Fig. 7

Preservation of Helenodora inopinata (FMNH PE29049, part). a Specimen photographed wet under cross-polarised light, with locations of element maps highlighted. Scale bar = 10 mm (b, c) Back-scattered electron micrographs with selected element maps generated using EDX analysis and false coloured for comparative purposes. b Limb, triangular structure in the top and left of the image, is richer in aluminium and silica but poorer in iron than the surrounding nodule, suggesting replacement by clay minerals, concentrated at the tip of the limb. sed = sediment. fos = fossil. c Boundary between annulated central region and remainder of fossil. Annulated region is on the bottom left of the field of view, and is richer in iron and poorer in aluminium and silica compared to the remainder of the fossil; the bulk composition is indistinguishable from the siderite nodule with the addition of patchy framboidal pyrite. ann = annulated region. fos = remainder of fossil. Scale bar = 1 mm