New fossil assemblages from the Early Ordovician Fezouata Biota

The Fezouata Biota (Morocco) is an exceptionally well-preserved fossil community of Early Ordovician age and although its oldest units are comparable with Burgess Shale-type localities of the Cambrian Explosion, little attention has been paid to the younger units despite potential to reveal the conditions of the Ordovician Radiation. Herein, we describe a new middle to upper Floian Fezouata locality (Taichoute) encompassing an assemblage dominated by large bivalved euarthropods and giant filter-feeding radiodonts, which were transported and preserved in concretions associated with density-flow deposits. Taichoute captures the closing of the taphonomic window that characterizes exceptional fossil preservation during the Cambrian Explosion (i.e., carbonaceous compressions) as well as the faunal transition to assemblages dominated by typical Palaeozoic taxa.

OOIMMURATION: ENHANCED FOSSIL PRESERVATION BY OOIDS, WITH EXAMPLES FROM THE MIDDLE JURASSIC OF SOUTHWESTERN UTAH, USA

ABSTRACT Ooimmuration is here defined as a taphonomic process by which fossils are preserved within ooids. It is a form of lithoimmuration, although depending on the role of microbes in the formation of the ooid cortex, ooimmuration can also be considered a type of bioimmuration. Fossils enclosed within ooids are protected from bioerosion as well as the abrasion common in energetic depositional environments such as ooid shoals. Many taxa in some fossil assemblages may be known only because they were ooimmured. We describe as examples of ooimmuration fossils preserved in an oolite from the Middle Jurassic (Bajocian) Carmel Formation in southwestern Utah.

Improving the Adoption and Evolution of Data Standards for Fossil Specimens

As we atomize and expand the digital representation of specimen information through data standards, it is critical to evaluate the implementation of these developments, including how well they serve discipline-specific needs. In particular, fossil specimens often present challenges because they require information to be captured that is seemingly parallel to, but not entirely aligned with, that of their extant counterparts. Previous work to evaluate data sharing practices of paleontology collections has shown an imbalance in the use of Darwin Core (DwC) (Wieczorek et al. 2012) terms and many instances of underutilized terms (Little 2018). To expand upon that broad assessment and encourage better adoption of evolving standards and data practices by fossil collections, a more in-depth review of term usage is necessary. Here we review specific DwC terms that are underutilized or that present challenges for fossil occurrence records, and we examine the subsequent impact on data discovery of paleo specimens. We conclude by sharing options for improving standards implementation within a paleo context. We see key patterns and challenges in current implementation of DwC in paleo collections, as evidenced by evaluations of the typical mappings found in occurrence records for fossil specimens, data flags applied by aggregators, and discussions within the paleo collections community. These can be organized into three broad groupings. Group 1: Some DwC terms (or classes of terms) are clear to implement, but are underutilized due to issues that are also found within the neontological community. Example: Location. In the case of terms related to the Location class, paleontology has a need for a way to deal with sensitive locality information. The sensitivity here typically relates to laws restricting the sharing of locality information to protect fossil sites versus neontological requirements to protect threatened, rare, or endangered species. The end goal of needing to fuzz locality information without completely making the specimen record undiscoverable or unusable is the same. There is a need for better education at the paleo data provider-level related to standards for recording and sharing information in this category, which could be based on existing neontological community standards. Group 2: A second group of DwC terms often seem clear to implement, but the terminology used to describe and define them might be unfamiliar to paleontologists or read as unnecessary for fossil occurrences. This uncertainty about the applicability of a term to paleo data can often result in data not being mapped or fully shared. Example: recordedBy (= collector). In these cases, a simple translation of what the definition means in verbiage that is familiar to paleontologists, or the inclusion of paleo-oriented examples in the DwC documentation, can make implementation clear. Group 3: A third group of issues relates to DwC terms, classes, and/or extensions that are more complicated in the context of fossil vs. neontological data. In some cases use of these terms is complicated for neontological data as well, but perhaps for different reasons. The terms impacted by these challenges can sometimes have the same general use, but due to the nature of fossil preservation, or because a term has a different meaning within the discipline of paleontology, additional layers of uncertainty or ambiguity are present. Examples: Resource Relationship/Interactions, Individual count, Preparations, Taxon. Review of these terms and their related classes and/or the extensions they are part of has revealed that they might require qualification, further explanation, additional vocabulary terms, or even the need for special handling instructions when data are ingested and normalized at the aggregator level. This group of issues is more complicated to resolve, but the problems are not intractable and can progress toward solutions through further discussion within the community, active participation in the standards development and review process, and development of clear guidelines. Strategically assessing these terms and generating discipline-specific guidelines to be used by the paleo community can improve the mobilization and discovery of fossil occurrence data. Documenting these paleo data practices not only helps data providers, it also increases the utility of these data within the broader research community by clearly outlining how the terms were used. Overall, this discipline-focused approach to understanding the implementation of data standards like DwC at the term level, helps to increase knowledge sharing across the paleo community, improves data quality and standards adoption, and moves these datasets towards alignment with best practices like the FAIR (Findable, Accessible, Interoperable, Reusable) data principles.

