In this study we report on the occurrence and potential significance of Atlantic sturgeon (Acipenser oxyrhynchus) feeding traces observed in the Bay of Fundy in great abundance on the intertidal mud flats of Mary's Point, New Brunswick, Canada. The traces comprise a crescent-shaped impression and a plug-shaped excavation and are considered to be a modern analogue for the trace fossil Piscichnus. Local areas exhibit relatively great numbers of the feeding structure: the sediment in these zones contains bivalves (primarily Macoma balthica), worms (generally nereid polychaetes), and amphipods (Corophium volutator). Analysis of the feeding-trace distribution and orientation shows that activity is greatest within 500 m of mean high water and coincides with the highest population densities of amphipods (up to 30,000 individuals per m²). Where sturgeon feeding is most intense, voluminous quantities of clay and silt are redistributed. Within the study area, as much as 1,220 m³ of intertidal sediment is resuspended during the 6 summer weeks that mark peak sturgeon activity. The reworked sediment contributes to the extensive soupy substrate, which accumulates from suspension deposition of silts and minor amounts of clay during slack tide. Subsequent to their excavation, feeding depressions trap sediment. Thus, feeding by the Atlantic sturgeon locally represents an important erosional-depositional agent in the intertidal mud flat zone within Mary's Point.

We interpret 13 large subcircular or horseshoe-shaped depressions discovered in Late Triassic peritidal carbonate rocks of the Dogna Valley in Udine Province, northeastern Italy, to be reptile nests. These trace fossils show truncation of strata, elevated ridges of massive sediment, and sediment infill within the depression differing in shape and sedimentary structures from the host sediment. The palynological assemblage of a shaly interbed close to the nest layer indicates a Tuvalian age (late Carnian). Archosaurian footprints, produced possibly by aetosaurs, are on a surface 130 cm above the nest-bearing layer. The trackmakers are considered the most probable nest makers.

In the Ordovician bryozoan genus, Peronopora, stratigraphic occurrences and cladistic branching order are significantly correlated, indicating sequential development of both patterns in geological time. Five species have stratigraphic first appearances in the exact order predicted by cladistics, but eleven species require downward-range extensions to match cladistic order. Reduced major-axis regression-based corrections and ghost range extensions represent two alternative modifications of first appearance data, with the latter more strongly supported by stratigraphic congruence indices. Tests of the robustness of observed first appearances, based on the density of sampled horizons and magnitudes of stratigraphic gaps, support the probabilistic appearance of descendant species stratigraphically above their putative ancestors in eight of fifteen ancestor-descendant pairs. A 24 m sampling gap occurs below the base of the Brannon Member of the Lexington Limestone, a unit marking the first appearances, or extended ranges, of nine species of Peronopora. A test for the presence of a uniform distribution of occurrence probabilities indicates that seven of the nine species could have originated during the time interval represented by the gap. The early branching rate within Peronopora, during the time span encompassing all first appearances of species, is 1.05 cladogram nodes per meter of strata. The rate of clade production within that interval is 0.73 (baseline) clades per meter of strata. Extrapolating downward using both rates indicates that the median position of the root of the generic clade is approximately 1.08 myr earlier than sampled. The estimated speciation rate in Peronopora is 5.73 species per myr, while the average time between speciation events is 186 kyr. Intraspecific clades, possibly including cryptic species, formed at a rate of 19.35 clades per myr, with an average waiting time per clade of 48.107 kyr. These metrics indicate very short origin times for species within the genus compared to their total stratigraphic ranges, a pattern consistent with punctuated speciation.

