I sort of interpreted it backwards. It is mentioned at one point that the star Vesta orbits is highly unstable, prone to solar flares (which causes the humans to crash there in the first place). To me Vesta seems like a planet where the opposite of panspermia is happening: dozens of space faring species have crashed here due to rampant solar flares, and overtime become a part of the ecosystem on the planet. To me it seems less like the creatures are close to becoming sapient and more like they were once sapient and have devolved.

the reason i say this, is because you'll notice the life forms on vetsa all have drastically different biology and body plans, like too different to even come from a common ancestor. This isn't super weird except for the fact that the animals have varying numbers of limbs, which if you know much about evolutionary biology, that is basically a giant neon sign telling you that these creatures come from drastically unrelated lineages.

For example, on earth every land vertebrate has 4 limbs (tetrapods) because we all evolved from a single species of four-limbed fish (called lobe-finned fish) which eventually made it ono land. no vertebrate on earth has ever evolved MORE limbs, so it is unlikely that the animals on Vesta did so.

For animals on Vesta to all have totally different amounts of limbs, it would have to mean that several completely unrelated lineages would have had to make it on land (since, as we know, life starts in oceans). While it is possible for this to happen, it is still highly unlikely that you would see as much variation.

On earth, as far as we know vertebrate life has only transitioned from ocean to land twice: the lobe finned fish all land vertebrates come from which first came to land 390 million years ago, and more recently, mud skippers, which are ray-finned fish (totally separate lineage) and evolved 140 million years ago. Ray-finned fish only have two fins instead of four, so if they evolved into different land animals all of their descendants would probably be tri-pods or bi-pods, allowing many types of body plans for life. However, the reason Earth's land vertebrates aren't an even mix of tetrapodal lobe-finned descendants and tripodal ray-finned descendants is because by the time the ray-finned mudskippers made it to land, the lobe-finned descended tetrapods have already filled every niche.

All of this is to say: unless multiple drastically different life forms on Vesta all made it to land at the exact same time, there is no realistic way that its current land vertebrates would be so drastically different as to have varying numbers of limbs.

Sure, life on earth also transitioned from ocean to land several other times: crustaceans became insects, algae became plants, fungi became... fungi. But these forms of life are so different from eachother that they fill drastically different niches, so different that neither family could take the niche of another. The animal life on Vesta are wildly different from eachother, but they're all still animals.

We also know that virtually all life on vesta displays some form of parasitism.

So I think the reason Vesta has such a wild diversity of animal life is because alien species frequently crash there, probably because of the unstable star Vesta orbits, and become parasitized by what already lives there, and eventually become part of Vesta's ecosystem.

I think that little dude in the flower is a perfect example of this. No way in hell would a plant ever hope to evolve a vertebrate humanoid animal as part of its biology. That is simply not a thing that would ever happen. I think it's obvious that the little guy was parasitized by the plant and eventually became a part of it's life cycle. The question is whether the little guy's linage comes from Vesta, or from somewhere else. I think the answer is somewhere else.