Which term describes thin, dry, or oily plates of epidermal flakes?

The term that describes thin, dry, or oily plates of epidermal flakes is "Scale." Scales are formed when there is an abnormal shedding or different appearance of skin cells, often as a result of conditions like psoriasis or eczema. They can vary in thickness and texture, and can be dry, oily, or even a combination of both, depending on the underlying skin condition.

The other terms do not accurately represent the description given. "Wheal" refers to a raised, itchy area of skin that is typically a sign of an allergic reaction. A "Fissure" describes a deep crack or split in the skin, often caused by dryness or a skin condition but does not denote flaking. An "Ulcer" is a sore that forms on the skin or mucous membranes, which involves tissue loss and is often associated with more severe conditions, rather than just simply flaky skin. Therefore, "Scale" is the most appropriate term in this context.