a different Spine Evolution

I was discussing with other people if a creature could life with endosceleton and a spine on the front and not the back. (we discussed this because lobsters and crabs have it like this)

Because i knew it wouldn't work with our sceleton i decide to evolve a new one (main focus on the body, therefore nearly no big changes in the skull and the arms and legs or fins)

The creatures:
1. I started with a fish, i need one with a eye down the jaw, because all fish skeletons i saw started the spine by the eyes - and underwater it can be as importand to see creatures that are under you as creatures over you (without birds - it is even more impirtand to see those below yourself)

2. First steps on land - the last fin becomes an aditional leg, because it helps to keep the spine above the ground!

3. The rips become protecting shileds, because of predators

4. The creature uses the aditional leg more often, because it helps the creature standing up and get food thats higher

5. The lowest protecting plate becomes a hip-like bone for holding the organs down there - four of the other boneplates fuse to be more stabile when the creature stands

6. The creature has now a hip and the boneplates/rips become more flexible with the holes for better movingoptions


And now for the people that don't know why there is a black line, this should be the spine and the big thing up there is the brain
This creature evolved walking really fast because of the aditional leg