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Abstract The Ordovician Macquarie Arc is faulted against and surrounded by coeval Gondwana-derived quartz turbidites, in the Lachlan Orogen of southeastern Australia. How these juvenile, island arc rocks were emplaced and structurally interleaved with continental margin sequences of eastern Gondwana is an ongoing debate. Understanding the inception of this arc is critical in building an accurate Early Paleozoic reconstruction for eastern Gondwana. However, the arc's inception and early evolution are poorly-constrained due to the lack of reliable geochronological data. Integrated field observations, zircon U-Pb-Hf, mineral and whole rock geochemistry are presented here for the oldest units of the Molong Volcanic belt, which is a central strand of the dissected Macquarie arc. Geochemistry indicates that these are calc-alkaline rocks with high-K (locally shoshonitic) to medium-K affinities. The stratigraphically-lowest mafic volcanic and volcano-sedimentary rocks of the Mitchell Formation have a unimodal earliest Ordovician zircon U Pb age of 479.8 ± 3.8 Ma, with uniform depleted mantle like initial zircon εHf values of +12 to +13. The lack of pre-Ordovician zircons and the uniform positive initial εHf value indicate that the Macquarie arc was initiated in an intra-oceanic setting, far from the influence of eastern Gondwana. The stratigraphically overlying Fairbridge Volcanics includes some more evolved volcano-sedimentary components and has a polymodal, but mostly Ordovician, zircon U Pb age population, with a youngest component at 444.3 ± 2.4 Ma. Overall, its Ordovician grains show a greater spread in initial εHf values from +14 down to +8 than the Mitchell Formation, which suggests some continental influence, at least 35 million years after the arc was initiated. The lack of any significant Gondwanan inheritance in Early Ordovician volcaniclastic rocks of the Macquarie Arc along with geochemical comparisons with modern island arcs, suggest that the arc evolved outboard of Gondwana probably as a result of steep, easterly-directed subduction. As the Macquarie arc approached eastern Gondwana there would have been increasing quantities of continent derived sediment subducted beneath the arc which may account for the decreasing and more variable zircon initial εHf values and the appearance of sparse Precambrian continental detritus at the arc's moribund stage. The collision of the Macquarie island arc with Gondwana initiated the Benambran Orogeny and reflects an important mechanism of episodic continental growth involving the addition of juvenile oceanic crust to a continental margin, which contrasts and alternates with periods of purely accretionary growth. Highlights • Zircon ages indicate the latest initiation of the Macquarie Arc is at ~480 Ma. • The arc initiated far from the influence of any continental crust. • The inheritance did not appear until Middle-Late Ordovician. • The early Macquarie Arc sequence was revised with new U Pb data. • The arc initiation is possibly related with steep, east-dipping subduction. [ABSTRACT FROM AUTHOR]

Abstract In this contribution, systematic petrographical, whole-rock geochemical, geochronological and zircon Lu-Hf isotopic investigations were conducted on Paleozoic (ca. 410–400 Ma) metamorphic-magmatic rocks from Mt. Dongbatu in the central Dunhuang terrane. The metamorphic rocks in the Shangkouzi area are of meta-calcsilicate rocks, and granitoid rocks occurring within these rocks are geochemically of trondhjemite. Whereas, metamorphic rocks in the Gangou area are metabasaltic rocks. LA-ICP MS zircon U-Pb dating results reveal that these metamorphic-magmatic rocks recorded ca. 1.6 Ga magmatic event and metamorphic events of ca. 410–400 Ma and ca. 370 Ma. Field occurrence, whole-rock geochemistry, mineral composition and zircon Hf isotopes suggest that the 1.6 Ga mantle-derived basaltic magma, together with iron-rich and Ca-rich components and mica-quartz schist of Paleoproterozoic supracrustal rocks probably contributed to protolith of meta-calcsilicate rocks in the Shangkouzi area, and granitoid rocks within meta-calcsilicate rocks were possibly generated by partial melting of calcsilicate rocks. Combined with previously published data, it is suggested that the protoliths of Paleozoic high-grade metamafic rocks in the Dunhuang terrane are predominantly composed at least of basaltic rocks produced by magmatic events of 2.5–1.8 Ga, ca. 1.8 Ga and ca. 1.6 Ga. The Paleozoic granitoid rocks in the Dunhuang terrane might have been derived from different magma sources as partial melting of subducted plate, or thickened lower continental crust, or pre-existing basaltic rocks produced by 1.6 Ga and 1.8 Ga magmatic activities, and calcsilicate rocks genetically associated basaltic magmatism at ca. 1.6 Ga. Considering regional tectonic evolution, it can be concluded that the Dunhuang terrane was probably in a post-collisional extension setting at ca. 1.6 Ga, producing certain amount of basaltic and calcsilicate rocks. From the beginning of Silurian (ca. 440 Ma), the Dunhuang terrane was involved in the orogenic processes related to the closure of the southern Paleo-Asian Ocean, becoming the active continental margin of the southernmost CAOB. Graphical abstract Unlabelled Image Highlights • Calcsilicate rock was regionally formed during 1.6 Ga magmatic process. • Paleozoic metamorphism-magmatism widely took place in the Dunhuang terrane. • Protolith of Paleozoic metamafic rocks is mainly of Paleoproterozoic basic rocks. • Paleozoic granitoids derived from various magmatic sources. • Dunhuang terrane witnessed Paleozoic geological evolution of southernmost CAOB. [ABSTRACT FROM AUTHOR]

