The Global Ordovician Biodiversification Event (GOBE) was undoubtedly one of the most significant evolutionary events in the history of the marine biosphere. A continuous increase in ichnodiversity occurs through the Ordovician in both shallow- and deep-marine environments. The earlier view that early Paleozoic deep-marine ichnofaunas are of low alpha diversity has been challenged by discoveries of moderately diverse associations. Interestingly, however, the increase in global ichnodiversity through the Ordovician is not paralleled by an increase in ichnodisparity of bioturbation structures. In fact, whereas global ichnodiversity in the Ordovician almost doubled Cambrian levels, Ordovician ichnodisparity of bioturbation structures is roughly similar to that resulting from the Cambrian explosion. Macroboring organisms also display significant evolutionary innovation and diversification in shallow-water hardgrounds and other carbonate substrates, resulting in the Ordovician Bioerosion Revolution. Along with this macroboring ichnodiversity and ichnodisparity increase is a significant rise in the rate of bioerosion in carbonate substrates. Ichnofaunal changes in lower-shoreface and offshore siliciclastic deposits through the Ordovician reveal faunal turnovers resulting from the evolutionary radiation. Lower Ordovician deposits tend to be dominated by abundant trilobite-produced trace fossils. Middle to Upper Ordovician shallow-marine ichnofaunas tend to show more varied behavioral patterns and trilobite trace fossils are rarely the dominant components. During the early Paleozoic, the tiering structure of ichnofaunas became more complex, as a result of both the addition of deeper tiers and of a wider variety of biogenic structures in previously occupied tiers. Infaunalization by deposit feeders in offshore siliciclastic environments was most likely diachronous, with the establishment of a mid-tier infauna first in Laurentia and Baltica, and only subsequently in Gondwana.

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The Great Ordovician Biodiversification Event

Early hominid evolution and ecological change through the African Plio-Pleistocene

Taphonomy plays diverse roles in paleobiology. These include assessing sample quality relevant to ecologic, biogeographic, and evolutionary questions, diagnosing the roles of various taphonomic agents, processes and circumstances in generating the sedimentary and fossil records, and reconstructing the dynamics of organic recycling over time as a part of Earth history. Major advances over the past 15 years have occurred in understanding (1) the controls on preservation, especially the ecology and biogeochemistry of soft-tissue preservation, and the dominance of bi- ological versus physical agents in the destruction of remains from all major taxonomic groups (plants, invertebrates, vertebrates); (2) scales of spatial and temporal resolution, particularly the relatively minor role of out-of-habitat transport contrasted with the major effects of time-averaging; (3) quantitative compositional fidelity; that is, the degree to which different types of assemblages reflect the species composition and abundance of source faunas and floras; and (4) large-scale var- iations through time in preservational regimes (megabiases), caused by the evolution of new bod- yplans and behavioral capabilities, and by broad-scale changes in climate, tectonics, and geochem- istry of Earth surface systems. Paleobiological questions regarding major trends in biodiversity, major extinctions and recoveries, timing of cladogenesis and rates of evolution, and the role of environmental forcing in evolution all entail issues appropriate for taphonomic analysis, and a wide range of strategies are being developed to minimize the impact of sample incompleteness and bias. These include taphonomically robust metrics of paleontologic patterns, gap analysis, equal- izing samples via rarefaction, inferences about preservation probability, isotaphonomic compari- sons, taphonomic control taxa, and modeling of artificial fossil assemblages based on modern an- alogues. All of this work is yielding a more quantitative assessment of both the positive and neg- ative aspects of paleobiological samples. Comparisons and syntheses of patterns across major groups and over a wider range of temporal and spatial scales present a challenging and exciting agenda for taphonomy in the coming decades.

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Taphonomy and paleobiology

Transgressive deposits: a review of their variability

Pairs of platinum mesh or graphite fiber-based electrodes, one embedded in marine sediment (anode), the other in proximal seawater (cathode), have been used to harvest low-level power from natural, microbe established, voltage gradients at marine sediment−seawater interfaces in laboratory aquaria. The sustained power harvested thus far has been on the order of 0.01 W/m2 of electrode geometric area but is dependent on electrode design, sediment composition, and temperature. It is proposed that the sediment/anode−seawater/cathode configuration constitutes a microbial fuel cell in which power results from the net oxidation of sediment organic matter by dissolved seawater oxygen. Considering typical sediment organic carbon contents, typical fluxes of additional reduced carbon by sedimentation to sea floors < 1000 m deep, and the proven viability of dissolved seawater oxygen as an oxidant for power generation by seawater batteries, it is calculated that optimized power supplies based on the phenomenon demonstr...

Harvesting Energy from the Marine Sediment−Water Interface

Taphonomy: releasing the data locked in the fossil record

The origin of sedimentary organic matter (kerogen) has been attributed to random recombination reactions of biological components in sediments or to selective preservation of decay-resistant macromolecules. Neither hypothesis explains the aliphatic composition of the cuticle of fossil arthropods. Thermal maturation experiments on modern arthropods, involving confined pyrolysis at 250–360 °C, degrade the chitin-protein complex of the cuticle and transform free aliphatic components into a polymeric structure. The results of the application of electron microscopy and spectroscopic methods to modern, thermally matured, and fossil arthropod cuticles indicate that in situ polymerization of free and ester-bound cuticular lipids can lead to kerogen formation. Thus, fossil arthropod fragments can contribute to sedimentary organic matter.

