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Biogenic low-Mg calcite (brachiopods) Burial calcite cements lREE, REESN seawater compositions Diagenetic lREE and REEsN variations The l;REE and shale-normalized (PAAS) REEsN values of modern brachiopods (biogenic low-Mg calcite: blMC) represented by several species from high-to low latitudes, from shallow-to deep waters and from warm-and cold-water environments, define three distinct average 'seawater' trends. The warm-and cold-water brachiopods define two indistinguishable (p < O.OSO) groups that mimic open -ocean seawater REE chemistry, exhibiting the typical LREE enrichment with a slightly positive to negative Ce anomaly followed by an otherwise invariant series. Other recent brachiopods from an essentially siliciclastic seabed environment are distinct in both l;REE and REEsN trends from the previous two populations, showing a slight enrichment in the MREEs and an increasing trend in the HREEs. Other groups of modern brachiopods are characterized by elevated REEsN trends relative to the 'normal'groups as well as by complexity of the series trends.The most characteristic feature is the decrease in the HREEs in these brachiopods from areas of unusual productivity (i.e., such as upwelling currents, fluvial input and aerosol dust deposition). Preserved brachiopods from the Eocene and Silurian exhibit REEsN trends and Ce anomalies similar to that of the 'open-ocean' modern brachiopods, although, their enriched l;REE concentrations suggest precipitation ofblMC influenced by extrinsic environmental conditions. Preservation of the bLMC was tested by comparing the l;REE and REEsN trends of preserved Eocene brachiopods to those of Oligocene brachiopods that were altered in an open diagenetic system in the presence of phreatic meteoric-water. The altered blMC is enriched by approximately one order of magnitude in both l;REE and REEsN trends relative to that in blMC of their preserved counterparts. Similarly, the l;REE and REEsN of preserved Silurian brachiopod blMC were compared to those of their enclosing altered lime mudstone, which exhibits features of partly closed system, phreatic meteoric-water diagenesis. Despite these differences in the diagenetic alteration systems and processes, the l;REEs and REEsN trends of the blMC of altered brachiopods and of originally mixed mineralogy lime mudstones (now diagenetic low-Mg caldte) are enriched by about one order of magnitude relative to those observed in the coeval and preserved blMC. In contrast to the changes in l;REE and REEsN of carbonates exposed to phreatic meteoric-water diagenesis, are the REE compositions oflate burial calcite cements precipitated in diagenetically open systems from burial fluids. The l;REE and REEsN trends of the burial cements mimic those of their host lime mudstone, with all showing slight LREE enrichment and slight HREE depletion, exhibiting a 'chevron' pattern of the REEsN trends.The overall enrichment or depletion of the cement REEsN trends relative to that of their respective host rock material reflects not only the openness of the diag...

Strontium isotopes of marine archives provide a significant means for tracing physical and chemical processes operating over geologic time. Modern articulated brachiopods and halite samples were collected from all depths of the world’s main water bodies. Material from the Arctic, North and South Atlantic, North and South Pacific, Indian and Southern oceans, as well as Caribbean and Mediterranean seas provide baseline parameters for diagenetic screening and reconstruction of seawater curves. The Sr isotopic ratio of modern brachiopods is unobscured by latitude, depth, and biologic factors (Order, valves, and shell segment). However, there is a small but significant impact of external sources reflected by salinity and temperature on the Sr isotope ratio of modern brachiopods. We found a significant difference in 87Sr/86Sr of brachiopods from polar and temperate-tropical habitats (p = 0.001), which should be considered when working with deep-time archives. The average 87Sr/86Sr value of all our modern shells (0.709160 ± 0.000019; N = 95) and halite (0.709153) is similar to values measured for modern seawater (0.710167 ± 0.000009; p = 0.118). The radiogenic Sr content of present-day seawater does not vary significantly, and modern biogenic-calcite 87Sr/86Sr ranges from 0.709126 to 0.709233 with a fluctuation of about ±0.000054. With the most rigorous diagenetic evaluations and stratigraphic assignment of deep-time samples, and applying the Sr isotope fluctuation recorded by modern biogenic calcite to ancient carbonates and a 1 Myr interval, reconstructions resulted in a seawater-87Sr curve with greater details during the Phanerozoic and Neoproterozoic.

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The fossil record holds a wealth of ecological data, including data on biotic interactions. For example, holes in the skeletons of invertebrates produced by drilling activities of their enemies are widely used for exploring the intensity of such interactions through time because they are common and easily distinguished from non‐biotic holes or holes produced by other types of interactions. Such drill holes have been described in numerous studies of Palaeozoic brachiopods but rarely in those focusing on brachiopods of the post‐Palaeozoic, a striking pattern given that in the late Mesozoic and Cenozoic drilling gastropods diversified and frequencies of drilled molluscs increased dramatically. During the past several years, however, drilled brachiopods were reported in several studies of the Mesozoic and Cenozoic, suggesting that this phenomenon may be more common than has been previously assumed. Here we report on drilled brachiopods from a Pliocene locality in Algeria where 90 of 261 (34.5%) specimens of Megerlia truncata show evidence of predatory drilling. These data confirm that Cenozoic drilling frequencies of brachiopods may be locally high and, when taken together with other published data, that drilling frequencies are highly heterogeneous in space and time.