Within the northern fringe of the western (Khangai) flank of the Mongol-Okhotsk fold belt, magmatic complexes of intermediate to moderately acidic rocks occur. They comprise widely distributed gabbro-diorites, diorites, tonalites, and granodiorites. Geochronological studies have demonstrated that these rocks were formed in the time span of 437 to 375 Ma. The geochemical affinities of the rocks suggest their formation in subduction tectonic settings; hence, their paleotectonic position corresponds to the continental margin of the Mongol-Okhotsk paleoocean. It has been concluded that this Middle Paleozoic igneous activity occurred in the active continental margin settings, formed by subduction of the paleooceanic plate under the Siberian continent. [ABSTRACT FROM AUTHOR]

The upper Paleozoic (Carboniferous to Permian) succession of the Sverdrup Basin in the Canadian Arctic Islands has the potential to contain significant hydrocarbon reserves, though it has never been a primary exploration target. To better constrain previous estimates and hydrocarbon play possibilities, this study completed evaluations of source rock quality and extent and thermal maturity. This study also incorporated new understandings of reservoir units and their stratigraphic relation to source rocks, trapping configurations and timing of hydrocarbon migration. Several hydrocarbon source units were identified within the upper Paleozoic formations of the Sverdrup Basin including the Emma Fiord, Trappers Cove, Antoinette, Assistance, Sabine Bay, van Hauen and Trold Fiord formations. The Emma Fiord and Trold Fiord formations are both found to be oil prone, with the remainder of the sources being gas prone. The upper Paleozoic succession is interpreted to be gas prone due to dominant kerogen types and high average thermal maturity. Many of the older concept plays put forth for the upper Paleozoic succession have been determined to be unviable. However, modern plays that implement new understandings of the basin have the potential to be viable. This study has found that the upper Paleozoic succession of the Sverdrup Basin is promising for gas discoveries with new plays such as salt diapirism plays, or plays similar to the Barents Sea Gohta play. New hydrocarbon rock source data also suggests the potential for a new oil and gas play on northern Prince Patrick Island. This new research could lead to significant resource discoveries that have been previously overlooked. [ABSTRACT FROM AUTHOR]

In this paper we describe fossil remains of an indeterminate species of the genusParacamelus(Artiodactyla, Camelidae) from the Messinian post-evaporitic deposits (5.55–5.40 Ma) of Verduno (Piedmont, NW Italy). Camelins dispersed into Eurasia from North America in the late Miocene and almost instantaneously spread in western Europe and Africa. The size and morphology of the fossils found at Verduno are consistent in with those ofParacamelus,the earliest Old World camelin. Up to now, the only fossil camels recovered in the Neogene of Western Europe have been found at Venta del Moro and Librilla in Spain at 6.2 Ma. The remains from Verduno represent the first evidence of a camelin in the Neogene of Italy and they considerably expand the paleobiogeographic range of the Old World early camelins. The presence of a camelid at Verduno reinforces and confirms the importance of the fossiliferous deposits of NW Italy in defining the complex paleobiogeographic patterns of Europe during the Messinian, at the end of the Messinian salinity crisis. [ABSTRACT FROM PUBLISHER]

Trochotomidae is a small but distinctive extinct family of pleurotomarioidean gastropods characterized by trochiform shells with an elliptical trema. Two new species of trochotomids are described from Pliensbachian deposits in the Neuquén Basin, Argentina. The new genus-group name Placotoma is proposed to replace the pre-occupied name Discotoma Haber non Mulsant. The record of Trochotoma (Trochotoma) protonotialis new species and Trochotoma (Placotoma) neuquensis new species in the early Jurassic of Argentina extends the paleobiogeographical distribution of the genus (and the family) to the Southern Hemisphere. The new taxa reported here represent a component of the pleurotomarioidean adaptive radiation that took place in the Tethyan region during the earliest Jurassic. They are related to local patch coral reefs of shallow, open-marine paleoenvironments, agreeing with the known habitat of most species of this family. The group was well represented in the Tethyan region during the Mesozoic, especially during the Jurassic, and the new species represent its southernmost occurrence. [ABSTRACT FROM PUBLISHER]

