Search

Over the past 3.8 billion years, the maximum size of life has increased by approximately 18 orders of magnitude. Much of this increase is associated with two major evolutionary innovations: the evolution of eukaryotes from prokaryotic cells approximately 1.9 billion years ago (Ga), and multicellular life diversifying from unicellular ancestors approximately 0.6 Ga. However, the quantitative relationship between organismal size and structural complexity remains poorly documented. We assessed this relationship using a comprehensive dataset that includes organismal size and level of biological complexity for 11 172 extant genera. We find that the distributions of sizes within complexity levels are unimodal, whereas the aggregate distribution is multimodal. Moreover, both the mean size and the range of size occupied increases with each additional level of complexity. Increases in size range are non-symmetric: the maximum organismal size increases more than the minimum. The majority of the observed increase in organismal size over the history of life on the Earth is accounted for by two discrete jumps in complexity rather than evolutionary trends within levels of complexity. Our results provide quantitative support for an evolutionary expansion away from a minimal size constraint and suggest a fundamental rescaling of the constraints on minimal and maximal size as biological complexity increases. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the potential of using surficial shell accumulations for paleoenvironmental studies, an extensive time series of individually dated specimens of the marine infaunal bivalve mollusk Semele casali was assembled using amino acid racemization (AAR) ratios (n=270) calibrated against radiocarbon ages (n=32). The shells were collected from surface sediments at multiple sites across a sediment-starved shelf in the shallow sub-tropical São Paulo Bight (São Paulo State, Brazil). The resulting 14C-calibrated AAR time series, one of the largest AAR datasets compiled to date, ranges from modern to 10,307calyr BP, is right skewed, and represents a remarkably complete time series: the completeness of the Holocene record is 66% at 250-yr binning resolution and 81% at 500-yr binning resolution. Extensive time-averaging is observed for all sites across the sampled bathymetric range indicating long water depth-invariant survival of carbonate shells at the sediment surface with low net sedimentation rates. Benthic organisms collected from active depositional surfaces can provide multi-millennial time series of biomineral records and serve as a source of geochemical proxy data for reconstructing environmental and climatic trends throughout the Holocene at centennial resolution. Surface sediments can contain time-rich shell accumulations that record the entire Holocene, not just the present. [Copyright &y& Elsevier]

Ecosystems changed dramatically during the Mesozoic marine revolution, including the rise of decapod crustaceans such as lobsters, shrimp, true crabs, and squat lobsters. However, quantitative patterns of decapod biodiversity through geological time are virtually unknown. This hampers our understanding of their importance in past ecosystems and timing and causes of their radiations and extinctions. Based on our compilation of ~1300 Mesozoic decapod species, we document a long-term shift in diversity of dominant groups, marked by the first appearance and increasing presence of true crabs and, to a lesser extent, squat lobsters. By the end of the Mesozoic, true crabs became the primary contributor to decapod diversity, a pattern that has persisted until the present time. This "Mesozoic decapod revolution" was advanced by a major radiation of reef-dwelling crabs, which coincided with a dramatic expansion of reefs in the Late Jurassic. The subsequent collapse of reefs near the end of the Jurassic was mirrored by a sharp (albeit temporary) drop in decapod diversity driven primarily by extinctions of numerous species of crabs. This concurrent decline also suggests that decapods inhabiting reefs, especially obligatory reef dwellers, may face elevated extinction risks today as reef ecosystems continue to deteriorate. The reef-related diversification of Late Jurassic decapods and the significant correlation between decapod diversity and reef abundance throughout the Mesozoic underscore the macroevolutionary importance of biotic interactions and ecosystem engineering. [ABSTRACT FROM AUTHOR]

