What naturally occurring fungus is sometimes referred to as pityrosporum ovale?

The correct answer is Malassezia, which is a genus of fungi that includes several species, one of which is indeed known as Pityrosporum ovale. This particular fungus is commonly found on the skin of humans and can be associated with various skin conditions, such as dandruff and seborrheic dermatitis. Malassezia thrives in oily environments, which is why it's often found on areas of the skin that have more sebaceous (oil) glands.

The other options refer to different types of fungi or fungus-related organisms. Dermatophytes, for example, are a group of fungi that primarily infect keratinized tissues such as skin, hair, and nails, and are not synonymous with Pityrosporum ovale. Aspergillus and Penicillium are genera of fungi that are more often associated with food spoilage and environmental mold rather than skin conditions in humans. Thus, Malassezia is the most accurate choice in this context, primarily due to its direct association with the condition referenced in the question.