| 1. |
- Cunningham, John A., et al.
(author)
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The Weng’an Biota (Doushantuo Formation): an Ediacaran window on soft bodied and multicellular microorganisms.
- 2017
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In: journal of the geological society. - London : Geological Society. - 2041-479X .- 0016-7649. ; 174:5, s. 793-802
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Journal article (peer-reviewed)abstract
- The Weng’an Biota is a fossil Konservat-Lagerstätte in South China that is approximately 570-600 million years old and provides an unparalleled snapshot of marine life during the interval in which molecular clocks estimate that animal clades were diversifying. It yields specimens that are three-dimensionally preserved in calcium phosphate with cellular and sometimes subcellular fidelity. The biota includes candidates for the oldest animals in the fossil record, including embryonic, larval and adult forms. We argue that, while the Weng’an Biota includes forms that could be animals, none can currently be assigned to this group with confidence. Nonetheless, the biota offers a rare and valuable window on the evolution of multicellular and soft-bodied organisms in the prelude to the Cambrian radiation.
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| 2. |
- Cunningham, John, et al.
(author)
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Critical appraisal of tubular putative eumetazoans from the Ediacaran Weng’an Doushantuo biota
- 2015
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In: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 282, s. 1-9
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Journal article (peer-reviewed)abstract
- Molecular clock analyses estimate that crown-group animals began diversifying hundreds of millions of years before the start of the Cambrian period. However, the fossil record has not yielded unequivocal evidence for animals during this interval. Some of the most promising candidates for Precambrian animals occur in theWeng’an biota of South China, including a suite of tubular fossils assigned to Sinocyclocyclicus, Ramitubus, Crassitubus and Quadratitubus, that have been interpreted as soft-bodied eumetazoans comparable to tabulate corals. Here, we present new insights into the anatomy, original composition and phylogenetic affinities of these taxa based on data from synchrotron radiation X-ray tomographic microscopy, ptychographic nanotomography, scanning electron microscopy and electron probe microanalysis. The patterns of deformation observed suggest that the cross walls of Sinocyclocyclicus and Quadratitubus were more rigid than those of Ramitubus and Crassitubus. Ramitubus and Crassitubus specimens preserve enigmatic cellular clusters at terminal positions in the tubes. Specimens of Sinocyclocyclicus and Ramitubus have biological features that might be cellular tissue or subcellular structures filling the spaces between the crosswalls. These observations are incompatible with a cnidarian interpretation, in which the spaces between cross walls are abandoned parts of the former living positions of the polyp. The affinity of the Weng’an tubular fossils may lie within the algae.
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| 3. |
- Dong, Xi-ping, et al.
(author)
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Developmental biology of the early Cambrian cnidarian Olivooides.
- 2016
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In: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 59:3, s. 387-407
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Journal article (peer-reviewed)abstract
- Fossilized embryos afford direct insight into the pattern of development in extinct organisms, providing unique tests of hypotheses of developmental evolution based in comparative embryology. However, these fossils can only be effective in this role if their embryology and phylogenetic affinities are well constrained. We elucidate and interpret the development of Olivooides from embryonic and adult stages and use these data to discriminate among competing interpretations of their anatomy and affinity. The embryology of Olivooides is principally characterized by the development of an ornamented periderm that initially forms externally and is subsequently formed internally, released at the aperture, facilitating the direct development of the embryo into an adult theca. Internal anatomy is known only from embryonic stages, revealing two internal tissue layers, the innermost of which is developed into three transversally arranged walls that partly divide the lumen into an abapertural region, interpreted as the gut of a polyp, and an adapertural region that includes structures that resemble the peridermal teeth of coronate scyphozoans. The anatomy and pattern of development exhibited by Olivooides appears common to the other known genus of olivooid, Quadrapyrgites, which differs in its tetraradial, as opposed to pentaradial symmetry. We reject previous interpretations of the olivooids as cycloneuralians, principally on the grounds that they lack a through gut and introvert, in embryo and adult. Instead we consider the affinities of the olivooids among medusozoan cnidarians; our phylogenetic analysis supports their classification as totalgroup Coronata, within crown-Scyphozoa. Olivooides and Quadrapyrgites evidence a broader range of life history strategies and bodyplan symmetry than is otherwise commonly represented in extant Scyphozoa specifically, and Cnidaria more generally.
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| 4. |
- Yin, Zongjun, et al.
(author)
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Nuclei and nucleoli in embryo-like fossils from the Ediacaran Weng’an Biota.
- 2017
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In: Precambrian Research. - Amsterdam : Elsevier. - 0301-9268 .- 1872-7433. ; 301, s. 145-151
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Journal article (peer-reviewed)abstract
- The embryo-like microfossils from the Ediacaran Weng’an Biota (ca. 609 million years old) are among the oldest plausible claims of animals in the fossil record. Fossilization frequently extends beyond the cellular, to preserve subcellular structures including contentious Large Intracellular Structures (LISs) that have been alternately interpreted as eukaryote nuclei or organelles, degraded remains, or abiological structures. Here we present new data on the structure, morphology, and development of the LISs in these embryo-like fossils, based on Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) and quantitative computed tomographic analysis. All the lines of evidence, including consistency in the number, shape, position, and relative size (LIS-to-cytoplasm ratio) of the LISs, as well as their occurrence within preserved cytoplasm, support their interpretation as cell nuclei. Our results allow us to reject the view that nuclei cannot be preserved in early eukaryote fossils, offering new potential for interpreting the fossil record of early eukaryote evolution.
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| 5. |
- Yin, Zongjun, et al.
(author)
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The early Ediacaran Caveasphaera foreshadows the evolutionary origin of animal-like embryology.
- 2019
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In: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 29:25, s. 4307-4314
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Journal article (peer-reviewed)abstract
- The Ediacaran Weng’an Biota (Doushantuo Formation, 609 Ma old) is a rich microfossil assemblage that preserves biological structure to a subcellular level of fidelity and encompasses a range of developmental stages [1]. However, the animal embryo interpretation of the main components of the biota has been the subject of controversy [2, 3]. Here, we describe the development of Caveasphaera, which varies in morphology from lensoid to a hollow spheroidal cage [4] to a solid spheroid [5] but has largely evaded description and interpretation. Caveasphaera is demonstrably cellular and develops within an envelope by cell division and migration, first defining the spheroidal perimeter via anastomosing cell masses that thicken and ingress as strands of cells that detach and subsequently aggregate in a polar region. Concomitantly, the overall diameter increases as does the volume of the cell mass, but after an initial phase of reductive palinotomy, the volume of individual cells remains the same through development. The process of cell ingression, detachment, and polar aggregation is analogous to gastrulation; together with evidence of functional cell adhesion and development within an envelope, this is suggestive of a holozoan affinity. Parental investment in the embryonic development of Caveasphaera and co-occurring Tianzhushania and Spiralicellula, as well as delayed onset of later development, may reflect an adaptation to the heterogeneous nature of the early Ediacaran nearshore marine environments in which early animals evolved.
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