Silicified Cambrian agnostid trilobites from IranStaff: L.E.M. McCobb
Agnostids are some of the most widespread of all Cambrian trilobites, and many, down to species level, have a global distribution. They are thus valuable as zonal indexes, and for correlation between successions on different palaeocontinents and terranes. The silicified specimens were found in the residues of samples initially dissolved in acid for the extraction of brachiopods. Morphological features are preserved in minute detail, and the study of this material will lead potentially to a far greater knowledge of the character sets of the species concerned.