[5] The family Phaeomoniellaceae was proposed by Paul Kirk in 2015, using a reference to the description of the order Phaeomoniellales,[6] circumscribed earlier that year.

The exciple, transitioning in colour from pale to dark brown, blends with the involucrellum, but appears colourless and subtle beneath the asci.

[7] The hamathecium (sterile cells and tissue in the hymenium) consists of a network of branched and interconnected paraphysoids, lacking periphyses, and a hymenial gel that does not turn deep blue when stained with iodine.

Asci are typically eight-spored, narrowly elongate-cylindrical, fissitunicate in form and occasionally have a small internal apical rostrum (beak-like structure).

Chemically, an unidentified yellow pigment has been observed on the exciple of Celothelium lutescens when treated with a solution of potassium hydroxide (K).