Fig. 3: Microscopic mineralogy in ichthyosaur vertebra.
a Thin section map of 25 mm cored vertebra sample Vert-E under plain polarized light (PPL). The thin section was sliced through the transverse plane of the vertebra. b Map a under cross polarized light (XPL). A mineral boundary (blue dashed line) between calcite infilling peripheral cavities and barite filling the interior cavities. Scale bar for a, b 10 mm. c, Micrograph of spongy bone trabeculae and marrow cavities under PPL. d Same view of c under XPL. e Inset of c. Tb = trabeculae, MC = marrow cavities, Lm = lamellae (black dashed lines), Os = osteocytes (dark spots). f Inset of d with identified minerals. Barite = BaSO4, calcite = CaCO3, fluorapatite = Ca5(PO3)4F. g Backscatter electron (BSE) micrograph of Vert-B with identified minerals. Voids marked in blue dotted lines were calcite crystals dissolved during acid treatment. h Secondary electron (SE) micrograph of Vert-D. i, BSE view of h. Energy Dispersive X-ray Spectroscopy (EDS) maps of view (h, i), for j barium, k sulfur, l calcium and m phosphorous. j and k indicate barite in marrow cavities, l, m indicate fluorapatite composing trabeculae. Scale bar for c–m 500 μm. Larger thin-section maps are shown in Supplementary Fig. 6a, b.
