Isn't this the lifecycle of Scyphozoans a.k.a. true jellyfish? (Except the spore thing. Animals don't do spores.) And, yes, some scyphozoans do have symbiotic photosynthetic dinoflagellates. I have always been of the opinion that jellyfish are aliens.

This looks a lot like jellyfish life cycle. See eg. ocean.si.edu/sites/default/files/jellyfish-lifecycle-blue.jp‌​g

Hi @LordMalecith. For future reference, asking if something is "plausible" on a site dedicated to helping you build a fictional world rarely makes sense. As a rule, try to avoid (at all costs) words like "plausible" and "realistic" and "feasible." You'll actually ask a better question because what you're looking for is a way to rationalize and idea and when you avoid those kinds of words your question will focus on the effort to rationalize rather than be misconstrued as "can this be real?" which isn't what we do. Thanks.

Does this answer your question? A semi-plausible planimal?

Isn't this basically what coral does, except with the children being released into the current, rather than the adults? Or by "animal" you mean "can move around on it's own"? Then there's all kinds of insects that are pretty close to immobile while larvae, but then come out of the tree and fly around as an adult. If you're looking for a real mix of heterotroph and autotroph, well, that would probably require a symbiosis.

WH40k Orks, basically

Sea cucumbers do something similar as well as I recall.

I apologize that this post won't really be an answer, but I can't "Comment", yet. For some inspiration about plants acting as animals check out the novel "Hothouse" by Brian W. Aldiss. (by some wierd coincidence, the Kindle version is on sale right now).

Could you bother yourself to Post an updated image, with clearly readable words?

Other than the lack of detail in your exposition, what doubts could you have? Egg/seed/spore goes to plantoid polyp goes to animaloid adult doesn't seem to break many grammatical rules but what might it mean in every-day English?

Perhaps not v. relevant to this specific Q, but on matters of plausibility, I once asked my guru SF critic Damien Walter "What makes stories believable to some people, but not others?" and he replied that readers are prepared to do the creative work of building mental scaffolding around the necessarily limited construction they are presented with, in order to make it believable to them, if and only if the story fulfills some psychological need of the reader. Other readers, if the story conflicts with their worldview, will refuse to try and fill in the blanks, declaring it "unbelievable".

@RobbieGoodwin Seems clear to me, but then I've spent much time working alongside doctors... You get used to scrawl.

@JonathanHartley Not at all relevant to this Q, and I suggest your guru SF critic Damien Walter got that largely backwards. Since no, it isn't at all relevant to this Q you're welcome to try supporting Damien's view in Chat…

Do you mean plantimal? Or is this something else and not a typo?

@elemtilas I do indeed mean planimal - organisms which share traits unique to both Earth plants and animals.

@LordMalecith --- Okay. Yeah, that's a plantimal! Interesting. I've only ever seen plantimal, but I see that planimal is synonymous. Carry on!

@RobbieGoodwin "Not at all" is a bit of a stretch. Clearly a reader invested in a worldview which, for example, doesn't accept evolution, would be disincentivized from accomodating stories about alternate evolutions, and this would manifest as them dismissing the story as "not plausible". Other, more nuanced variations on this clearly exist. Thanks for the needlessly hostile reply though!

Well... @RobbieGoodwin Not very. We should perhaps point out to the OP the network-wide policy of not only having text in an image, but also in the body of the post . That is to do with inclusion of those who have sight issues and use a machine to read for them, which is in accordance with disability laws in many jurisdictions.

I thought you meant "planet-animal" first, space whales. Much cooler.

@pipe That would certainly be much more fun lol

@JonathanHartley Sorry you took it that way and 'Not at all relevant' referred to my Comment, not yours. It was an effort not to enter into a discussion likely to lead way off topic. You're entitled to follow Damien Walter as far as you like. I happen to believe both that he's mistaken, and that this isn't the place for that quite separate discussion.

I'm also reminded of sea squirts that digest their own brain and spend the remainder of their life anchored in place. They don't turn into plants though.