scholarly journals A novel tool to untangle the ecology and fossil preservation knot in exceptionally preserved biotas

2021 ◽  
Vol 569 ◽  
pp. 117061
Author(s):  
Farid Saleh ◽  
Orla G. Bath-Enright ◽  
Allison C. Daley ◽  
Bertrand Lefebvre ◽  
Bernard Pittet ◽  
...  
Keyword(s):  
Fossil Preservation

Late Cretaceous stratigraphy and vertebrate faunas of the Markagunt, Paunsaugunt, and Kaiparowits plateaus, southern Utah

2016 ◽  
Vol 3 ◽  
pp. 229-291 ◽  
Author(s):  
Alan L. Titus ◽  
Jeffrey G. Eaton ◽  
Joseph Sertich
Keyword(s):  
Late Cretaceous ◽  
Foreland Basin ◽  
Alluvial Plain ◽  
Terrestrial Vertebrate ◽  
The North ◽  
Single Region ◽  
The World ◽  
Kaiparowits Plateau ◽  
Fossil Preservation ◽  
Fossil Records

The Late Cretaceous succession of southern Utah was deposited in an active foreland basin circa 100 to 70 million years ago. Thick siliciclastic units represent a variety of marine, coastal, and alluvial plain environments, but are dominantly terrestrial, and also highly fossiliferous. Conditions for vertebrate fossil preservation appear to have optimized in alluvial plain settings more distant from the coast, and so in general the locus of good preservation of diverse assemblages shifts eastward through the Late Cretaceous. The Middle and Late Campanian record of the Paunsaugunt and Kaiparowits Plateau regions is especially good, exhibiting common soft tissue preservation, and comparable with that of the contemporaneous Judith River and Belly River Groups to the north. Collectively the Cenomanian through Campanian strata of southern Utah hold one of the most complete single region terrestrial vertebrate fossil records in the world.

Total organic carbon and the preservation of organic-walled microfossils in Precambrian shale

Geology ◽  
2020 ◽  
Author(s):  
C.R. Woltz ◽  
S.M. Porter ◽  
H. Agić ◽  
C.M. Dehler ◽  
C.K. Junium ◽  
...  
Keyword(s):  
Species Richness ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Microbial Degradation ◽  
Sedimentation Rate ◽  
Surface Pattern ◽  
Causal Factors ◽  
Eukaryotic Diversity ◽  
High Concentrations ◽  
Fossil Preservation

Much of our understanding of early eukaryote diversity and paleoecology comes from the record of organic-walled microfossils in shale, yet the conditions controlling their preservation are not well understood. It has been suggested that high concentrations of total organic carbon (TOC) inhibit the preservation of organic fossils in shale, and although this idea is supported anecdotally, it has never been tested. Here we compared the presence, preservational quality, and assemblage diversity of organic-walled microfossils to TOC concentrations of 346 shale samples that span the late Paleoproterozoic to middle Neoproterozoic in age. We found that fossil-bearing samples have significantly lower median TOC values (0.32 wt%, n = 189) than those containing no fossils (0.72 wt%, n = 157). Preservational quality, measured by the loss of surface pattern, density of pitting, and deterioration of wall margin, decreases as TOC increases. Species richness negatively correlates with TOC within the ca. 750 Ma Chuar Group (Arizona, USA), but no relationship is observed in other units. These results support the hypothesis that high TOC content either decreases the preservational quality or inhibits the preservation of organic-walled microfossils altogether. However, it is also possible that other causal factors, including sedimentation rate and microbial degradation, account for the correlation between fossil preservation and TOC. We expect that as TOC varies in space and time, so too does the probability of finding well-preserved fossils. A compilation of 13,940 TOC values spanning Earth history suggests significantly higher median TOC levels in Mesoproterozoic versus Neoproterozoic shale, potentially biasing the interpreted pattern of increased eukaryotic diversity in the Tonian.

Pyrite geochemistry and fossil preservation in shales

1985 ◽  
Vol 311 (1148) ◽  
pp. 167-169 ◽  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Sulphate Reduction ◽  
Pore Waters ◽  
Anoxic Waters ◽  
Iron Sulphides ◽  
Diagenetic Reaction ◽  
Fossil Preservation

As emphasized by Dr Seilacher in his introduction to this symposium, and illustrated in the contribution by Mr Martill, some of the most important examples of fossil Lagersätten occur in marine shales of Mesozoic age. Many of the factors that control the types and preservation of fossils are the same as those that affect the authigenic mineralogy and geochemistry of the shales, notably the degree of aeration or stagnation of the water column and the quantity and quality of the organic matter supplied to the sediment. Perhaps the most important diagenetic reaction in marine shales is sulphate reduction by bacteria that are obligate anaerobes. They can operate in anoxic waters or in ‘reducing microenvironments’ (such as concentrations of organic matter, or enclosed voids within shells) in sediments whose pore waters are kept generally oxic by the effects of burrowing organisms. Sulphate is reduced to sulphide and in the presence of reduced iron this can be precipitated as iron sulphides, normally found in ancient sediments in the form of pyrite. Pyrite is thus a key mineral in studying shale diagenesis, for its geochemistry as well as for its direct importance in preserving fossils by replacement of soft-parts (see, for example, Stürmer 1984), of aragonitic shells (see, for example, Fisher 1985) and by forming internal moulds of chambered shells (see, for example, Hudson & Palframan 1969; Hudson 1982).