In this article the potential paleoecologic boundary conditions are discussed favoring prasinophyte prosperity commonly associated with sediments rich in organic carbon, as exemplified by palynologic case studies from the Northwest European Basin (Lower Jurassic Posidonia shale, Cretaceous Cenomanian-Turonian Boundary Event). Based on the literature of nutrient requirements of modern green algae and the evolution of photic-zone water chemistry throughout earth history, it is suggested that the enhanced availability of reduced nitrogen chemospecies, especially ammonium, in photic-zone waters is the ultimate cause for stimulating prasinophyte productivity. It is also suggested that the erosional suspension of suboxic-to-anoxic pore waters from shelf sediments or the vertical expansion of the redox zones from within sediments or the oceanic oxygen minimum zone are the main mechanisms for introducing reduced nitrogen chemospecies into these waters. Thus, changes in intensity and duration of suboxic-to-anoxic water conditions within the photic zone may be reflected by the corresponding presence and change respectively of significant proportions of prasinophyte phycomata within associated sediments. In addition, with respect to general water mass character, several arguments for a principal cooler water affinity of prasinophytes are suggested: (1) the accumulation of fossil—almost rock-building—prasinophyte deposits in higher paleolatitudes or in close temporal proximity to major global glaciation episodes; (2) the enhanced biochemical stability of ammonium within cooler waters; and (3) the principal modern main distribution of prasinophytes in cool-temperate waters and aquatic ice-covered regions.

The Crystal Geyser Dinosaur Quarry contains a large monospecific accumulation of bones from a basal therizinosaur, Falcarius utahensis. The quarry is located approximately 16 km south of Green River, Utah, at the base of the early Cretaceous (Barremian) Yellow Cat Member of the Cedar Mountain Formation. Fossil bones in the quarry occur in three units that have distinct taphonomic, lithologic, and geochemical characteristics. Rare earth element compositions of fossils suggest that bones from each unit were drawn from different reservoirs or sources having distinctly different compositions, and fossils were not reworked between units. Compositions of bones differ greatly within Units 1 and 2, even within the same 1-m² quarry grid. These chemical differences and taphonomic characteristics, such as current orientation, hydraulic sorting, and occasional extensive abrasion, suggest that bones from these two units are allochthonous and were fossilized at other localities, possibly over an area of several kilometers, and were then eroded, transported, and concentrated in a spring-influenced fluvial environment. Bones in Unit 3 have very similar rare earth element signatures, suggesting that they were probably fossilized in situ at a separate time from bones in Units 1 and 2. At least two mass mortality events were responsible for the monospecific assemblage of bones at the quarry. Because bones may have been concentrated from a wide area, causes of mass mortality must have been regionally extensive, possibly owing to seasonal drought, sudden changes in weather, or disease.

The Crystal Geyser Dinosaur Quarry, near Green River, Utah, is located at the base of the Lower Cretaceous (Barremian) Yellow Cat Member of the Cedar Mountain Formation. The quarry preserves a nearly monospecific accumulation of a new basal therizinosauroid, Falcarius utahensis. We used field descriptions and petrographic analysis to determine the depositional environment and development of the quarry strata. Results of these analyses suggest that the quarry represents multiple episodes of bone accumulation buried by spring and overbank flood deposits. Evidence for these previously undescribed spring deposits includes calcite macroscopic structures within the quarry strata—such as pisolites and travertine fragments—and calcite micromorphologies—including radial-fibrous, feather, and scandulitic dendrite morphologies and tufa clasts. At least two episodes of bone incorporation are preserved in the quarry based on their stratigraphic position and lithologic associations. The unique depositional setting in and around the Crystal Geyser Dinosaur Quarry appears to have been favorable for the preservation of vertebrate fossils and provides insight into early Cretaceous environments in North America.

We report the effects of charring on the ferns Osmunda, Pteridium, and Matteucia with coniferous wood (Sequoia) for comparison. Like charred wood, charred ferns shrink, become black and brittle with a silky sheen, and retain three-dimensional cellular structure. Ferns yield recognizable charcoal (up to 800°C) that could potentially survive in the fossil record enabling reconstruction of ancient fire-prone vegetation containing ferns. Charred fossils of herbaceous ferns would indicate surface fires. Like charred wood, cell-wall layers of charred ferns homogenize, and their reflectance values increase with rising temperature. Charcoalified fragments of thick-walled cells from conifer wood or fern tissues are indistinguishable and so cannot be used to infer the nature of source vegetation. Charred conifer wood and charred fern tissues show a relationship between mean random reflectance and temperature of formation and can be used to determine minimum ancient fire temperatures. Both charred conifer wood and charred fern tissues show some tendency toward increasingly lighter δ¹³C values up to charring temperatures of 600°C, which should be taken into account in analyses of δ¹³C in charcoals. Charred fern tissues consistently have significantly more depleted δ¹³C values (≤4‰) than charred wood. Therefore, if an analysis of δ¹³C through time included fern charcoal among a succession of wood charcoals, any related shifts in δ¹³C could be misinterpreted as atmospheric changes or misused as isotope stratigraphic markers. Thus, charcoals of comparable botanical origin and temperatures of formation should be used in order to avoid misinterpretations of shifts in δ¹³C values.

