The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China)
Scale bars = 1 mm. Top right and left panels show elemental maps of Fe (yellow), Si (pink), O (green), and Al (cyan) concentrations in the areas indicated by black rectangles in the central photography. All other panels show elemental maps of just Fe concentrations (yellow) in the indicated areas. Note that here and in elemental maps in other figures, some areas where iron concentrations are expected but not evident are in ‘shadow’ due to the orientation of the specimen or because that part of the specimen is outside of the width of detection, so no elemental composition is available (compare the top two panels showing Fe, Si, O, and Al with those just below showing only Fe). See Figs B-G in S1 File for additional elemental maps of different parts of this specimen.