scholarly journals Bioimmuration: exceptional fossil preservation made routine

1992 ◽  
Vol 6 ◽  
pp. 287-287 ◽  
Author(s):  
Paul D. Taylor ◽  
Jonathan A. Todd
Keyword(s):  
Soft Tissues ◽  
Soft Part ◽  
High Fidelity ◽  
Marine Deposits ◽  
Living Space ◽  
Extant Genus ◽  
Fossil Preservation ◽  
Sessile Organisms ◽  
Nw Europe ◽  
Hard Substrates

Bioimmuration, broadly defined as fossilization by virtue of organic overgrowth, allows preservation of soft-bodied organisms and soft parts of organisms with mineralized skeletons. Sessile organisms attached to hard or firm substrates are routinely overgrown by other organisms competing for living space. If the overgrowing organism has a mineralized skeleton which is likely to be fossilized, then it may carry a high fidelity (sub-micron scale) impression of the overgrown organism on its underside. This is a mould bioimmuration, the simplest mode of preservation. A diagenetic infilling of the mould, commonly by calcite, produces a cast bioimmuration. In addition, the protected microenvironment between the overgrowing organism and the substratum favours early diagenetic permineralization of the soft tissues of the bioimmured organism and the development of more complex preservational styles.In spite of its potential for soft part fossilization, very little research has been undertaken on bioimmuration, with the notable exception of the work of Ehrhard Voigt principally on Maastrichtian sea-grass communities. Research in progress is revealing a great abundance of bioimmured fossils in Mesozoic shallow marine deposits of NW Europe where oysters and serpulids overgrew a variety of other organisms.Bioimmured soft-bodied bryozoans belonging to the Order Ctenostomata are very common and display a range of preservational styles. Minute spines and pores ornamenting the cuticular zooidal walls are sometimes present, as are permineralized pore chambers. The high diversity of stoloniferan and carnosan ctenostomes encrusting hard substrates in the Oxfordian and Kimmeridgian is striking and contrasts with the depauperate fauna of calcified cyclostome bryozoans.Oyster shells in the Kimmeridge Clay are often encrusted by myriads of tiny individuals of the inarticulate brachiopod Discinisca, previously known from comparatively few specimens of this age. Emerging from the fragile commissures are setae several times the length of the delicate phosphatic shells. Setae of neighbouring individuals may be aligned in parallel facing away from the direction of approach of the overgrowing organism.The hemichordate Rhabdopleura is common as a bioimmured fossil in the Oxford Clay. Overgrowth protects the periderm and the black stolons, and colonies are much more intact than previously described examples of this genus from the Jurassic.The Phylum Entoprocta had no unequivocal fossil record before the recent discovery of bioimmured entoprocts in the Kimmeridge Clay. Colonies comprise stolons linking erect zooids which have been pushed flat against the substratum during overgrowth. The existence of thickened sockets at the base of the zooids permits assignment of the fossils to the extant genus Barentsia. Permineralization of the entoproct cuticle has occurred, leaving minute pores apparently once occupied by epithelial microvilli.Pedunculate barnacles are commonly found bioimmured by oysters in the mid-Cretaceous Cambridge Greensand. Normally the cirri are retracted but in one exceptional example their outlines are clearly visible as moulds on the attachment area of an oyster.

Phosphates and Fossil Preservation

1991 ◽  
pp. 389-409 ◽  
Author(s):  
Jacques Lucas ◽  
Lilian E. Prévôt
Keyword(s):  
Fossil Preservation

Fossil preservation and the stratigraphic ranges of taxa

Paleobiology ◽  
1996 ◽  
Vol 22 (2) ◽  
pp. 121-140 ◽  
Author(s):  
Mike Foote ◽  
David M. Raup
Keyword(s):  
Fossil Record ◽  
Mammalian Species ◽  
Evolutionary Rates ◽  
Extinction Rate ◽  
Mammal Species ◽  
Original Distribution ◽  
Lower Ordovician ◽  
Stratigraphic Ranges ◽  
Fossil Preservation ◽  
Rule Out