Quarry walls in Pleistocene marginal-marine coarse-grained deposits adjacent to Willapa Bay, Washington, expose a contact from which unusual sedimentary structures originate. These structures have two distinct occurrences: (1) vertical-to-subvertical columns where laminae and bedding deflect downward, and (2) normally graded beds with symmetric or asymmetric U-shaped structures with flared limbs. The scale, morphology, and distribution of the features suggest these are not physical sedimentary structures. Rather, they are more akin to biogenic sedimentary structures generated by the predatory action of marine animals on deep-burrowing bivalves. Several animals are known to forage sediment: elasmobranch fishes, fish, crabs, sea stars, sea otters, whales, and walruses. In particular, walruses generate distinctive excavations on the sea floor as they root for prey with their snouts and emit a jet of water that liquefies the bottom sediments where a bivalve has burrowed. The trace fossils reported likely represent the first examples of walrus feeding from the geologic record. Documentation in recent years of sea-floor furrows and pits on the Bering Shelf and Chukchi Sea produced by the Pacific Walrus (Odobenus rosmarus Linnaeus) provides modern analogues for the ancient trace fossils described from Willapa Bay. We present three significant implications from this comparison: (1) The method of hydraulic jetting employed by walruses for extraction of their prey leaves a distinctive trace fossil that can be used to identify the presence and activities of foraging walruses. (2) These predation structures are temporally significant in that they provide a minimum time of exposure and corresponding rate of accretion for the ancient estuary inlet. (3) Feeding excavations in paleo-Willapa Bay, Washington, were produced by walrus herds that wandered from the northern Pacific ice front during the Pleistocene after becoming barricaded from their present habitat in the Bering Shelf and Chukchi Sea.

We use isotopic analyses of authigenic siderite and calcite cements within Rosselia socialis burrows from shoreface deposits in the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada, to reveal the early cementation history of the burrow and geochemical conditions of the initial sedimentary environment. Within the Horseshoe Canyon Formation, two forms of the Rosselia burrows are present: bulbous in situ burrows, and transported, spindlelike burrows, which display similar internal shaft diameters but smaller overall size compared to in situ forms. Transverse, incremental sampling of calcite and siderite cements in the Rosselia burrows reveals symmetrical isotopic deviation in δ¹³C and δ¹⁸O around the burrow core, representing accretionary records of evolving pore-water conditions. The number of isotopic deviations recorded in bulbous specimens is equal to those observed in spindle-shaped burrows, suggesting that in situ and transported burrows underwent similar periods of cementation. Cementation, however, was limited during each accretionary event in the spindle-shaped burrows, making them more susceptible to transport by storm waves because of their small size. Early cementation of Rosselia, thus, took place very close to the sediment-water interface at depths where storm waves could rework sediments (i.e., less than 1 m sediment depth). The enriched δ¹³C values for calcite and siderite (3.06-9.45‰ PDB [Peedee belemnite]) suggest that cement precipitation followed bacterially mediated decomposition of the organic matter concentrated within Rosselia in the zone of methanogenesis. Oxygen isotope compositions are enriched also, ranging in siderite from 17.5‰ to 29.4‰ SMOW (standard mean ocean water) and in calcite from 16.8‰ to 23.0‰ SMOW, and are more akin to the composition of subsurface groundwater than marine waters. Freshwater discharging through shoreface sediments explains the δ¹⁸O isotopic signature of calcite and accounts for the early diagenetic precipitation of siderite in shallow marine sediments. In addition, the coexistence of authigenic calcite and siderite cements was most likely controlled by variation in the mixing ratio of meteoric and marine fluids related to variable discharge rates for the freshwater aquifer.

