This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. A fauna characterized by members whose typical life sites are on the outer surface of their environment, as opposed to within it, e.g. animals living on top of the sediment at the seafloor.

"This species is found in high densities along with a very rich epifauna, including a high diversity of sponges."

epifaunal