Patterns of brachiopod paleobiogeographic regionalization in Central Asia reveal a coevolution between brachiopod paleobiogeography and tectonopaleogeography during the Early Devonian, Early Carboniferous, Late Carboniferous, Early Permian, and Middle Permian. The coevolutionary relationship reasonably accounts for the formation mechanisms of brachiopod paleobiogeography in this region, and also provides a basis for studies on the location and configuration of oceans and plates (blocks) during the late Paleozoic in Central Asia. [ABSTRACT FROM AUTHOR]

Abstract: The southwestern Gondwana basement block configuration in the central Argentinean offshore area was analyzed using gravimetric, magnetic and seismic data and existing onshore tectonic models. The resultant maps, the distribution of the Mesozoic and Cenozoic basins and Paleozoic structural features were used to validate the interpretations and to produce a new regional tectonic model. Pre-Carboniferous southwestern Gondwana of South America was interpreted as an open margin formed from east to west by the Dom Feliciano Belt, the Río de la Plata Craton, the Pampean Belt and the Pampia and Cuyania terranes. The collision of the Patagonia allochthonous terrane during the Late Paleozoic resulted in the development of the Ventania-Cape Fold Belt, which was mapped for the first time off the Argentinean coast out to 600 km from the shore. A strong change in the orientation of the Fold Belt is referred to as the Colorado Syntaxis, a mirror image of the Cape Syntaxis in South Africa. This change reflects the buttressing effect of the cratonic blocks that hamper the northward propagation of syncollisional deformation and resulted in a 180-km shift of the orogenic front. The Mesozoic basins and the basement block distribution were analyzed. The Pampean Belt, a deformed area produced by the Pampia accretion to the cratonic area, is the locus to two episutural basins, the General Levalle and Macachín basins. The Salado Basin was interpreted as an episutural basin controlled by a 2.1–2.0 Ga suture within the Rio de la Plata Craton. The Colorado Basin is composed of four segmented depocenters that reflect different emplacement controls: the location of the western Colorado Basin was controlled by the Upper Paleozoic orogen; the distributions of the central and eastern Colorado depocenters, orthogonal to the continental boundary, were also strongly influenced by the Upper Paleozoic structures and were offset by lineaments that reflect Dom Feliciano fabric; the Colorado Basin external depocenter that parallels the continental margin was also controlled by these lineaments. We interpret a time gap of some 50 Ma between the beginning of the evolution of the margin-orthogonal depocenters and the Atlantic breakup. [Copyright &y& Elsevier]

The article focuses on a study which examined brachiopod biogeographic patterns in the late Early Devonian to early Middle Devonian in North America. Samples were collected from the Eifelian brachiopod genera from 14 regions. Results of the study showed the possible disappearance of the Eastern Americas Realm during the late Emsian to early Eifelian. It also observed that the removal of barriers to migration led to increased dispersal rates in the region.

Understanding the influence of aragonite/calcite sea conditions on the evolution of biocalcification relies strongly on the correct interpretation of the original composition of calcareous taxa. Aragonite dissolves or inverts into calcite over geological time, and its preservation is currently unknown to predate the Pennsylvanian. Here we present direct evidence for the common occurrence of relic aragonite in Ordovician and Silurian trimerellid brachiopods, thereby extending the known range of aragonite preservation by more than 130 million years. Together with associated hypercalcifying taxa of putatively original aragonite or high-magnesium calcite composition and considerations of the temperature dependence of aragonite and calcite precipitation, our results suggest that the evolution of aragonite biomineralization might have presented an adaptive advantage in shallow marine tropical waters of calcite seas. A targeted search for Paleozoic aragonite should both resolve the original composition of consistently recrystallized taxa and enable the reassessment of the aragonite/calcite sea paradigm in a paleoenvironmental context. [ABSTRACT FROM AUTHOR]

Abstract: Conodonts are an extinct group of organisms, known from the Upper Cambrian to the Triassic. They have no extant representatives, and tooth-like buccal elements are usually the only remains of the animal found in the sediments. Therefore, most of their taxonomy rests on these elements that are good stratigraphic tools for these ancient periods, due to their rapid morphological evolution. Conodont species are usually described species that are based on either clusters of elements corresponding to an entire apparatus (natural assemblages), or on the most frequently preserved element. These described species are acceptable stratigraphic tools, but hardly consider the dimension of the variation that a biological species can encompass through time and space. In order to tackle temporal, environmental and biogeographical changes, recent studies have shown that morphological variation should be taken into account by quantitative analyses, aiming at getting at the closest of what the former species might have been. [Copyright &y& Elsevier]

