Overall better than DinoRexmon. Wish they hadn't given it those ridiculous claws.
They're based on the claws of a Deinonychus, the thing Jurassic Park's Velociraptors are based on. Arguably possibly mixed with the massive clawed hands of Therizinosaurus, too? But I doubt that a bit, it's the wrong limbs for it in any case.
Ankylomon is a neat design, but it suffers in being its own thing. What direction they intended with Armadillomon is anyone's guess. Is it meant to be broadly armored/plated, a dinosaur, or just generally ancient?
Given the "ancient" nature, the fact that they're associated with water to some degree (they've been Deep Savers several times, a number of herbivorous dinosaur Digimon have, it's a thing), and the general way it looks, you could make it evolve into a tortoise if you wanted to make your own evolution. Think Meiolana, with the large lumpy shell and the big spiked tail. Failing that there's always good old Doedicurus and other glyptodonts. I guess you could also maybe fudge it and say Vermillimon since it and Monochromon follow the really old paleoart interpretations of monoclonius as having heavily armored backs.
They've never really seen the point of doing this, though, since they always end up associating it with Holy stuff. But you could do it.
If you want my take on an Armadimon -> Ankylomon -> Dinosaur line though? Well... one of the really annoying things Digimon did that fouls up the creation of good dinosaur lines is that when they were making Armor forms they used a lot
of the big, important dinosaurs in them. In specific for this case, Stegomon is a big issue, because Stegosaurs and Ankylosaurs were as far as we can tell actually really closely related - like, shockingly closely, there are some primates less related to humans than stegosaurs and ankylosaurs generally were - and it's also a big dinosaur with a spiked tail and deadly weapons and armor on its back. Still, the thing about Armors is that they have a bit of wiggle room... so if you use it as a Perfect, and given an Ultimate it's already been associated with...
You'd have to fudge Stegomon a bit to make it slightly more aquatic in nature for it all to fit perfectly, but given they even gave Spinomon attack names reminiscent of Stegomon, it works. You're even working a little bit of Patamon in there in theory, since that's what Stegomon's usually associated with, more for a lack of appearances than anything else granted - which helps with the fudging of course because who knows, maybe it is that way, we'd never be able to tell because it's been playable in like two products ever, and those were the D3 and the old card game.
Ceratopsian is a dinosaur, right?*
Thanks for the knowledge but if the answer to my question above (*) is yes please don't reply to this.
Semi-yes, I guess? They are all dinosaurs, but they're specific
dinosaurs - a sub-order
going from as early as the Late Jurassic (possibly a bit earlier, but there was a lot of turnover around that point, that's why the End-Jurassic is one of the only ends to a Period to not have a noteworthy extinction associated with it - and why it's one of the least locked-in period changes) until the Cretaceous extinction.
They're the ones with the big crested heads and the large horns on the front. It's a body plan that's been replicated a few times since then.