Abstract: Exceptionally preserved Devonian lingulides, found in spherical-to-subspherical mudstone concretions (Paraná Basin, Brazil), were analyzed using an electron microscopy-based approach (scanning electron microscopy, secondary and backscattered electron imaging) augmented with semi-quantitative elemental analyses (energy dispersive X-ray spectroscopy). Elemental composition, spatial biomineralization gradients, microstructural details, and growth banding patterns are similar to those observed in live-collected lingulid brachiopods (Glottidia palmeri and Lingula sp.). These parallels suggest a faithful preservation of primary biomineralization and microstructure in the Devonian lingulides. While our results suggest that physicochemical aspects of lingulide shells have been conserved throughout their evolutionary history, comparisons of carbon and phosphorus elemental maps and transects indicate that the Devonian lingulides may have been more extensively biomineralized than their present-day relatives, a pattern suggestive of their greater intrinsic fossilization potential. These Devonian shells, some of which are preserved in situ and in interpreted life position (with both valves intact and oriented vertically relative to bedding), tend to be associated with pyrite and rarer sphalerite grains at much higher concentrations than the surrounding matrix. This localized sulfide-mineral enrichment suggests that organic-rich lingulide shells may have acted as focal zones for bacterial sulfate reduction, resulting in degradation of the shell-associated organics and enhanced sulfide mineral precipitation. In addition to sulfide minerals, barite is also observed in direct proximity to the surfaces of some lingulide shells. Their in-situ preservation indicates rapid burial and a lack of reworking, and the early-diagenetic precipitation of sulfide and sulfate minerals suggests microbially-mediated authigenic processes in an anoxic microenvironment. In addition, the presence of three-dimensionally preserved acanthomorphic acritarchs indicates that the concretions were likely lithified rapidly prior to the degradation and compaction of these comparatively labile organisms. This combination of sedimentological, microbial, and geochemical conditions may have enhanced preservation of the lingulide shells, conserving original microstructural and biomineral details, as well as the acritarch fossils. The data presented here indicate that concretion-hosted organo-phosphatic shells may offer an exceptional taphonomic view into lingulide biomineralization and taphonomic processes. [Copyright &y& Elsevier]

Abstract: Doushantuo acanthomorphic acritarchs are large morphologically complex organic-walled microfossils broadly constrained between the ∼635Ma Nantuo glaciation and the ∼551Ma Miaohe Biota. They are potential biostratigraphic tools for subdivision and correlation of the Ediacaran System in South China. However, major variations in sedimentary facies and stratigraphic thickness present challenges in understanding the spatial and temporal distribution of these acritarchs. Further, the distribution of acritarchs in the Doushantuo Formation is associated with the presence of early diagenetic chert and phosphate, implying a certain degree of preservational bias and/or environmental control. The purpose of this paper is to document the stratigraphic distribution of Doushantuo acritarchs and to quantitatively evaluate their biostratigraphic significance and possible taphonomic–environmental biases, based on high-resolution paleontological data from six sections over ∼100km in the Yangtze Gorges area, South China. A total of 1082 acritarch fossils were recorded from 84 chert horizons in the six sections of the study area. These chert horizons are not uniformly distributed throughout the Doushantuo Formation, thus the presence/absence of early diagenetic chert does play a role in controlling the distribution of acritarchs. The sampled chert horizons can be grouped into two stratigraphic intervals in the lower and upper Doushantuo Formation, respectively, based on regional stratigraphic correlation. Quantitative analysis shows that the two intervals are distinct taxonomically and largely independent of taphonomic or facies controls. Thus, the two intervals can be regarded as assemblage biozones. The lower biozone (biozone 1) is numerically dominated by Tianzhushania spinosa (n =587; 68.3%) and Meghystrichosphaeridium magnificum (n =74; 8.6%), whereas the upper biozone (biozone 2) is dominated by Ericiasphaera rigida (n =104; 47.1%) and Tianzhushania spinosa (n =34; 14.1%). The three most common genera, Meghystrichosphaeridium, Tianzhushania, and Ericiasphaera, have been identified in all sections. Correspondence analysis (CA), detrended correspondence analysis (DCA), discriminant analysis (DA), and pairwise comparisons of samples (Spearman rank coefficient and Jaccard–Chao index), all consistently support biostratigraphic zonations. Thus, the distribution of the Doushantuo acanthomorphs is primarily controlled by biostratigraphic position of samples, with facies and taphonomic differences playing a secondary role. Our case study suggests that acanthomorphic acritarchs can offer a viable tool for regional correlation of the Ediacaran System. [Copyright &y& Elsevier]

