A character with animal genitalia, or an animal anus, that matches the character's species. The genitalia does not have to be naturally proportionate, or naturally colored to be anatomically correct. Anatomically correct:

A feral dog with a canine penis.
An anthro horse with either, or both, an equine penis or an equine pussy.
A hyena with a rainbow-colored pseudo-penis.
A fox with a canine penis which happens to be 3 times the length of its own body.
A rockruff with a canine penis.

Not anatomically correct:

A mouse with a canine penis.
    Wrong species.
Tentacles on a squid or udders on a cow.
    Doesn't involve genitalia.
A human or humanoid with a humanoid_penis (or animal genitalia for that matter).
    Humans and humanoids don't count for tagging purposes.
The majority of alien, monster, demon, pokémon, hippogriff, gryphon, draconequus, dragon, and other hybrid or bizarre (non-real) species.
    It can't be anatomically_correct if you cannot define which genitalia is even supposed to be correct in the first place.
    Fictional species that greatly resemble a real-life species such that they can be tagged as a member of that species, however, can be anatomically correct (e.g. Houndoom, which can be tagged as canine).