Myzostome galls on arms of the Early Jurassic (Pliensbachian) Balanocrinus gracilis provide the first unequivocal evidence of such parasitic infestation in a post-Paleozoic crinoid. [ABSTRACT FROM AUTHOR]

Abstract: The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and δ 13Ccarb chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than ±100kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (δ 13Ccarb) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. [Copyright &y& Elsevier]

Abstract: An extensive collection of compressed altered remains, including leafy shoots and ovules similar to specimens described as Buriadia, is reported from Lower Permian rocks on Mount Gran, Victoria Land, Antarctica. The specimens, preserved as a thin layer of aluminosilicate film in a fine-grained black shale, show a number of morphological features like those reported from the type species, B uriadia heterophylla. The leaves are highly polymorphic and appear to be helically arranged. The ovules are orthotropous and attached to leafy shoots by a short stalk; they do not appear to be organized into distinct zones along the axis. The ovules are obovate, with a conspicuous bifid apex and prominent chalazal disk. The combination of features in these Antarctic specimens indicates affinities with the putative Permian coniferophyte, B. heterophylla, originally described from India. The discovery of a presumed coniferophyte with erect terminal ovules from the Permian of Antarctica adds support to the hypothesis that there were at least two major groups of conifer-like plants present during the late Paleozoic. Differences in the ovulate parts of these plants suggest a unique evolutionary history for the late Paleozoic coniferophytes from the Southern Hemisphere. [Copyright &y& Elsevier]

A response by Linda E. Graham and colleagues to commentaries on their article "Structural, Physiological, and Stable Carbon Isotope Evidence That the Enigmalic Paleozoic Fossil Prototaxites Formed From Rolled Liverwort Mats," published in the 2010 issue is presented. The authors argue that the their critics did not completely understand the biology of relevant extant organisms, particularly liverworts. They add that the commentary authors applied insufficiently detailed approach to evaluate the larger scale structure of the fossil.

The authors comment on the article "Structural, Physiological, and Stable Carbon Isotope Evidence That the Enigmalic Paleozoic Fossil Prototaxites Formed From Rolled Liverwort Mats," by L. E. Graham and colleagues, published in the 2010 issue. They describe the anatomy of Prototaxites, along with the problems with the anatomical comparisons presented in the article. They note the obstacles related to the rolling mat hypothesis on Prototaxites. The authors also argue against the article's carbon isotope analysis.

The article discusses research on diversity and gigantism patterns in eurypterids and Palaeozoic vertebrates. Family-level originations and extinctions and among eurypterids and Palaeozoic vertebrates were analyzed and revealed that the diversity of Eurypterina waned during the Devonian period. It was noted that the casual mechanisms for gigantism and extinction could be due to abiotic or biotic factors.

Morphological similarities indicate that Palaeozoic problematic tubeworms, e.g. tentaculitids, cornulitids, microconchids, trypanoporids, Anticalyptraea, and Tymbochoos, form a monophyletic group. This group may also include hederelloids. Members of this group share affinities with lophophorates and their evolution could have partly been driven by predation. The extinction of Palaeozoic tubeworms in the Middle Jurassic was possibly at least partly caused by the ecological pressure by serpulid and sabellid polychaetes. The input of Palaeozoic tubeworms to the general ocean biocalcification system may have been smaller in the Ordovician to Jurassic than that of calcareous polychaetes in the Late Triassic to Recent. There seems to have been some correlation between the aragonite—calcite seas and the skeletal mineralogy of Triassic—Recent polychaete tubeworms. [ABSTRACT FROM AUTHOR]

