Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, and they are often preserved in life position within the structure of partially degraded feathers and filaments. Furthermore, the data here provide empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the dark-coloured stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to reddish-brown tones.

Although the evolutionary importance of the Burgess Shale is universally acknowledged, there is disagreement on the mode of preservation of the fossils after burial. Elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens. These differences reflect the compositions of the minerals that replicated the decaying organism, which were controlled by contrasts in tissue chemistry. Delicate morphological details are replicated in the elemental maps, showing that authigenic mineralization was fundamental to preserving these fossils, even though some organic remains are also present.

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The Ediacaran Doushantuo biota has yielded fossils that include the oldest widely accepted record of the animal evolutionary lineage, as well as specimens with alleged bilaterian affinity. However, these systematic interpretations are contingent on the presence of key biological structures that have been reinterpreted by some workers as artefacts of diagenetic mineralization. On the basis of chemistry and crystallographic fabric, we characterize and discriminate phases of mineralization that reflect: (i) replication of original biological structure, and (ii) void-filling diagenetic mineralization. The results indicate that all fossils from the Doushantuo assemblage preserve a complex mélange of mineral phases, even where subcellular anatomy appears to be preserved. The findings allow these phases to be distinguished in more controversial fossils, facilitating a critical re-evaluation of the Doushantuo fossil assemblage and its implications as an archive of Ediacaran animal diversity. We find that putative subcellular structures exhibit fabrics consistent with preservation of original morphology. Cells in later developmental stages are not in original configuration and are therefore uninformative concerning gastrulation. Key structures used to identify Doushantuo bilaterians can be dismissed as late diagenetic artefacts. Therefore, when diagenetic mineralization is considered, there is no convincing evidence for bilaterians in the Doushantuo assemblage.

Electron-beam irradiation causes permanent damage to hydrous, silica-rich glasses. The extent of electron-beam damage is quantiÞ ed using data generated by SIMS analysis of points subjected to previous electron microprobe analysis (EPMA). Even optimum EPMA conditions cause damage to the glass, manifest as a marked depletion in alkali ions at the surface of an irradiated sample. Deeper in the sample, an enrichment in alkali ions to above-baseline levels is followed by a decay back to baseline. The depth of the Þ nal decay correlates with species diffusivity and increases in the order K-Li-Na. H-bearing species are also affected by electron beam irradiation, but in the opposite sense to the alkalis, i.e., they are enriched at the surface. Migration of alkaline earth cations is not observed because of their low diffusivities. Ion depletion or enrichment results from simple migration of ions toward or away from electrons implanted by the beam. Migration depth depends on species diffusivity and heating caused by the electron beam, and therefore increases with increasing electron beam current. Because of the reverse behavior of H, the mobile hydrous species in the presence of an electric Þ eld is probably OH-. The extent of electron beam damage to glasses may increase with total water content. Critically, SIMS measurements of H, Li, Na, D/H, and 6 Li/ 7 Li after electron-probe analysis are compromised by the damage. Despite the damage caused by the electron beam, use of appropriate electron-beam conditions (e.g., 2 nA, 15 kV) gives volatiles by difference accurate to ~0.6 wt%.

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