Caloplaca arenaria (Granite Firedot)

Caloplaca arenaria

Caloplaca arenaria (Pers.) Müll. Arg.

Caloplaca lamprocheila (DC.) Flagey

Granite Firedot, Sandwort Orange Lichen

Kingdom	Fungi	Mushrooms, lichens, gel fungi, yeasts, and molds; also called eukaryotes
Division	Ascomycota	Sac fungi
Subdivision	Pezizomycotina	Sac fungi with filaments
Class	Lecanoromycetes	“Lichenized” fungi
Order	Lecanorales	Mostly lichen-forming fungi
Suborder	Teloschistineae	Includes Caloplaca, Fulgensia, Teloschistes, Xanthoria, others
Family	Teloschistaceae	Includes Caloplaca, Teleschistes, Xanthoria
Genus	Caloplaca	Colorful rock-growing lichens
Species	arenaria	From the Latin arena, “sand,” referring to the sandy habitats of many species

About plant names...

Granite firedot lichen occurs worldwide.

Identification: This rock-dwelling lichen is so thin that it looks at first like rust on the rock. It appears most commonly on granite, but can appear on other non-calcareous rocks. Its fruiting structures (apothecia) are dark red and very small, less than a millimeter across, wide and flat, like irregular tiles, without the white powdery covering that occurs in some other lichens. This is the only rock-dwelling lichen with such a dark red appearance.

Online References:

Caloplaca arenaria on Stephen Sharnoff Photography

Caloplaca arenaria on the Mushroom Observer

Caloplaca arenaria on CalPhotos

Caloplaca arenaria at Wisconsin Mushrooms

Caloplaca arenaria description by Thomas H. Kent, last updated 12 Oct 2018.

9/6/2018 ID is uncertain