Littérature scientifique sur le sujet « Daonella »

Halobia daonellaformis new species is described from the lowermost Carnian of northeast British Columbia. Halobia daonellaformis n. sp. is regarded as a primitive Halobia characterized by external ornamentation similar to Daonella lommeli, but with a poorly developed anterior auricle. Morphologic characters of H. daonellaformis n. sp. suggest that Halobia may be not a natural taxon but a polyphyletic group with one or more ancestors from Daonella and Aparimella and/or other posidoniid(s). The sudden appearance of Halobia throughout the marine Triassic suggests a rapid dispersal mechanism following a Ladinian origin. Larval shell morphology indicates a planktotrophic developmental strategy for H. daonellaformis n. sp., and by extension to other halobiids, which may explain the widespread distribution of many halobiid species.

DOI: 10.17014/ijog.v5i1.91The interregional and global correlation of the Triassic biota of Indonesia was based on the review of previous workers and the author himself. Scythian Epoch (Early Triassic) in Timor is subdivided into Early Scythian with Ophiceras demisso, Meekoceras sp., Pseudomonotis subaurita, Gervillia subpannonica, and Myophoria sp., whilst Late Scythian is indicated by the presence of Owenites egrediens and Sibirites sp. The presence of Anisian Stage (Middle Triassic) in Misool is indicated by ammonite Beyrichites and bivalve Daonella lilintana. In Timor, this stage is pointed out by the presence of Joannites cymbiformis, Monophyllites wengensis, Protrachyceras archaelus, Daonella indica, Tracyceras cf. aon, Brochidium timorense, and Lima subpunctatoides. Terebellina mackayi found above Beyrichites-bearing bed in Misool has an age range from Anisian to Ladinian. It is concluded that the boundary between Anisian and Ladinian lies between beds with Beyrichites and Terebellina mackayi. Early Carnian Stage (Late Triassic) in Timor is indicated by the presence of Joanites cymbiformis, Waldhausenites sp., Miltites sp., and Halogyra cipitiensis; whereas Late Carnian is indicated by the presence of Cladicites crassestriatus and Tropites subbulatus. The presence of Halobia verbeeki, Pinacoceras parma, Neobetites sp., Parabetites sp., Malayites sp., Amarassites sp., and Halorites sp., indicates the Early Norian Stage, whilst the presence of Cladiscites tornatus, Cyrtopleurits malayicus, and Trachypleuraspidites sp. implies the Late Norian. The Rhaetian Stage in Timor contains Choristoceras indoaustralicum, whereas in Misool it contains Choristoceras sp. and Cochloceras sp.

The black shales of the Middle Triassic Botneheia Formation in Svalbard are known for their fossil richness with abundant ichthyosaur remains and beds of the bivalve Daonella. Vertebrate remains from the Muen Mountain on Edgeøya are shown to have exceptional X-ray contrast due to a combination of sulphide and sulphate permineralisation and pseudomorphing. Radiography imaging of a previously described specimen, PMO 219.250, revealed new and spectacular details such as more carpals, teeth, and skull sutures. Teeth and skull characters are taxonomically significant. supporting the referral of PMO 219.250 to Phalarodon and further suggesting an affinity to P. atavus. Three sulphur phases were identified, with the sulphide sphalerite (ZnS) being the highest temperature phase, followed by the sulphate baryte (BaSO4), and the sulphide pyrite (FeS2). Sulphate permineralisation is also seen in specimens from the Upper Jurassic on Svalbard. We suggest that sulphur-rich fluids have flowed and dissolved barium from the shales and deposited the sphalerite and baryte, and that this could be linked to the Cretaceous HALIP. The Jurassic specimens are only permineralised by baryte, while the Triassic specimens have also been permineralised, but mainly pseudomorphed by baryte with crystals of sphalerite. Lithology differences appear to have controlled the compaction of the Triassic specimens, while the Jurassic specimens have retained their three-dimensional shape due to the baryte emplacement relatively earlier in their depositional history. Although soft tissues are not preserved, the excellent X-ray contrast in the Middle Triassic specimens is reminiscent of pyritised fossil sites such as the Hunsrück Slate (Devonian), Beecher’s Trilobite Bed (Ordovician), and the La Voulte-sur-Rhône marls (Jurassic).