Abstract: The Late Palaeozoic, glaciomarine Talchir Formation in the Satpura Gondwana basin, central India hosts sparse to profuse trace fossils of various kinds, although sporadically. Among the three principal depositional systems that gave rise to the Talchir succession, deposits of the ice-contact fan delta system and the glacial outwash braidplain delta system lack trace fossils of any kind. On the other hand, within the deposits of the storm wave-dominated, shoreface–shelf system a variety of animal traces is present including simple locomotion traces and non-descript bioturbation. Three trace fossil assemblages could be recognized within these deposits. Assemblage-I is dominated by Cylindrichnus of the Skolithos ichnofacies that occurs in storm laid, medium to fine sandstones deposited in shoreface and transitional shoreface–inner shelf environments. In contrast, assemblage-II comprising dominantly horizontal, grazing-cum-deposit-feeding traces Cochlichnus, Helminthopsis, Phycosiphon, Planolites, Archaeonassa and Psammichnites occurs on decimeter-thick sandstone beds interlayered with mudstones deposited in lower shoreface to inner shelf environments. Trace fossil assemblage-III is known from a 6.9m thick, outer shelf to lower shoreface, progradational succession showing a vertical transition from dark gray mudstone to fine sandstone. The middle part of this particular section shows Rhizocorallium and flat-type Zoophycos, whereas the upper part hosts profuse Cylindrichnus along with Rosselia and Teichichnus in lesser proportions. This assemblage is comparable to the marine ichnofacies succession combining elements of both Skolithos and Cruziana ichnofacies. The characteristic features of the Talchir trace fossil assemblages are: (i) low ichnodiversity, (ii) presence of forms typically found the in marine environment, (iii) co-occurrences of vertical and horizontal traces of Skolithos and Cruziana ichnofacies, (iv) presence of simple structures formed by trophic generalists, (v) abundance of certain forms, and (vi) presence of monospecific suites. These characters are akin to those of brackish water ichnofaunas. In the Talchir succession, the transition from an ice-contact fan delta system to a relatively ice-free open marine system indicates an enormous flux of fresh water into the sea reducing its overall salinity. Predominance of annelid and worm traces and the rarity of crustacean burrows in the Talchir strata also suggest a stressful environment due to the prevailing cold climate and a lower than normal marine salinity. It thus appears that mixing of fresh water during deglaciation might be a key controlling factor in shaping the characters of ichnofaunas in glacially influenced shallow marine environments. [Copyright &y& Elsevier]

Abstract: The event across the Paleozoic–Mesozoic transition involved the greatest mass extinction in history together with other unique geologic phenomena of global context, such as the onset of Pangean rifting and the development of superanoxia. The detailed stratigraphic analyses on the Permo-Triassic sedimentary rocks documented a two-stepped nature both of the extinction and relevant global environmental changes at the Guadalupian–Lopingian (Middle and Upper Permian) boundary (G-LB, ca. 260Ma) and at the Permo-Triassic boundary (P-TB, ca. 252Ma), suggesting two independent triggers for the global catastrophe. Despite the entire loss of the Permian–Triassic ocean floors by successive subduction, some fragments of mid-oceanic rocks were accreted to and preserved along active continental margins. These provide particularly important dataset for deciphering the Permo-Triassic paleo-environments of the extensive superocean Panthalassa that occupied nearly two thirds of the Earth’s surface. The accreted deep-sea pelagic cherts recorded the double-phased remarkable faunal reorganization in radiolarians (major marine plankton in the Paleozoic) both across the G-LB and the P-TB, and the prolonged deep-sea anoxia (superanoxia) from the Late Permian to early Middle Triassic with a peak around the P-TB. In contrast, the accreted mid-oceanic paleo-atoll carbonates deposited on seamounts recorded clear double-phased changes of fusuline (representative Late Paleozoic shallow marine benthos) diversity and of negative shift of stable carbon isotope ratio at the G-LB and the P-TB, in addition to the Paleozoic minimum in 87Sr/86Sr isotope ratio in the Capitanian (Late Guadalupian) and the paleomagnetic Illawarra Reversal in the late Guadalupian. These bio-, chemo-, and magneto-stratigraphical signatures are concordant with those reported from the coeval shallow marine shelf sequences around Pangea. The mid-oceanic, deep- and shallow-water Permian records indicate that significant changes have appeared twice in the second half of the Permian in a global extent. It is emphasized here that everything geologically unusual started in the Late Guadalupian; i.e., (1) the first mass extinction, (2) onset of the superanoxia, (3) sea-level drop down to the Phanerozoic minimum, (4) onset of volatile fluctuation in carbon isotope ratio, 5) 87Sr/86Sr ratio of the Paleozoic minimum, (6) extensive felsic alkaline volcanism, and (7) Illawarra Reversal. The felsic alkaline volcanism and the concurrent formation of several large igneous provinces (LIPs) in the eastern Pangea suggest that the Permian biosphere was involved in severe volcanic hazards twice at the G-LB and the P-TB. This episodic magmatism was likely related to the activity of a mantle superplume that initially rifted Pangea. The supercontinent-dividing superplume branched into several secondary plumes in the mantle transition zone (410–660km deep) beneath Pangea. These secondary plumes induced the decompressional melting of mantle peridotite and pre-existing Pangean crust to form several LIPs that likely caused a “plume winter” with global cooling by dust/aerosol screens in the stratosphere, gas poisoning, acid rain damage to surface vegetation etc. After the main eruption of plume-derived flood basalt, global warming (plume summer) took over cooling, delayed the recovery of biodiversity, and intensified the ocean stratification. It was repeated twice at the G-LB and P-TB. A unique geomagnetic episode called the Illawarra Reversal around the Wordian–Capitanian boundary (ca. 265Ma) recorded the appearance of a large instability in the geomagnetic dipole in the Earth’s outer core. This rapid change was triggered likely by the episodic fall-down of a cold megalith (subducted oceanic slabs) from the upper mantle to the D″ layer above the 2900km-deep core-mantle boundary, in tight association with the launching of a mantle superplume. The initial changes in the surface environment in the Capitanian, i.e., the Kamura cooling event and the first biodiversity decline, were probably led by the weakened geomagnetic intensity due to unstable dipole of geodynamo. Under the low geomagnetic intensity, the flux of galactic cosmic radiation increased to cause extensive cloud coverage over the planet. The resultant high albedo likely drove the Kamura cooling event that also triggered the unusually high productivity in the superocean and also the expansion of O2 minimum zone to start the superanoxia. The “plume winter” scenario is integrated here to explain the “triple-double” during the Paleozoic–Mesozoic transition interval, i.e., double-phased cause, process, and consequence of the greatest global catastrophe in the Phanerozoic, in terms of mantle superplume activity that involved the whole Earth from the core to the surface biosphere. [Copyright &y& Elsevier]

