Neoproterozoic-Cambrian microbialite record

2004 ◽  
Vol 10 ◽  
pp. 5-16 ◽  
Author(s):  
Russell S. Shapiro
Keyword(s):  
Simple Model ◽  
Environmental Conditions ◽  
Fossil Record ◽  
Sedimentary Record ◽  
Early Ordovician ◽  
Geochemical Conditions ◽  
Abundance Trends ◽  
Invertebrate Abundance ◽  
Global Oceans

Microbes and the sedimentary record of their activity, microbialites, have existed since the Archaean. During the Neoproterozoic-Cambrian interval, there is a marked shift in the fossil record of microbialites with the widespread proliferation of thrombolites (clotted microbialites) and the appearance and proliferation of dendrolites (microbialites composed of dendritic clusters) alongside stromatolites (laminated microbialites). Calcimicrobes also diversified during this interval. The end of this resurgence coincided with the increase in invertebrate taxa at the end of the Early Ordovician. The ìMicrobialite Resurgenceî has long been recognized but the importance of the Neoporoterozoic microbialite record for deciphering trends of this interval has not been so widely realized. It is critical to note that some of the oldest skeletal invertebrates and calcimicrobes are found in Neoproterozoic microbial reefs. Also, microbe-invertebrate synecology and invertebrate abundance trends during this interval suggests that a simple model that keys the resurgence tied in to a lack of competition from reef-building sponges and corals may not be valid. Current re-evaluation of the environmental conditions, principally the fluctuations in the geochemical conditions of the global oceans and atmosphere, will likely shed new light on understanding the Neoproterozoic-Cambrian microbialite record.

scholarly journals Two new long-rostrum cranefly species from the Cretaceous Iberian amber (Diptera, Limoniidae, Helius)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iwona Kania-Kłosok ◽  
Wiesław Krzemiński ◽  
Antonio Arillo
Keyword(s):  
Environmental Conditions ◽  
Lower Cretaceous ◽  
Fossil Record ◽  
First Record ◽  
Northern Spain ◽  
Fossil Species ◽  
Body Morphology ◽  
Cretaceous Period ◽  
Basque Cantabrian Basin

AbstractFirst record of the genus Helius—long-rostrum cranefly from Maestrazgo Basin (eastern Spain, Iberian Penisula) is documented. Two new fossil species of the genus Helius are described from Cretaceous Spanish amber and compared with other species of the genus known from fossil record with particular references to these known from Cretaceous period. Helius turolensis sp. nov. is described from San Just amber (Lower Cretaceous, upper Albian) Maestrazgo Basin, eastern Spain, and Helius hispanicus sp. nov. is described from Álava amber (Lower Cretaceous, upper Albian), Basque-Cantabrian Basin, northern Spain. The specific body morphology of representatives of the genus Helius preserved in Spanish amber was discussed in relation to the environmental conditions of the Maestrazgo Basin and Basque-Cantabrian Basin in Cretaceous.

Stratigraphic biases in the analysis of taxonomic survivorship

Paleobiology ◽  
1975 ◽  
Vol 1 (4) ◽  
pp. 343-355 ◽  
Author(s):  
J. John Sepkoski
Keyword(s):  
Simple Model ◽  
Lognormal Distribution ◽  
Fossil Record ◽  
The Other ◽  
Time Intervals ◽  
Survivorship Analysis ◽  
Other Hand ◽  
Incomplete Sampling ◽  
Biologic Factors

Taxonomic survivorship curves may reflect stratigraphic as well as biologic factors. The approximately lognormal distribution of lengths of Phanerozoic time intervals produces an error in the estimation of taxonomic durations that is also lognormally distributed. As demonstrated by several simulated examples, this error may cause concave taxonomic survivorship curves to appear linear, especially if the maximum durations involved are relatively short. The error of estimation also makes highly concave taxonomic survivorship curves virtually unrecognizable. Incomplete sampling of the fossil record, on the other hand, may not be a serious problem in survivorship analysis. Simulated paleontological sampling employing a simple model suggests that survivorship curves tend to retain their original shapes even when as few as 20% of the taxa have been discovered. However, concave taxonomic survivorship curves tend to lose their concavity as efficiency of sampling declines.

The greatest hits of all time: the histories of dominant genera in the fossil record

Paleobiology ◽  
2018 ◽  
Vol 44 (3) ◽  
pp. 368-384 ◽  
Author(s):  
Roy E. Plotnick ◽  
Peter Wagner
Keyword(s):  
Simple Model ◽  
Fossil Record ◽  
Target Groups ◽  
Higher Taxa ◽  
Occurrence Data

