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Hundreds of reservoirs in the western United States are managed on public lands and often contain significant paleontological resources. GIS (Geographic Information Systems) analysis of fossil collecting can help identify factors that affect fossil conservation in these multiuse facilities. Eighty years of collection history by Idaho Museum of Natural History personnel of Pleistocene vertebrates at the American Falls Reservoir, Idaho, United States, show that collections by the museum do not correlate with points of reservoir access or to coastal slope, and suggest that instead, collection history most likely tracks actual fossil productivity. Land management practice to install riprap rock barriers to mitigate coastal erosion is effective at reducing exposure of fossils at the decadal scale, thereby meeting the avoidance criterion of fossil preservation which seeks to limit exhumation of fossil resources. However, the first five years following riprap installation show a significant increase in fossil collection. This finding suggests that fossil surveys should be incorporated not only as part of the installation process, but as part of monitoring efforts for at least five years following installation.
The Upper Triassic/Lower Jurassic Nugget Sandstone represents a portion of a vast inland erg of eolian sand dunes that were populated by diverse vertebrates and invertebrates, represented primarily by their trace fossils. Body fossils are rare, making the trace fossil record essential for deciphering the paleoecology of the ancient dune system. Trace fossils in the Nugget Sandstone near Vernal, Utah, include invertebrate burrows (Entradichnus meniscus, Entradichnus isp., Planolites beverleyensis, Taenidium isp. “A”, Taenidium isp. “B”, Skolithos, and Planolites isp., burrow clusters, large oblique burrows, flared burrows) and trackways (Paleohelcura and Octopodichnus). Arthropods (insects and arachnids) probably were the tracemakers of most, if not all, the trace fossils. Sediment moisture must have played a key role in the production and preservation of the trace fossils, indicating that moisture was important for supporting such complex ecosystems. Extended wet climatic intervals must have persisted intermittently between arid intervals. New fossil evidence for plants (sphenophytes, cycads, and algal buildups), ichnologic evidence of herbivorous insects and carnivorous arachnids, as well as indirect evidence for environmental moisture content during deposition of the Nugget Sandstone, provide a picture of the paleoecology of this ancient sea of sand.
Drillholes represent direct evidence of ecological interactions in the fossil record. Most of them have been interpreted as predatory in origin and enable the analysis of behavioral information of both predator and prey. Drillholes have been found in a variety of fossil organisms, but this is the first report of a bored fossil chiton plate. It was found in the La Coronilla deposit, a Late Pleistocene invertebrate assemblage from southeastern Uruguay. The drillhole belongs to the ichnospecies Oichnus simplex and is attributed to a muricid gastropod, which could likely have been the ocenebrinid Urosalpinx haneti, recorded in the fossil assemblage. The drillhole features all traits for a predatory origin. However, the rareness of this particular interaction between chitons and gastropods in the fossil record and in the recent, could signify an event of arbitrary drilling. The reported occurrence here raises the question as to whether this behavior represents an understudied ecological interaction between polyplacophorans and gastropods.
Surface locomotory trace fossils from the Mistaken Point Formation of Newfoundland, dated at ∼ 565 Ma, suggest that organisms capable of controlled locomotion and possessing muscular tissue may have existed among Avalonian Ediacaran macrofossil assemblages. Here we describe the Mistaken Point trace-fossil assemblage in full, discuss its stratigraphic context within the Mistaken Point Formation, and explore the competing hypotheses for the formation of the traces. We find that the trace fossils, preserved within a turbidite succession in a deep-marine depositional environment, are not attributable to abiogenic structures, to Ediacaran tubular or filamentous body fossils, to rangeomorph stems, or to a host of late Ediacaran and early Phanerozoic ichnofossils. Specimens within the assemblage show some similarities to the ichnogenera Helminthoidichnites and Archaeonassa, but discrepancies in certain aspects of their structure mean that we do not formally attribute them to these ichnotaxa at this time. The Mistaken Point ichnofossils possess morphological characteristics indicative of formation by an organism with a round base. Comparison with traces formed by modern organisms of such character appears to rule out formation by protistan, echinoderm, or annelid styles of movement, but is consistent with organisms moving via muscular controlled locomotion in a similar way to some modern mollusks and actinian cnidarians. We suggest therefore that the Mistaken Point trace-fossil assemblage reveals the presence of muscular metazoans in late Ediacaran deep-marine ecosystems. Such organisms cannot yet be attributed to specific phyla, but their inferred locomotory mechanisms share closest similarities with those utilized by extant actinians.
Eurypterids are generally rare in the fossil record, but occasionally occur in abundance. The genus Eurypterus, in particular, is well known from certain upper Silurian Lagerstätten of the northern Appalachian basin (New York and Ontario), but occurs far less frequently in the central and southern Appalachian basin (Pennsylvania, Maryland, and West Virginia, respectively). The recent discovery of an exceptionally preserved mass assemblage of Eurypterus in the upper Tonoloway Formation (upper Ludlow–Přídolí) of Pennsylvania provides new information on the behavior and life habitat of the genus in this region. Eurypterids at this locality are found in thinly laminated, calcareous shale deposited within the lower intertidal to shallow subtidal zone of a coastal mudflat or sabkha. Rare associated fauna of limited diversity, and evaporitic and desiccation features in associated beds, suggest a stressed environment with variable salinity and possible hypoxic conditions. Most eurypterids are disarticulated and fragmentary, but several fully articulated, exceptionally preserved specimens are present. Exoskeletal features and taphonomic indices values indicate a molt rather than death assemblage, and the presence of arthropod trackways suggests that Eurypterus sp. may have molted en masse in the vicinity of the burial site. Sequence stratigraphic interpretation of the site suggests that preservation of eurypterid remains is the result of occupation of ephemeral environmental (salinity/oxygen) conditions during a transgression. The occurrence of this new Lagerstätte within the upper Silurian succession of the central Appalachians, an interval which had heretofore yielded only rare, fragmentary remains, indicates that eurypterids were more prevalent in this region than previously thought.