A machaeridian, Lepidocoleus hohensteini sp. nov., is described from the Hunsrück Slate (Lower Emsian) of Germany. The available material includes a unique example preserving evidence of the soft tissues, only the second machaeridian specimen to do so and the first lepidocoleid. This specimen shows that the plates are attached to alternate segments in the trunk. The morphology is consistent with an annelid affinity of the Lepidocoleidae and confirms the unity of the Machaeridia. This discovery adds an important group to the known diversity of this famous late Palaeozoic marine Konservat-Lagerstätte. [ABSTRACT FROM AUTHOR]

Abstract: The subphylum Blastozoa is the most abundant and among the most diversified of echinoderm groups during the Early Paleozoic. Reappraisal of their highly diverse anatomies suggests that their superficially incomparable morphologies are actually relatively homogeneous among the major blastozoan clades. Their generic diversity shows two peaks (Drumian, Sandbian), linked by a single origination event during the Cambrian-Lower Ordovician interval. During the lower Middle Ordovician, blastozoans were distributed in distinct provinces, but became progressively more cosmopolitan during the Upper Ordovician. After the Late Ordovician crisis event, blastozoans were restricted to the Laurentian and the Baltic margins. [Copyright &y& Elsevier]

Abstract: Evolution and adaptative radiations in echinoids. Echinoids (sea urchins) originated in the Early Paleozoic and, after a first period of diversification during that era, participated in an intense evolutionary radiation during the Mesozoic and Cenozoic. In the context of a reconsideration of homologies for echinoderm body regions, we present several major aspects of echinoid evolution: the origins of irregularity and bilateral symmetry; a model of radiation exemplified by the spatangoids; the diversification of modes of echinoid reproduction. These examples allow us to understand the extent of and capacity for innovation demonstrated by sea urchins during their post-Paleozoic radiation. [Copyright &y& Elsevier]

Abstract: Evidence of sustained environmental degradation associated with the end-Guadalupian, end-Permian, and end-Triassic extinctions has been inferred from numerous geochemical and sedimentological studies, but the long-term impacts of this extinction-associated stress on the evolutionary trajectories of marine invertebrates have not been explored. An examination of the diversity, extinction, paleoenvironmental range, and geographical distribution of marine stenolaemate bryozoans during the Permian to Jurassic interval provides striking new evidence of the taxonomic and ecological influence of these mid-Phanerozoic extinctions on one of the most abundant components of the Paleozoic Fauna. Elevated bryozoan extinction rates during the Late Permian and Late Triassic were coupled with major changes in their habitats. Bryozoans gradually disappeared from deep-water offshore settings during the Late Permian and from nearshore and offshore settings during the Late Triassic. Re-colonization of these environments in the wake of each crisis was delayed but coupled with increases in global generic diversity. The taxonomic effects of the end-Guadalupian extinction were milder than previously described, even though ecologically bryozoans were becoming restricted to nearshore settings. The end-Permian mass extinction remained the largest for bryozoans, drastically reducing global and assemblage generic diversity and triggering a permanent change in their paleoenvironmental preferences from nearshore to mid-shelf settings. The 285 Myr dominance of stenolaemate bryozoans ended during the Late Triassic when all but one order (Cyclostomata) became extinct, initiating a taxonomic switch between stenolaemate and gymnolaemate bryozoans. Moreover, spatio-temporal variations in the paleoenvironmental history of bryozoans imply that Late Permian and Late Triassic marine environmental instability resulted largely from some stressful deep-water phenomenon. High extinction rates in nearshore environments in the Late Permian provide a link between marine and terrestrial/atmosphere extinction-related perturbations. [Copyright &y& Elsevier]