AbstractCertain taxa are noticeably common within collections, widely distributed, and frequently long-lived. We have examined these dominant genera as compared with rarer genera, with a focus on their temporal histories. Using occurrence data from the Paleobiology Database, we determined which genera belonging to six target groups ranked among the most common within each of 49 temporal bins based on occurrences. The turnover among these dominant taxa from bin to bin was then determined for each of these groups, and all six groups when pooled. Although dominant genera are only a small fraction of all genera, the patterns of turnover mimic those seen in much larger compilations of total biodiversity. We also found that differences in patterns of turnover at the top ranks among the higher taxa reflect previously documented comparison of overall turnover among these classes. Both dominant and nondominant genera exhibit, on average, symmetrical patterns of rise and fall between first and last appearances. Dominant genera rarely begin at high ranks, but nevertheless tend to be more common when they first appear than nondominant genera. Moreover, dominant genera rarely are in the top 20 when they last appear, but still typically occupy more localities than nondominant genera occupy in their last interval. The mechanism(s) that produce dominant genera remain unclear. Nearly half of dominant genera are the type genus of a family or subfamily. This is consistent with a simple model of morphological and phylogenetic diversification and sampling.

Preservation is predictable: quantifying the effect of taphonomic biases on ecological disparity in birds

Paleobiology ◽  
2015 ◽  
Vol 41 (2) ◽  
pp. 353-367 ◽  
Author(s):  
Jonathan S. Mitchell
Keyword(s):  
Sample Size ◽  
Environmental Conditions ◽  
Fossil Record ◽  
Large Scale ◽  
Morphological Disparity ◽  
Bird Assemblages ◽  
Lacustrine Deposits ◽  
Fossil Assemblages ◽  
Fossil Data ◽  
Relative Scarcity

AbstractEvolutionary inferences from fossil data often require accurately reconstructing differences in richness and morphological disparity between fossil sites across space and time. Biases such as sampling and rock availability are commonly accounted for in large-scale studies; however, preservation bias is usually dealt with only in smaller, more focused studies. Birds represent a diverse, but taphonomically fragile, group commonly used to infer environmental conditions in recent (Pleistocene and later) fossil assemblages, and their relative scarcity in the fossil record has led to controversy over the timing of their radiation. Here, I use simulations to show how even weak taphonomic biases can distort estimates of richness, and render variance sensitive to sample size. I then apply an ecology-based filtering model to recent bird assemblages to quantify the distortion induced by taphonomy. Certain deposit types, such as caves, show less evidence of taphonomic distortion than others, such as fluvial and lacustrine deposits. Archaeological middens unsurprisingly show some of the strongest evidence for taphonomic bias, and they should be avoided when reconstructing Pleistocene and early Holocene environments. Further, these results support previously suggested methods for detecting fossil assemblages that are relatively faithfully preserved (e.g., presence of difficult-to-preserve taxa), and I use these results to recommend that future large-scale studies include facies diversity along with metrics such as rock volume, or compare only sites with similar taphonomic histories.

Gastropod Paleoecology

1985 ◽  
Vol 13 ◽  
pp. 174-189
Author(s):  
Alan J. Kohn
Keyword(s):  
Environmental Factors ◽  
Environmental Conditions ◽  
Fossil Record ◽  
Environmental Relationships ◽  
Fossil Assemblages

Paleoecology concerns the life processes and patterns of environmental relationships of groups of ancient organisms during their lifetimes. Two assumptions are fundamental to paleoecological theory: observed patterns in populations, associations, communities and ecosystems represented in the fossil record were imposed by contemporaneous physical and biological environmental factors and their interactions, and at least some past environmental conditions can be discerned from fossil assemblages and their rock matrices.

scholarly journals Beyond a single patch: local and regional processes explain diversity patterns in a seagrass epifaunal metacommunity

2018 ◽  
Author(s):  
Keila A Stark ◽  
Patrick L Thompson ◽  
Jennifer Yakimishyn ◽  
Lynn Lee ◽  
Emily M Adamczyk ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Spatial Scales ◽  
Interspecific Interactions ◽  
Ecosystem Functions ◽  
Seagrass Meadows ◽  
High Dispersal ◽  
Invertebrate Abundance ◽  
Local And Regional Processes ◽  
Abundance And Distribution ◽  
Regional Processes

AbstractEcological communities are jointly structured by dispersal, density-independent responses to environmental conditions and density-dependent biotic interactions. Metacommunity ecology provides a framework for understanding how these processes combine to determine community composition among local sites that are regionally connected through dispersal. In 17 temperate seagrass meadows along the British Columbia coast, we tested the hypothesis that eelgrass (Zostera marinaL.) epifaunal invertebrate assemblages are influenced by local environmental conditions, but that high dispersal rates at larger spatial scales dampen effects of environmental differences. We used hierarchical joint species distribution modelling to understand the contribution of environmental conditions, spatial distance between meadows, and species co-occurrences to epifaunal invertebrate abundance and distribution across the region. We found that patterns of taxonomic compositional similarity among meadows were inconsistent with dispersal limitation and meadows in the same region were often no more similar to each other than meadows over 1000 km away. Abiotic environmental conditions (temperature, dissolved oxygen) explained a small fraction of variation in taxonomic abundances patterns across the region. We found novel co-occurrence patterns among taxa that could not be explained by shared responses to environmental gradients, suggesting the possibility that interspecific interactions influence seagrass invertebrate abundance and distribution. Our results add to mounting evidence that suggests that the biodiversity and ecosystem functions provided by seagrass meadows reflect ecological processes occurring both within meadows and across seascapes, and suggest that management of eelgrass habitat for biodiversity may be most effective when both local and regional processes are considered.