Abstract: Stable isotopes of oxygen and carbon extracted from fossil land snail shells have been used increasingly to interpret past environments. To evaluate the utility of this approach for low-latitude oceanic islands, populations of the modern helicid land snail Theba geminata – a species also abundant in the Quaternary fossil record of the region – were sampled at ten low altitude (<300 m) sites from coastal areas of the eastern Canary Islands. The results include stable isotopes of (1) 17 aragonite shells of live-collected adult snails; (2) 17 body tissue samples from the same snail individuals; (3) 10 samples of carbonate sediments; (4) 69 plant tissue samples representing all 24 identified species; and (5) 7 rain water samples. The mean isotopic composition of the rain water is −5‰ (V-SMOW) for δD and −2‰ (V-SMOW) for δ 18O, ranging from −11‰ to +2‰ (V-SMOW) and from −2.6‰ to −0.7‰ (V-SMOW), respectively. The local vegetation is heterogeneous, including C3, C4, and CAM plants. δ 13C values vary from −13.0‰ to −29.0‰ (V-PDB) across plant species. Of the 24 species, five are C4, 15 are C3, and four are CAM plants. The δ 18O values for shells represent a narrow range of values (from −0.3‰ to +2.5‰ [V-PDB]), which is consistent with the low climate seasonality typifying low-latitude oceanic settings. Hypothetical model of the expected δ 18O value for shell aragonite precipitated in equilibrium suggests that the most negative δ 18Oshell represent the closest estimate for δ 18Orain water. The δ 13C values of shells range from −9.4‰ to +1.7‰ (V-PDB). The most positive δ 13C values are attributed to a diet based on C4 plants. The comparison of δ 13C values of soft tissues and shells suggests that snails ingested notable amounts (from ~20% up to ~40%) of foreign carbonates. Consequently, fossil shells with the most negative δ 13C values should be selected for radiocarbon dating in future geochronological studies of the region. The δ 13C values of body tissues vary from −12.0‰ to −27.2‰ (V-PDB), indicating that land snails consumed C3 and C4 plants indiscriminately. The mean carbon isotopic composition, averaged across multiple fossil specimens, may thus provide a useful tool for reconstructing paleoclimates and paleoenvironments throughout the Quaternary history of the Canary Islands and other comparable low-latitude oceanic settings. [Copyright &y& Elsevier]

Ediacara fossils [575 to 542 million years ago (Ma)] represent Earth's oldest known complex macroscopic life forms, but their morphological history is poorly understood. A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage-the Avalon assemblage (575 to 565 Ma)-already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea (560 to 550 Ma) and Nama (550 to 542 Ma) assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. These diversity changes, occurring while morphospace range remained relatively constant, led to inverse shifts in morphological variance. The Avalon morphospace expansion mirrors the Cambrian explosion, and both events may reflect similar underlying mechanisms. [ABSTRACT FROM AUTHOR]

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum, mean and median body size increased, but no increase in minimum size was observed. This increase is not expressed within lineages, but is rather a product of the appearance and/or diversification of new clades of larger, primarily burrowing to shelter-seeking decapods. This argues against directional selective pressures within lineages. Rather, the trend is a macroevolutionary consequence of species sorting: preferential origination of new decapod clades with intrinsically larger body sizes. Furthermore, body size evolution appears to have been habitat-controlled. In the Cretaceous, reef-associated crabs became markedly smaller than those in other habitats, a pattern that persists today. The long-term increase in body size of crabs and lobsters, coupled with their increased diversity and abundance, suggests that their ecological impact may have increased over evolutionary time. [ABSTRACT FROM AUTHOR]

Long-term baseline data that allow tracking how predator-prey interactions have responded to intensifying human impacts are often lacking. Here, we assess temporal changes in benthic community composition and interactions between drilling predatory gastropods and their molluscan prey using the Holocene fossil record of the shallow northern Adriatic Sea, which is characterized by a long history of human transformation. Molluscan assemblages differ between the Isonzo and Po prodelta, but both show consistent temporal trends in the abundance of dominant species. Samples of mollusc prey collected at high stratigraphic resolution indicate that drilling frequencies have drastically declined in the Po prodelta since the mid-twentieth century, while a weaker trend in the more condensed sediments of the Isonzo prodelta is not statistically significant. The decrease in drilling predation intensity and the community turnover are linked to the loss of predatory gastropods and the increased relative abundance of less-preferred prey during the most recent decades. Our results align with data showing the substantial depletion of marine resources at higher trophic levels in the region and indicate that the strong simplification of the food web initiated in the late nineteenth century accelerated further since the mid-twentieth century.

