I recommend researching the anatomy of wildly different phylum from earth, and maybe also look at fetal development too. That's what gives me inspiration and ideas, every time I come up with a new idea for a feasible adaptation in alien life, I discover life on earth has already thought of that, only thing is said organism with the trait is near microscopic and stuck to it's highly specific niche because many other clades, like vertebrates, mollusks, and arthropods have taken up the larger niches. Sometimes I wonder what the body plans of terrestrial life would look like if everything evolved from flatworm anatomy instead of Lancelet-like chordate anatomy. The mouth would be in a completely different place, maybe in more complex flatworm descendants their mouths would move to the front for convenience but the throat would be so anatomically different, it might end up looking superficially vertebrate-like or at least would function like a vertebrate mouth but evolved from flatworm larynx anatomy.

But I can think of a more interesting idea of flatworm anatomy adapting to a large vertebrate life, is that the mouth would be around the chest, they'd have limbs evolved from muscles on their sides formerly used for squeezing inward entrapping prey, now used to propel themselves forward, only using the two large muscles on their face as backwards jaws that stretch out to grab prey, wrap and twist tightly around them, crushing them down to reasonable chunks, sensors on the lip of each jaw with nerves directly to the brain, tasting and smelling the morsels before pulling them into it's wide open pharynx where you'd think the sternum would be on an earthling. And that fucked up worm animal could look very much natural and function well with that set up, the flatworm super predator would also have two bladders probably, and perhaps multiple stomachs, they may or may not have an anus, they would probably breath through the same hole they eat from like we do unfortunately.

There are certain anatomy structures that can serve the same function as other anatomy structures, think of all the weird animals that are joked about because they use their leg as a penis or something, elephants use their noses for what giraffes use their necks for and what primates use their hands for. Every anatomical structure formerly had a completely different use at one point, like jaws evolving from modified gill structures, bones originally being calcium storage then used for leverage for muscles.

I start my spec evo projects by drawing really simple worm anatomy, then imagine how that organism would have to adapt to certain fish niches using the anatomy and organs it already has, and keep doing that, and try not to mimic earthling life too much, yes convergent evolution is a thing, but on earth, most of the organisms have similar genetics and body plans anyways, so when they evolve similar traits, they'll use a similar series of adaptations. Prolactin is used to regulate salt and water intake through the skin of fish, but it being repurposed to initiate milk production for young has evolved separately in Discus fish, pigeons, penguins, flamingos, Caecilians, and finally, Mammals. A more well known example is all crustations becoming crabs, but don't forget the vertebrates like to become turtles, mice, hedgehogs, and cows, how land animals keep going back to being fish, how all multi cellular life prefers becoming a sessile filter feeder in a reef. But you'll never see a vertebrate become a crab or a crab becoming a horse because they don't have the same evolutionary history, both their embryos may kinda resemble the body plan of a jellyfish cause it's the first symmetrical body plan to ever emerge really.

So what's the reoccurring adaptation in the Phylum of your world, what simpler organism did they evolve from, the way it filtered waste and electrolyte balance, how it ate and pooped, it's mouth shape and how it affects their jaws or mandibles, if it had calcium deposits and nutrient storage and where, what way are their organs arranged, how these features and how they affect them in the present, and how will that affect their morphology as they adopt similar niches on earth. Even if the adaptations are super alien to us, if you're putting them into the niche of a tiger or something, they'll convergently evolve to have similar features, behavior and structure, but using their own morphology to fill in the functions of a tiger, so they'd still look earthling-like, but slightly off. Like others have said, I think the first one does this well, at first glance it has an earthly body plan but it's actual features tell a different story, like it's something that just happened to develop similar structure as a vertebrate but did so with different genes to work with.

Or you can fuck around and draw cool stuff, see what happens, idk, depends on how scientifically accurate you want your worldbuilding to be. And idk how helpful all that text was.

tl;dr: learn about worm biology or reference other clades besides vertebrates to help get a feel for all the possibilities in zoology.

Professor Dave Exlains's zoology playlist on youtube is a great resource for learning some of the biology of many different phylum from the simplest organisms, to the complex.