scholarly journals The advent of animals: The view from the Ediacaran

2015 ◽  
Vol 112 (16) ◽  
pp. 4865-4870 ◽  
Author(s):  
Mary L. Droser ◽  
James G. Gehling
Keyword(s):  
Sexual Reproduction ◽  
Marine Environments ◽  
Phylogenetic Reconstructions ◽  
Ediacara Biota ◽  
Fossil Assemblages ◽  
Multicellular Organisms

Patterns of origination and evolution of early complex life on this planet are largely interpreted from the fossils of the Precambrian soft-bodied Ediacara Biota. These fossils occur globally and represent a diverse suite of organisms living in marine environments. Although these exceptionally preserved fossil assemblages are typically difficult to reconcile with modern phyla, examination of the morphology, ecology, and taphonomy of these taxa provides keys to their relationships with modern taxa. Within the more than 30 million y range of the Ediacara Biota, fossils of these multicellular organisms demonstrate the advent of mobility, heterotrophy by multicellular animals, skeletonization, sexual reproduction, and the assembly of complex ecosystems, all of which are attributes of modern animals. This approach to these fossils, without the constraint of attempting phylogenetic reconstructions, provides a mechanism for comparing these taxa with both living and extinct animals.

scholarly journals Biostratinomy of the Ediacara Member (Rawnsley Quartzite, South Australia): implications for depositional environments, ecology and biology of Ediacara organisms

2020 ◽  
Vol 10 (4) ◽  
pp. 20190100 ◽  
Author(s):  
Mary L. Droser ◽  
Lidya G. Tarhan ◽  
Scott D. Evans ◽  
Rachel L. Surprenant ◽  
James G. Gehling
Keyword(s):  
Fossil Record ◽  
South Australia ◽  
Depositional Environments ◽  
Bedding Planes ◽  
Ediacara Biota ◽  
National Heritage ◽  
Fossil Site ◽  
Fossil Assemblages ◽  
Multicellular Organisms

The Precambrian Ediacara Biota—Earth's earliest fossil record of communities of macroscopic, multicellular organisms—provides critical insights into the emergence of complex life on our planet. Excavation and reconstruction of nearly 300 m 2 of fossiliferous bedding planes in the Ediacara Member of the Rawnsley Quartzite, at the National Heritage Ediacara fossil site Nilpena in South Australia, have permitted detailed study of the sedimentology, taphonomy and palaeoecology of Ediacara fossil assemblages. Characterization of Ediacara macrofossils and textured organic surfaces at the scale of facies, bedding planes and individual specimens has yielded unprecedented insight into the manner in which the palaeoenvironmental settings inhabited by Ediacara communities—particularly hydrodynamic conditions—influenced the aut- and synecology of Ediacara organisms, as well as the morphology and assemblage composition of Ediacara fossils. Here, we describe the manner in which environmental processes mediated the development of taphofacies hosting Ediacara fossil assemblages. Using two of the most common Ediacara Member fossils, Arborea and Dickinsonia , as examples, we delineate criteria that can be used to distinguish between ecological, environmental and biostratinomic signals and reconstruct how interactions between these processes have distinctively shaped the Ediacara fossil record.

scholarly journals Ediacara biota flourished in oligotrophic and bacterially dominated marine environments across Baltica

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Kelden Pehr ◽  
Gordon D. Love ◽  
Anton Kuznetsov ◽  
Victor Podkovyrov ◽  
Christopher K. Junium ◽  
...  
Keyword(s):  
Marine Environments ◽  
Ediacara Biota

scholarly journals How well do fossil assemblages of the Ediacara Biota tell time?: REPLY

Geology ◽  
2014 ◽  
Vol 42 (4) ◽  
pp. e333-e333 ◽  
Author(s):  
James G. Gehling ◽  
Mary L. Droser
Keyword(s):  
Ediacara Biota ◽  
Fossil Assemblages

The Shibantan Lagerstätte: insights into the Proterozoic–Phanerozoic transition

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-135
Author(s):  
Shuhai Xiao ◽  
Zhe Chen ◽  
Ke Pang ◽  
Chuanming Zhou ◽  
Xunlai Yuan
Keyword(s):  
South China ◽  
Carbonate Rocks ◽  
Microbial Mats ◽  
Ecological Interactions ◽  
Benthic Organisms ◽  
Important Data ◽  
Ediacara Biota ◽  
Marine Carbonate ◽  
Fossil Assemblages ◽  
Marine Carbonate Rocks

The Shibantan Lagerstätte (551–543 Ma) in the Yangtse Gorges area in South China is one of the best-known examples of terminal Ediacaran fossil assemblages preserved in marine carbonate rocks. Taxonomically dominated by benthic organisms, the Shibantan Lagerstätte preserves various photoautotrophs, biomineralizing tubular fossils, Ediacara-type macrofossils (including rangeomorphs, arboreomorphs, erniettomorphs, palaeopascichnids, a possible dickinsoniomorph, the mobile bilaterian Yilingia and soft-bodied tubular fossils), abundant ichnofossils and a number of problematic and dubious fossils. Shibantan fossils provide intriguing insights into ecological interactions among mobile bilaterians, sessile benthic Ediacara-type organisms and microbial mats, thus offering important data to test various hypotheses accounting for the decline of the Ediacara biota and the concurrent expansion of bilaterian bioturbation and mobility across the Proterozoic–Phanerozoic transition.