Species diversity increases with the temporal grain of samples according to the species-time relationship (STR), impacting palaeoecological analyses because the temporal grain (time averaging) of fossil assemblages varies by several orders of magnitude. We predict a positive relation between total abundance and sample size-independent diversity (ADR) in fossil assemblages because an increase in time averaging, determined by a decreasing sediment accumulation, should increase abundance and depress species dominance. We demonstrate that, in contrast to negative ADR of non-averaged living assemblages, the ADR of Holocene fossil assemblages is positive, unconditionally or when conditioned on the energy availability gradient. However, the positive fossil ADR disappears when conditioned on sediment accumulation, demonstrating that ADR is a signature of diversity scaling induced by variable time averaging. Conditioning ADR on sediment accumulation can identify and remove the scaling effect caused by time averaging, providing an avenue for unbiased biodiversity comparisons across space and time., (© 2024 John Wiley & Sons Ltd.)

Although the fossil record preserves a wealth of historical data about past ecosystems, the current paradigm, which postulates that fossils provide faithful archives of ecological information, stems from research primarily focused on a single group of organisms known for their high fossilization potential: molluscs. Here, we quantify the fidelity of higher taxa (six phyla and 11 classes) by comparing live communities and sympatric dead remains (death assemblages) using comprehensive surveys of benthic marine invertebrates from coastal habitats in North Carolina (U.S.A). We found that although community composition differed between the two assemblages across phyla and classes, these differences were predictable with an overabundance of robust and more preservable groups. In addition, dead molluscs appear to be an excellent proxy for all taxa when tracking spatio-temporal patterns and shifts in community structure using a variety of ecological metrics, including measures of α , γ , and β diversity/evenness. This suggests that despite filters imposed by differential preservation of taxa and time-averaging, the fossil record is likely to be reliable with respect to relative comparisons of composition and diversity in shallow benthic marine paleocommunities. This is consistent with previous work indicating that shallow marine death assemblages can yield robust ecological estimates adequate for assessing the variability of ecosystems that existed under natural, pre-anthropogenic conditions., Competing Interests: The authors declare there are no competing interests., (©2023 Tyler and Kowalewski.)

Background: Irregular echinoids are ecosystem engineers with diverse functional services. Documenting present-day distribution of those widespread organisms is important for understanding their ecological significance and enhancing our ability to interpret their rich fossil record., Methods: This study summarizes SCUBA surveys of clypeasteroid and spatangoid echinoids conducted in 2020 and 2021 along the central part of the Florida Keys. The survey included observations on both live and dead specimens, their distribution, habitat preferences, abundance, and live-dead comparison., Results: Echinoids were found at 17 out of 27 examined sites (63%) and occurred across a wide range of habitats including coastal seagrass meadows, subtidal sand and seagrass settings of the Hawk Channel, backreef sands, and fine muddy sands of deeper forereef habitats. The encountered species, both dead and alive, included Clypeaster rosaceus (four sites), Clypeaster subdepressus (five sites), Encope michelini (three sites), Leodia sexiesperforata (eight sites), Meoma ventricosa (nine sites), and Plagiobrissus grandis (four sites). All sites were dominated by one species, but some sites included up to five echinoid species. Live-dead fidelity was high, including a good agreement in species composition of living and dead assemblages, congruence in species rank abundance, and overlapping spatial distribution patterns. This high fidelity may either reflect long-term persistence of local echinoid populations or fragility of echinoid tests that could prevent post-mortem transport and the formation of time-averaged death assemblages. Regardless of causative factors, the live-dead comparisons suggest that irregular echinoid assemblages, from settings that are comparable to the study area, may provide a fossil record with a high spatial and compositional fidelity. The survey of live fauna is consistent with past regional surveys in terms of identity of observed species, their rank abundance, and their spatial distribution patterns. The results suggest that despite increasingly frequent hurricanes, active seasonal fisheries, massive tourism, and urban development, irregular echinoids continue to thrive across a wide range of habitats where they provide diverse ecosystem services by oxygenating sediments, recycling organic matter, supporting commensal organisms, and providing food to predators. Results reported here document the present-day status of local echinoid populations and should serve as a useful reference point for assessing future regional changes in echinoid distribution and abundance., Competing Interests: The authors declare that they have no competing interests., (© 2022 Grun and Kowalewski.)

