This is a proposed name for the porcini that comes up in the Sierra Nevada mountain in the spring. They are pretty clearly distinct from the European Boletus edulis and I believe there is some genetic evidence to that effect. Some have taken to calling them Boletus pinophilus since they are associated with pines. But that is a European species that is very close to the European Boletus edulis. See Fungi of Switzerland Vol. 3 for a photo of B. pinophilus which doesn’t look much like the spring Sierran porcini.

Distinctive characteristics of the B. “rexvernus” are a pinkish tone to the cap, the whitish blush when young, and the tendancy to fruit in small clusters.