Diromma

This species was first described in 1882 by Finnish lichenologist William Nylander as Platygrapha dirinella, from specimens collected in Sardinia, Italy.[4] It was transferred to Schismatomma in 1923 by Alexander Zahlbruckner,[5] and considered a member of that genus for nearly a century. The genus Diromma was circumscribed in 2014 by Anders Tehler and Damien Ernst, following molecular phylogenetic analysis and revision of the Roccellaceae. This analysis showed that the species was a quite distinct lineage in the Roccellaceae. The genus name alludes to both its phylogenetic closeness to Dirina, and its morphological similarity with Schismatomma.[2]

Diromma dirinellum has a crustose thallus with a cortex. Its ascomata, which are immersed (or partly so) in the thallus, measure 0.2–0.6 mm in diameter, and have a more or less circular to irregular outline. Ascospores are hyaline with 3 septa, and measure 20–30.5 by 4.5–5.5 μm; they are not enclosed in a gelatinous sheath. The photobiont partner is trentepholioid – green algae from genus Trentepohlia. The lichen contains roccellic acid, but does not react with any of the standard chemical spot tests (K–, C–, P–).[2]