Preserving adaptive capacities of coastal ecosystems, which are currently facing the ongoing climate warming and a multitude of other anthropogenic impacts, requires an understanding of long-term biotic dynamics in the context of major environmental shifts prior to human disturbances. We quantified responses of nearshore mollusk assemblages to long-term climate and sea-level changes using 223 samples (~71,300 specimens) retrieved from latest Quaternary sediment cores of the Adriatic coastal systems. These cores provide a rare chance to study coastal systems that existed during glacial lowstands. The fossil mollusk record indicates that nearshore assemblages of the penultimate interglacial (Late Pleistocene) shifted in their faunal composition during the subsequent ice age, and then reassembled again with the return of interglacial climate in the Holocene. These shifts point to a climate-driven habitat filtering modulated by dispersal processes. The resilient, rather than persistent or stochastic, response of the mollusk assemblages to long-term environmental changes over at least 125 thousand years highlights the historically unprecedented nature of the ongoing anthropogenic stressors (e.g., pollution, eutrophication, bottom trawling, and invasive species) that are currently shifting coastal regions into novel system states far outside the range of natural variability archived in the fossil record., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

The hypothesis of the Great Evolutionary Faunas is a foundational concept of macroevolutionary research postulating that three global mega-assemblages have dominated Phanerozoic oceans following abrupt biotic transitions. Empirical estimates of this large-scale pattern depend on several methodological decisions and are based on approaches unable to capture multiscale dynamics of the underlying Earth-Life System. Combining a multilayer network representation of fossil data with a multilevel clustering that eliminates the subjectivity inherent to distance-based approaches, we demonstrate that Phanerozoic oceans sequentially harbored four global benthic mega-assemblages. Shifts in dominance patterns among these global marine mega-assemblages were abrupt (end-Cambrian 494 Ma; end-Permian 252 Ma) or protracted (mid-Cretaceous 129 Ma), and represent the three major biotic transitions in Earth's history. Our findings suggest that gradual ecological changes associated with the Mesozoic Marine Revolution triggered a protracted biotic transition comparable in magnitude to the end-Permian transition initiated by the most severe biotic crisis of the past 500 million years. Overall, our study supports the notion that both long-term ecological changes and major geological events have played crucial roles in shaping the mega-assemblages that dominated Phanerozoic oceans.

Palaeoecological data are unique historical archives that extend back far beyond the last several decades of ecological observations. However, the fossil record of continental shelves has been perceived as too coarse (with centennial-millennial resolution) and incomplete to detect processes occurring at yearly or decadal scales relevant to ecology and conservation. Here, we show that the youngest (Anthropocene) fossil record on the northern Adriatic continental shelf provides decadal-scale resolution that accurately documents an abrupt ecological change affecting benthic communities during the twentieth century. The magnitude and the duration of the twentieth century shift in body size of the bivalve Corbula gibba is unprecedented given that regional populations of this species were dominated by small-size classes throughout the Holocene. The shift coincided with compositional changes in benthic assemblages, driven by an increase from approximately 25% to approximately 70% in median per-assemblage abundance of C. gibba . This regime shift increase occurred preferentially at sites that experienced at least one hypoxic event per decade in the twentieth century. Larger size and higher abundance of C. gibba probably reflect ecological release as it coincides with an increase in the frequency of seasonal hypoxia that triggered mass mortality of competitors and predators. Higher frequency of hypoxic events is coupled with a decline in the depth of intense sediment mixing by burrowing benthic organisms from several decimetres to less than 20 cm, significantly improving the stratigraphic resolution of the Anthropocene fossil record and making it possible to detect sub-centennial ecological changes on continental shelves.

