The Silurian Period

Melchin, Michael J.; Sadler, Peter M.; Cramer, Bradley D.

doi:10.1016/b978-0-12-824360-2.00021-8

Cited by 39 publications

(53 citation statements)

References 156 publications

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“…We use relatively short, equal-length intervals rather than conventional stratigraphic zones to take maximal advantage of temporal resolution in the data and to avoid well-known artefacts, whereby variable interval length may distort taxonomic rates of evolution [25,26], especially when taxonomic turnover is used to delineate intervals [26], as is the case with biozones. An Interval-length variation would be especially problematic in the present case, as graptolite zones vary in length by over an order of magnitude, from approximately 0.1 Myr to nearly 4.0 Myr [27,28].…”

Section: (B) Methodsmentioning

confidence: 89%

Diversity-dependent evolutionary rates in early Palaeozoic zooplankton

et al. 2018

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The extent to which biological diversity affects rates of diversification is central to understanding macroevolutionary dynamics, yet no consensus has emerged on the importance of diversity-dependence of evolutionary rates. Here, we analyse the species-level fossil record of early Palaeozoic graptoloids, documented with high temporal resolution, to test directly whether rates of diversification were influenced by levels of standing diversity within this major clade of marine zooplankton. To circumvent the statistical regression-to-the-mean artefact, whereby higher- and lower-than-average values of diversity tend to be followed by negative and positive diversification rates, we construct a non-parametric, empirically scaled, diversity-independent null model by randomizing the observed diversification rates with respect to time. Comparing observed correlations between diversity and diversification rate to those expected from this diversity-independent model, we find evidence for negative diversity-dependence, accounting for up to 12% of the variance in diversification rate, with maximal correlation at a temporal lag of approximately 1 Myr. Diversity-dependence persists throughout the Ordovician and Silurian, despite a major increase in the strength and frequency of extinction and speciation pulses in the Silurian. By contrast to some previous work, we find that diversity-dependence affects rates of speciation and extinction nearly equally on average, although subtle differences emerge when we compare the Ordovician and Silurian.

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Section: (B) Methodsmentioning

confidence: 89%

Diversity-dependent evolutionary rates in early Palaeozoic zooplankton

et al. 2018

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“…The Silurian Period has been considered as a stable interval characterized by gradual, long-term climatic change starting from the Middle to Late Ordovician cold climate and culminating in Silurian greenhouse conditions [ 56 , 57 ]. The Silurian, lasting from approximately 443.1 to 419.0 million years [ 22 ], represents a key interval in the biological evolution of marine ecosystems [ 58 , 59 , 60 , 61 ]. The transitional character of the Silurian is not illustrated only by the changes of marine communities and ecosystems, but also by the instability of the global carbon cycle including rapid changes in atmospheric pO 2 and pCO 2 [ 62 , 63 , 64 ].…”

Section: Resultsmentioning

confidence: 99%

“…The data on Llandoverian plants are not included in the latter analysis because 1) observations of well-preserved macroplants below the Wenlock are extremely rare and 2) the plants are represented only by sterile bifurcated axes [19]. 13 Ccarb curve, modified from [20][21][22], combined with isotopic temperature curves (blue Figure 2. Silurian palaeocontinental reconstructions according to Scotese [76] plotting palaeogeographical distribution of plants (rectangle) or plant assemblages (circle).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Silurian Plants as Response to Climate Changes

Pšenička¹,

Bek

Frýda

et al. 2021

Life

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The most ancient macroscopic plants fossils are Early Silurian cooksonioid sporophytes from the volcanic islands of the peri-Gondwanan palaeoregion (the Barrandian area, Prague Basin, Czech Republic). However, available palynological, phylogenetic and geological evidence indicates that the history of plant terrestrialization is much longer and it is recently accepted that land floras, producing different types of spores, already were established in the Ordovician Period. Here we attempt to correlate Silurian floral development with environmental dynamics based on our data from the Prague Basin, but also to compile known data on a global scale. Spore-assemblage analysis clearly indicates a significant and almost exponential expansion of trilete-spore producing plants starting during the Wenlock Epoch, while cryptospore-producers, which dominated until the Telychian Age, were evolutionarily stagnate. Interestingly cryptospore vs. trilete-spore producers seem to react differentially to Silurian glaciations—trilete-spore producing plants react more sensitively to glacial cooling, showing a reduction in species numbers. Both our own and compiled data indicate highly terrestrialized, advanced Silurian land-plant assemblage/flora types with obviously great ability to resist different dry-land stress conditions. As previously suggested some authors, they seem to evolve on different palaeo continents into quite disjunct specific plant assemblages, certainly reflecting the different geological, geographical and climatic conditions to which they were subject.

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“…The low CAI of these specimens demonstrates a very low likelihood of pyrolysis of the original organic matter in the bioapatite due to metamorphism. The St Clair Formation records the Wenlock Epoch of the Silurian Period and spans an interval from approximately 433 to 426.75 Ma [32,33]. Carbonate and carbonaceous shale samples from the core ranged in size from 7.5 to 15 cm in stratigraphic thickness and were digested in the University of Iowa Micropaleontology Laboratory using the standard double-buffered formic acid technique [34].…”

Section: Methodsmentioning

confidence: 99%

Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry

et al. 2020

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X-ray diffraction data from Silurian conodonts belonging to various developmental stages of the species Dapsilodus obliquicostatus demonstrate changes in crystallography and degree of nanocrystallite ordering (mosaicity) in both lamellar crown tissue and white matter. The exclusive use of a single species in this study, combined with systematic testing of each element type at multiple locations, provided insight into microstructural and crystallographic differentiation between element type ( S a , S b - c , M ) as well as between juveniles and adults. A relative increase in the unit cell dimensions a / c ratio of nanocrystallites during growth was apparent in areas demonstrating single-crystal behaviour, but no such relationship was seen in dominantly polycrystalline areas. Systematic variations in mosaicity were identified, with mosaicity (as a proxy for disorder) increasing during growth, as well as along elements from tip to base. These results provide potential insight into the integrity of conodont apatite as a recorder of palaeoseawater chemistry, as well as demonstrate the need to consider the influence of ontogeny and element type on the use of conodonts in palaeothermometry and geochemical investigations.

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The Silurian Period

Cited by 39 publications

References 156 publications

Diversity-dependent evolutionary rates in early Palaeozoic zooplankton

Diversity-dependent evolutionary rates in early Palaeozoic zooplankton

Dynamics of Silurian Plants as Response to Climate Changes

Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry

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