None of those species you just mentioned are starting species. Nasutoceratops is, Ceratosaurus is, Struthiomimus is, and Amargasaurus is. Also they're very cheap and easily unlocked.
Brachiosaurus is the stepping stone towards Quetzalcoatlus. It's cheaper and has a very long lifespan which makes it useful to unlock early.
The reason why I view Compsognathus, Moros Intrepidus, and Sinosauropteryx to be starting species because they are small to be the first viewing gallery attraction. If Microceratus is added, I would prefer it to be a starting herbivore species.
Struthiomimus will do as a starting herbivore; but I still think it is too early to have Ceratosaurus, Nasutoceratops, and Amargasaurus.
If I were to do the official Germany challenge mode in Jurassic difficulty, Brachiosaurus is one of the species I intend to put, not Quetzalcoatlus.