Soils contain complex ecosystems with a diverse micro- and macrofauna including arthropod predators. Our knowledge of arthropod predators in ancient soil ecosystems, however, is limited. This project involved the laboratory study of Mastigoproctus giganteus, or giant whip scorpion, to describe its burrowing behaviors and resulting burrow morphologies to aid the recognition of their burrows in the fossil record. Specimens were placed in sediment-filled terrariums for 14–60 days. Experiments were run with variations in sediment density and moisture to evaluate the effects of environmental conditions. The burrows were cast, described qualitatively and quantitatively, and then compared to each other and to scorpion burrows using nonparametric statistical methods. Six different burrow architectures were produced by the whip scorpions including vertical shafts, subvertical ramps, J-, U-, and Y-shaped burrows, and mazeworks. Despite these different architectures, the whip scorpion burrows possessed statistically similar properties that allowed them to be distinguished from burrows produced by scorpions. Sediment density and moisture had little influence on burrow properties but did affect the diversity of architectures produced. The greatest diversity of burrow architectures occurred in low-density sediment with moderate moisture levels. Results from this study show that whip scorpions produce unique biogenic structures possessing architectural and surficial properties that can be used to distinguish them from the burrows of other soil organisms. Data collected from these and similar experiments can be applied to ichnofossil assemblages found in middle Paleozoic to Pleistocene paleosols in order to better interpret the paleobiology and paleoecology of ancient soil ecosystems.

We characterize forest floor leaf litter and transported leaf samples from several depositional environments in both a temperate and a tropical forest to provide well-characterized modern analogs for the evaluation of fossil leaf localities. We compare the low-diversity, deciduous, temperate Wharton Brook forest (Connecticut, United States) with the high-diversity, evergreen, tropical Noah Creek Rainforest (Queensland, Australia) by mapping one half-hectare of each forest, collecting 25–29 leaf litter samples from four to five depositional settings in each forest and analyzing the relative abundance of species based on >31,750 leaves. In both studies, we analyze the samples as if they were fossil sites, evaluating floral composition, numerical diversity measures, rarefied richness, and climate estimates based on leaf physiognomy. We compare this analysis with data from the standing mapped forest to evaluate the biases inherent in the data derived from fossil assemblages from different depositional settings. In both forests, sample sites that were revisited over multiple years produced different species on subsequent visits, suggesting that fossil sites with close stratigraphic spacing and different composition may actually represent the same source forest. In both forests, species diversity in laterally transported samples appears to increase as the distance of transport increases. Because the species richness of a leaf sample is impacted by the diversity of the original forest, the amount of time the leaf sample spent accumulating, and the effect of transport distance, it is not possible to interpret the diversity of ancient forests without also evaluating the sedimentary facies of the fossil collections.

Microdigitate stromatolites (MDS) are common in Neoarchean–Paleoproterozoic successions but declined and gradually disappeared in Meso- and Neoproterozoic carbonates. The abundance of well-preserved fibrous fabrics and the absence of identifiable microbial fossils in MDS have been taken as evidence of their abiotic origin in carbonate-supersaturated and anoxic Precambrian oceans. Micron- and nanometer-scale features of MDS from the Mesoproterozoic Wumishan Formation (ca. 1.45–1.5 Ga) of the North China platform composed of alternating submillimetric dark and light laminasets are morphologically similar to those reported from elsewhere in the geological record. The dark laminasets are micritic and contain abundant fuzzy-edged micropeloids and filaments. The micropeloids are commonly 10–70 µm in diameter and commonly surrounded by thin (<10 µm) rims composed of amorphous micrite or microsparite (some rims now replaced by silica). The filaments are morphologically similar to the bacterial filaments in modern microbialites and contain kerogenous components as indicated by Raman spectrometry analysis. All the laminasets are characterized by fibrous fabrics that are expressed by alternating brown fibers (<10–25 µm) and light microsparitic strips of approximately equal width in transverse direction. Filaments, relics of putative extracellular polymeric substances (EPS), micropeloids, and nanoglobules are closely associated with the brown fibers. These organomineralization-related features suggest a biogenic origin for the MDS of the Wumishan Formation and may have an implication to other MDS from the Neoarchean–Paleoproterozoic successions. Microbially induced micro- and ultrastructures including fibrous fabrics, filaments, micropeloids, and nanoglobules are best preserved in silicified MDS samples, implying that early silicification is critical for the preservation and recognition of organominerals.

Stable isotope analyses (δ¹⁸O_PO4, δ¹⁸O_CO3, and δ¹³C) are reported for the first time on crocodilian, theropod, and sauropod teeth from two stratigraphic levels (G1 and G2) from the late Campanian–early Maastrichtian “Lo Hueco” fossil site (Cuenca, Spain) in order to better understand paleoclimatic and paleoenvironmental conditions existing in the Iberian Peninsula during the Late Cretaceous. Diagenetic alteration was evaluated using three tests: (1) consistent differences in enamel and dentine δ¹⁸O_PO4 values, (2) crocodilian δ¹⁸O_PO4 values consistently lower than dinosaur δ¹⁸O_PO4 values in agreement with the proposed latitudinal distribution between ectotherms and endotherms, and (3) a Δδ¹⁸O_CO3-PO4 value of 9.1 ± 1.7‰ for dinosaurs in accordance with the expected equilibrium fractionation between carbonate and phosphate in unaltered modern mammalian bioapatite. Calculated δ¹⁸O_H2O values are slightly higher in crocodilians compared to dinosaurs since semiaquatic ectothermic taxa δ¹⁸O_H2O represents local meteoric waters in a brief window of time when the conditions are favorable for apatite synthesis, whereas terrestrial endothermic taxa δ¹⁸O_H2O records ingested water year-round. Mean air temperature calculated using crocodilian and dinosaur δ¹⁸O_H2O values shows an increase between G1 and G2, which may be related to differences in the sedimentological setting and/or to a shift toward warmer conditions over time. Finally, the sauropod mean δ¹³C value (−11.1 ± 0.2‰, VPDB) is in the predicted range for C₃ vegetation.