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Bonebeds are remarkable features of the vertebrate fossil record that can embody ancient environmental catastrophes and, thus, reveal some of the most dramatic aspects of past ecosystems. They can also serve as less sensational but equally informative gauges of sedimentary dynamics and biological recycling. Regardless of their particular mode(s) of origin, bonebeds, in their many forms, provide exceptional opportunities to investigate a variety of paleobiological and geological questions. This chapter proposes a system for the categorization and analysis of bonebeds analogous to the genetic classification scheme proposed by Kidwell et al. (1986) for marine macrobenthic concentrations. It explains how vertebrate hardparts accumulate and discusses biogenic concentrations, physical concentrations, fluvial channels, strandlines, bioclasts, obrution concentration, and sediment deposition.

Bonebeds have attracted great interest for centuries and remain a source of many important specimens that document the history of the vertebrates. Perhaps in part because of the sheer diversity of bonebed types and ages, there has been little previous synthetic work on their taphonomy and importance in paleontology. This chapter provides an overview of bonebeds through time, based on the analysis of a bonebed database derived from publications on the Phanerozoic terrestrial record, and proposes hypotheses for any significant patterning observed in this record. In particular, it explores how bonebed frequency and type correlate with broad climatic and other environmental trends in Phanerozoic history, whether some ecomorphs or taxonomic groups were more susceptible to mass deaths, or whether changes in the bonebed record relate to evolutionary trends in skeletonization, body size, habitat utilization, and bone-ingesting capabilities of vertebrates. Since bonebeds provide a significant portion of the vertebrate fossil record, the chapter also considers how secular changes in taphonomic processes that create bonebeds might affect our view of vertebrate history.

This chapter, which presents and reviews a database of 383 citations that refer to more than 1,000 bonebeds, offers additional insight into how bonebeds formed in the past and what they can tell us about the ancient environments within which they formed. Its goals are to: identify, characterize, and document different types of bonebed; identify historical and scientific biases in the treatment of bonebeds; demonstrate the relative frequency of different types of bonebed in the database; identify and quantify patterns of occurrence for the different types of bonebed; and identify and quantify patterns of association between bonebed type and paleoenvironment. Most bonebeds in the database are easily classified using one or more of the following three measures: element size, taxonomic diversity, and relative taxonomic abundance. In addition, patterns of occurrence are identified in relation to the relative abundance of different types of bonebed, inferred mechanisms of origin, and recurrent associations of bonebed type and paleoenvironment.

Bonebeds are of interest to paleobiologists because they yield large numbers of fossils and, thus, provide important morphologic and taxonomic data sets that are the primary basis for integrative studies of paleobehavior, paleoecology, and paleocommunity structure. This chapter reviews paleobiological inferences that can be drawn from bonebed data sets, and explores the pertinent issues and biases that relate to framing testable paleobiological hypotheses. It first reviews the data gathered from bonebeds that are often used to characterize species (morphology and variation) and to describe patterns of ontogenetic growth and sexual dimorphism, and then explores various characteristics of bonebed assemblages that provide information leading to reconstructions of inter- and intraspecific paleobehaviors. The chapter concludes by analyzing the more synthetic paleobiological issues that relate to faunal analyses and paleocommunity reconstructions. It considers the ways in which taphonomic and geological biases affect the paleobiological signals recorded in bonebeds, and how understanding these biases allows for a reasonable reconstruction of the paleobiology of extinct species. Ultimately, the paleobiological inferences drawn from bonebeds relate to fundamental questions in evolution and ecology.

Every bonebed preserved in the stratigraphic record reflects the interplay of complex physical, chemical, and biological phenomena. Rocks provide the overall context for bonebeds preserved in the stratigraphic record, and a thorough understanding of sedimentology and stratigraphy is needed before the formative history of a bonebed can be accurately reconstructed. Given the myriad events and interactions that follow death, deciphering the formative pathway(s) that led to skeletal accumulation is no easy task. Clearly, the best hope for a successful study hinges upon the careful collection of data, and fortunately the methods of data collection and analysis in relation to bonebeds have evolved and improved over time. This chapter examines bonebeds from a practical standpoint and addresses four main concerns that pertain to effective site management and data collection: preliminary site assessment, considerations that arise when the real work begins, collection of geological data, and the types of taphonomic information that should be retrieved from a bonebed assemblage. It concludes by focusing on the reconstruction of the taphonomic history of a bonebed assemblage.

This chapter discusses several kinds of quantitative analysis of bonebed assemblages in relation to particular research questions, first reviewing protocols for counting specimens recovered from bonebeds, a crucial initial step that lays the foundation for further analyses. Second, it considers the evaluation of taphonomic equivalence among bonebeds, a consideration that is crucial for comparisons of faunal counts among fossil localities, and third, discusses comparisons of species richness among localities, particularly with respect to sampling intensity. Fourth, the chapter assesses approaches for estimating taxonomic abundance in ancient ecosystems based on species abundances in fossil assemblages. Finally, it looks at several techniques for the quantitative analysis of changes in lineages and faunas among fossil bonebeds, illustrating all of the quantitative methods presented with case studies.

Fossil bones and teeth are the last physical remains of once-living vertebrates, and the chemistry of these fossils at least in part reflects the biochemistry of the individual. If the mineral phase of bone remains unaltered during diagenesis and fossilization, then the bone will contain a biogenic signal that can be used to infer directly physiological, dietary, and climatic information about the animal and its environment. Geochemical analyses of trace elements are particularly well suited to the study of bonebeds. Trace element analyses can be used to assess the extent of mixing within a bonebed, to determine the origin of reworked bones within a mixed assemblage, and to help distinguish between catastrophic and attritional modes of accumulation. This chapter discusses the trace element geochemistry of bonebeds, focusing on the importance of diagenesis in understanding geochemical taphonomy, the use of rare earth elements in geochemistry, applications of geochemical provenance techniques in the fossil record, reworking of bones, and paleoenvironmental reconstruction.

The tissues of living animals contain carbon, oxygen, and nitrogen, which are sourced from the food, water, and air that animals ingest and respire. This linkage holds true for vertebrate hardparts such as bones and teeth, which consist of a matrix of organic molecules (mostly collagen) surrounded by crystals of bioapatite. The ratio of stable isotopes of carbon, oxygen and nitrogen in plants and surface waters can vary considerably. This chapter explains how stable isotope geochemistry of fossils in bonebeds can be used to reconstruct paleoenvironments, paleoecology, and paleobiology. It begins with a review that focuses on isotopic variability in plants and surface waters, isotopic relations between these ingested materials and vertebrate remains, and the preservation of primary isotopic information over time. The chapter then considers study design in relation to bonebed type, summarizes the critical assumptions and unknowns that may impact study design, and concludes by presenting specific examples of paleoenvironmental and paleoecological reconstructions using stable isotope data.