Genjar said:
If I remember right, the anus_only tag was made for that. But the current wiki description doesn't match that usage, so it's bit of a mess.. Half of the posts are tagged by the original usage, and the other half by the wiki.

*blinks*

Well. I should have looked to see if that tag existed before I mentioned it.

That said, looking at the tags posted with anus_only, I see 3 things:

1 - "I don't have genitals, only an anus"
(see above)

2 - "Through camera angles, nothing but my anus is visible"
post #1555532 post #1554003 post #1554455

3 - "My other genitals are covered in some fashion and the attention is mostly on my anus." ... This one is split into two categories:

3a - the 'clothing aside' method: post #1530670 post #1534785 post #1457285

3b - And the pussy_tape method: post #1562384

Generally speaking, I see the following tags here

1. No genitals, only an anus - Aka, the topic of these posts genital-less? anus_only? no_genitals_only_anus?
2. Only_anus_exposed?
3a. ...some combination of Presenting_anus + something else?
3b. Pussy_tape

I dunno. I has a tired.

Edit: I remembered one more circumstance for anus only, involving various forms of castration, neutering and other horrifying things.