I start a new set of observations from this locations with one that comes in the sequel of MO79464, since for that observation I only had very bad photos that didn't permit to see the details of the lichen under consideration. I think that these more clear photos show that the genus Cetraria must be ruled out. In fact, it now seems clear to me that a foliose lichen as to be considered. According to a Jason's suggestion in a comment to that observation, I saw a description of the species Leptogium palmatum in CNALH and it fits perfectly to this specimen, except for the existence of apothecia.