Middle Jurassic (upper Bajocian) marine vetigastropods from the Western Saharan Atlas,Algeria

Whereas Middle Jurassic gastropods are very well known in Europe and other regions of the world, these faunas have been much less studied from northern Africa and most contributions available in literature have been based on relatively well-preserved material. Except a little lower Bajocian fauna from the Central High Atlas (Morocco) described at the turn of the 21th century, nothing is known about the Middle Jurassic gastropods of the southwestern Tethyan margin. The present paper aims to update the systematics of two vetigastropod species: Obornella cf. granulata (Sowerby, 1818) and Ambercyclus ornatus (Sowerby, 1819) recently found in the upper Bajocian succession of the Ksour Mountains (Tniet el Klakh Formation) at western Saharan Atlas (northern Algeria). The new Ambercyclus material found in well-preserved conditions confirms the absence of umbilicus in Ambercyclus; thus, we emend the original generic diagnosis. The specimens of Obornella cf. granulata and Ambercyclus ornatus represent the first occurrence of both genera and species in the upper Bajocian marine deposits of the western Saharan Atlas, and provide new taxonomic and palaeobiogeographic information about Middle Jurassic vetigastropods in Algeria.     

Discovery of Middle Jurassic (Bajocian) Radiolaria from the sedimentary cover of the Vedi ophiolite (Lesser Caucasus,Armenia)

The Vedi ophiolite, situated southeast of Yerevan (Armenia), represents part of the Neotethyan oceanic lithosphere preserved in the Lesser Caucasus. This ophiolite unit constitutes a large tectonic klippe, a result of obduction during the Upper Cretaceous (Coniacian–Santonian). Relatively well-preserved Radiolaria extracted from radiolarites overlying ophiolitic lavas along the Vedi River consist of Middle Jurassic (Bajocian, U.A.Z. 3–4) species, typical of the Tethyan tropical bioprovince. Assemblages are dominated by Nassellaria and characterised by the presence of species Cyrtocapsa mastoidea, Hexasaturnalis hexagonus, Laxtorum (?) hichioense, Stichocapsa japonica and Striatojaponocapsa plicarum s.l. This microfauna provides evidence for the oldest age available so far for the sedimentary cover of the Vedi ophiolite.     

First occurrence of the Ichnogenus Selenichnites from the Middle Jurassic Strata of the Skoura Syncline (Middle Atlas,Morocco); Palaeoecological and palaeoenvironmental context

Mesozoic strata of North Africa yield the first occurrence of the ichnogenus Selenichnites. The trace fossils occur on the top surface of a sandy carbonate deposit in the axis of a Middle Atlas syncline (Skoura Syncline, NE Morocco). The ichnofossil-bearing horizon belongs to the Late Bajocian–Early Bathonian Ich Timellaline/Bou Akrabene Formation. The trace fossils are crescent-shaped and the best preserved exhibits a posterior central axial impression (possible telson tail impression). They are interpreted as feeding burrows (fodinichnia) or hiding depressions of Xiphosurids or Limulids (horseshoe crabs) on a sandy carbonate substrate beneath a veneer of muddy deposits. The sedimentological character suggests a relatively protected shallow water subtidal palaeoenvironment preceding the Bathonian regression of the Atlas domain. This discovery provides the first evidence of xiphosurans or xiphosuran-like organisms inhabiting the southern shores of the Tethys in the Middle Jurassic.     