Ecological studies indicate that structurally complex habitats support elevated biodiversity, stability and resilience. The long-term persistence of structured habitats and their importance in maintaining biodiverse hotspots remain underexplored. We combined geohistorical data (dead mollusc assemblages, 'DA') and contemporary surveys (live mollusc assemblages, 'LA') to assess the persistence of local seagrass habitats over multi-centennial timescales and to evaluate whether they acted as long-term drivers of biodiversity, stability and resilience of associated fauna. We sampled structured seagrass meadows and open sandy bottoms along Florida's Gulf Coast. Results indicated that: (i) LA composition differed significantly between the two habitat types, (ii) LA from seagrass sites were characterized by significantly elevated local biodiversity and significantly higher spatial stability, (iii) DA composition differed significantly between the two habitat types, and (iv) fidelity between LA and DA was significantly greater for seagrass habitats. Contemporary results support the hypotheses that local biodiversity and spatial stability of marine benthos are both elevated in structured seagrass habitats. Geohistorical results suggest that structured habitats persist as local hotspots of elevated biodiversity and faunal stability over centennial-to-millennial timescales; indicating that habitat degradation and concomitant loss within structurally complex marine systems is a key driver of declining biodiversity and resilience.

Stratigraphic patterns of last occurrences (LOs) of fossil taxa potentially fingerprint mass extinctions and delineate rates and geometries of those events. Although empirical studies of mass extinctions recognize that random sampling causes LOs to occur earlier than the time of extinction (Signor-Lipps effect), sequence stratigraphic controls on the position of LOs are rarely considered. By tracing stratigraphic ranges of extant mollusc species preserved in the Holocene succession of the Po coastal plain (Italy), we demonstrated that, if mass extinction took place today, complex but entirely false extinction patterns would be recorded regionally due to shifts in local community composition and non-random variation in the abundance of skeletal remains, both controlled by relative sea-level changes. Consequently, rather than following an apparent gradual pattern expected from the Signor-Lipps effect, LOs concentrated within intervals of stratigraphic condensation and strong facies shifts mimicking sudden extinction pulses. Methods assuming uniform recovery potential of fossils falsely supported stepwise extinction patterns among studied species and systematically underestimated their stratigraphic ranges. Such effects of stratigraphic architecture, co-produced by ecological, sedimentary and taphonomic processes, can easily confound interpretations of the timing, duration and selectivity of mass extinction events. Our results highlight the necessity of accounting for palaeoenvironmental and sequence stratigraphic context when inferring extinction dynamics from the fossil record., (© 2018 The Authors.)

The escalation hypothesis posits that predation by increasingly powerful and metabolically active carnivores has been a major driver of metazoan evolution. We test a key tenet of this hypothesis by analyzing predatory drill holes in fossil marine shells, which provide a ~500-million-year record of individual predator-prey interactions. We show that drill-hole size is a robust predictor of body size among modern drilling predators and that drill-hole size (and thus inferred predator size and power) rose substantially from the Ordovician to the Quaternary period, whereas the size of drilled prey remained stable. Together, these trends indicate a directional increase in predator-prey size ratios. We hypothesize that increasing predator-prey size ratios reflect increases in prey abundance, prey nutrient content, and predation among predators., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Rigorous documentation of spatial heterogeneity (β-diversity) in present-day and preindustrial ecosystems is required to assess how marine communities respond to environmental and anthropogenic drivers. However, the overwhelming majority of contemporary and palaeontological assessments have centred on single higher taxa. To evaluate the validity of single taxa as community surrogates and palaeontological proxies, we compared macrobenthic communities and sympatric death assemblages at 52 localities in Onslow Bay (NC, USA). Compositional heterogeneity did not differ significantly across datasets based on live molluscs, live non-molluscs, and all live organisms. Death assemblages were less heterogeneous spatially, likely reflecting homogenization by time-averaging. Nevertheless, live and dead datasets were greater than 80% congruent in pairwise comparisons to the literature estimates of β-diversity in other marine ecosystems, yielded concordant bathymetric gradients, and produced nearly identical ordinations consistently delineating habitats. Congruent estimates from molluscs and non-molluscs suggest that single groups can serve as reliable community proxies. High spatial fidelity of death assemblages supports the emerging paradigm of Conservation Palaeobiology. Integrated analyses of ecological and palaeontological data based on surrogate taxa can quantify anthropogenic changes in marine ecosystems and advance our understanding of spatial and temporal aspects of biodiversity., (© 2017 The Author(s).)

