Fig. 3: Photographs of unstained paraffin sections and SEM images of the demineralized cartilage of STM4-3.

a One example of a 10 µm thick paraffin section of unstained, demineralized cartilage shows a dark brown material overall. b A close-up on this material shows that it is made of numerous globular structures representing fossilized chondrocytes. Some of them are transparent, others are brown. They represent alumino-silicified cells and ironized cells respectively. c Close-up on brown, ironized cartilage cells showing some striations. d Close-up on some ironized cells showing an iron sheath (is) that is peeling off. Other cells are apparently open (oc, open cell) and some show potential intracellular content (picc). e Close-up on transparent silicified cells showing two types of cells (smooth cells, sc; and porous cells, pc). f SEM image of a slide of demineralized cartilage sprayed with gold. g SEM image of two smooth silicified cells paired with an EDS analysis at the pink cross. h SEM-EDS image of a porous silicified cell. i SEM-EDS image of a striated ironized cell. Additional abbreviations: cd, cell doublet; gbicc, group of brown ironized cartilage cells; gtscc, group of transparent silicified cartilage cells; tscc, transparent silicified cartilage cell.