A list of quantum singularity lifeform individuals.
Female in Romulan form
This was a member of the quantum singularity lifeforms who took the form of a Romulan female. She was initially in sickbay, but later attacked Data in main engineering. She then disappeared. (TNG: "Timescape")
Male in Romulan form
One of these lifeforms assumed the form of a Romulan male. He would attack Geordi La Forge, almost killing him and leaving him with a neural shock. The alien explained later that a nest of their young had been mistakenly placed in the engine of the warbird, causing engine failure. The alien then disappeared. (TNG: "Timescape")
This young quantum singularity lifeform was trapped in the engine core of a Romulan Warbird after it was inadvertently nested there. Two individuals of that species took Romulan form to save their trapped young and return it to their time. (TNG: "Timescape")