crinoid is assigned to the aspidocrinid phyllocrinid (Apsidocrinus, Phyllocrinidae), and constitutes the first phyllocrinid from the African continent, the second from the southern margin of the Tethys (after New Zealand), and also from the southern hemisphere. This specimen represents the youngest occurrence of a phyllocrinid in the world as well, and constitutes one of the youngest occurrences of cyrtocrinids from shallow sea environments, before predation-induced migration of the stalked crinoids to the deep sea refugia due to the so-called Mesozoic Marine Revolution. This finding highlights that ammonite shells may also be a convenient material for studying echinoderms.

Mineralogy of interior jewellery ammonites of the Samara region

Background. Ammonite products are increasingly gaining in popularity. Ammonites are characterised by a variety of colour shades, shapes and sizes, making them suitable for manufacturing a wide range of souvenir and jewellery products. Russia enjoys significant resources of ammonites of interior and jewellery-ornamental quality; however, these materials remain insufficiently studied from the mineralogical point of view. This article presents the mineral composition and gemological characteristics of the Upper Jurassic interior jewellery ammonites of the Samara region for the first time.Aim. To describe the stratigraphic position and mineral composition of interior jewellery ammonites of the Samara region.Materials and methods. Late Jurassic ammonites (45 samples) were collected from a number of their main locations. The characteristic types of ammonites of interior-jewellery quality were distinguished and studied. Experiments included the determination of microhardness (25 determinations), density (12 determinations), luminescence features (10 samples), optical and petrographic analysis (5 thin sections), as well as the quantitative determination of mineral and chemical composition (3 samples), and electron probe studies (2 samples).Results. Ammonites are characterized by the presence of a mother-of-pearl layer with multi-coloured iridescence. The ammonites under study consist mainly of apatite (21—70 wt. %) and calcite (21—87 wt. %) along with quartz, aluminosilicates, gypsum, pyrite, zeolites, goethite, ilmenite and organic matter. The chambers of ammonite shells are made of phosphorite and calcite. The walls and partitions of shells have completely lost their original aragonite composition and consist of apatite and calcite with pyrite inclusions. The increased content of Sr (up to 0.17 wt. %) and Ba (up to 0.01 wt. %) are recorded as trace elements in ammonites. Calcite contains the following trace elements (wt. %): Mg — 0.17, Mn — 0.17, Fe — 1.14, Sr — 0.11, and Y — 0.17.Conclusion. The mineral and chemical (including microinclusions and trace elements) composition of interior-jewellery ammonites was established for the first time. The ammonites of the Samara region are of commercial interest as interior samples. Their shell fragments can be used in jewellery production. The ammonites under study can be collected along the coastal cliffs and beach area of the Volga river, thereby requiring no capital investments and producing no environmental pollution.

LATE JURASSIC INTERIOR-JEWELRY QUALITY AMMONITES FROM THE ULYANOVSK REGION: THE MINERAL COMPOSITION AND GEMOLOGICAL CHARACTERISTICS

Decorative articles made of ammonites are currently in high demand. The mineral composition and gemological characteristics of interior-jewelry ammonites from the Upper Jurassic of the Ulyanovsk Region have first been studied in detail. The ammonites are characterized by a pearl layer showing a bright varycolored iridescence. A complex of ammonite investigations comprised determinations of their microhardness, density, and luminescence; their optical-petrographic analysis; determinations of the mineral and chemical composition; and the electron-probe and electron-microscopic investigations. The ammonites consist mainly of apatite (22-88 wt. % ) and calcite (6-64 wt. %). Quartz, gypsum, pyrite, zeolites, ilmenite, rutile, goethite, zircon, and organic matter are present. Impurity elements recorded in elevated concentrations are (in wt. % ) Sr, 0.237; Ba, 0.011; and Pb, 0.023; and those recorded in low concentrations (less than 0.01 wt. %) are Ni, Cu, Zn, Rb, U, Th, Y, and As. The outer walls and septa of an ammonite shell have completely lost their original aragonite composition and consist of apatite and calcite with inclusions of pyrite and organic matter. The pearl layer iridescence is related to lamellar layers of apatite, that inherited the structure of lamellar layers of aragonite. The iridescence color is determined by the size and order of the lamellars and does not depend on their mineral composition. Ammonites of the Ulyanovsk Region are of commercial interest as interior-decorative specimens. Internal fragments of the shells can be used in jewelry. Ammonites are collected in steep ravine walls, which requires no capital investment and does not violate the environment.

