Opeltia

Opeltia is a genus of lichen-forming fungi in the family Teloschistaceae. It has four species of corticolous (bark-dwelling), crustose lichens.

Taxonomy
The genus was circumscribed in 2017 by lichenologists Sergey Kondratyuk and Laszlo Lőkös, with O. neobaltistanica assigned as the type species. The genus name honours lichenologist Josef Poelt, "in recognition of his enormous contribution to lichenology".

Opeltia occupies a distinct monophyletic branch within the Mikhtomia clade, a phylogenetically related group of taxa that also includes the genera Hanstrassia, Laundonia, and Oxneriopsis. This clade is in the subfamily Caloplacoideae of the family Teloschistaceae.

Description
Opeltia shares similarities with Blastenia. However, it can be distinguished by certain key characteristics. The thallus of Opeltia has a crustose form, appearing to  with an abrupt margin. Its colouration varies, typically presenting in shades of whitish, dirty white, and occasional yellowish tones. Opeltia lacks asexual propagules or soredia.

The apothecia of Opeltia are, occasionally manifesting as , biatorine, or. The distinctive feature is the dark reddish-orange to rusty brown colouration of the apothecial. The in Opeltia has a  structure in the basal portion, transitioning into a mesodermatous paraplectenchymatous form with a well-developed matrix. A noteworthy trait is the presence of oil in the hymenium and subhymenium. Reproduction in Opeltia is characterized by eight-spored asci and ascospores that can be quite variable in shape.

Habitat and distribution
Opeltia neobaltistanica, and O. juniperina occur in Eurasia, while O. arizonica occurs in southern North America.

Species

 * Opeltia arizonica
 * Opeltia flavorubescens
 * Opeltia juniperina
 * Opeltia neobaltistanica