From my point of view this observation has several points of interest. The first one is that it puts the usual question, at least for me, about what species to consider for the classification of the specimen: Lecanora gangaleoides or Tephromela atra? The second point of interest and that can help to solve the initial question is that it displays a well known parasitic relation between Lecanora gangaleoides and a Diploschistes sp._: According to Alan Silverside in lastgragoncaesioplumbeus.html, D. caesioplumbeus "Initially a parasite on Lecanora gangaleoides, invading and killing the host and taking over the algae, then extending as a thick, cracked, smooth to slightly lustrous, pale to lead-grey crust; apothecia sunken in the thallus, opening via minute pores in the thallus surface" (see, at the top of the photos, the lichen incrusted at several places in the thallus of the subject of this observation). Finally, in the second photo attached one can see, on the left hand side, another Lecanora with completely different looking: Lecanora rupicola (I think), which is not so common here, seeming to be also parasitised. Unfortunately, all this I only realized when doing the home work concerning this observation and so I only collected a sample of the protagonist.