Currently, Tail_penis describes a tail that has a penis on the tip. However, the name of the tag implies that it can be anywhere on the tail. The issue is that the tag is aliased to several tags, all of which describe a penis that is a tail (ie, penis_tail (penis_for_a_tail)).

I believe that the Tail_penis tag should be repurposed to mean a penis on any part of the tail. The current aliases should removed, and one chosen to be the new tag that takes the current function of Tail_penis, which will have the current aliases as it's alias's, and will imply Tail_penis.

It should be noted that the other tags that imply tail genitals only specify the genitals are often at the tip.

In other words, (italics represent possible changes)

Currently:
Tail_penis (entire tail is a penis)
- aliased : penis_for_a_tail - related (entire tail is a penis)
(No tag for a penis only being attached to tail, other than unusual placement, and tail_genitals which is up to interpretation)

Proposed: The following imply Tail_penis:
penis_for_a_tail-related (entire tail is a penis)
tail_tip_penis (tip of tail is a penis)
tail_with_penis (tail has a penis attached to it)

One other possibility would to be to also change tail genitals, and have a tail_with_genitals

Tag naming isn't final, the names here are being used like this for clarity.

edit: penis_on_tail -> tail_with_penis
for reference, see post #795243