I am putting this here simply because there isn't enough room in the "Ask the Asker" box: Could this be a distinction between porphyries and a larger class of porphyrin? It's definition is:

Any of a group of reddish brown to purplish black metal-free usually octa-substituted derivatives of porphin (as protoporphyrin or coproporphyrin) that emit an intense red fluorescence in ultraviolet light and are photosensitizing agents, that are components often in combination with proteins of most respiratory pigments of plants and animals and some enzymes (as cytochrome oxidase, catalase, and peroxidase), that are found in oil, shale, petroleum, asphalts, and coal, and that are obtained especially from chlorophyll or hemoglobin.