Article: Small spheres in fossil bones: blood corpuscles or diagenetic products?

Mineralized spherical structures within blood vessels of an archosaurian (possibly pterosaurian) limb bone from the Lower Cretaceous of the Isle of Purbeck, Dorset, England, superficially resemble blood corpuscles, but are shown here to be pyrite framboids. Slightly weathered pyrite framboids in which the outer surface has oxidized, probably to goethite, may resemble nucleated cells when viewed in thin section. Previous records of so-called blood corpuscles within dinosaur bones may also be of a purely diagenetic origin and should be re-examined.