The central muscle scar field of the beyrichioidean palaeocopid ostracodes includes an adductor muscle scar composed of many polygonal scars, a long mandibular scar composed of eight individual scars, and an oval frontal muscle scar. Probably, as in the extant ostracodes, the muscle scars served as attachment points for the closing muscles as well as for the muscles and chitinous supporting structures from the appendages. The fulcral depression, on which the dorsal apex of the mandible pivots in recent ostracodes, has also been recognized in the Early Carboniferous beyrichiids and paraparchitids. The pore systems of the beyrichioideans are more advanced than assumed so far, and they include, documented for the first time, the secretory ('exocrine') pores and 'marginal' pores in Paleozoic beyrichioideans. It seems likely that the development of these pores, was related to the transition of beyrichioideans from shallow marine into unstable, possibly brackish, water paleoenvironments. The partially calcified inner lamella and the 'marginal' pore canals are apomorphies of some Early Carboniferous beyrichioideans. Internal features of the paraparchitids confirm their beyrichioidean affinity. The adductor and mandibular scars are plesiomorphic in the Beyrichiidae and Paraparchitidae. The presence of mandibular scars and fulcral depressions may indicate that these ostracodes were actively feeding bottom crawlers. [ABSTRACT FROM AUTHOR]

The ages of subcontinental lithospheric mantle beneath the North China and South China cratons are less well-constrained than the overlying crust. We report Re–Os isotope systematics of mantle xenoliths entrained in Paleozoic kimberlites and Mesozoic basalts from eastern China. Peridotite xenoliths from the Fuxian and Mengyin Paleozoic diamondiferous kimberlites in the North China Craton give Archean Re depletion ages of 2.6–3.2 Ga and melt depletion ages of 2.9–3.4 Ga. No obvious differences in Re and Os abundances, Os isotopic ratios and model ages are observed between spinel-facies and garnet-facies peridotites from both kimberlite localities. The Re–Os isotopic data, together with the PGE concentrations, demonstrate that beneath the Archean continental crust of the eastern North China Craton, Archean lithospheric mantle of spinel- to diamond-facies existed without apparent compositional stratification during the Paleozoic. The Mesozoic and Cenozoic basalt-borne peridotite and pyroxenite xenoliths, on the other hand, show geochemical features indicating metasomatic enrichment, along with a large range of the Re–Os isotopic model ages from Proterozoic to Phanerozoic. These features indicate that lithospheric transformation or refertilization through melt-peridotite interaction could be the primary mechanism for compositional changes during the Phanerozoic, rather than delamination or thermal-mechanical erosion, despite the potential of these latter processes to play an important role for the loss of garnet-facies mantle. A fresh garnet lherzolite xenolith from the Yangtze Block has a Re depletion age of ∼1.04 Ga, much younger than overlying Archean crustal rocks but the same Re depletion ages as spinel lherzolite xenoliths from adjacent Mesozoic basalts, indicating Neoproterozoic resetting of the Re–Os system in the South China Craton. [ABSTRACT FROM AUTHOR]

There are few body fossil biotas known from early Paleozoic accretionary shorelines, and very few examples of Ordovician soft-bodied assemblages. This study documents two recently discovered biotas from separate sedimentary basins in Manitoba, Canada, that provide unique information about tropical shoreline communities shortly before the Late Ordovician extinction event. Each site represents a distinct depositional environment, but they share biotic elements, including eurypterids, xiphosurids, and large problematic tubes. The William Lake biota, representing more restricted conditions, includes jellyfish that are among the best hydromedusan body fossils known. Rocks at the Airport Cove site, deposited under more open circulation, contain scolecodonts and noncalcified algae. These biotas have some parallels with the recently described Middle Ordovician Winneshiek Lagerstätte, but are also similar to some Late Silurian assemblages. Considered together, early Paleozoic marginal marine deposits are a rich but as yet poorly known source of paleobiodiversity data. [ABSTRACT FROM AUTHOR]