Responses of ecosystems to environmental changes vary greatly across habitats, organisms and observational scales. The Quaternary fossil record of the Po Basin demonstrates that marine communities of the northern Adriatic re-emerged unchanged following the most recent glaciation, which lasted approximately 100,000 years. The Late Pleistocene and Holocene interglacial ecosystems were both dominated by the same species, species turnover rates approximated predictions of resampling models of a homogeneous system, and comparable bathymetric gradients in species composition, sample-level diversity, dominance and specimen abundance were observed in both time intervals. The interglacial Adriatic ecosystems appear to have been impervious to natural climate change either owing to their persistence during those long-term perturbations or their resilient recovery during interglacial phases of climate oscillations. By contrast, present-day communities of the northern Adriatic differ notably from their Holocene counterparts. The recent ecosystem shift stands in contrast to the long-term endurance of interglacial communities in face of climate-driven environmental changes., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

The high concentration of molecular oxygen in Earth's atmosphere is arguably the most conspicuous and geologically important signature of life. Earth's early atmosphere lacked oxygen; accumulation began after the evolution of oxygenic photosynthesis in cyanobacteria around 3.0-2.5 billion years ago (Gya). Concentrations of oxygen have since varied, first reaching near-modern values ~600 million years ago (Mya). These fluctuations have been hypothesized to constrain many biological patterns, among them the evolution of body size. Here, we review the state of knowledge relating oxygen availability to body size. Laboratory studies increasingly illuminate the mechanisms by which organisms can adapt physiologically to the variation in oxygen availability, but the extent to which these findings can be extrapolated to evolutionary timescales remains poorly understood. Experiments confirm that animal size is limited by experimental hypoxia, but show that plant vegetative growth is enhanced due to reduced photorespiration at lower O(2):CO(2). Field studies of size distributions across extant higher taxa and individual species in the modern provide qualitative support for a correlation between animal and protist size and oxygen availability, but few allow prediction of maximum or mean size from oxygen concentrations in unstudied regions. There is qualitative support for a link between oxygen availability and body size from the fossil record of protists and animals, but there have been few quantitative analyses confirming or refuting this impression. As oxygen transport limits the thickness or volume-to-surface area ratio-rather than mass or volume-predictions of maximum possible size cannot be constructed simply from metabolic rate and oxygen availability. Thus, it remains difficult to confirm that the largest representatives of fossil or living taxa are limited by oxygen transport rather than other factors. Despite the challenges of integrating findings from experiments on model organisms, comparative observations across living species, and fossil specimens spanning millions to billions of years, numerous tractable avenues of research could greatly improve quantitative constraints on the role of oxygen in the macroevolutionary history of organismal size.

The Ediacara biota include macroscopic, morphologically complex soft-bodied organisms that appear globally in the late Ediacaran Period (575-542 Ma). The physiology, feeding strategies, and functional morphology of the modular Ediacara organisms (rangeomorphs and erniettomorphs) remain debated but are critical for understanding their ecology and phylogeny. Their modular construction triggered numerous hypotheses concerning their likely feeding strategies, ranging from micro-to-macrophagus feeding to photoautotrophy to osmotrophy. Macrophagus feeding in rangeomorphs and erniettomorphs is inconsistent with their lack of oral openings, and photoautotrophy in rangeomorphs is contradicted by their habitats below the photic zone. Here, we combine theoretical models and empirical data to evaluate the feasibility of osmotrophy, which requires high surface area to volume (SA/V) ratios, as a primary feeding strategy of rangeomorphs and erniettomorphs. Although exclusively osmotrophic feeding in modern ecosystems is restricted to microscopic bacteria, this study suggests that (i) fractal branching of rangeomorph modules resulted in SA/V ratios comparable to those observed in modern osmotrophic bacteria, and (ii) rangeomorphs, and particularly erniettomorphs, could have achieved osmotrophic SA/V ratios similar to bacteria, provided their bodies included metabolically inert material. Thus, specific morphological adaptations observed in rangeomorphs and erniettomorphs may have represented strategies for overcoming physiological constraints that typically make osmotrophy prohibitive for macroscopic life forms. These results support the viability of osmotrophic feeding in rangeomorphs and erniettomorphs, help explain their taphonomic peculiarities, and point to the possible importance of earliest macroorganisms for cycling dissolved organic carbon that may have been present in abundance during Ediacaran times.

