@Background Pony #52BA
Tagging species to specify demi-creature† body composition: there is no hard rule on this as far as I know, but based on precedent of not tagging constituent species for species like
cockatrice or “human” for
anthro even though anthro is, by definition, a mix of some animal and human—and the fact using species tags for body parts would just mess searches and filters up to the Nth degree—I would advise NOT to use “human” to indicate that a part of a creature is human.
Whether “mermaid” should be reserved only for human-or-eqg + fish is another thing completely, but we already have (multiple) tags for pony + fish, and it would make perfect sense to specify anthro + fish by its own species tag, such as “anthro mer” or “mer anthro”.
† demi-creature: creature with “mix and match” composition combining multiple species, as seen in many Greek mythical beasts such as centaurs (human + horse), griffons (eagle + lion), hippocampi (horse + fish), Wu Zetian (dragon + phoenix) etc.
Overall, I’m planning a wide scope proposal for cases like this, but that won’t happen until June at the earliest.
Before an official decree is given about tagging body constituents, I think the safest way to tag would be to either leave “mermaid” as the only species tag, or use “demi-human”. Latter option has the benefit that if (IF) the rule ends up being “tag demi-human creatures with ‘human’ if the human parts are human”, “demi-human” can simply be aliased into “human”, so tagging work is not going to waste.
Hornless Raven: as far as I know the only case when tagging takes artist intent into account is when a picture could be shipping or not. All other cases, such as this one, would be “tag what is there”. The picture would need to be very specific to qualify a hornless Raven as being Raven. If it was any other design, would you tag “unicorn” if the horn was visibly missing? That should be the yardstick here.