Early Ordovician (Tremadocian) brachiopods from the Eastern Alborz Mountains, Iran

Six linguliform and two rhynchonelliform brachiopods, including three new species Eurytreta ahmadii, Wahwahlingula kharbashi and Nanorthis bastamensis are described from Tremadocian strata (Paltodus deltifer deltifer conodont Biozone) in the Deh-Molla area southwest of Shahrud, Northern Iran. The fauna is dominated by micromorphic lingulides and acrotretides and shows distinct similarity to the contemporaneous micromorphic brachiopod association from Tremadocian chalcedonites of the Holy Cross Mountains, Poland. New data on the early ontogeny of the enigmatic lingulide Diencobolus show a very distinct pattern, including the presence of a metamorphic protegulum ornamented with flat-based pits and a single pair of larval setal bundles, which links this taxon to Paterula and suggests close phylogenetic relationships of both taxa to the Discinoidea

Climatic changes and astrochronology: an Ordovician perspective

Review of current progress in Mid to Late Ordovician astrochronological studies exposes some important issues related to cyclostratigraphical studies, including the completeness and correlation of successions, and the connection between inferred astronomical cycles and geological events recorded in the sedimentary record. While bulk, low-field, mass specific magnetic susceptibility methods are widely applied in studies of high resolution cyclostratigraphy, they require close support from sequence stratigraphy and biostratigraphy, and should be linked back to outcrop patterns. Otherwise they risk distortion in the calibration against geological time, through lack of anchoring to well-defined biostratigraphical horizons and unrecognised condensed intervals and larger hiatuses. A significant limitation currently is that few high-resolution radio-isotope ages are linked to well-defined biostratigraphical boundaries. Nevertheless, fourth order sedimentary sequences linked to 405 kyr orbital eccentricity cycles, and longer orbital cyclicity impressed in third-order sequences, represent good grounds for development of a reliable astrochronological scale. The astrochronologically calibrated sequence-stratigraphical record documented from high latitude Gondwana shows significant impact from orbital forcing on the Mid to Late Ordovician global climate

Fourth Amendment Accommodations: (UN)Compelling Public Needs, Balancing Acts, and the Fiction of Consent

The problems of public housing-including crime, drugs, and gun violence- have received an enormous amount of national attention. Much attention has also focused on warrantless searches and consent searches as solutions to these problems. This Note addresses the constitutionality of these proposals and asserts that if the Supreme Court\u27s current Fourth Amendment jurisprudence is taken to its logical extremes, warrantless searches in public housing can be found constitutional. The author argues, however, that such an interpretation fails to strike the proper balance between public need and privacy in the public housing context. The Note concludes by proposing alternative consent-based regimes that would pass constitutional muster

Siphonotretoid brachiopods – a thorny problem

Siphonotretoids are presently placed within the subphylum Linguliformea and the class Lingulata, where they constitute a small, relatively short-lived superfamily and order, appearing near the end of the mid-Cambrian, with most forms becoming extinct near the end of the Late Ordovician, but with some rare forms ranging through the Silurian and even into the early Devonian. It has been noted previously that siphonotretides are very different from all other lingulates in shell structure, ontogeny and ornamentation, and may have diverged from other lingulates already during the early Cambrian. Findings of exceptionally preserved âsoft-shelledâ possible early stem-group setigerous representatives such as Acanthotretella in the Burgess Shale and the Chengjiang fauna have strengthened this view. Exceptionally preserved siphonotretides from Iran clearly show that they are provided with organic setal structures associated with spines, and similar setal structures are known from stem brachiopods, such as Micrina and Mickwitzia, as well as from some later true rhynchonelliforms. Evidence for preserved setal structures is now also recorded from the CambrianâOrdovician boundary beds in Wyoming. In the Ordovician, the spinous structures include complex branching forms, such as the widely distributed Alichovia, and Siphonotreta itself has clear evidence of branching spines. The branching spines probably also contained setal structures, and similar forked setae are known from living annelids

