[1][2] The genus is known only from the holotype specimen, a single fruit body (mushroom) currently residing in the private collection owned by Ettore Morone of Turin, Italy.

The specific epithet electra was coined by the authors from the Latin or Greek word for "amber", in reference to the mode of preservation.

[1][2] With the 2007 publication of a fifth extinct agaric species, Palaeoagaracites antiquus, the minimum age for the order Agaricales was pushed back to the Albian (approximately 100 Ma).

[5] The holotype of Protomycena is a single fruit body without any associated structures, preserved in a piece of clear light yellow polished amber approximately 4.5–2.5 cm (1.77–0.98 in) wide.

The pale flesh appears yellowish in the amber, and is smooth and glossy, changing to striate and slightly translucent towards the margin.

Protomycena is distinct from other amber-preserved mushroom taxa such as Coprinites, in the grooved surface of its pileus and its anastomosing gills.