Arthonia radiata

Arthonia radiata produces dark, radiating apothecia—its reproductive structures—that form star-like or branching patterns across the bark surface. These dark markings are embedded in the otherwise inconspicuous crust-like thallus, making the radiating apothecia the most visible feature of the lichen.

This crustose lichen grows on tree bark in woodland habitats, forming a thin layer tightly bound to the substrate that cannot be peeled away. Its bark-dwelling habit makes it common on the trunks and branches of deciduous trees in shaded or semi-shaded forest environments.

The radiating, star-like pattern of its apothecia is the key distinguishing feature of A. radiata compared to other Arthonia species, which may have more linear, irregular, or dot-like fruiting structures. The dark branching reproductive markings on bark set it apart from species with rounded or lirellate (slit-like) apothecia.

While the thallus itself is inconspicuous and blends into the bark, the dark radiating apothecia make A. radiata one of the more recognizable crustose lichens on tree trunks. The star-like or branching patterns created by the reproductive structures are often the first feature noticed when scanning bark surfaces.