Why does the second specimen's vertebra look leagues different than the first one's? Or is it just broken?

It is different, it is thin-spined

Ethrastospinax should it's name

Ethraso = éfthrafsto = Greek for fragile, spinax = spine or Leptospinax (leptós = thin)

Interesting

Might be the smallest spinosauruid,it looks roughly 5 meters in length.

It is 9 m