scholarly journals Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Robert S. Sansom
Keyword(s):  
Experimental Decay

Rapid incorporation of lipids into macromolecules during experimental decay of invertebrates: Initiation of geopolymer formation

2009 ◽  
Vol 40 (5) ◽  
pp. 589-594 ◽  
Author(s):  
Neal S. Gupta ◽  
George D. Cody ◽  
O. Erik Tetlie ◽  
Derek E.G. Briggs ◽  
Roger E. Summons
Keyword(s):  
Experimental Decay ◽  
Rapid Incorporation

scholarly journals Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Richard J. Howard ◽  
Gregory D. Edgecombe ◽  
Xiaomei Shi ◽  
Xianguang Hou ◽  
Xiaoya Ma
Keyword(s):  
Feeding Strategy ◽  
Phylogenetic Analyses ◽  
Morphological Diversity ◽  
Early Cambrian ◽  
Ancestral State ◽  
Crown Group ◽  
Stem Group ◽  
Chengjiang Biota ◽  
Fossil Records ◽  
Experimental Decay

Abstract Background Ecdysozoa are the moulting protostomes, including arthropods, tardigrades, and nematodes. Both the molecular and fossil records indicate that Ecdysozoa is an ancient group originating in the terminal Proterozoic, and exceptional fossil biotas show their dominance and diversity at the beginning of the Phanerozoic. However, the nature of the ecdysozoan common ancestor has been difficult to ascertain due to the extreme morphological diversity of extant Ecdysozoa, and the lack of early diverging taxa in ancient fossil biotas. Results Here we re-describe Acosmia maotiania from the early Cambrian Chengjiang Biota of Yunnan Province, China and assign it to stem group Ecdysozoa. Acosmia features a two-part body, with an anterior proboscis bearing a terminal mouth and muscular pharynx, and a posterior annulated trunk with a through gut. Morphological phylogenetic analyses of the protostomes using parsimony, maximum likelihood and Bayesian inference, with coding informed by published experimental decay studies, each placed Acosmia as sister taxon to Cycloneuralia + Panarthropoda—i.e. stem group Ecdysozoa. Ancestral state probabilities were calculated for key ecdysozoan nodes, in order to test characters inferred from fossils to be ancestral for Ecdysozoa. Results support an ancestor of crown group ecdysozoans sharing an annulated vermiform body with a terminal mouth like Acosmia, but also possessing the pharyngeal armature and circumoral structures characteristic of Cambrian cycloneuralians and lobopodians. Conclusions Acosmia is the first taxon placed in the ecdysozoan stem group and provides a constraint to test hypotheses on the early evolution of Ecdysozoa. Our study suggests acquisition of pharyngeal armature, and therefore a change in feeding strategy (e.g. predation), may have characterised the origin and radiation of crown group ecdysozoans from Acosmia-like ancestors.

Using experimental decay of modern forms to reconstruct the early evolution and morphology of fossil enteropneusts

Paleobiology ◽  
2015 ◽  
Vol 41 (3) ◽  
pp. 460-478 ◽  
Author(s):  
Karma Nanglu ◽  
Jean-Bernard Caron ◽  
Christopher B. Cameron
Keyword(s):  
Fossil Record ◽  
Morphological Characters ◽  
Early Diagenesis ◽  
Body Plan ◽  
Morphological Features ◽  
Laboratory Setting ◽  
Burgess Shale ◽  
Comprehensive Understanding ◽  
Fossil Preservation ◽  
Experimental Decay

AbstractDecay experiments are becoming a more widespread tool in evaluating the fidelity of the fossil record. Character interpretations of fossil specimens stand to benefit from an understanding of how decay can result in changes in morphology and, potentially, total character loss. We performed a decay experiment for the Class Enteropneusta to test the validity of anatomical interpretations of the Burgess Shale enteropneust Spartobranchus tenuis and to determine how the preservation of morphological features compares with the sequence of character decay in extant analogues. We used three species of enteropneust (Saccoglossus pusillus, Harrimania planktophilus, and Balanoglossus occidentalis) representing the two major families of Enteropneusta. Comparisons between decay sequences suggest that morphological characters decay in a consistent and predictable manner within Enteropneusta, and do not support the hypothesis of stemward slippage. The gill bars and nuchal skeleton were the most decay resistant, whereas the gill pores and pre-oral ciliary organ were unequivocally the most decay prone. Decay patterns support the identification of the nuchal skeleton, gill bars, esophageal organ, trunk, and proboscis in Spartobranchus tenuis and corroborate a harrimaniid affinity. Bias due to the taphonomic loss of taxonomically informative characters is unlikely. The morphologically simple harrimaniid body plan can be seen, therefore, to be plesiomorphic within the enteropneusts. Discrepancies between the sequence of decay in a laboratory setting and fossil preservation also exist. These discrepancies are highlighted not to discredit the use of modern decay studies but rather to underline their non-actualistic nature. Paleoenvironmental variables besides decay, such as the timeframe between death and early diagenesis as well as postmortem transport, are discussed relative to decay data. These experiments reinforce the strength of a comprehensive understanding of decay sequences as a benchmark against which to describe fossil taxa and understand the conditions leading to fossilization.

scholarly journals Poincaré-covariant quark model of electroweak light mesons decays

2019 ◽  
Vol 204 ◽  
pp. 08006 ◽  
Author(s):  
Viktor Andreev ◽  
Vadzim Haurysh
Keyword(s):  
Quantum Mechanics ◽  
Vector Meson ◽  
Quark Model ◽  
Radiative Decay ◽  
Mixing Angles ◽  
Decay Constants ◽  
Point Form ◽  
Experimental Decay ◽  
Invariant Quantum ◽  
Covariant Quark Model

The procedure for obtaining the radiative decay constants of pseudoscalar and vector unflavored mesons in point–form of Poincaré-invariant quantum mechanics is presented. In the course of the work the authors determine the remaining parameters from V → Pγ and P → Vγ experimental decay value, using the obtained earlier parameters of the model for light (u, d and s) quarks. As a result, the mixing angles for pseudoscalar and vector meson sector were obtained taking into account gluonium content for η – η′ meson sector.

WHY IS THE δ(983)→2γ WIDTH SO SMALL?

1994 ◽  
Vol 09 (26) ◽  
pp. 2381-2388 ◽  
Author(s):  
A.S. DEAKIN ◽  
V. ELIAS ◽  
D.G.C. MCKEON ◽  
M.D. SCADRON ◽  
A. BRAMON
Keyword(s):  
Decay Width ◽  
Quark Mass ◽  
Light Quark ◽  
Decay Amplitude ◽  
Model Framework ◽  
Quark Masses ◽  
Measured Rate ◽  
Light Quark Mass ◽  
Experimental Decay

The δ0(983)→2γ decay width is calculated in a linear σ-model framework, in which both quark and meson loops contribute to the decay amplitude, and compared to the experimental decay width. The result is seen to depend strongly on the magnitude of the light quark mass and is compatible with the present measured rate, up to experimental uncertainties, for quark masses of order 300 MeV.

Comparison between experimental decay of the compound nuclei150Gd and evaporation calculations

1977 ◽  
Vol 282 (1) ◽  
pp. 75-82 ◽  
Author(s):  
S. Negra ◽  
H. Gauvin ◽  
H. Jungclas ◽  
Y. Beyec ◽  
M. Lefort
Keyword(s):  
Experimental Decay
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