Regurgitalites (fossilized regurgitates) can provide insight into the behavioral ecology and physiology of extinct species but they are rarely reported because they are difficult to identify and distinguish from coprolites. A compact mass of skeletal material from the Owl Rock Member of the Upper Triassic Chinle Formation of Arizona reveals features that identify it as a regurgitalite. Characteristics of the teeth and osteoderms in the specimen indicate that these remains belong to the pseudosuchian archosaur Revueltosaurus. Chemical and microstructural analysis revealed a dearth of gastric etching, the preservation of muscle fibers, and the absence of a phosphatic matrix, indicating that this bone mass is a regurgitalite and not a coprolite. It was probably produced by a phytosaur, rauisuchid, or temnospondyl, all of which occur in the Owl Rock Member. We offer an identification key to assist in distinguishing between different types of digestive remains produced by vertebrate carnivores.

During the late Permian, an alluvial environment prevailed along the northern margin of the North China Plate in the Xingcheng area, Liaoning Province, China. In this region, the middle–late Permian Shihhotse Formation and the late Permian Hamashan Formation record this transition from previous swamp-dominated settings. The two formations are mainly coarse-grained deposits and can be correlated with the Pingdingshan Sandstone, which developed as widespread alluvial facies in the central and southern parts of the North China Plate. Tectonic uplift around the plate due to Variscan orogenic activities probably contributed to the onset of alluvial prevalence, but the sedimentary characteristics in the Xingcheng area indicate that aridification was also an important driver. This is supported by the presence of root systems composed of rhizoliths in the Shihhotse Formation and Stigmaria fossils at the top of the alluvial conglomerate of the Hamashan Formation. Viewed at a larger scale, this basin-wide alluvial episode on the North China Plate was contemporaneous with the Wuchiapingian extreme aridity and followed a short humid interval. The overlying Changhsingian–Induan redbeds mark a paleoclimatic change to semiarid and arid again. The paleoenvironmental changes recorded in the upper Permian and Lower Triassic strata of the North China Plate, therefore, provide essential information for the understanding of late Paleozoic terrestrial evolution.

Previous studies have yielded mixed results as to whether authigenic mineral infill in fossilized bone tracks specific lithologies or depositional environments, with most suggesting weak to no correlation between infill composition and host lithofacies. This study documents infill patterns in a suite of fossil bones from the Upper Cretaceous Two Medicine and Judith River formations of Montana. The composition and distribution of void-filling materials, including authigenic mineral precipitates (e.g., calcite, chlorite, iron oxides/hydroxides, sulfides, and sulfates) and sedimentary detritus, were identified (petrography and SEM-EDS), imaged (photomicrographs, BSE maps), and quantified on false color maps using ImageJ. The authigenic cement content of fossil bone is distinct at the formation scale, with Two Medicine specimens characterized by pervasive calcite infill (non-ferroan followed by ferroan phase) and local chlorite infill. In contrast, Judith River specimens are characterized by abundant unfilled primary void space, with iron oxides and sulfides, along with rare sulfates, present in all bones, albeit in low abundance. Calcite infills are rare, chlorite is absent, and detrital infill is more abundant in Judith River specimens, presumably reflecting the rapid and more complete permineralization of Two Medicine bones. The sequencing of mineral cements in voids is generally consistent within formations, but is more complex in Two Medicine specimens. Authigenic cement content does not serve to effectively distinguish among facies or localities in either formation. This study compliments previous work on rare earth element (REE) content in the same general suite of fossil bones. In the previous study, patterns in REE uptake also served to readily distinguish fossils at the formation scale, and proved more effective than authigenic cements at differentiating fossils recovered from different facies.

Cold methane seeps were common in the Late Cretaceous Western Interior Seaway of North America. They provided a habitat for a diverse array of fauna including ammonites. Recent research has demonstrated that ammonites lived at these sites. However, it is still unknown if they hatched at the seeps or only arrived there later in ontogeny. To answer this question, we documented the abundance and size distribution of small specimens of Baculites and Hoploscaphites at eight seep sites in the Pierre Shale of South Dakota. The specimens of Hoploscaphites range from 0.8 to 8.1 mm in shell diameter, with most of them falling between 1 and 1.5 mm. The specimens of Baculites range from 0.7 to 19.2 mm in length, with most specimens falling between 6 and 8 mm. The small size and morphology of these specimens indicate that they are neanoconchs, that is, newly hatched individuals that lived for a short time after hatching. We also analyzed the isotope composition (δ¹³C and δ¹⁸O) of 12 small specimens of Baculites and one specimen of Hoploscaphites with excellent shell preservation from one seep deposit. The values of δ¹³C and δ¹⁸O range from -16.3 to -2.5‰ and -3.0 to -0.9‰, respectively. The values of δ ¹⁸O translate into temperatures of 19–28°C, which are comparable to previous estimates of the temperatures of the Western Interior Seaway. The low values of δ¹³C suggest that the tiny animals incorporated carbon derived from anaerobic oxidation of ¹²C-enriched methane into their shells. Evidently, they must have lived in close proximity to seep fluids emerging at the sediment-water interface and the associated microbial food web. However, this may have contributed to their demise if they were exposed to elevated concentrations of H₂S derived from the anaerobic oxidation of methane.