Drowning of a Lower Jurassic carbonate platform: Jbel Bou Dahar, High Atlas, Morocco

Summary The high-plateau of the Jbel Bou Dahar, situated in the Central and Eastern High Atlas of Morocco, represents a Lower Jurassic carbonate platform that drowned at the beginning of the Toarcian. Three phases of platform evolution can be distinguished: During thepre-drowning phase (upper Sinemurian— upper Pliensbachian) the platform interior facies reflects a restricted-marine lagoonal environment, protected by scattered buildups and cemented debris at the platform margin. Upper and mid-slope are dominated by coarse-grained, poorly sorted limestones, deposited through debris flows during sea-level lowstands. Sea-level highstand deposits occur at the toe of slope and are formed by an alternation of fine-grained litho- and bioclastic pack- to grainstones (turbidites), marls and mud- to wackestones (hemipelagic oozes). A condensed section, reflecting an abrupt and fundamental environmental change along the entire platform, characterises thedrowning phase (upper Pliensbachian— lower Toarcian). Within the platform interior densely packed biosparites represent the switch to high-energy environments, causing erosion of the former pre-drowning lagoonal sediments. These erosional products were redeposited on the platform slope, leading to the formation of coarse-grained non-skeletal sparites and micrites. Both platform interior and slope successions show a series of cyclic variations in sediment composition that could have been triggered by small-scale sea-level fluctuations. In contrast to the abrupt facies change at the pre-drowning —drowning boundary, the transition to thepost-drowning phase (lower Toarcian—Aalenian) is gradual. During this phase, biopelmicrites and pure micrites were deposited in all platform sections, followed by the deposition of calcistiltites. The facies point to quiet-water conditions below storm-wave base and display a uniform deep-marine sedimentation. This analysis shows that the drowning of the Jbel Bou Dahar carbonate platform was caused by abrupt and fundamental changes in the shallow-water realm. After exposure of the platform, these changes prevented the carbonate factory from re-establishing itself and made it impossible for the platform to keep up with the subsequent rise in sea level. These local changes were probably triggered by high-frequency sealevel variations in combination with regional or even worldwide changes in ocean circulation patterns.     

Late Triassic Tetrapod-Dominated Ichnoassemblages from the Argana Basin (Western High Atlas,Morocco)

Diverse tetrapod track assemblages with Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations of the Argana Basin (Western High Atlas, Morocco). The ichnofossils occur in alluvial plain sandstones and mudstones of the Irohalène Member (T5) and Tadart Ouadou Member (T6) considered Carnian-Norian in age by vertebrate remains and palynomorphs. Tetrapod footprints are assigned to Apatopus, Atreipus-Grallator, Eubrontes isp., Parachirotherium, cf. Parachirotherium postchirotherioides, Rhynchosauroides ispp., and Synaptichnium isp. They can be referred to lepidosauromorph/ archosauromorph, basal archosaur, and dinosauromorph trackmakers. Apatopus, represented by 11 tracks of a more than 4 m long trackway, is recorded for the first time outside of North America and Europe. The assemblage concurs with the proposed Late Triassic age of the track-bearing beds by the occurrence of Apatopus, Atreipus-Grallator, and Eubrontes. If this is accepted, the stratigraphic range of Synaptichnium and Parachirotherium, hitherto known only from Early or Middle Triassic deposits, has to be extended to the Carnian-Norian. The occurrence of Eubrontes in the Irohalene Member (T5) provides further evidence for large theropods in pre-Jurassic strata. All assemblages are referred to the Scoyenia ichnofacies indicating continental environments with alternating wet and dry conditions.     

Toarcian carbon isotope shifts and nutrient changes from the Northern margin of Gondwana (High Atlas, Morocco, Jurassic): Palaeoenvironmental implications