Stratigraphy 12 (2) Biostratigraphy of the Cambrian-Ordovician boundary beds at Kopet-Dagh, Iran

ABSTRACT: A continuous succession comprising upper Cambrian (Furongian) to Lower Ordovician (Tremadocian) conodont biozones is reported for the first time from the Kopet-Dagh Region of northeastern Iran. Seven biostratigraphical units are recognized, including the Proconodontus tenuiserratus and Proconodontus posterocostatus zones; these two lowermost biostratigraphical units are defined by euconodont species which have not been previously reported from Iran and temperate latitude peri-Gondwana. The conodont diversity and abundance decreased significantly above the Eoconodontus notchpeakensis Zone; the conodont faunas of the succeeding Cordylodus proavus, Cordylodus lindstromi (sensu lato) and Cordylodus angulatus zones are characterised by oligotaxic to monotaxic associations dominated by species of Cordylodus. In the absence of diagnostic conodont species, the position of the lower boundary of the Ordovician System in the Kalat Valley Section can be placed somewhat below the first occurrence of the early planktonic graptolite Rhabdinopora flabelliformis, which approximately coincides with the onset of black shale deposition

Stegocornu and associated brachiopods from the Silurian (Llandovery) of Central Iran

A Llandovery (mid-upper Aeronian) brachiopod fauna is described for the first time from the Niur Formation of Central Iran. It is dominated by two succeeding rhynchonellide species Stegocornu procerum Dürkoop, 1970 and Stegocornu denisae sp. nov. In addition, there are three common and four rarer brachiopod species, including Dalejina? rashidii sp. nov., Isorthis (Ovalella) inflata sp. nov. and Striispirifer? ocissimus sp. nov. The Stegocornu Association gives a distinct biogeographic signature to the mid to late Llandovery rhynchonellide-dominated shallow-water brachiopod faunas of Central Iran, Kope-Dagh and Afghanistan. Its proliferation in temperate latitude peri-Gondwana was one of the earliest signs of biogeographical differentiation of the brachiopod faunas in the early Silurian. The affinities of Stegocornu and Xerxespirifer are discussed

Ordovician ostracods from east central Iran

International audienceOrdovician ostracods are described for the first time from Iran, enhancing the record of this group from the Lower Palaeozoic of the Middle East. The ostracods occur in the Shirgesht Formation, in the east central part of the country, and comprise Ogmoopsis achaemenid sp. nov., Cerninella aryana sp. nov., Ordovizona amyitisae sp. nov., cf. Aechmina? ventadorni, Vogdesella sp., and podocope taxa tentatively identified as species of Longiscula, Pullvillites, and Rectella. These taxa were hitherto unknown from this region. The ostracod−bearing interval is associated with trilobites (Neseu− retinus) and brachiopods (Nicolella) that suggest a late Middle Ordovician age. Although the ostracod fauna is small, it demonstrates biogeographical links at genus−level, and possibly at species−level, with the fauna of the late Middle Ordo− vician Travesout Formation of western France, which also lay in a peri−Gondwanan palaeogeographical setting. It also suggests the potential use of some ostracods as stratigraphical tools for correlating Ordovician rock successions between Europe and the Middle East

Data from: Ecology, biofacies, biogeography and systematics of micromorphic lingulate brachiopods from the Ordovician (Darriwilian–Sandbian) of south-central China

