Placomaronea candelarioides

Placomaronea candelarioides is a species of saxicolous (rock-dwelling), foliose lichen in the family Candelariaceae. It is found in South America. This lichen species can be recognised by its distinct (single attachment point),  (single ) growth form.

Taxonomy
Placomaronea candelarioides was formally described as a new species in 1944 by Finnish lichenologist Veli Räsänen. It is the type species of the genus Placomaronea, which was circumscribed by Räsänen to contain this species. The type specimen of P. candelarioides was found in Mendoza, Argentina. A variety of this lichen, Placomaronea candelarioides var. lacinulata, was proposed by Rolf Santesson in 1944.

Description
Placomaronea candelarioides has a leaf-like (foliose) structure, uniquely anchored by a single point, a trait referred to as and. Though most specimens adhere to this typical appearance, some have shown variations, such as having numerous individual, little branched, and ascending lobes that attach to the at the base. The lichen's overall shape is circular and can span up to 20 mm across. It has extensions or that radiate from its centre, each measuring between 0.4 and 1.7 mm in width and potentially growing up to 7 mm in length. These lobes sometimes have smaller offshoots or and can occasionally take on a round shape, layering over each other and forming cushion-like clusters. The colour of the lichen's upper surface ranges from dark yellow to brownish-yellow, presenting a smooth, shiny, and unpigmented appearance. The lichen's underside can display colours from white to grey or even brown, influenced by the dust it accumulates.

Prominently, the lichen's apothecia appear as darker yellow spots that often densely populate the central regions of the lichen. They sit raised on the surface, measure between 0.5 and 1.6 mm in diameter, and sometimes have a slightly jagged or edge. Internally, the lichen comprises several layers. Just beneath the surface, there is a cortex layer about 15–35 μm thick. Below this, a white layer of medulla. The base of the lichen has another layer, which is similar in structure but slightly thicker, ranging between 25 and 45 μm.

Each ascus holds over 30. These spores are narrowly oval in shape, measuring between 8–12.5 μm in length and 3–4 μm in width. Another distinguishing feature is the presence of, which appear as darker yellow dimples on the lichen's surface.

In chemical spot tests, the lichen reacts weakly red when a solution of potassium hydroxide (K) is applied, a feature helpful for its identification.

Habitat and distribution
Placomaronea candelarioides thrives on acidic rocks within open montane environments. It has been identified in numerous locations along the Andes, extending from Mendoza, Argentina in the south, up to Ancash, Peru in the north.