Rare assemblages of woody coprolites from different strata of the Two Medicine Formation provide surprising perspectives on the feeding behavior of Late Cretaceous ornithischian dinosaurs. Most of the irregularly shaped, calcareous specimens are largely composed of fragmented conifer wood (13%–85%) and can be identified as coprolites by the presence of distinctive backfilled dung beetle burrows. The large size (up to 7 L in volume), fibrous contents, and associated bones and eggshell strongly suggest that the source animals at one site were Maiasaura hadrosaurs. The wood-bearing coprolites occur in strata ranging in age from ∼74–80 Ma, revealing a recurring (possibly seasonal) habit of wood ingestion. The preponderance of wood in the specimens and the absence of recognizable small-diameter twig fragments suggest that wood ingestion was intentional—that the coprolite producers had not merely consumed wood inadvertently when feeding on the leaves and bark of terminal branches. Because undegraded wood provides inconsequential nutritive value for vertebrates, it is unlikely that ornithischians would have expended the energy to masticate intact wood for little benefit. Furthermore, patterns of tissue damage in the fecal wood fragments suggest fungal degradation. Thus, the most parsimonious explanation for the high fecal wood content is that the coprolite producers consumed decomposing wood to capitalize on resources released by fungal attack, along with the tissues of the decomposers and associated invertebrate detritivores. These multiple coprolite deposits provide direct fossil evidence of recurring dinosaur diets and suggest that some ornithischians at least occasionally tapped detrital resources. Although such feeding behavior is rare in large extant herbivores, utilization of rotting wood would have augmented the resource options of Cretaceous ecosystems that lacked fodder provided by grasses and other derived angiosperms.

We encountered a highly diverse ichnofauna within the deep-sea fan deposits of the Upper Triassic Al Ayn Formation in Oman. It comprises 32 ichnogenera: 18 ichnogenera represent predepositional graphoglyptids and other trace fossils that are preserved as casts on turbidite soles, and 14 ichnogenera represent postdepositional trace fossils that penetrate turbidite beds. The relatively large size of the area studied certainly favors encountering a high number of ichnogenera. The diversity we found approximately doubles the value that has often been stated in the literature and contradicts the paradigm that the Triassic represents a time of low ichnodiversity in the deep sea. Although the data are limited, in general the recovery of deep-sea tracemakers has been very slow owing to environmental disturbances that resulted from cold-bottom-water circulation after the Carboniferous–Permian glaciation. The high ichnodiversity in the Al Ayn Formation is explained by its paleogeographic position and locally formed warm bottom waters. The Al Ayn deposits accumulated adjacent to wide evaporitic and carbonate shelves, indicating continuous warm conditions. The Al Ayn clastic system was likely influenced by dense, salt-rich, warm water flowing back to the ocean from the carbonate and evaporitic shelf area. The downwelling water may have reduced the effects of cold water that formed during the Late Paleozoic glaciation and the Permian–Triassic anoxia, and, thus, it may have provided a refuge habitat. Despite the global trend of low-diversity deep-sea ichnocoenoses, refuge habitats may have been established in areas less affected by the otherwise harsh conditions.

Wyoming is famous for its deep structural basins containing both abundant vertebrate fossils and uranium-ore deposits in the form of roll fronts. Research conducted in The Breaks, an area of badlands in the northeastern corner of the Hanna Basin, south-central Wyoming, shows that these two disparate phenomena have an important relationship. Vertebrate bones and teeth, composed of bioapatite, are chemically stable under most diagenetic conditions. The chemical changes that occur at the leading edge of a propagating roll front, however, are capable of eliminating these fossils. This happens as pyrite is oxidized, which releases sulfuric acid to the ground water. Sulfuric acid reacts vigorously with apatite, releasing soluble phosphate. Phosphate liberated from the dissolved bones and teeth provides a valuable, often limiting, nutrient to plants or lichens once the roll front is exposed on the ground surface. In The Breaks, bedrock permeability is the most important factor controlling the distribution of roll fronts and, therefore, also of vertebrate fossils. Thus, patterns of roll-front distribution, observed from differing lithologic characteristics or floral assemblages growing on the rock, might provide a useful prospecting tool for paleontologists.