Uncertainty, Interference, and Communication in Bereaved Parent-Child Relationships

Research on familial loss has centered individualized experiences with grief, constructing a disconnect between family members that works to weaken interdependence and create additional coping challenges. Through a family systems lens, the current study explored family loss from a relational perspective, centering the parent-child experience as a unique and conflictual one. Drawing from the Relational Turbulence Model (RTM) and the Theory of Motivated Information Management (TMIM), this work used actor partner interdependence models (APIM) to test a dyadic and integrated model that centered relational experiences with uncertainty, interference, and information management for 29 bereaved parent-child dyads. Further, to understand more about how lived experience of family loss relate to quantitative measures, this study incorporated a convergent mixed methods design, and used analysis of variance to identify connections between interval variables and themes that arose from a qualitative thematic analysis. Findings from this study extended knowledge of family loss on theoretical and conceptual levels. Theoretically, the quantitative analysis revealed connections between the RTM and the TMIM, and identified both actor and partner effects related to uncertainty, interference and information management that help to further recognize the importance of exploring death from a family perspective. Conceptually, the qualitative analysis revealed that bereaved parents and children face unique challenges related to uncertainty and interference, and further that their information management goes beyond an open/closed binary. Taken together, the analysis worked to improve current knowledge of family loss by extending how death is defined and studied, and in doing so expanded the reach of the field of family communication by revealing the potential of dyadic and mixed methodological approaches

New Approaches to Understanding the Mechanics of Burgess Shale-type Deposits: From the Micron Scale to the Global Picture

Cambrian Burgess Shale-type (BST) deposits are among the most significant deposits for understanding the “Cambrian explosion” because they contain the fossilized tissues of nonmineralized organisms and provide a substantially different window on the radiation of the Metazoa than is afforded by the more “typical” fossil record of skeletal parts of biomineralized organisms. Despite nearly a century of research, BST deposits remain poorly investigated as sedimentologic entities largely because they comprise fine-grained mudrocks. Here,we describe a new, integrative approach to understanding a single BST deposit, the middle Cambrian Wheeler Formation of Utah, which reveals a dynamic interplay of paleoenvironmental, paleoecologic, and sedimentologic/diagentic factors within a superficially homogeneous lithofacies.This millimeter-scale microstratigraphic and paleontologic approach is augmented by both outcrop and microscopic study.These types of data are applicable to issues of quite different scales, including micron-scale diagenetic processes involved in fossil preservation, organism-environment interactions and paleoecology of the early Metazoa, and regional and global controls on the distribution of BST deposits

Remarkable preservation of microbial mats in Neoproterozoic siliciclastic settings : Implications for Ediacaran taphonomic models

The authors thank Duncan McIlroy and Alex Liu for their discussions, help, comments and field support, the National Trust for access to Longmyndian localities, and the staff of the British Geological Survey Palaeontology unit and the Oxford University Museum of Natural History for their assistance with access to materials. The comments and suggestions of two anonymous reviewers and Nora Noffke significantly improved the manuscript.Peer reviewedPostprin

La transición ediacárico-cámbrica: facies sedimentarias versus extinción

Recent analysis of the terminal Ediacaran, Rawnsley Quartzite, in the Flinders Ranges of South Australia, demonstrates that key taxa of the Ediacara biota are restricted to certain sedimentary facies and stratigraphic levels. The Rawnsley Quartzite consists of three members separated by disconformities: (i) the basal, shallow marine Chace Sandstone Member is unfossiliferous, but replete with textured organic surfaces; (ii) the overlying Ediacara Sandstone Member fills submarine incisions cut through the underlying Chace Quartzite Member and paralic Bonney Sandstone below the Rawnsley Quartzite; and (iii) the Ediacara Sandstone Member is incised by the less fossiliferous Nilpena Sandstone Member that caps the Rawnsley Quartzite.Un estudio reciente de la Cuarcita de Rawnsley, en el Ediacárico terminal Ediacaran de la Cordillera de Flinders, Australia meridional, demuestra cómo algunos taxones clave de la biota de Ediacara están restringidos a ciertas facies sedimentarias y determinados niveles estratigráficos. La Cuarcita de Rawnsleycomprende tres miembros separados por discotinuidades: (i) el Miembro basal de la Arenisca de Chace es somera y azoica, aunque destacan las superficies con texturas orgánicas; (ii) el Miemrbo de la Arenisca de Ediacara rellena un Sistema de incisiones submarinas que recortan el miembro inferior de Chace y la Arenisca parálica de Bonney, infrayacente a la Cuarcita de Rawnsley; y (iii) el Miembro de la Arenisca de Ediacara es asimismo recortada de forma erosiva por el Miembro de la Arenisca de Nilpena, menos fosilífera