Ontogeny-based intraspecific variability of the lower Turonian Choffaticeras (Choffaticeras) segne (Solger, 1903): taxonomic and biostratigraphic implications

The ontogeny-induced intraspecific variability of ammonite shells produce significant morphologic changes, and therefore, should be carefully considered in taxonomic classifications to avoid species oversplitting and misplacement. This study demonstrates the necessity of ontogenetic studies through a case study from the lower Turonian choffaticerids of the Egyptian Eastern Desert. The three choffaticerid taxa (Choffaticeras (Choffaticeras) segne, Ch. (Ch.) quaasi, and Ch. (Ch.) securiforme) previously used in literature are considered herein as belonging to a single species with three ontogenetic phases. Taxonomically, by applying the priority principle, Choffaticeras (Choffaticeras) sege is the only valid name, where the other two names were considered as junior synonyms. The species show three stages during the entire lifespan, each with discrete morphologic features. The robust ribs characteristic for the juveniles diminishes gradually throughout the maturation. Furthermore, the venter developed from tricarinate in the juveniles to sharp in the intermediates and keeled in the adults. Our viewpoint is supported by the presence of several oxycons with a considerable degree of disarticulation that facilities the examination of these successive ontogenetic phases. In biostratigraphic terms, the subdivision of the choffaticerid interval into three zones/subzones, based on stepwise lineage erected by the different authors, would be untenable.

Taphonomic history and trophic interactions of an ammonoid fauna from the Upper Triassic Polzberg palaeobiota.

The taphonomic mechanisms of a mono- to pauci-specific ammonoid fauna comprising 3565 specimens from the lower Carnian Polzberg Konservat-Lagerstätte near Lunz am See (Northern Calcareous Alps, Lower Austria) is described. The fossiliferous layers were deposited during the Julian 2 Ib (Austrotrachyceras austriacum Zone, Austrotrachyceras minor biohorizon). The deposits comprise abundant nektic ammonoids of the trachyceratid genus Austrotrachyceras. The bivalve Halobia, dominant among the invertebrates, is followed in abundance by the ammonoids Austrotrachyceras and Paratrachyceras, the coleoid Phragmoteuthis and frequent vertebrate actinopterygian fish. The monotonous ammonoid assemblage comprises abundant Austrotrachyceras, frequent Paratrachyceras, rare Carnites and Simonyceras. Recently collected ammonoids were sampled bed-by-bed and compared to extensive historical collections from the same localities. Bromalites (coprolites and regurgitalites) produced by large durophagous fish comprise ammonoid and fish masses and accompany the ammonoid-dominated Polzberg palaeobiota. The ammonoid fauna here presents a window into the nektic cephalopod world of the Upper Triassic assemblage and palaeoenvironment during the deposition of the fossiliferous layers. The frequent occurrence of the vertically oriented (external side horizontal to bedding plane) ammonoid shell fragments hint at a deposition after lethal fish or coleoid attacks. The Polzberg ammonoids were deposited under calm and dysoxic conditions in fine-laminated marlstones and shales of the lower Carnian Polzberg Sub-Basin within the Polzberg Konservat-Lagerstätte.

Fractal structures and mechanical properties of ammonite shells

The fractal structure of the blade-type lines of shells of extinct forms of ammonites of various types is investigated. These lines correspond to the connecting seams between the previous and new chambers that the mollusc builds during its gradual growth. Evolutionarily older forms have nearly straight or wavy seams with low tortuosity (the ratio of line length to end-point distance). Over the course of evolution, the shape of these lines has become more complex and acquired fractal properties, so that evolutionarily new types have connecting seams of a very complex shape. The fractal dimensions Df of the blade lines were measured using the box-counting method. It was shown that the fractal dimensions of the lobed lines of shells of different evolutionary ages increase from Df= 1.1 to Df = 1.9. In addition, with an increase in the chamber number, the Df values increase and remain larger on the outer surface of the chamber than on the inner one. The relationship between the fractal structure and an increase in the mechanical strength of the weld is discussed.

Reevaluating hydrodynamic performance of Late Triassic–Early Jurassic ammonoid shells with a 1D trajectory model

