|Spawn & Sacs|
|Plesiosaurus egg sac|
Spawn and Sacs all follow the same creation process as the eggs. DNA must be put in a culture vat to produce a sac or spawn, giving the player the achievement "What Species is this?". The sac or spawn will always match the species of the DNA cultivated. The cultivation process can sometimes fail, producing a failuresaurus and not an spawn or sac. When a male and female plesiosaurus, mosasaurus, or liopleurodon breed, they will drop an amniotic sac item that will not hatch unless used by a player. Fish and nautilus will occasionally drop spawn without mating (since they do not have genders), which also do not hatch unless used by a player.
Spawn/sacs can also be analyzed to revert them back into their DNA forms.