A new hypothesis for organic preservation of Burgess Shale taxa in the middle Cambrian Wheeler Formation

Abstract Cambrian konservat-lagerstätten are the most significant fossil deposits for our understanding of the initiation of Phanerozoic life. Although many modes of preservation may occur, these deposits most frequently contain nonmineralized fossils preserved in the form of kerogenized carbon films, a rare yet important taphonomic pathway that has not previously been explained for any unit by a comprehensive model. The middle Cambrian Wheeler Formation of Utah, one of these lagerstätten, contains abundant kerogenized preservation of nonmineralized tissues, which occurs within a distinctive taphofacies that accumulated under the following conditions: (1) domination of the siliciclastic fraction by clay-sized particles, (2) close proximity to a carbonate platform, which resulted in mixed carbonate-clay sediments, (3) a well-developed oxygen minimum precluding benthic colonization and burrowing, and (4) relative proximity to oxic bottom-waters, facilitating transport of organisms from a habitable environment to one that favored their preservation. We propose that preservation of nonmineralized tissues in the Wheeler Formation may have resulted from a combination of influences that reduced permeability and, thus, lowered oxidant flux, which in turn may have restricted microbial decomposition of some nonmineralized tissues. Those influences include near bottom anoxia, preventing sediment irrigation by restriction of bioturbation; reducing conditions near the sediment-water interface that may have acted to deflocculate aggregations of clay minerals, resulting in low permeability face-to-face contacts; early diagenetic pore occluding carbonate cements; and an absence of coarse grains such as silt, skeletonized microfossils, fecal pellets, or bioclasts. This model may be applicable to kerogenized preservation of macrofossils in other fossil lagerstätten.

Elucidating the morphology and ecology of Eoandromeda octobrachiata from the Ediacaran of South Australia

Eoandromeda octobrachiata is a poorly understood Ediacaran organism, with spiral- octoradial arms, found in South Australia and South China. The informal Nilpena member of the Rawnsley Quartzite, Flinders Ranges in South Australia preserves more than 200 specimens of Eoandromeda. Here we use the novel application of rotational geometric morphometrics together with palaeoenvironmental information to provide a better insight into their palaeobiology and ecology and to address conflicting hypotheses regarding mode of life and taxonomic affinity. We find that Eoandromeda likely had a radially symmetrical shape in life, was cone-shaped and had a high relief off the microbial mat. Analysis of the symmetric and asymmetric shape components revealed they deform strongly in the direction of palaeocurrent, therefore are thought to be made of a flexible material. Almost all specimens are compressed flat. Specimens that appear to have not fully collapsed support the idea that Eoandromeda was likely cone-shaped and further suggest that they possibly collapsed spirally. Our shape analysis along with observed morphological features support the benthic mode of life hypothesis rather than pelagic. Morphological and ecological inconsistencies such as a lack of biradial symmetry and a benthic mode of life do not support the hypothesis of a Ctenophora taxonomic affinity.Tory L. Botha, Emma Sherratt, Mary L. Droser, Jim G. Gehling and Diego C. García-Bellid

Considering the Case for Biodiversity Cycles: Reexamining the Evidence for Periodicity in the Fossil Record