The incompleteness of the fossil record hinders the inference of evolutionary rates and patterns. Here, we derive relationships among true taxonomic durations, preservation probability, and observed taxonomic ranges. We use these relationships to estimate original distributions of taxonomic durations, preservation probability, and completeness (proportion of taxa preserved), given only the observed ranges. No data on occurrences within the ranges of taxa are required. When preservation is random and the original distribution of durations is exponential, the inference of durations, preservability, and completeness is exact. However, reasonable approximations are possible given non-exponential duration distributions and temporal and taxonomic variation in preservability. Thus, the approaches we describe have great potential in studies of taphonomy, evolutionary rates and patterns, and genealogy.Analyses of Upper Cambrian-Lower Ordovician trilobite species, Paleozoic crinoid genera, Jurassic bivalve species, and Cenozoic mammal species yield the following results: (1) The preservation probability inferred from stratigraphic ranges alone agrees with that inferred from the analysis of stratigraphic gaps when data on the latter are available. (2) Whereas median durations based on simple tabulations of observed ranges are biased by stratigraphic resolution, our estimates of median duration, extinction rate, and completeness are not biased. (3) The shorter geologic ranges of mammalian species relative to those of bivalves cannot be attributed to a difference in preservation potential. However, we cannot rule out the contribution of taxonomic practice to this difference. (4) In the groups studied, completeness (proportion of species [trilobites, bivalves, mammals] or genera [crinoids] preserved) ranges from 60% to 90%. The higher estimates of completeness at smaller geographic scales support previous suggestions that the incompleteness of the fossil record reflects loss of fossiliferous rock more than failure of species to enter the fossil record in the first place.

Flapper Valve and Hayfork: Functional anatomy and taxonomic potential of the Gastric Mill of Bairdioidea (Ostracoda, Podocopida)

Zootaxa ◽  
2018 ◽  
Vol 4378 (1) ◽  
pp. 1 ◽  
Author(s):  
ROSALIE F. MADDOCKS
Keyword(s):  
Particle Size ◽  
Functional Anatomy ◽  
Check Valve ◽  
Lateral Wall ◽  
Gastric Mill ◽  
Taxonomic Significance ◽  
Decapod Crustaceans ◽  
It Projects ◽  
Anatomical Analysis ◽  
Fossil Preservation

The chewing apparatus of the Bairdioidea has been described just once and is rarely illustrated, but it might have more taxonomic significance than commonly supposed. It is constructed as a flapper valve (hinged check valve), which is unique among Ostracoda and unusual among animals. It projects into the midgut and is substantially enveloped by it. It serves three functions: to move bites of food into the stomach, to close the esophagus against back-flow, and to pack strands of food and mucus onto the rotating food ball. It is probably less effective for macerating the food to reduce particle size. Two braces anchor this structure to the lateral wall of the forehead. It is lined by cuticle that is shed at each molt, and the formation of food balls is interrupted during molting. In its construction and action, this apparatus is quite unlike the gastric mill of decapod crustaceans, and it shows only distant homology to the dorsal Wulst of Cypridoidea. Some architectural details differ among families and genera. The well-sclerotized plate has some potential for fossil preservation in exceptional circumstances. A revised anatomical analysis is presented, together with an annotated glossary of terms. 

scholarly journals Exceptional preservation of reproductive organs and giant sperm in Cretaceous ostracods

2020 ◽  
Vol 287 (1935) ◽  
pp. 20201661
Author(s):  
He Wang ◽  
Renate Matzke-Karasz ◽  
David J. Horne ◽  
Xiangdong Zhao ◽  
Meizhen Cao ◽  
...  
Keyword(s):  
Reproductive Organs ◽  
Depositional Environments ◽  
Ct Reconstruction ◽  
Origin And Evolution ◽  
Exceptional Preservation ◽  
Morphological Adaptations ◽  
Single Piece ◽  
Evolutionary Success ◽  
Fossil Preservation ◽  
A New Species

The bivalved crustacean ostracods have the richest fossil record of any arthropod group and display complex reproductive strategies contributing to their evolutionary success. Sexual reproduction involving giant sperm, shared by three superfamilies of living ostracod crustaceans, is among the most fascinating behaviours. However, the origin and evolution of this reproductive mechanism has remained largely unexplored because fossil preservation of such features is extremely rare. Here, we report exceptionally preserved ostracods with soft parts (appendages and reproductive organs) in a single piece of mid-Cretaceous Kachin amber (approximately 100 Myr old). The ostracod assemblage is composed of 39 individuals. Thirty-one individuals belong to a new species and genus, Myanmarcypris hui gen. et sp. nov., exhibiting an ontogenetic sequence from juveniles to adults (male and female). Seven individuals are assigned to Thalassocypria sp. (Cypridoidea, Candonidae, Paracypridinae) and one to Sanyuania sp. (Cytheroidea, Loxoconchidae). Our micro-CT reconstruction provides direct evidence of the male clasper, sperm pumps (Zenker organs), hemipenes, eggs and female seminal receptacles with giant sperm. Our results reveal that the reproduction behavioural repertoire, which is associated with considerable morphological adaptations, has remained unchanged over at least 100 million years—a paramount example of evolutionary stasis. These results also double the age of the oldest unequivocal fossil animal sperm. This discovery highlights the capacity of amber to document invertebrate soft parts that are rarely recorded by other depositional environments.

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