The paper you are looking for is http://artemis.austincollege.edu/acad/bio/sgoldsmith/abpdfs/...

Many placental mammals, including the other great apes, have a baculum, while humans do not. I'm not even sure how to start comparing human genitalia to those of jellyfish or tubular worms, to be honest. The animal kingdom is quite broad.

Probably worthwhile to consider it as familiarity bias -- as claimed by the article, the male researchers missed the vaginal shapes, so it's not just anthropocentricism.

I've heard humans have larger penises in proportion to our size than usual with mammals. Not sure how unique it is but the human glans is speculated to be shaped like it is to scoop out sperm from competing males. Since human vaginas aren't "wild" like that of a goose, maybe that is how we have evolved to handle competition? This must go far back though, way before we became humans...

Well, that’s a disturbing and quite gross image.