They're both sepentine in nature, and the sprites are postured the exact same way. Same body shape, same everything except the colors were tweaked.
Actually, they aren't. The poses are different, look at the tail, direction of head, etc. Small details like the thickness of the body are different as well, especially the 'front' section below the head.
on the second, Notice the fingers, they're the same as rhyperiors.
Similar fingers, not the same. Other Pokémon also have similar fingers, such as Metang.
Same with the 3rd as the 1st. the sprites are identical in posture. looks like dialga's body with a narwal horn. all these are, are good examples of spriting, nothing more.
Not identical at all, the 'new' one has much of a seal-like structure to its legs, especially how they are splayed out how Dialgas are not. The tail joins at a different position too.
There are always similarities between Pokémon, poses are often recycled since these are ANIME art not SPRITE art anyway.
I even stated in my post that I don't think they are real anyway, despite all the above. I think the odd colouration of the water evolutions (2nd and 3rd) as well as Pokabu's evolution seeming more cartoony than normal as more important factors.