Foxtrot94 said:
Is there any tag for animal genitalia but without a knot

We don't tag the absence of a knot; there's no "knotless" tag (nautilus?). Instead, the automatic response is to tell users to search animal_penis -knot or animal_genitalia -knot if that's indeed what you meant. canine_penis -knot erection returns over 5600 results, but most of those are missing the knot tag. That's certainly a tagging project.

Check the penis, animal_penis, and animal_pussy wikis for lists of the different types we tag.

But your example makes this more interesting.

like this
post #650512

0. thumb #[post's ID] to embed a post's thumbnail. So that post is thumb #650512.

1. Actually, that post was first tagged animal_genitalia in May 2015, which is before animal_penis got its wiki in January 2016 and probably before it existed as a proper tag. In May 2017, someone did tag it canine_penis, which implicated animal_penis, and knot. In October 2017, someone else removed canine_penis and knot but left the implicated animal_penis.

FWIW, canine_penis got its wiki in 2011, animal_genitalia in 2014, and knot in 2007.

2. Now for the good part. If you zoom in that post to 100%, that guilmon's penis has a small swell of what looks like knot. Given the shape of the penis tip, it's reasonable to assume that is, in fact, a knot and the penis is a canine penis. The knot is there, but only about 5% is visible.