The Early Toarcian is marked by a global perturbation of the carbon cycle and major marine biological changes. These coincide with a general decrease in calcium carbonate production and an increase in organic carbon burial, and culminate in the so-called Toarcian Oceanic Anoxic Event. It is believed that the environmental crisis was triggered by the activity of the Karoo-Ferrar large igneous province. In order to further document the Early Toarcian palaeoenvironmental perturbations, carbon isotope, total organic matter, calcareous nannofossils and phosphorus content of the Amellago section in the High Atlas rift basin of Morocco were investigated. This section is extremely expanded compared to the well-studied European sections. Its position along the northern margin of the Gondwana continent is of critical importance because it enables an assessment of changes of river nutrient input into the western Tethyan realm. The carbon isotope curve shows two negative excursions of equal thickness and amplitude, at the Pliensbachian-Toarcian boundary and at the transition from the Polymorphum to the Levisoni Zone. This confirms the supra-regional nature of these shifts and highlights the possible condensation of the first “boundary” shift in European sections. Phosphorus content is used to trace palaeo-nutrient changes and shows that the two negative carbon isotope shifts are associated with increased nutrient levels, confirming that these episodes are related to enhanced continental weathering, probably due to elevated greenhouse gases in the atmosphere. In the High Atlas Basin, the increase in nutrient levels at the Pliensbachian-Toarcian boundary is moreover likely to be the main factor responsible for the coeval demise of the Saharan carbonate platform. A middle Toarcian event, centered on the boundary between the Bifrons and Gradata Zones, characterized by a positive carbon isotope excursion and nutrient level rise, is documented in the Amellago section.     

Early Triassic Archosaur-Dominated Footprint Assemblage from the Argana Basin (Western High Atlas,Morocco)

An assemblage of abundant and well-preserved tetrapod footprints has been discovered in the Tanamert Member (T3) of the Triassic Timezgadiouine Formation (Argana basin, western High Atlas, Morocco). It is the first fossil record from T3. Surfaces from different localities show a uniform tetrapod ichnofauna that consists of chirotherian and small lacertoid forms. The chirotherians are assigned to the plexus Protochirotherium—Synaptichnium, their trackmakers interpreted as basal archosaurs. The lacertoid imprints show close affinities with Rhynchosauroides and may reflect archosauromorphs or lepidosauromorphs. Protochirotherium—Synaptichnium assemblages are characteristic of the Early Triassic and were known previously only from units of this age in central Europe. Biostratigraphically, the European record implies a wide-spread pre-Anisian Protochirotherium—Synaptichnium dominated assemblage preceding the first appearance of Chirotherium barthii near the Olenekian-Anisian boundary. The stratigraphic position of T3 between Late Permian (uppermost T2) and Middle Triassic (T4) and the European correlatives suggest an Early Triassic age of this unit. It is the first record of Early Triassic continental deposits in Morocco. The surfaces from T3 open up perspectives for further contributions to ecology, biogeography and locomotion of early archosaurs. Furthermore, excellent outcrops and quality of footprint preservation in the Argana basin offer a potential for clarification of ichnotaxonomic and biostratigraphic issues.     

Oldest camarasauromorph sauropod (Dinosauria) discovered in the Middle Jurassic (Bajocian) of the Khadir Island, Kachchh, western India

Fragmentary isolated remains of large (up to 20 m or more) sauropods from the Middle Jurassic (Bajocian) Khadir Formation of Khadir Island (Kachchh, W India) are described and compared in detail. Three of the bone fragments (a metacarpal, a first pedal claw and a fibula) can be assigned with confidence to the Camarasauromorpha and represent the oldest known record of that derived dinosaur group. The new finds from western India further close a temporal and geographical gap in our knowledge of sauropods and contribute to understanding their early phylogeny.      

Ammonite fauna from uppermost Bajocian (Middle Jurassic) calcitic concretions from the Polish Jura—biogeographical and taphonomical implications