Biomechanical analyses provide unique insights on state shifts in the ecology of extinct communities. Ammonoids present a compelling case study for coupling biomechanical analysis with ecology given their robust fossil record of external conchs. We present a trajectory model to evaluate hydrodynamical advantages and challenges associated with ammonoid conch form. The model is a one-dimensional calculation estimating the dynamic feedbacks between different components of an ammonite’s motion including thrust, drag, acceleration, and distance traveled. Computational fluid dynamics simulations were performed on eleven different ammonoid conch morphotypes and integrated into a mathematical model to analyze the dynamics of swimming across a combination of conch diameters (5, 10, and 20 cm) and jet rhythms (a single jet or series of three pulses). We compared the efficacy of short-term bursts of motion to that of long-term cruising and found: inflated shapes (i.e., spherocones) offer the fastest short-term motion, but at the greatest costs; heavily streamlined shapes (i.e., platycones) offer long cruise distances, but with ineffective short-term motion; and visibly-coiled shapes (i.e., serpenticones) appear to offer intermediate performance in both locomotion styles. Size is critical in ranking the performance of different conch shapes in both locomotion styles because ranking is determined predominantly by the amount of thrust an animal is capable of generating. With increasing size, Reynolds number increases and the effects of second-order morphological characters become more pronounced and alter the performance ranking of conchs. Finally, we present a visual analysis of the flow regimes and shape details that may drive these hydrodynamic consequences. We speculate that serpenticone morphologies capitalized on these subtleties with a morphology that provided reasonably high-speed swimming at small sizes relevant to juveniles while maintaining relatively efficient coasting locomotion at the larger sizes relevant to adult animals. We highlight the ubiquitous serpenticones of the Early Jurassic as a case study for applying biomechanical data to a paleoecological context. The broad range of morphotypes expressed by ammonoids in the Late Triassic is dramatically pared down during the End Triassic extinction. In the few million years following the extinction, ammonoids diversify into a suite of shapes with a more restricted range of locomotor performance, and only much later is the full range of morphology recovered.

Upper Callovian and Oxfordian molluscs and brachiopods from selected localities of the Kraków-Częstochowa Upland and the Świętokrzyskie Mountains, Poland

The aim of the study was the taxonomic, morphological, ecological and stratigraphic characterization of marine invertebrate groups from the localities of Wiek and Wysoka (Krakow-Częstochowa Upland) and Gnieździska (Świętokrzyskie Mountains). All of these three localities were unused quarries where limestone was once mined. The material consisted of a total of 756 fossils collected by the author from the studied sites or constituting part of the collections of the Department of Vertebrate Ecology and Palaeontology at the University of Environmental and Life Sciences in Wrocław. When describing and marking the fossils, attention was paid to the state of preservation, morphology, size, shape and the presence of structures characteristic of a given taxon. Among the studied material were fossils of gastropods, bivalves, ammonites, belemnites, and brachiopods. These organisms were found in upper Callovian (Middle Jurassic) and Oxfordian (Upper Jurassic) sediments and are approximately 157.3–166.1 million years old. Different groups of invertebrates dominated in the material collections from individual sites. Among the fossils from the Wiek quarry, the most numerous were brachiopods, the material from the Wysoka locality was dominated by ammonites, and the most numerous group in the collection from the Gnieździska quarry were belemnites. In total, 18 genera belonging to 13 families were recorded. The most numerous group among the studied fossils were Ammonitida, mostly represented by the genus Perisphinctes. In the collection from the Wysoka quarry, a single ammonite shell belonging to the genus Horioceras was recorded, which has not been recorded at this site so far. Among the collected ammonites, the genera Cardioceras, Lissoceratoides, and Trimarginites were also distinguished. The most diverse group among the collected fossils were brachiopods, of which eight genera were recorded: Lacunosella, Septaliphoria, Epithyris, Juralina, Loboidothyris, Sellithyris, Zeillerina, and Terebratulina. The studied material also revealed the presence of one genus of gastropods—Nerinea, two genera of bivalves—Lima and Posidonia, and two general of belemnites—Belemnopsis and Hibolites. These organisms inhabited the shallow and warm shelf sea that covered a large area of present territory of Poland during the Jurassic period.

Stable isotopes and predation marks shed new light on ammonoid habitat depth preferences

Ammonoids are extinct cephalopods with external shells which predominated in many late Paleozoic and Mesozoic marine ecosystems. Stable isotope data from ammonoid shells constitute primary tools for understanding their palaeohabitats. However, in most sedimentary successions globally the aragonitic shells of ammonoids are dissolved during fossilisation process and therefore not available for geochemical studies. We overcome this taphonomic bias by analysing the better preservable calcitic elements of the ammonoid jaws (aptychi). We study moulds and aptychi of two successive members, temporal subspecies in our interpretation, of a scaphitid evolutionary lineage from a Late Cretaceous chalk succession in Poland. In order to reconstruct their habitat depth preferences, we apply the powerful combination of stable isotope data from aptychi and co-occurring benthic and planktic foraminifera with an analysis of predation marks preserved on scaphitid specimens. On this basis we conclude that the populations of the older subspecies led a nektic, and those of the younger subspecies, a nektobenthic lifestyle. The shift in habitat depth preferences took place probably as a response of local populations to the shallowing of the sea. Previous studies largely assumed stable depth preferences for ammonoid species, genera and even higher clades. Our study casts doubts over such generalizations by pointing out that ammonoids could have been more flexible in their depth-related behaviour than anticipated.