The maximum size of organisms has increased enormously since the initial appearance of life >3.5 billion years ago (Gya), but the pattern and timing of this size increase is poorly known. Consequently, controls underlying the size spectrum of the global biota have been difficult to evaluate. Our period-level compilation of the largest known fossil organisms demonstrates that maximum size increased by 16 orders of magnitude since life first appeared in the fossil record. The great majority of the increase is accounted for by 2 discrete steps of approximately equal magnitude: the first in the middle of the Paleoproterozoic Era (approximately 1.9 Gya) and the second during the late Neoproterozoic and early Paleozoic eras (0.6-0.45 Gya). Each size step required a major innovation in organismal complexity--first the eukaryotic cell and later eukaryotic multicellularity. These size steps coincide with, or slightly postdate, increases in the concentration of atmospheric oxygen, suggesting latent evolutionary potential was realized soon after environmental limitations were removed.

Loosening of an artificial joint is a common complication in orthopedic surgery. It is estimated that bacteriological implant contamination is responsible for its loosening in 2-5 percent of cases, and in most cases aseptic loosening takes place. Despite low percentage of positive microbiological studies, histopathological examinations and modern laboratory techniques, including PCR (Polymerase Chain Reaction) allow to diagnose the bacterial contamination of the loose implant to ca 70 percent. Those observations point out to the high coincidence of bacterial contamination with implant loosening strongly suggesting its influence on activation of the inflammatory process destabilizing an implant. But the question, why in those cases bacterial contamination does not lead to clinically obvious suppuration, remains unknown. The possibility to activate the immune system by the subcellular elements of the bacterial cells leading to persistent inflammation with granulation tissue formation is likely. Presented paper discusses the process of orthopedic prosthesis loosening, the role of bacterial contamination in it. and the newest techniques for their examination.

Background. Ozone therapy - i.e. the treatment of patients by a mixture of oxygen and ozone - has been used for many years as a method ancillary to basic treatment, especially in those cases in which traditional treatment methods do not give satisfactory results, e.g. skin loss in non-healing wounds, ulcers, pressure sores, fistulae, etc. Material and methods. In the Department of Phisiotherapy of the Medical Faculty and the Department of the Orthopedics and Traumatology of the Locomotor System at the Medical University of Warsaw in the period from January 2001 until November 2002, 23 patients with heavy,chronic, antibiotic resistants septic complications after trauma, surgical procedures and secundary skin infetions were treated with ozone. The ozone therapy was administered using an authorial technique of superficially, longer, intermittent ozone application. Results. In the wounds of the all experienced patients the inhibition of septic processes and wound healing was much faster than normal. Conclusions. Our data confirm the advantages wich result from the technique of superficially, longer, intermittent ozone theraphy in combined treatment for septic complications in the soft tissue, especially in the locomotor system. These technique makes posttraumatic infections and promotes quicker healing of post-surgical and post-traumal complications - chronic septic infections. This method also lowers the cost of antibiotic therapy and is sometimes the only available auxiliary technique to support surgical procedures.

Background. Brodie's abscess is a kind of rare subacute or chronic osteitis. It is probably caused by mistreated or non-treated osteitis, or by bacteria of low virulence., Material and methods. In the Orthopedic and Traumatology Clinic of our medical school 5 patients were diagnosed with Brodie's obsecess between 1999 and 2002. all the patients had conventional x-rays, while one also had CT and MRI., Results and conclusions. The typical x-ray image shows an osteolytic lesion with sclerotic margin in the diametophysis. Each of the 5 patients had surgery. In 4 cases the histopatological results confirmed the radiological diagnosis. In one case fibrous dysplasia was found.

On the basis of many years of clinical experience, the authors discuss the role and place of antibiotics in contemporary combined treatment for chronic osteomyelitis.

The authors reviewed the medical records of 457 patients who underwent a hemiarthroplasty procedure for the treatment of displaced femoral neck fracture. The age of the patients ranged from 60 to 103 years (mean age: 83 years). Follow-up evaluation of 331 patients was done 4-114 months post-op (mean follow-up time 52 months). 19 patients (4.2%) died in hospital, 67 patients (14.6%) developed systemic conditions during hospitalisation. 12 months post-op the mortality rate was 15.7%. Mean survival was 36.5 months. According to the Merle d'Aubigne-Postel evaluation system there were 154 satisfactory results (75.9%). Cemented or uncemented implantation techniques had no influence on long term results. 94 patients (4.2%) achieved pre-injury mobility. The reoperation rate was 8.1%. Poor general conditions at admission that postponed surgery and impaired mobility were strong negative prognostic factors.