Rhynchonellida is the stratigraphically oldest and phylogenetically most basal of the extant rhynchonelliform brachiopod orders, yet phylogenetic relationships among rhynchonellides are poorly known. The fourteen named rhynchonellide superfamilies (four of which have extant representatives) were defined primarily on the basis of features of the dorsal cardinalia, particularly crural morphology, but their homology and polarity have not been investigated rigorously. Superfamily monophyly is unclear, as is the evolution of several distinctive rhynchonellide morphological features, such as crura.The purpose of this study is to investigate the phylogenetic relationships among extant rhynchonellide genera using skeletal characters, and to compare the results with the current classification, elucidating the evolution of morphological features in the process. We completed parsimony-based and Bayesian analyses using fifty-eight characters of the interior and exterior of the shell that vary among the nineteen extant genera. Our results are readily interpretable with respect to the classification, and indicate that Hemithiridoidea, Dimerelloidea, and (in some analyses) Pugnacoidea appear to be monophyletic. Species classified in Dimerelloidea and Pugnacoidea, and in certain cases Hemithiridoidea, each form derived subclades that evolve from within a paraphyletic Norelloidea at the base of each subclade. Raduliform crura appear to be the most basal, phylogenetically; five other crural morphologies evolve from the raduliform state. However, morphological characters currently uniting genera in rhynchonellide superfamilies are not clearly diagnostic and exhibit a relatively high degree of homoplasy overall, suggesting that consistency with the classification may be based on a false sense of confidence in rhynchonellide morphology to clearly elucidate evolutionary relationships. Published molecular phylogenetic hypotheses conflict with the morphological topologies, further supporting this possibility.The evolutionary trends among diagnostic characters of Recent rhynchonellides appear to reflect successive juvenilization in adult morphology in several subclades, suggesting that heterochrony may have played an important role in the evolution of the group.

Twenty-two brachiopod species belonging to 19 genera have been recognized in the material collected during two cruises, Norfolk 1 and Norfolk 2, to the Norfolk Ridge south of New Caledonia, at depths of 180 to 1150 m. Thirteen species are reported for the first time from this locality, while four genera, Aulites, Septicollarina, Annuloplatidia and Campages, are noted for the first time from the New Caledonian region. Thecidellina minuta is recorded for the first time from the Pacific. Four new species are described ― Cryptopora norfolkensis sp. nov., Aulites crosnieri sp. nov., Septicollarina zezinae sp. nov. and Annuloplatidia richeri sp. nov. The distribution of the particular species and their abundance vary considerably between the 15 sampled seamounts, with Stenosarina crosnieri and Fallax neocaledonensis being most widely distributed, and the seamount Crypthelia having the highest biodiversity. The seamount brachiopods show considerable affinity to the brachiopods of adjacent regions, and only three species ― C. norfolkensis, A. crosnieri and A. richeri ― can be regarded as potential endemics. The brachiopod fauna is more similar to that in the area around Fiji than to that around Australasia.

We present here the first report based on phylogenetic analyses of small subunit (SSU/18S) and large subunit (LSU/28S) ribosomal DNA (rDNA) sequences from a wider-than-token sample of rhynchonellide articulate brachiopods, with data from 11 of ∼20 extant genera (12 species) belonging to all four extant superfamilies. Data exploration by network and saturation analyses shows that the molecular sequence data are free from major aberrations and are suitable for phylogenetic reconstruction despite the presence of large deletions in four SSU rDNA sequences. Although molecular sequence analyses cannot directly illuminate the systematics of fossils, the independent, genealogical evidence and phylogenetic inferences about extant forms that they make possible are highly relevant to paleontological systematics because they highlight the limitations of evolutionary inference from morphology. Parsimony, distance, maximum likelihood (no clock) and Bayesian (relaxed-clock) analyses all find a tree topology that disagrees strongly with the existing superfamily classification. All tested phylogenetic reconstructions agree that the taxa analyzed fall into three clades designated A1, A2, and B that reflect two major divergence events. The relaxed-clock analysis indicates that clades A and B diverged in the Paleozoic, while clades A1 and A2 reflect Permo-Triassic (and later) events. Morphological homoplasy and possible gene co-option are suggested as the main sources for the discord between the morpho-classification, the results of cladistic analyses of morphology, and the relationships reconstructed from molecular sequences. The origin, function and evolutionary implications of the deletion-bearing rhynchonellide SSU rDNA sequences are briefly discussed in relation to pseudogenes and concerted evolution in the rDNA genomic region.