scholarly journals Paleoecologic and Biostratigraphic Significance of Trace Fossils From Shallow- to Marginal-Marine Environments From the Middle Cambrian (Stage 5) of Jordan

2012 ◽  
Vol 86 (6) ◽  
pp. 931-955 ◽  
Author(s):  
Richard Hofmann ◽  
M. Gabriela Mángano ◽  
Olaf Elicki ◽  
Rafie Shinaq
Keyword(s):  
Trace Fossils ◽  
Trace Fossil ◽  
Type Locality ◽  
Early Cambrian ◽  
Marine Environments ◽  
Middle Cambrian ◽  
Fossil Assemblages ◽  
Maximum Flooding Surface

The Hanneh Member (Cambrian Stage 5) of the Burj Formation and the Umm Ishrin Formation of Jordan represent a transgressive-regressive succession that contains twenty-eight ichnotaxa, including vertical burrows (Arenicolitesisp.,Diplocraterionisp.,Gyrolithes polonicus,Rosseliaisp.,Skolithos linearis, escape trace fossils), horizontal simple burrows and trails (Archaeonassa fossulata,Gordia marina,Helminthoidichnites tenuis,Palaeophycus tubularis,Planolites beverleyensis,P. montanus), plug-shaped burrows (Bergaueria sucta), horizontal branched burrows (Asterosomaisp.,Phycodesisp.,Treptichnuscf.T. pedum), bilobate structures (various ichnospecies ofCruzianaandRusophycus), and trackways and scratch marks (Diplichnitesisp.,Dimorphichnuscf.D. obliquus,Monomorphichnusisp.). Eleven trace-fossil assemblages are identified. TheArenicolitesisp. andDiplocraterionisp. assemblages occur in transgressive tidal dunes and bars whereas theRosseliaisp. assemblage characterizes areas between tidal dunes. TheCruziana salomonisassemblage reflects a wide variety of environmental settings including channels within tidal-bar complexes, bottomsets of tidal dunes, and interdune areas. TheGordia marinaassemblage is present between dune patches. TheGyrolithes polonicusassemblage penetrates into firmground mudstone below the maximum flooding surface. TheBergaueria sucta,Archaeonassa fossulata,Rusophycus aegypticusandCruziana problematicaassemblages occur in different subenvironments of the progradational delta.Cruziana salomonisandRusophycus burjensis, originally considered indicative of an early Cambrian age, are actually middle Cambrian in their type locality. Occurrences ofCruziana jordanicaandRusophycus aegypticusprovide evidence that these ichnospecies are of the same age in Jordan and may co-exist in terms of stratigraphic distribution withC. salomonisandR. burjensis.

scholarly journals Cell fusion and fusogens - an interview with Benjamin Podbilewicz

2020 ◽  
Vol 52 ◽  
Author(s):  
Jesús Chimal-Monroy ◽  
Diana María Escalante-Alcalde
Keyword(s):  
Caenorhabditis Elegans ◽  
Embryonic Development ◽  
Sexual Reproduction ◽  
Cell Fusion ◽  
Myoblast Fusion ◽  
Personal Life ◽  
Exciting Field ◽  
Animal Development ◽  
Multicellular Organisms

Cell fusion is a process in which cells unite their membranes and cytoplasm and is fundamental for sexual reproduction and embryonic development. Among the best-known cell fusion processes during animal development are fertilization, myoblast fusion, osteoclast generation, and vulva formation in Caenorhabditis elegans. Although it is involved in many other functions in unicellular and multicellular organisms, little is known about the mechanisms of cell fusion and the genes that code for the proteins participating in this process. Benjamin Podbilewicz has dedicated many years to understanding the process and mechanisms of cell fusion. In this interview, he spoke to us about how he began his studies of this process, his contributions to this exciting field, scientific ties with Ibero-America and his strategies for a well-balanced scientific/personal life.

The Leeuwenhoek Lecture - Microbial genetics: retrospect and prospect

1963 ◽  
Vol 158 (970) ◽  
pp. 1-23 ◽  
Keyword(s):  
Genetic Analysis ◽  
Sexual Reproduction ◽  
Germ Cells ◽  
Somatic Cells ◽  
Clear Distinction ◽  
Genetic Constitution ◽  
Microbial Genetics ◽  
The Past ◽  
Multicellular Organisms ◽  
Micro Organisms

I wonder whether Anthony van Leeuwenhoek would have considered me as an appropriate choice for this lecture. For the past six years my interests have been in the rather unmanageable field of the genetics of cultured human somatic cells. These cells are animalcules only because we make them so. I can therefore look at the genetics of micro-organisms as an outsider, admittedly not wholly dispassionate. This is a pleasant task, because if there is a field of biology which has made great, unexpected and illuminating advances since 1940, this is it. Genetic analysis up to that time consisted in deducing the genetic constitution (‘genotype’) of an individual, which underlies its relevant somatic characters (‘phenotype’), from the distribution of these characters among its ascendants and its descendants. It therefore required the analysis of the results of breeding— experimental or not—and was limited to organisms with sexual reproduction. It was particularly illuminating in those multicellular organisms in which there is a clear distinction between germ cells (‘gametes’) and soma. Here, short of a preformistic process, it is clear that we can distinguish between determinants of hereditary characters and the characters themselves.