A Tethys közép-európai triász időszaki fejlődéstörténetének nyomozása az egymástól távolabbi területeken található nem vulkanogén üledékes kőzetek összehasonlító vizsgálatával régóta eredményesen zajlik. A térben és időben is sokkal változatosabb kifejlődésű vulkanogén képződmények ezirányú vizsgálatában rejlő lehetőségek még messze nincsenek kihasználva. Ennek leginkább az lehet az oka, hogy ezeknek a hazai kőzeteknek a részletes kőzettani leírása még nem történt meg. Ladin vulkanogén törmelékes képződmények a Dunántúli-középhegységen belül a Keleti-Bakony területéről ismertek. Az itt található középső–késő-triász vulkanogén kőzetek részletes petrográfiai vizsgálata lehetőséget teremtett arra, hogy kőzettani alapon is összevessük más hasonló korú, képződésük idején egymáshoz sokkal közelebb elhelyezkedett Dunántúli-középhegységben és Déli-Alpokban megtalálható vulkáni képződményekkel.A vizsgált keleti-bakonyi összletek az inotai Hideg-völgy útbevágásában lévő egykori felszíni feltárásban, valamint a Várpalota Vpt–3 és a Bakonykúti Bút–2 fúrások anyagában tanulmányozhatók. A vulkanogén összlet két részre tagolható: az alsó részben uralkodóan vulkanit törmelékszemcsékből álló, szenesedett növénymaradványt és elszórtan crinoidea váztöredékeket tartalmazó finomszemcsés üledékes kőzetet, fölül vulkanit- és mészkőkavicsokat nagy mennyiségben tartalmazó, Daonella vázelemekben gazdag durvaszemcsés rétegcsoportot találhatunk. A vulkáni törmelék szemcsék között döntően intermedier (andezit), kisebb mennyiségben bázisos (bazaltsalak, bazalt és mikrodolerit) és savanyú (riolit, aplit) vulkanitok és ezekhez kapcsolódó kristálytörmelékek jelennek meg.A vulkanogén összlet forrását olyan középső- és felső-triász vulkáni kőzetek (bázisos-intermedier lávakőzetek és freatomagmás kitörések termékei) szolgáltatták, melyeknek mai rokon képviselői a Dunántúli-középhegységben (legközelebb a balatonfői területen), de legnagyobb kiterjedésben a vele ezen időszakban szomszédos Déli-Alpokban fordulnak elő. A felső vulkanogén konglomerátum / kavicsos homokkő képződésére jó analógia a déli-alpi Wengeni Formáció és Marmoladai Konglomerátum keletkezése. E formációk nagy vastagságú törmelékes összlete szárazulatra került, döntően mészkő és bázisos-intermedier kőzetek lepusztulásával, majd tenger alatti tömegmozgásokkal üledékgyűjtő medencékbe történő felhalmozódásával keletkezett. Az alsó vulkanogén homokkő keletkezése ettől némiképp eltér. Bázisos-intermedier összetételű törmelékanyaga első lépésben sekélytengeri/szárazföldi környezetben freatomagmás kitörés eredményeként halmozódott fel, majd közvetlen ezután tenger alatti lejtő mentén történő áthalmozódás után ülepedett le véglegesen.

Early to Middle Triassic marine successions are remarkably lacking in the Southern Hemisphere. It would seem that the best developed and most fossiliferous sequences are preserved in New Zealand. To a lesser extent, successions of Early to Middle Triassic age are known from New Caledonia, New Guinea, the Gympie Basin of Eastern Australia, offshore Western Australia, and western South America (in particular Chile).Anisian marine faunas were first collected in New Zealand (Etalian local stage) in the 1940s but it was not until 1953 that their age significance was correctly recognised by Marwick. This was later confirmed by Kummel. Since then an unpublished doctoral study has been completed on the paleontology and biostratigraphy of the Anisian succession within the Murihiku terrane of Southland, South Island, New Zealand. A conclusion of this study, based on ammonoid correlations, was that the cosmopolitan halobiid bivalve Daonella appears earlier in New Zealand than it does in North America.Recent investigations post-date the advent of the tectonostratigraphic terrane concept and suggest that an Anisian fossil record is preserved in at least three terranes in New Zealand (Murihiku, Dun Mountain - Maitai and Torlesse terranes), and two terranes in New Caledonia (probably correlatives of the Murihiku and Torlesse terranes of New Zealand). Analysis of the faunal content of these various terranes suggests that although there are some facies differences (litho and bio), there is little obvious basis for recognition of distinct paleobiogeographic provenance.A corollary to this research on Anisian faunas is the recognition that the New Zealand ammonoid faunas previously considered to be Early Triassic (Malakovian local stage; Murihiku terrane) by Kummel are almost certainly Anisian. However, this does not imply that there isn't an Early Triassic sedimentary record. Significant thicknesses of apparently unfossiliferous sequence are present in each of the relevant terranes. Two isolated Early Triassic ammonoid faunas are now known from elsewhere in New Zealand but from tectonically complex settings in Brook Street (?) and Dun Mountain - Maitai terranes.

