Organic geochemical characteristics of the Mississippian black shales from Wardie, Scotland

Trojan, Agata; Bojanowski, Maciej J.; Gola, Marek R.; Grafka, Oliwia; Marynowski, Leszek; Clarkson, Euan N. K.

doi:10.1017/s1755691015000225

Cited by 1 publication

(1 citation statement)

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“…Second, the probability of discovery is likely limited by the abundance of these sorts of localities. Within the Lower Carboniferous, only three localities contain this level or preservation: the nearshore marine Wardie Shale (Trojan et al, 2015) and Cheese Bay Shrimp Bed (Hesselbo and Trewin, 1984), and the thermally altered lake deposits at East Kirkton (Clarkson et al, 1993). Of these, the only locality that has yielded more than a single tetrapod fossil is East Kirkton.…”

Section: Preservational Heterogeneity and Small Body Sizementioning

confidence: 99%

Can We Reliably Calibrate Deep Nodes in the Tetrapod Tree? Case Studies in Deep Tetrapod Divergences

2020

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Recent efforts have led to the development of extremely sophisticated methods for incorporating tree-wide data and accommodating uncertainty when estimating the temporal patterns of phylogenetic trees, but assignment of prior constraints on node age remains the most important factor. This depends largely on understanding substantive disagreements between specialists (paleontologists, geologists, and comparative anatomists), which are often opaque to phylogeneticists and molecular biologists who rely on these data as downstream users. This often leads to misunderstandings of how the uncertainty associated with node age minima arises, leading to inappropriate treatments of that uncertainty by phylogeneticists. In order to promote dialogue on this subject, we here review factors (phylogeny, preservational megabiases, spatial and temporal patterns in the tetrapod fossil record) that complicate assignment of prior node age constraints for deep divergences in the tetrapod tree, focusing on the origin of crown-group Amniota, crown-group Amphibia, and crown-group Tetrapoda. We find that node priors for amphibians and tetrapods show high phylogenetic lability and different phylogenetic treatments identifying disparate taxa as the earliest representatives of these crown groups. This corresponds partially to the well-known problem of lissamphibian origins but increasingly reflects deeper instabilities in early tetrapod phylogeny. Conversely, differences in phylogenetic treatment do not affect our ability to recognize the earliest crown-group amniotes but do affect how diverse we understand the earliest amniote faunas to be. Preservational megabiases and spatiotemporal heterogeneity of the early tetrapod fossil record present unrecognized challenges in reliably estimating the ages of tetrapod nodes; the tetrapod record throughout the relevant interval is spatially restricted and disrupted by several major intervals of minimal sampling coincident with the emergence of all three crown groups. Going forward, researchers attempting to calibrate the ages for these nodes, and other similar deep nodes in the metazoan fossil record, should consciously consider major phylogenetic uncertainty, preservational megabias, and spatiotemporal heterogeneity,

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Section: Preservational Heterogeneity and Small Body Sizementioning

confidence: 99%