Medvedev and Melott (2007) have suggested that periodicity in fossil biodiversity may be induced by cosmic rays which vary as the Solar System oscillates normal to the galactic disk. We re-examine the evidence for a 62 million year (Myr) periodicity in biodiversity throughout the Phanerozoic history of animal life reported by Rohde & Mueller (2005), as well as related questions of periodicity in origination and extinction. We find that the signal is robust against variations in methods of analysis, and is based on fluctuations in the Paleozoic and a substantial part of the Mesozoic. Examination of origination and extinction is somewhat ambiguous, with results depending upon procedure. Origination and extinction intensity as defined by RM may be affected by an artifact at 27 Myr in the duration of stratigraphic intervals. Nevertheless, when a procedure free of this artifact is implemented, the 27 Myr periodicity appears in origination, suggesting that the artifact may ultimately be based on a signal in the data. A 62 Myr feature appears in extinction, when this same procedure is used. We conclude that evidence for a periodicity at 62 Myr is robust, and evidence for periodicity at approximately 27 Myr is also present, albeit more ambiguous.Comment: Minor modifications to reflect final published versio

Reconstructing the reproductive mode of an Ediacaran macro-organism.

Enigmatic macrofossils of late Ediacaran age (580-541 million years ago) provide the oldest known record of diverse complex organisms on Earth, lying between the microbially dominated ecosystems of the Proterozoic and the Cambrian emergence of the modern biosphere. Among the oldest and most enigmatic of these macrofossils are the Rangeomorpha, a group characterized by modular, self-similar branching and a sessile benthic habit. Localized occurrences of large in situ fossilized rangeomorph populations allow fundamental aspects of their biology to be resolved using spatial point process techniques. Here we use such techniques to identify recurrent clustering patterns in the rangeomorph Fractofusus, revealing a complex life history of multigenerational, stolon-like asexual reproduction, interspersed with dispersal by waterborne propagules. Ecologically, such a habit would have allowed both for the rapid colonization of a localized area and for transport to new, previously uncolonized areas. The capacity of Fractofusus to derive adult morphology by two distinct reproductive modes documents the sophistication of its underlying developmental biology.This work has been supported by the Natural Environment Research Council [grant numbers NE/I005927/1 to C.G.K., NE/J5000045/1 to J.J.M., NE/L011409/1 to A.G.L. and NE/G523539/1 to E.G.M.], and a Henslow Junior Research Fellowship from Cambridge Philosophical Society to A.G.L.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nature1464

On the edge of exceptional preservation: insights into the role of redox state in Burgess Shale-type taphonomic windows from the Mural Formation, Alberta, Canada

Animals originated in the Neoproterozoic and ‘exploded’ into the fossil record in the Cambrian. The Cambrian also represents a high point in the animal fossil record for the preservation of soft tissues that are normally degraded. Specifically, fossils from Burgess Shale-type (BST) preservational windows give paleontologists an unparalleled view into early animal evolution. Why this time interval hosts such exceptional preservation, and why this preservational window declines in the early Paleozoic, have been long-standing questions. Anoxic conditions have been hypothesized to play a role in BST preservation, but recent geochemical investigations of these deposits have reached contradictory results with respect to the redox state of overlying bottom waters. Here, we report a multi-proxy geochemical study of the Lower Cambrian Mural Formation, Alberta, Canada. At the type section, the Mural Formation preserves rare recalcitrant organic tissues in shales that were deposited near storm wave-base (a Tier III deposit; the worst level of soft-tissue preservation). The geochemical signature of this section shows little to no evidence of anoxic conditions, in contrast to published multi-proxy studies of more celebrated Tier I and II deposits. These data help confirm that ‘decay limited’ BST biotas were deposited in more oxygenated conditions, and support a role for anoxic conditions in BST preservation. Finally, we discuss the role of iron reduction in BST preservation, including the formation of iron-rich clays and inducement of sealing seafloor carbonate cements. As oceans and sediment columns became more oxygenated and more sulfidic through the early Paleozoic, these geochemical changes may have helped close the BST taphonomic window.