Metamorphism obscures primary taphonomic pathways in the early Cambrian Sirius Passet Lagerstätte, North Greenland

Correct interpretation of soft-bodied fossils relies on a thorough understanding of their taphonomy. While the focus has often been on the primary roles of decay and early diagenesis, the impacts of deeper burial and metamorphism on fossil preservation are less well understood. We document a sequence of late-stage mineral replacements in panarthropod fossils from the Sirius Passet Lagerstätte (North Greenland), an important early Cambrian Burgess Shale–type (BST) biota. Muscle and gut diverticula were initially stabilized by early diagenetic apatite, prior to being pervasively replaced by quartz and then subordinate chlorite, muscovite, and chloritoid during very low- to low-grade metamorphism. Each new mineral replicates the soft tissues with different precision and occurs in particular anatomical regions, imposing strong biases on the biological information retained. Muscovite and chloritoid largely obliterate the tissues’ original detail, suggesting that aluminum-rich protoliths may have least potential for conserving mineralized soft tissues in metamorphism. Overall, the fossils exhibit a marked shift toward mineralogical equilibration with the matrix, obscuring primary taphonomic modes. Sequential replacement of the phosphatized soft tissues released phosphorus to form new accessory monazite (and apatite and xenotime), whose presence in other BST biotas might signal the prior, more widespread, occurrence of this primary mode of preservation. Our results provide critical context for interpreting the Sirius Passet biota and for identifying late-stage overprints in other biotas.

The promise of taphonomy as a nomothetic discipline: taphonomic bias in two dinosaur-bearing faunas in North America

The fossil record of dinosaurs is a rich, if biased, one with nearly complete skeletons, partial skeletons, and isolated parts found in diverse, well-studied faunal assemblages around the world. Among the recognized biases are the preferential preservation of large dinosaurs and the systematic underrepresentation of small dinosaurs. Such biases have been quantitatively described in the Upper Cretaceous (Campanian) Dinosaur Park Formation of Alberta, where large, nearly complete dinosaurs were found and described early in collecting history and small, very incomplete dinosaurs were found and described later. This pattern, apparently replicated in the Maastrichtian Hell Creek Formation of Montana, is so striking that it begs the question of whether this is a nomothetic principle for the preservation of dinosaur faunas elsewhere. We tested this hypothesis by analyzing the very well-studied dinosaur fauna of the Upper Jurassic (Kimmeridgian) Morrison Formation of the western United States. The Morrison Formation fails to show any correlation between body size and completeness, order of discovery, or order of description. Both large and small dinosaurs of the Morrison include highly complete as well as highly incomplete taxa, and both large and small dinosaurs were discovered and described early in collecting history as well as more recently. The differences in preservation between the Dinosaur Park Formation and the Morrison Formation are so striking that we posit a Dinosaur Park model of dinosaur fossil preservation and a Morrison model. Future study will show whether either or both represent durable nomothetic models for dinosaur fossil preservation.

Taxonomic identification bias does not drive patterns of abundance and diversity in theropod dinosaurs

The ability of palaeontologists to correctly diagnose and classify new fossil species from incomplete morphological data is fundamental to our understanding of evolution. Different parts of the vertebrate skeleton have different likelihoods of fossil preservation and varying amounts of taxonomic information, which could bias our interpretations of fossil material. Substantial previous research has focused on the diversity and macroevolution of non-avian theropod dinosaurs. Theropods provide a rich dataset for analysis of the interactions between taxonomic diagnosability and fossil preservation. We use specimen data and formal taxonomic diagnoses to create a new metric, the Likelihood of Diagnosis, which quantifies the diagnostic likelihood of fossil species in relation to bone preservation potential. We use this to assess whether a taxonomic identification bias impacts the non-avian theropod fossil record. We find that the patterns of differential species abundance and clade diversity are not a consequence of their relative diagnosability. Although there are other factors that bias the theropod fossil record that are not investigated here, our results suggest that patterns of relative abundance and diversity for theropods might be more representative of Mesozoic ecology than often considered.

Evolutionary drivers, morphological evolution and diversity dynamics of a surviving mammal clade: cainotherioids at the Eocene–Oligocene transition

The Eocene–Oligocene transition (EOT) represents a period of global environmental changes particularly marked in Europe and coincides with a dramatic biotic turnover. Here, using an exceptional fossil preservation, we document and analyse the diversity dynamics of a mammal clade, Cainotherioidea (Artiodactyla), that survived the EOT and radiated rapidly immediately after. We infer their diversification history from Quercy Konzentrat–Lagerstätte (south-west France) at the species level using Bayesian birth–death models. We show that cainotherioid diversity fluctuated through time, with extinction events at the EOT and in the late Oligocene, and a major speciation burst in the early Oligocene. The latter is in line with our finding that cainotherioids had a high morphological adaptability following environmental changes throughout the EOT, which probably played a key role in the survival and evolutionary success of this clade in the aftermath. Speciation is positively associated with temperature and continental fragmentation in a time-continuous way, while extinction seems to synchronize with environmental change in a punctuated way. Within-clade interactions negatively affected the cainotherioid diversification, while inter-clade competition might explain their final decline during the late Oligocene. Our results provide a detailed dynamic picture of the evolutionary history of a mammal clade in a context of global change.

Distraction sinking and fossilized coleoid predatory behaviour from the German Early Jurassic

Exceptional fossil preservation is required to conserve soft-bodied fossils and even more so to conserve their behaviour. Here, we describe a fossil of a co-occurrence of representatives of two different octobrachian coleoid species. The fossils are from the Toarcian Posidonienschiefer of Ohmden near Holzmaden, Germany. The two animals died in the act of predation, i.e. one had caught the other and had begun to nibble on it, when they possibly sank into hypoxic waters and suffocated (distraction sinking). This supports the idea that primitive vampyromorphs pursued diverse feeding strategies and were not yet adapted to being opportunistic feeders in oxygen minimum zones like their modern relative Vampyroteuthis.