My Question: "What's a spider agave? Or a tykva? Or a bird agave? Or a rossette plant?"
Your Answer: "These are all....PLANTS. so what?"
Um, no, they are not. They are imaginary creatures exhibiting the traits of both plants and animals, invented (not by me) for an imaginary planet. They are fascinating because they play directly off of observed niche adaptations that make your favorite catch phrase more likely to be "a fish is a mammal is a bird."
Not unlike, say, a walking catfish or a porpoise or a penquin.
Indeed, what we can imagine is often less unlikely than what we observe. Morphology can be very deceptive. You say that "a wooly mammoth is still recognizable as a type of elephant." What's a manatee recognizable as? Or a hyena?
Oh - incidentally, as I was unfamiliar with these plants - I assumed they were plants - I googled them to come up with descriptions. I'm sure you think you were very clever in coming up with fake plants - maybe you could have a career in designing sets for Star Wars. It's irrelevant to the argument, however. Moreoever, there actually ARE plants right here on earth that do eat flesh. Venus fly-traps for one, which reminded me of the Google descriptions I read. But you know what...a plant is still a plant is still a plant.