I've re-added the dinosuar tag back. While the Dimetrodon may not be a formal dinosuar, I think the point of the tag is to cover any large prehistoric reptiles (ie the informal/loose definition).
I'd probably also favor leaving the dinosaur tag on this one. I added the Dimetrodon tag, and theropsid is correct so it should stay, but honesty no one is ever going to search for either. And even if it's not technically correct, this pic is one someone searching for dinosaur would want to find. Danbooru isn't always scientifically sound, nor does it need to be.
The girl who leapt through time... Encountered a gravity wave that sent her back farther than she ever expected. I'm sure the Dimetrodon is enjoying the view up her skirt.
That was really poor of you Rider to remove the dinosaur tag months later like that. Seriously you don't need to be so anal retentive on the definition.
RiderFan said: The dinosaur tag just doesn't belong in this picture. It's like tagging Black Rock Shooter as Vocaloid.
Then you fail at understanding the purpose of tags and should stop tagging images. The dinosuar tag is not specifically only for scientifically defined "dinosaurs" its also covers "any of various large extinct reptiles other than the true dinosaurs." As far as visual information of this image goes, we can follow the obsolete "mammal-like reptiles" description for theropsid, and thus can slap on the dinosuar tag.
I'm just going to keep adding the tag back, so you might as well stop removing it.