Ordovician (Darriwilian to Sandbian) micromorphic linguliform lingulate brachiopods are described from the Guniutan Formation at the Fenxiang section in Hubei province, and the Maocaopu and Cili sections in Hunan province of south-central China, situated on the Yangtze Platform. A total of 7560 specimens from 155 limestone samples (within the interval of Lenodus variabilis – Pygodus anserinus biozones) are assigned to 22 species, representing a low taxonomic diversity and low abundance fauna. The fauna is dominated by the Acrotretoidea, mainly species of the Torynelasmatidae, with Torynelasma the most abundant (more than 40% of total number of specimens), along with the Eoconulidae and Eoconulus (18% of total) representing the second most common forms. Species of the Ephippelasmatidae are also common (16% of total) diverse, and include representatives of Myotreta and Numericoma, as well as Ephippelasma, whereas species of the Scaphelasmatidae are somewhat less common (13% of total). All three investigated sections represent outer shelf environments, but the Maocaopu section is situated in a relatively deeper position, in proximity of the south-eastern outer margin of the Upper Yangtze Platform, close to its boundary with the Jiangnan Slope. A quantitative analysis of the relative abundance data was carried out in order to investigate the biofacies distribution of the micromorphic brachiopod communities across the Yangtze Platform, something that has not been attempted before with Palaeozoic linguliforms. Six lingulate microbrachiopod communities could be recognized in the sections. The major biofacies shift, which occurred in the Cili section in the upper part of the Microzarkodina ozarkodella Zone, at the time of the onset and initial rise of the Mid Darriwilian Carbon Isotope Excursion (MDICE) suggests that these biofacies may have been depth controlled

Eutrophication by biogenic phosphate pollution as a triggering factor for the collapse of oboliddominant brachiopod communities in the early Tremadocian of East Baltica

Trabajo presentado en el 61th Annual Meeting of the Palaeontological Association, celebrado en Londres (Reino Unido), del 17 al 20 de diciembre de 2017In the early Tremadocian (Cordylodus lindstromi and Cordylodus angulatus zones) the Baltoscandian epicratonic basin was environmentally heterogeneous and comprised a black shale depocentre, rimmed in North Estonia by coastal plain and shoal complexes composed of extensive brachiopod shell accumulations. By that time, nearshore obolid-dominant brachiopod communities were extinct; while allochthonous shell beds (biogenic phosphorites) were inherited relics, eroded from Furongian shoal bioaccumulations. Unlithified quartzose sand packages, exhibiting bidirectional cross laminae and commonly punctuated by thin black shale intercalations, accumulated in tidally influenced foreshore-to-shoreface settings. Nearshore reworking and condensation of sand phosphorites is a sign of coastal eutrophication, which resulted in significant seasonal enrichment of the water column by nutrients associated with dissolved oxygen fluctuations. A possible major cause of eutrophication and water pollution, coeval with widespread deposition of kerogenous clay and extinction of shallow marine biota, not previously considered, was the increase in phosphate nutrients and increased biomass of phytoplankton. Toxicity effects would be triggered by the extensive Furongian obolid shelly substrates, flooded during the marine transgression. The presence of significant amounts of dissolved phosphate in the water at that time was marked by deposition of concretions and crusts of chemogenic phosphorites outlining the periphery of the black shale depocentre.Peer reviewe

Biogeography of Ordovician linguliform and craniiform brachiopods

The biogeographical patterns shown by Ordovician linguliform and craniiform brachiopods are greatly influenced by their dominance in low-diversity associations in marginal environments. This is particularly evident in the Early Ordovician, when linguliform-dominated dysaerobic assemblages are widely distributed along the deep shelves of Gondwana, the Kazakhstanian terranes and in Baltica. By the Darriwilian, micromorphic linguliforms are characteristic components of the pantropical climatic-controlled faunas of Laurentia, Cuyania and Kazakhstanian terranes, which – in spite of separation by extensive oceans – retain a distinct similarity. Analysis of craniiform biogeographical distribution is impeded significantly by the poor state of craniide taxonomy and lack of reliable data from most regions. However, in general their biogeographical dispersion is similar to other groups of the Palaeozoic Evolutionary Fauna. Unlike the linguliforms, which are important members of the Cambrian Evolutionary Fauna, there is no convincing Cambrian craniiform record; they may have evolved and dispersed from Gondwana and associated microcontinents and island arcs. The earliest well-established record is from the late Tremadocian of temperate to high-latitude peri-Gondwana. During most of the Ordovician, they have a peri-Iapetus distribution. They are very rare or absent in tropical Gondwana, South China and Kazakhstanian terranes and are not yet documented from Siberia. The trimerellides probably evolved in tropical peri-Gondwanan island arc settings. Their dispersion and major features of biogeography mirror those of atrypides