scholarly journals The hexamer hypothesis explains apparent irregularities in the plating of early and extant crinoids

2015 ◽  
Author(s):  
Marc HE de Lussanet
Keyword(s):  
Fossil Record ◽  
Early Ordovician ◽  
Evolution And Development ◽  
New Hypothesis

In 2011, I proposed a new hypothesis for the evolution and development of the five-rayed structure of echinoderms, the Hexamer Hypothesis (Lussanet, 2011). According to this hypothesis, the five-rayed structure develops by reduction from a six-rayed Bauplan. Crinoids (sea lilies) are unique as the only extant clade with stalked representatives, reaching back at least to the early Ordovician. Their extraordinary rich fossil record and the known embryology of recent forms make them ideal to test the Hexamer Hypothesis. It is concluded that the plating of the calyx and the stalk can be explained by the new hypothesis.

scholarly journals Furongian (Jiangshanian) occurrences of radiodonts in Poland and South China and the fossil record of the Hurdiidae

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11800
Author(s):  
Xuejian Zhu ◽  
Rudy Lerosey-Aubril ◽  
Javier Ortega-Hernández
Keyword(s):  
South China ◽  
Fossil Record ◽  
Marine Ecosystems ◽  
Middle Cambrian ◽  
Early Devonian ◽  
Early Ordovician ◽  
Marine Life ◽  
Oral Cone ◽  
The Family ◽  
Sandstone Formation

The Furongian period represents an important gap in the fossil record of most groups of non-biomineralizing organisms, owing to a scarcity of Konservat-Lagerstätten of that age. The most significant of these deposits, the Jiangshanian strata of the Sandu Formation near Guole Township (Guangxi, South China), have yielded a moderately abundant, but taxonomically diverse soft-bodied fossil assemblage, which provides rare insights into the evolution of marine life at that time. In this contribution, we report the first discovery of a radiodont fossil from the Guole Konservat-Lagerstätte. The specimen is an incomplete frontal appendage of a possibly new representative of the family Hurdiidae. It is tentatively interpreted as composed of seven podomeres, six of which bearing laminiform endites. The best preserved of these endites is especially long, and it bears short auxiliary spines that greatly vary in size. This is the second occurrence of hurdiids and more generally radiodonts in the Furongian, the first being the external mould of an oral cone from Jiangshanian strata of the Wiśniówka Sandstone Formation in Poland. Restudy of this Polish specimen confirms that it belongs to a hurdiid radiodont and best compares to Peytoia. The family Hurdiidae includes the oldest (basal Cambrian Epoch 2) and youngest (Early Ordovician, possibly Early Devonian) representatives of the Radiodonta and as such, has the longest stratigraphical range of the group. Yet, hurdiids only became prominent components of marine ecosystems during the middle Cambrian (Miaolingian), and their fossil record in younger strata remains limited.

scholarly journals The hexamer hypothesis explains apparent irregularities in the plating of early and extant crinoids

2015 ◽  
Author(s):  
Marc HE de Lussanet
Keyword(s):  
Fossil Record ◽  
Early Ordovician ◽  
Evolution And Development ◽  
New Hypothesis

In 2011, I proposed a new hypothesis for the evolution and development of the five-rayed structure of echinoderms, the Hexamer Hypothesis (Lussanet, 2011). According to this hypothesis, the five-rayed structure develops by reduction from a six-rayed Bauplan. Crinoids (sea lilies) are unique as the only extant clade with stalked representatives, reaching back at least to the early Ordovician. Their extraordinary rich fossil record and the known embryology of recent forms make them ideal to test the Hexamer Hypothesis. It is concluded that the plating of the calyx and the stalk can be explained by the new hypothesis.

scholarly journals A simple model for cloud radiative forcing

2009 ◽  
Vol 9 (2) ◽  
pp. 8541-8560 ◽  
Author(s):  
T. Corti ◽  
T. Peter
Keyword(s):  
Energy Balance ◽  
Simple Model ◽  
Radiative Transfer ◽  
Environmental Conditions ◽  
Radiative Forcing ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radiative Forcing ◽  
Model Equations ◽  
Better Than

Abstract. We present a simple model for the longwave and shortwave cloud radiative forcing based on the evaluation of extensive radiative transfer calculations. The simplicity of the model equations fosters the understanding on how clouds affect the Earth's energy balance. In comparison with results from a comprehensive radiative transfer model, the accuracy of our parameterization is typically better than 20%. We demonstrate the usefulness of our model using the example of tropical cirrus clouds. We conclude that possible applications for the model include the fast estimate of cloud radiative forcing, the evaluation of the sensitivity to changes in environmental conditions, and as a tool in education.

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