Uppermost Bajocian (Parkinsoni Zone, Bomfordi Subzone) calcitic concretions from the epicratonic basin in South-Central Poland (Polish Jura) contain numerous, well-preserved ammonites unique for this area. Characteristic of the assemblages is the presence of small, juvenile specimens. Associated with dominant parkinsoniids (Parkinsonia (Parkinsonia) aff. dorni Arkell) are lytoceratids [Nannolytoceras tripartitum (Raspail)], lissoceratids [(Lissoceras (Lissoceras) oolithicum (d'Orbigny) and Lissoceras (Microlissoceras) solitarium Zatoń and Marynowski nov. sp.)], leptosphinctids (Vermisphinctes sp.) and strigoceratids [(Strigoceras (Strigoceras) sp. juv. gr. strigifer/pseudostrigifer)], as well as fragments of phylloceratids (Phylloceras sp.). Parkinsoniids (the most numerous) are considered here as host fauna. Other ammonites, especially phylloceratids and nannolytoceratids, are supposed migrants from the Mediterranean area into the shallow epicratonic Polish Basin during the Late Bajocian sea-level rise. N. tripartitum, which has a broad geographical range probably drifted as a plankton-feeder in the upper water column and, together with phylloceratids, are considered to be unsuccessful immigrants which did not adapt to the new environment. It seems that the whole fauna, inclusive of plant remains, was accumulated by bottom currents in randomly situated depressions on the sea-floor, where carcasses became ideal nucleation sites for concretion genesis. Early diagenesis, which played an important role, resulted in well-preserved ammonite assemblages close to the original biological assemblage. Most of described ammonites (nannolytoceratids, lissoceratids, strigoceratids and leptosphinctids) are reported from the Upper Bajocian epicratonic deposits of Poland for the first time. This makes the concretions a true “taphonomic window” into latest Bajocian census biocenosis. The organic geochemistry results suggest predominance of terrestrial organic matter in both concretions and surrounding clays, with well oxygenated conditions in the sedimentary basin. The large concentrations of Δ¹³⁽¹⁷⁾diasterenes in the analysed carbonate concretions indicates that these compounds must have been formed by contact with clay minerals before formation of the carbonate concretions. The processes described may have followed early stage of diagenesis, but certainly under tens of cm to even a few meters of burial. The high negative δC¹³ values in the inner zone of the concretions suggest that concretion growth began in the sulphate reduction zone and may have continued in the methanogenesis zone.     

Copper affects biofilm inductiveness to larval settlement of the serpulid polychaete Hydroides elegans (Haswell)

Copper (Cu) contamination is a potential threat to the marine environment due to the use of Cu-based antifouling paints. Cu stress on larval settlement of the polychaete Hydroides elegans was investigated, and this was linked to Cu stress on biofilms and on the biofilm development process. The inductiveness of young biofilms was more easily altered by Cu stress than that of old biofilms, indicating the relative vulnerability of young biofilms. This might result from changes in bacterial survival, the bacterial community composition and the chemical profiles of young biofilms. Cu also affected biofilm development and the chemical high performance liquid chromatograph fingerprint profile. The results indicate that Cu affected larval settlement mainly through its effect on the process of biofilm development in the marine environment, and the chemical profile was crucial to biofilm inductiveness. It is strongly recommended that the effects of environmentally toxic substances on biofilms are evaluated in ecotoxicity bioassays using larval settlement of invertebrates as the end point.     

A catalogue of teleosauroids (Crocodylomorpha: Thalattosuchia) from the Toarcian and Bajocian (Jurassic) of southern Luxembourg

Abstract

Teleosauroids were a clade of semi-marine crocodylomorphs that attained near-global distribution during the Jurassic Period. They were particularly common during the Toarcian (Early Jurassic) and are well documented throughout the UK and Germany. However, Toarcian teleosauroids discovered in Luxembourg have been little studied and rarely discussed in the scientific literature. Here we present a comprehensive catalogue of Luxembourg thalattosuchian specimens, including nine teleosauroids (all from the Toarcian) and five Thalattosuchia indeterminate (four from the Toarcian and one from the Bajocian), many of which are noted in the literature for the first time. We describe these specimens and identify two distinct genera (Steneosaurus and Platysuchus) as present in the sample as well as three, or possibly four, distinct species. This represents a high diversity of teleosauroid taxa (both common and rare forms) from the Toarcian rarely seen elsewhere in the world.     

