The δ¹³C of fossil leaf cuticle is frequently used for paleoenvironment interpretation. A tacit assumption that is common in such studies is that the δ¹³C of the cuticle is the same as the δ¹³C of the original whole leaf. We tested this assumption by measuring the isotopic fractionation between cuticle and whole leaves (ϵ¹³C_cuticle-leaf) in 175 phylogenetically diverse species. The average ϵ¹³C_cuticle-leaf is indistinguishable from zero (-0.04 ±1.2‰ 1σ), in keeping with the few previously published data and with studies that have tracked the evolution of leaf δ¹³C during decomposition. Across species, ϵ¹³C_cuticle-leaf spans over 9‰: this variability does not covary with growth habit (woody vs. herbaceous) or climate, but does contain a strong phylogenetic signal. In particular, more basal groups (lycopsids and some gymnosperms, basal ferns, and basal angiosperms) tend to have negative ϵ¹³C_cuticle-leaf values. This variability should be accounted for in studies that wish to estimate whole-leaf δ¹³C from cuticle δ¹³C.

We use experimental taphonomy of embryos and larvae to determine the mechanisms by which endogenous bacteria stabilize rather than destroy soft tissues. Here, we show that bacteria can rapidly move from one dead organism to another through the surrounding medium—donor and recipient tissue need not be touching. In most cases tissue destruction results, but in some cases the bacteria generate stabilizing biofilms on recipient tissue that preserve its shape. We isolated, cultured, and identified phylogenetically diverse bacterial strains from the endogenous microbiotas of brine shrimp larvae (Artemia sinica) and sea urchin embryos (Heliocidaris erythrogramma) that had been killed anaerobically and then incubated aerobically to allow proliferation of endogenous bacteria in the dead tissue. We found that one Artemia-derived isolate, Marinobacter sp., is a potent generator of stabilizing biofilms and that other isolates can participate in biofilm formation or cause destruction. These results show the relative frequency of stabilizing bacteria in the endogenous microbiotas of newly dead organisms. Their ease of transmission reveals the potential for generation of a shared microbiology among groups of dead organisms, a possible contributor to uniform preservation in fossil assemblages such as Neoproterozoic and Cambrian fossil embryos.

A cold seep is an extreme environment characterized by a specialized group of organisms generally referred to as “chemosynthetic communities”. Until recently, echinoderms were thought to be rare in cold seep environments and had not been treated as a member of chemosynthetic communities, which otherwise are composed of a variety of taxa. One fossil echinoderm assemblage associated with a cold seep comes from the middle Campanian Pierre Shale Formation of the U.S. Western Interior Seaway. In this study, the taxonomy, morphology, and paleoecology of fossil echinoderms (crinoids and echinoids) from the Pierre Shale are discussed. Elemental chemical analyses of the fossil echinoderm skeletons and stable carbon isotopes were used to clarify the influence of seep hydrocarbons chemistry on the formation and diagenesis of echinoderm skeletons. We show that the crinoids Lakotacrinus brezinai from seep carbonates developed highly specialized morphologies and skeletons with low δ¹³C values, suggesting that it was adapted to cold seep environments and might be an obligate member of the chemosynthetic community. The echinoids from the Western Interior Seaway seep carbonates have morphologies and skeletal δ¹³C values not significantly different from those from non-seep environments, suggesting that the echinoids were not obligate members of the chemosynthetic community, but opportunists living in the periphery of the cold seep habitat.

Fourteen types of symbiotic associations have been recognized in the Cambrian. Cambrian symbiotic associations are dominated by suspension feeding sessile benthic animals with brachiopods being the most important group. The major difference between Cambrian and Ordovician–Silurian symbiotic associations is the small number of colonial organisms among host taxa of Cambrian symbionts. Endobionts that are common in the Ordovician and Silurian are almost absent in Cambrian symbiotic associations. Most of the symbiotic associations in the Cambrian are restricted to a single paleocontinent with the highest number reported from tropical Laurentia.

This study tests the presence of differential preservation in the Devonian Malvinokaffric fauna from the Chapada Group (Paraná Basin, Brazil). Results of EDXRF, EDS, Raman Spectroscopy, and petrographic analyses show differential preservation of shells that were originally calcite as hematite and goethite fossils, while organisms with original calcium phosphate shells tend to be preserved inside phosphatic concretions. Both preservation types are commonly associated with pseudoframboids, while calcium sulfate minerals are commonly associated with hematized fossils. From this evidence, a diagenetic model for these fossils is proposed. The model includes an early diagenetic phase (characterized by anaerobic sulfate reduction and precipitation of pyrite and carbonate-fluorapatite) and a second, near-surface chemical weathering phase (characterized by the oxidation of pyrite and precipitation of iron oxyhydroxides and calcium sulfates). Acidic conditions in both phases may account for the dissolution of less stable minerals compared to calcium phosphate. It is considered that this model may assist in understanding other similarly preserved biotas, as well as enhancing understanding of the taphonomic overprint that may occur within this important and endemic Devonian biota.

Mean seasonal extreme temperatures on the seafloor calculated from the shell δ¹⁸O of the scallop Placopecten clintonius from the basal part of the early Pliocene Sunken Meadow Member (Yorktown Formation) in Virginia are very similar to those from the same horizon at the latitude of Cape Hatteras in North Carolina (∼ 210 km to the south). The lowest and highest temperatures calculated from each shell (using δ¹⁸O_seawater = 0.7‰) give mean values for winter and summer of 8.4 ± 1.1 °C (± 1σ) and 18.2 ± 0.6 °C in Virginia, and 8.6 ± 0.4 °C and 16.5 ± 1.1 °C in North Carolina (respective median temperatures: 13.3 °C and 12.6 °C). Patterns of ontogenetic variation in δ¹⁸O, δ¹³C and microgrowth increment size indicate summer water-column stratification in both areas, with summer surface temperatures perhaps 6 °C higher than on the seafloor. The low winter paleotemperatures in both areas are most simply explained by the greater southward penetration of cool northern waters in the absence of a feature equivalent to Cape Hatteras. The same current configuration but a warmer general climate can account for the high benthic seasonal range (over 15.0 °C in some cases) but warmer median temperatures (15.7–21.3 °C) derived from existing δ¹⁸O data from scallops of the higher Yorktown Formation (using δ¹⁸O_seawater = 0.7‰ for the upper Sunken Meadow Member and δ¹⁸O_seawater = 1.1‰ for the mid-Pliocene Rushmere, Morgarts Beach, and Moore House members). Existing δ¹⁸O data from the infaunal bivalve Mercenaria of the Rushmere Member yields a similarly high median temperature (21.6 °C) but a low seasonal range (9.2 °C), pointing to the periodic influence of warm currents, possibly at times when the Gulf Stream was exceptionally vigorous.