Psoroma spinuliferum (Pannariaceae), a new corticolous lichen species from Alaska with two different types of cephalodia

Abstract. The species Psoroma spinuliferum is described here as new to science. It is only known from the holotype on a Picea sitchensis trunk near a sea-shore in southern, coastal Alaska. The species is distinct in having short, brittle, spinule-like hairs on both apothecium margins, thalline squamules and on pulvinate to coarsely coralloid cephalodia with emerald-colored Nostoc photobionts. These spinules are unique within Pannariaceae as they are developed on both the chlorobiont and on one of two cyanobionts, but it is uncertain whether they can act as vegetative propagules. The presence of two types of cephalodia is also unique within Pannariaceae. The second type consists of glabrous, small-foliose, geotropically arranged cephalodia, containing a Nostoc strain with cells of an intense ultramarine color, when observed after long storage. The species also has shorter ascospores than Psoroma paleaceum, another hairy species. The hair types of Psoroma hypnorum and P. paleaceum are here by contrast refer...