Earth's oldest jellyfish strandings: a unique taphonomic window or just another day at the beach?

2016 ◽  
Vol 154 (4) ◽  
pp. 859-874 ◽  
Author(s):  
AARON D. SAPPENFIELD ◽  
LIDYA G. TARHAN ◽  
MARY L. DROSER
Keyword(s):  
Great Basin ◽  
Microbial Mats ◽  
Considerable Change ◽  
Coarse Grained ◽  
Significant Shift ◽  
Ediacara Biota ◽  
Mode Characteristic ◽  
Fossil Assemblages ◽  
Depositional Setting ◽  
Body Fossil

AbstractDiscoidal macrofossils reported herein from the lower Cambrian Zabriskie Quartzite (Great Basin, western United States) record the oldest Phanerozoic medusozoan body fossils, as well as the oldest medusozoan stranding event on record. Moreover, these fossils provide evidence of a significant shift in the taphonomic mode characteristic of preservation of nonmineralized taxa in coarse-grained siliciclastic successions near the onset of the Phanerozoic. Taphonomic and sedimentological evidence recorded by these and younger examples of stranded Cambrian medusae is consistent in suggesting that several of the requirements for preservation of these fossils were holdovers from the Ediacaran Period, including the presence of microbial mats and a lack of carcass disturbance by scavenging and/or bioturbating taxa. To shed further light upon the taphonomic factors necessary for the preservation of Cambrian medusae, we compared the biostratinomy and sedimentology of Cambrian medusa strandings to those of Ediacara Biota assemblages from lithologically similar successions. We find key secular disparities in the taphonomic histories of these two types of fossil assemblage. Inconsistencies between the preservational styles characteristic of fossil assemblages preserved in sandstone lithofacies on each side of the Precambrian–Cambrian boundary are explained by a considerable change in the preferred depositional setting in which these macrofossil assemblages are preserved. Thus, rather than documenting a single taphonomic continuum through the Precambrian–Cambrian transition, the Zabriskie and younger medusozoan body fossil assemblages record the advent of an entirely new, yet still very rarely exploited, taphonomic window exclusive to the Cambrian Period.

Embryological perspective of sexual somatic development in ciliated protozoa: implications on immortality, sexual reproduction and inheritance of acquired characters

1990 ◽  
Vol 329 (1254) ◽  
pp. 287-305 ◽  
Keyword(s):  
Sexual Reproduction ◽  
Ciliated Protozoa ◽  
Asexual Propagation ◽  
Somatic Development ◽  
New Information ◽  
Sexual Process ◽  
Phylogenetic Evolution ◽  
Acquired Characters ◽  
Multicellular Organisms

This essay addresses somatic development during sexual reproduction of ciliated protozoa, which is interpreted as an embryological phenomenon resembling embryogenesis of multicellular organisms. The uniqueness of this somatic development, as distinct from asexual development, resides in its dependence on new information associated with the germ nucleus, and on its involvement of both maternal and postzygotic informational inputs. This understanding derives from experimental dissection of nuclear control of somatic development in Paramecium , and in several hypotrichous ciliates. The embryological perspective enables us to reorganize our thinking on several historical issues of development and evolution: whether protozoa are immortal, and whether mortality only arose together with multicellularity; whether their sexual process can be regarded as reproduction, equivalent to sexual reproduction of multicellular organisms; whether the inheritance of acquired cortical variations of non- genic origins in ciliates constitutes a threat to neo-Darwinism. Conceptual predicaments on these issues have often stemmed from unwarranted parallelism drawn between asexual propagation of protozoa and sexual reproduction of multicellular organisms. The embryological reply to these questions is that ciliated protozoa are mortal, since during fertilization the maternal soma perishes by resorption, and is replaced by a new one which develops in situ in the maternal soma. The consequence of their sexual process is the same as in sexually reproducing multicellular organisms, in that the post-fertilization protozoan is an ontogenetically new individual, equipped with a new soma unlike those generated during asexual propagation. On the basis of the characteristic in situ development of the embryonic soma during sexual reproduction, two evolutionary perceptions are formulated. First, the extensiveness of resorption of the maternal soma, and release of development of the embryonic soma from cytotactic constraints imposed by the maternal soma, constitute major themes of phylogenetic evolution. Second, the evolutionary outcome of acquired cortical variations has to be evaluated in terms of the fidelity of perpetuation of such variations through sexual reproduction, and their potential of being assimilated into the genomic programme of embryonic development. The evolutionary predictions accordingly may turn out to be radically different from those based on the inheritance of such variations during asexual propagation alone.

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