Atmospheric carbon dioxide concentrations seem to have been several times modern levels during much of the Palaeozoic era (543–248 million years ago), but decreased during the Carboniferous period to concentrations similar to that of today. Given that carbon dioxide is a greenhouse gas, it has been proposed that surface temperatures were significantly higher during the earlier portions of the Palaeozoic era. A reconstruction of tropical sea surface temperatures based on the δ18O of carbonate fossils indicates, however, that the magnitude of temperature variability throughout this period was small, suggesting that global climate may be independent of variations in atmospheric carbon dioxide concentration. Here we present estimates of sea surface temperatures that were obtained from fossil brachiopod and mollusc shells using the ‘carbonate clumped isotope’ method—an approach that, unlike the δ18O method, does not require independent estimates of the isotopic composition of the Palaeozoic ocean. Our results indicate that tropical sea surface temperatures were significantly higher than today during the Early Silurian period (443–423 Myr ago), when carbon dioxide concentrations are thought to have been relatively high, and were broadly similar to today during the Late Carboniferous period (314–300 Myr ago), when carbon dioxide concentrations are thought to have been similar to the present-day value. Our results are consistent with the proposal that increased atmospheric carbon dioxide concentrations drive or amplify increased global temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The Southern Urals of Russia contain what is arguably one of the best-preserved examples of an arc–continent collision in any Paleozoic orogen. The arc–continent collision history recorded in the rocks of the Southern Urals began in the Early Devonian with the onset of intra-oceanic subduction and the formation of the Magnitogorsk Arc and ended with its collision with the margin of Baltica during the Late Devonian. The Baltica margin consisted of a basement that was composed predominantly of rocks of Archean and Proterozoic age that, by the time of arc–continent collision, was overlain by Cambrian, Ordovician, Silurian, and Devonian sediments interpreted to have been deposited in rift-related grabens on the continental slope and rise, and on the shallow marine platform. The Magnitogorsk Arc consists of Early to Late Devonian island arc volcanic rocks and overlying volcaniclastic sediments. Arc–continent collision led to the development of an accretionary complex that includes shallowly and deeply subducted continental margin rocks, ophiolite fragments, and sediments that were deposited in a foreland-basin setting. The geochemistry of the Magnitogorsk Arc volcanic rocks, the structure of the arc–continent collision accretionary complex and the forearc, the high-pressure rocks beneath and along the suture zone, the mafic and ultramafic ophiolitic material, and the syn-tectonic sediments show that the Paleozoic tectonic processes recorded in the Southern Urals can be favorably compared with those in currently active settings such as the west Pacific. [Copyright &y& Elsevier]

Abstract: There are few palaeolimnological studies of Palaeozoic lake deposits using methodologies developed for the study of Quaternary lakes. New research described here indicates the benefits of applying multidisciplinary high-resolution sampling and analysis on the Middle Devonian lake deposits of the Orcadian Basin in order to understand lake palaeoecology and response to water chemistry change and possible climate change. In a continuously sampled 4 m-thick lake cycle in two correlated boreholes in Caithness there are two distinct features. There is a broad trend in δ 13C of sedimentary organic matter from high values in the shallow water deposits to lower values in the deeper water deposits, attributed to changing contributions from terrestrial plant material (δ 13Corg c. −28‰) and algal material (δ 13Corg c. −33‰). This variation is consistent with palynological data and is best explained by proximal–distal variation as the lake filled. A smaller but well-correlated up-section decreasing δ 13Corg trend occurs over approximately 1 m, starting at the cycle centre where the lake was at its deepest. Since the same feature is seen in two boreholes, we suggest that local effects of migrated bitumen, diagenesis or facies changes are unlikely to be the cause, and that changes in the carbon cycle of the lake are responsible. Explanations for this trend may relate to the source of carbon that algae utilised as the lake changed from a fresher to a more saline environment, and to changes in the carbon isotope composition of the lake water during periods of enhanced productivity. [Copyright &y& Elsevier]

Sponges (phylum Porifera) were prolific reef-building organisms during the Paleozoic and Mesozoic ∼542 to 65 million years ago. These ancient animals inherited components of the first multicellular skeletogenic toolkit from the last common ancestor of the Metazoa. Using a paleogenomics approach, including gene- and protein-expression techniques and phylogenetic reconstruction, we show that a molecular component of this toolkit was the precursor to the a-carbonic anhydrases (α- CAs), a gene family used by extant animals in a variety of fundamental physiological processes. We used the coralline demosponge Astrosciera willeyana, a ‘living fossil’ that has survived from the Mesozoic, to provide insight into the evolution of the ability to biocalcify, and show that the α-CA family expanded from a single ancestral gene through several independent gene-duplication events in sponges and eumetazoans. [ABSTRACT FROM AUTHOR]

The article discusses research which evaluated how ceratitid ammonoids were affected by the end-Permian mass extinction, which occurred at the end of the Paleozoic Era. Within this extinction event, 85 percent of readily fossilizable marine species became extinct. It took five million years for the Earth to recover from the event, but this study found that ceratitid ammonoids recovered considerably faster than other marine species, acquiring extensive diversity one million years after the mass extinction. The author analyzes what this finding implies about the Early Triassic epoch.