The order Mytilinidiales is a group of fungi within the class Dothideomycetes, primarily characterized by their association with decaying plant material or lichens. Members of this order typically produce flask-shaped fruiting bodies called ascomata, where spores develop in sac-like structures called asci. Many species are saprobic, playing an important role in breaking down organic matter, while some may exist as lichenicolous fungi, living on or within lichens. Morphologically, Mytilinidiales fungi are often recognized by their dark, carbonaceous or leathery fruiting bodies and their bitunicate (double-walled) asci, which release spores through a unique splitting mechanism. Overall, this order represents an ecologically significant group involved in nutrient cycling and fungal diversity.