Toninia tecta, a non-lichenized obligately lichenicolous fungus, is described new to science. The species is known from several sites in midcontinental North America. Toninia tecta has an endokapylic thallus with dark superficial apothecia restricted to the sheltered undersides of thalli of saxicolous umbilicate species of Dermatocarpon. The new species is characterized by 3-septate ellipsoid ascospores, elongate filiform conidiospores, a reddish brown hypothecium and grey to greenish epithecium that reacts KOH–, HNO₃ violet. Features of the species are compared with those of other lichenicolous taxa in the genus.