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76 5.1. Hackberry endocarps, including specimens from the Brule Formation of Wyoming (top row and lower left three squares on the bottom row), and modern specimens (lower right square). The fossil endocarps are typically nearly smooth, with only a trace of the reticulation pattern seen in the modern specimens. The fossil endocarps occur in at least two size ranges. The original calcite shells have been recrystallized into coarse calcite crystals. The endocarps have two outer shells of calcium carbonate that can separate. The top row of fossils shows a progression from a complete endocarp (upper left) to an almost completely separated pair of shells (upper right). Grid in centimeters. Photo by the authors. 77 5 Bones That Turned to Stone: Systematics Introduction The sheer abundance and diversity of the paleontological record within the White River Badlands is indeed impressive. This has been well documented by the extensive amount of scientific literature that has been published on this region over the past 150 years. As a result, the fauna of the Big Badlands has played a key role in our understanding of how the North American biota has evolved and adapted in response to climatic change. The enormous depth of this topic has forced us to set some limits. The systematic discussions of paleontology are limited to taxa that have a published occurrence within a 100-mile radius of the Cedar Pass Area within Badlands National Park. However, many of the images featured in the systematics chapter come from areas outside the scope of this project but are of the same genus and species found in published records for Badlands National Park and the surrounding region. During our research, we encountered some contradictory systematic classifications. This reflects the dynamics of the ongoing paleontological research with regard to the evolution , taxonomy, and systematics of the fossil taxa we include. We followed the most current publications whenever possible . For many taxa, there is a general agreement on the name that should be used for a taxon, but this is not always the case. We were thus forced to select a name. We emphasize that this is not a formal taxonomic revision and that our selection of names was often a matter of convenience to facilitate our ability to convey information. In those cases we have often selected historic names that are well established in the literature rather than more obscure names or newly proposed replacement names, which have not yet been fully accepted or vetted by the professional paleontological community. We realize that research is ongoing and that systematic classifications will continue to change in the coming years. To those specialists in different taxonomic groups who may disagree with our name choices, we apologize if our taxonomy does not exactly match your preferences. Plantae Because of the highly alkaline oxidizing soils, the plant record within the White River Badlands is poor (Retallack, 1983b). There is no record of fossil leaves or pollen. Instead , we find root traces, the endocarps of hackberry seeds (Chaney, 1925), petrified wood (Troxell, 1925; Berry, 1926; Wieland, 1935; Lemley, 1971), and partially digested plant material in herbivore coprolites (Stovall and Strain, 1936). Even with such a limited record, important interpretations about the vegetation communities on the landscape and how they reflect the paleoclimate can be made from these materials. Fossil Root Traces There is a broad variety of fossil root traces preserved within the White River Group (Plates 6, 7). Root traces are an important indicator of pedogenic activity (soil formation) and are discussed in detail in chapter 3. They can also be an important indicator of ancient climate. According to Retallack (1983b), within a root trace, there is no evidence of original organic material nor any details of anatomy or surface detail. They are simply an opening in the soil left by the root and later filled with soil material or crystalline calcite or chalcedony . The root traces taper and branch downward and are irregular in width and direction, depending on the root structure of the original plant. Some of the most striking root traces are large metaisotubules of reddish clay washed into the yellowish C horizon of the type Yellow Mounds silty clay loam paleosol of the Pierre Shale and Fox Hills Formation. These root traces are up to 3 cm in diameter and indicate the presence of trees or large shrubs. In contrast, fine root traces of 1 to 2 mm are abundant on the surface of all paleosols of the White River and Arikaree...


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