The Besano Formation consists of an alternation of laminated dolomitic banks and bituminous shales, and sparse cineritic tuffs that are dated as Late Anisian–Early Ladinian. It is one of the richest fossil-bearing formations from the Monte San Giorgio area; on the Italian side of Monte San Giorgio, the Sasso Caldo site is the one from which the greatest part of the Besano collection housed at the Museo di Storia Naturale di Milano is from. This Ph.D. thesis aims to the study of the Besano Formation macrofauna, through biochronostratigraphic zonation of the Sasso Caldo Site, revision of the large ichthyosaur Besanosaurus leptorhynchus), and study of the most important specimens, chosen for their preservation and rarity, but also to test the hypothesis of variations in the influence of open sea on the Besano basin. All the available ammonoids and bivalves from the Sasso Caldo site (Besano Formation), housed in the collections of the Museo di Storia Naturale di Milano, were examined and determined. The systematic study led to the recognition of 15 ammonoid taxa belonging to 10 genera, and five species belonging to the bivalve genus Daonella. The study of bed-by-bed collected specimens allowed the biochronostratigraphic classification of the Sasso Caldo section and the time-calibration of invertebrate and vertebrate bioevents. Results evidence that at Sasso Caldo site crops out almost the entire middle to upper Besano Formation. corresponding the Nevadites secedensis ammonoid zone. The trend of distribution of specimens reflects the establishment of an intraplatform basin with discontinuous open-marine influence in the middle Besano Formation, while the upper Besano Formation corresponds to a shallower subtidal restricted platform environment. Among the terrestrial taxa recovered at Sasso Caldo from the upper Besano Formation, a remarkably well-preserved fossil scorpion (BES SC 1973) is described in this thesis. This finding corroborates the hypothesized existence of a near shoreline during the deposition of the upper Besano Formation. BES SC 1973 is assigned to a new taxon gen. et sp. nov., included in the family Protobuthidae. This finding represents the first arachnid recorded from the Besano Formation, and the second genus attributed to the family Protobuthidae. This specimen is also the first reported Italian Mesozoic fossil scorpion. Regarding vertebrates, MSNM V927 and 928, a portion of the axial skeleton of a large diapsid, is attributed to Helveticosaurus zollingeri, a rare diapsid known only from the Besano Formation. This animal was recovered in association with the ammonoid Ticinites, at the base of the N. secedensis Zone, in coincidence with the establishment of the intraplatform basin of the middle Besano Formation. This specimen is the first record of skeletal remains and the second specimen assigned to the taxon in Italy. In this work the niche occupied by this animal in the Middle Triassic coastal ecosystems and its swimming style are also revised and discussed. MSNM V926, and SMNS 50010, respectively a portion of ribcage and an isolated partial forefin of a large ichthyosaur, were attributed to Cymbospondylus buchseri. MSNM V926 represents the first specimen attributed to this taxon and recovered on the Italian side of Monte San Giorgio. A great part of this thesis is dedicated to the revision of Besanosaurus leptorhynchus. The specimens studied and attributed to Besanosaurus leptorhynchus preserve a remarkably complete cranial and postcranial anatomy so that this taxon can be now accounted among the best-understood Middle Triassic ichthyosaur taxa. The revision of the skull morphology of this taxon clarified long-standing controversies regarding its cranial anatomy and the taxonomy of shastasaurids from Monte San Giorgio. The six specimens here described represent a potential ontogenetic series composed of an embryo (inside the maternal cavity of BES SC 999), likely two subadults, and four adults. They can be ordered by increasing size as follows: embryonic material of BES SC 999, PIMUZ T 4376, PIMUZ T 1895, BES SC 999, BES SC 1016, GPIT 1793/1, PIMUZ T 4847. Also, Besanosaurus resulted the largest Middle Triassic ichthyosaur taxon of the Western Tethys to date, since a full adult size is confidently estimated to be almost 8 m in PIMUZ T 4847. Besanosaurus is characterized by a long, slender, and gracile snout, representing an ecological specialization never seen before the Anisian in a large-sized diapsid. The study of the postcranial anatomy of Besanosaurus leptorhynchus is based on four specimens: PIMUZ T 4376, PIMUZ T 1895, BES SC 999, PIMUZ T 4847. The results suggest that this taxon possesses a peculiar bauplan, which in its proportions fits in between Cymbospondylus and the shastasaur-grade ichthyosaurs. Swimming capabilities of Besanosaurus leptorhynchus were tested and compared with Cymbospondylus and Mixosaurus. Among the ichthyosaurs from the Besano-Monte San Giorgio fauna (Cymbopondylus, mixosaurids, and Besanosaurus), different hunting strategies, demonstrated by different morphologies and dimensions of the rostra, as well as different body proportions and swimming styles, should have led to niche partitioning. The key phylogenetic position occupied by Besanosausurus leptorhynchus in the ichthyosaurian phylogeny was investigated: the analysis shows that this taxon represents the basalmost member of shastasaur-grade ichthyosaurs, recovered to be a paraphyletic group. Eventually is addressed a study of the embryonic material preserved in BES SC 999. We deem the material in the body cavity of BES SC 999 unambiguously embryonic and attributable to Besanosaurus leptorhynchus. Here the embryonic material is described in detail and qualitatively compared with the maternal specimen and to other known ichthyosaur prenatal specimens.