The palynology of the Lower-Middle Jurassic transition of the North Caucasus (southwest Russian Federation), calibrated with index ammonites

Palynomorphs from the Toarcian and Aalenian Djigiat Formation of Karachay-Cherkessia in the Kuban River Basin (North Caucasus, southwest Russian Federation) are reported for the first time. Five samples carefully selected for their biostratigraphical content were studied to document the palynological assemblages. Four samples (1, 2, 3, 4) were collected from pieces of rock with key index ammonite specimens, and sample 5 comprises fragments of ammonite shells from a sideritic concretion. Three of these samples (4, 2 and 1) yielded relatively abundant and diverse aquatic microplankton (acritarchs, dinoflagellate cysts, prasinophytes and zygnematalean algae) and terrestrial palynomorphs (pollen and spores); the remaining two samples (3 and 5) were less productive and contained fewer than 50 palynomorph specimens. The study of the dinoflagellate assemblages provided characteristic and key information. These are the uppermost Toarcian Nannoceratopsis Assemblage and the uppermost Toarcian to lowermost Aalenian Parvocysta Suite Assemblage. The former is overwhelmingly dominated by Nannoceratopsis with sparse numbers of the Parvocysta suite, and the latter yielded more diverse and common specimens of Parvocysta and its relatives. This is consistent with the hypothesis that the Parvocysta suite migrated from the Boreal Realm further south into Laurasia during the Toarcian. Certain dinoflagellate cysts such as Mancodinium semitabulatum and Scriniocassis spp., which are typical of Europe and much of Greater Laurasia are absent. Composition of the pollen and spores proved relatively out to be monotonous, and cannot be subdivided. However, in general, the composition of the assemblages of spores and pollen is consistent with the Toarcian–Aalenian transition.

The thoracican cirripede genus Concinnalepas Gale, 2014 (Crustacea) from the Middle and Upper Jurassic of southern England and northern France

New material of the cirripede genus Concinnalepas is described from the Kimmeridge Clay (Tithonian) of Dorset (UK) and the Marnes de Port (Bathonian) of Port-en-Bessin in Normandy (France). Articulated specimens of C. costata (Withers, 1928), attached to driftwood from Kimmeridge, provide hitherto unknown details of tiered lateral plate formation in the species, and Concinnalepas bessinensis sp. nov. and C. rugosa sp. nov. are described from Normandy and Dorset, respectively. Concinnalepas bessinensis sp. nov. is the oldest calcite-shelled cirripede known to date. A review of the distribution of Jurassic calcareous cirripedes demonstrates that pre-Kimmeridgian records are very sparse and scattered and the early evolutionary history of the group is poorly known. The late Kimmeridgian and Tithonian saw a radiation of the Family Zeugmatolepadidae and a great increase in abundance of cirripedes that mostly lived as epiplankton, attached to driftwood and ammonite shells.

Material constitution of gem-quality ammonites – by-product of mining in the Saratov Region

Manufactured articles of ammonites have been in increasingly higher demand in the recent decades. Ammonites have appeal for the unique shapes, color and age. The top suppliers of ammonites to the world market are Madagascar, Morocco, Canada and Russia. In Russia, gem-quality ammonites occur in the Saratov Region, apart from other places. The regional open pit mine at the settlement Dubki situated 7.5 km northeastward of Saratov supplies ammonites both to the Russian and global markets. The submicroscopic and electron microprobe analyses presented details of mineral composition and structure of ammonite shells. The test shell fragments included walls and partitions with layers of pyrite. The pyrite layers lay symmetrically relative to the partitions and inside walls of ammonite, and feature pronounced structural zonality. The partitions and walls are adjoined with narrow zones of fine-crystal pyrite. Then, a zone of coarse-crystal pyrite lies, with fragments of colloform pyrite. The gem-quality ammonites have mostly pyrites in their composition (to 96 % by mass) and are connected with the Upper Jurassic deposits. Among other things, ammonites contain aragonite, calcite, apatite, jarosite, gypsum, ferrian carbonate and organic substance. The original aragonite is preserved in walls and partitions of shells. Morphologically, the large prismatic, fine-crystal, colloform and globular species of pyrite are distinguished. Pyrite is actively decomposed by bacteria. The Saratov Region ammonites possess high decorative and processing properties, can be widely used in manufacturing of jewelry and are by-produced in the course of large-scale mining.