Alternative origin of aliphatic polymer in kerogen

Flash pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) was used to assess the quality and mechanism of protein preservation in the tissue of Iron Age bog bodies from Lindow, UK, and south-eastern Drenthe, The Netherlands. Abundant pyrolysis products of the fresh skin tissue, including 2,5-diketopiperazines of Pro-Gly, Pro-Ala, Pro-Val, Pro-Pro and Hyp, were readily assigned to specific amino acid or dipeptide moieties. Comparison of the pyrolysates of the bog-body tissues with that of modern samples revealed qualitative similarities suggesting good preservation of the collagen and non-collagenous proteins in the ancient tissues. Examination of the pyrolysates of samples of fresh calf skin, which had been treated with various vegetable tanning agents, clearly revealed markers of non-hydrolysable tannins including 1,2-benzenediol, 1,3-benzenediol and 1,2,3-benzenetriol, although chromatographic quality inevitably diminished with increasing functionalization of the compounds. Such markers were not detected in the pyrolysates of the bog-body tissues. Instead 4-isopropenylphenol, a characteristic pyrolysis product of Sphagnum moss, was detected in both solvent-extracted and base-treated samples of tissue. The presence of 4-isopropenylphenol in the pyrolysates of the bog-body tissues provides evidence that their preservation involves reactions of amino acids with spagnum acid, and possibly other agents derived from the peat. The study constitutes the first chemical characterization of the pyrolysis products of modern and ancient collagen. © 1997 John Wiley & Sons, Ltd.

Assessment of bog‐body tissue preservation by pyrolysis‐gas chromatography/mass spectrometry

The cuticles of 15 fossil invertebrates ranging in age from Silurian to Cretaceous, and including both marine and terrestrial organisms, have been analyzed using pyrolysis−gas chromatography/mass spectrometry (py−GC/MS). Modern invertebrate cuticles were analyzed in the same way as a basis for comparison. The modern cuticles yielded pyrolysis products derived from chitin and proteins, but none of these components was detected in the pyrolysates of the fossil cuticles. The fossil cuticles fall into two, chemically distinct groups:  aliphatic, yielding pairs of n-alk-1-enes and n-alkanes upon pyrolysis, and aromatic, producing pyrolysates dominated by alkylbenzenes and alkylindenes. Aliphatic pyrolysates may derive through polymerization of lipids, e.g., epicuticular waxes, during diagenesis. Alternatively the aliphatic moieties found in algae (algaenan) or in plants (e.g., cutan, suberan) may have been incorporated into the animal cuticles by unknown diagenetic processes. Alkylindenes are major pyrolysis p...

Chemical composition of Paleozoic and Mesozoic fossil invertebrate cuticles as revealed by pyrolysis-gas chromatography/mass spectrometry

Analyses of identifiable organic fossil remains of animals and plants have considerable potential to resolve conflicting models of organic matter diagenesis and kerogen formation (e.g. selective preservation versus random polymerization). Fossil cuticles of arthropods (scorpion, eurypterid) and plants (cordaite, pteridosperm) from Upper Carboniferous strata of Lone Star Lake, Kansas, USA and Joggins, Nova Scotia, Canada were analysed by pyrolysis–gas chromatography/mass spectrometry and examined by electron microscopy. Recent Pandinus (scorpion) and Araucaria (conifer) provided a basis for comparison. Pyrolysis of Recent dewaxed scorpion cuticle yielded products derived from chitin and proteins. These products were absent in the fossil arthropod cuticles, however, which yielded an homologous series of alkanes and alkenes, together with phenolic and other aromatic constituents. Recent dewaxed plant cuticle yielded fatty acids, phenols and carbohydrate-derived compounds indicative of cutin polyester and associated lignocellulose. The pyrolysates of the fossil plant cuticles, on the other hand, were dominated by alkane–alkene doublets, with minor phenolic and other benzenoid components. There is no evidence that the preservation of these cuticles as particulate organic matter in kerogen is simply a result of selective preservation. Nonetheless, the chemistry and morphology remain characteristic of a particular taxon, thereby eliminating the possibility of incorporation of randomly repolymerized materials or the transfer of material between plant and animal residues. The aliphatic moieties in the fossil cuticles are thought to be the result of polymerization of the associated epicuticular, cuticular and/or tissue lipids during diagenesis.

Deg Briggs

Papers

Taphonomy: releasing the data locked in the fossil record

Alternative origin of aliphatic polymer in kerogen

Assessment of bog‐body tissue preservation by pyrolysis‐gas chromatography/mass spectrometry

Chemical composition of Paleozoic and Mesozoic fossil invertebrate cuticles as revealed by pyrolysis-gas chromatography/mass spectrometry

Molecular taphonomy of arthropod and plant cuticles from the Carboniferous of North America: implications for the origin of kerogen