View article

New crystalline structures have been observed in argon ion‐milled conodont elements from a diverse suite of Ordovician taxa (‘Cordylodus robustus’, Drepanoistodus suberectus, Panderodus gracilis, Plectodina? sp., Aphelognathus sp., Periodon aculeatus), using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate porosity, although a distinctly lamellar structure has also been observed within a large albid crystal positioned between hyaline lamellar and cancellate albid tissues. There is a distinct absence of ‘interlamellar space’ within all hyaline tissues examined, which are characterized by a polycrystalline matrix of micron‐scale elongate crystals that are both strongly aligned and tightly bound within a broader lamellar structure. Optical …