At the time of its release, Jurassic Park: Operation Genesis had managed to include nearly every on-screen prehistoric species found in the movies released up to that point ("Jurassic Park", "The Lost World: Jurassic Park" and "Jurassic Park III"), with only three notable exceptions:

•Pteranodon (featured in "The Lost World: Jurassic Park" and "Jurassic Park III")
•Compsognathus (featured in "The Lost World: Jurassic Park" and "Jurassic Park III")
•Mamenchisaurus (featured in "The Lost World: Jurassic Park")

Of these, the developers had mentioned they wanted to include flying reptiles earlier on in development but had to scrap them. In regards to Compsognathus, it was reportedly ruled out due to making gameplay difficult, because of their small size making them hard for players to see.