Gotlandicum

Gotlandicum is a term that can refer to several things, most notably a specific geological formation and a variety of the lichen Parmelia sulcata.

In geology, Gotlandicum is a term used to describe rock layers of Gotlandian age. The Gotlandian epoch, also known as the Late Silurian, spanned from approximately 443.8 to 419.2 million years ago. Rocks from this period are found in various parts of the world, with significant deposits on the island of Gotland in Sweden, from which the term derives. These geological formations often contain marine fossils and provide valuable insights into the ancient ecosystems and environmental conditions of that era.

In botany, Gotlandicum is sometimes used to refer to a specific form or variety of the lichen Parmelia sulcata. Parmelia sulcata is a common foliose lichen found globally, characterized by its greyish-green thallus and a network of raised, dark lines (costae) on its surface. While not universally recognized as a distinct taxonomic rank by all lichenologists, "Gotlandicum" might be used locally or in older literature to denote a particular morphotype of this lichen observed on the island of Gotland, potentially differing in growth habit, size, or the prominence of its surface features. Further clarification would be needed to ascertain its current taxonomic standing.