Modern surface pollen assemblages from the Middle and High Atlas,Morocco: insights into pollen representation and transport

Thirty-three modern surface samples were collected in the environmentally and climatologically contrasting regions of the Middle and High Atlas Mountains, Morocco. Samples representing forest and steppe montane environments (1935–2760 m above sea level) are clustered around study sites at Lake Tislit (High Atlas, semi-arid oro-Mediterranean bioclime) and Lake Sidi Ali and Michliffen (Middle Atlas, sub-humid montane Mediterranean bioclime). Good discrimination between regional pollen spectra is evident, with Middle Atlas samples reflecting higher arboreal cover (Cedrus and evergreen Quercus) and High Atlas samples with high abundances of non-arboreal taxa, including Artemisia and Fabaceae. These four taxa (Cedrus, evergreen Quercus, Artemisia and Fabaceae) are furthermore shown to be reliable indicators of local source vegetation within a 100 m² quadrat, taking into account threshold abundances of 7%, 20%, 4% and 10%, respectively. Deciduous Quercus, Olea and Phillyrea show long-distance pollen dispersal across both regions, contributing to non-trivial arboreal pollen (AP) values of up to 35% (typically 20–30%) in the High Atlas spectra. In the Middle Atlas, AP values of 40 to 50% occur in open sampling locations and > 60% under forest canopy cover. These insights should be taken into account when interpreting ancient pollen spectra from regional lakes and bogs for palaeoenvironmental reconstruction.     

A new hawker dragonfly from the Middle Jurassic of China (Odonata: Aeshnoptera)

A new genus and species Linqibinia panae of paracymatophlebiid hawker dragonfly is described from the Middle Jurassic Haifanggou Formation (Inner Mongolia, China). Previously only known from Karatau in Kazakhstan, the discovery of another member of this family extends its range across Central Asia. It confirms that the Aeshnoptera was among the most diverse odonatan clades during the Middle-Late Jurassic.     

A new lizard-like reptile (Diapsida: Lepidosauromorpha) from the Middle Jurassic of England

The Middle Jurassic (Late Bathonian) Mammal Bed at Kirtlington, Oxfordshire, has yielded a rich assemblage of small vertebrates including mammals, frogs, salamanders and small reptiles. This paper describes the skull of a new diapsid reptile, Marmorelta oxoniensis, which was common within the fauna. The skull is gracile with large orbits and relatively long external nares. The frontals and parietals are single in the adult and almost separated on the roof of the skull by the postfrontals. The temporal region shows a mosaic of primitive and derived character states. The quadrate was firmly held to the skull by a large squamosal and a small, free, quadratojugal was retained. However, reduction of the anterior process of the quadratojugal and of the posterior process of the jugal left the lower temporal fenestra broadly open. Comparison with other diapsids leads to the conclusion that Marmoretta was a lepidosauromorph, most probably the sister taxon of Lepidosauria.     

Intracolonial variability in new bryozoans from the Middle Jurassic of the Bryansk Region (Russia)

Two new species of encrusting bryozoans (Stenolaemata, Tubuliporida) from the Middle Callovian (Middle Jurassic) deposits of the Bryansk Region, Oncousoecia guzhovi sp. nov. and Microeciella fokinensis sp. nov., are described. Their intracolonial variability, which is due to differences in astogenetic stages and to external factors, is discussed.     

A new species of Pseudotorellia florin (Ginkgoales) from the Middle Jurassic of Eastern Mangyshlak (Kazakhstan)

A new species of Pseudotorellia Florin, Pseudotorellia papillata sp. nov., from the Middle Jurassic of Eastern Mangyshlak (Western Kazakhstan, Tonasha Formation) is described. The main distinction of the new species from the other species of this genus is the relief cutinization of periclinal walls of cells of the lower epidermis, especially within stomatal bands, expressed in prominent cuticular ridges and papillae of irregular shape.