The Basic Prehistoric Era is the oldest era known in SpongeBob SquarePants (series). It appeared in the episode SB-129, when Squidward accidentally used the time machine to go back home from the 40th Century.
The only known inhabitants are Primitive Sponge, Primitive Star, Jellyfish and Tapeworm. It wasn't so advanced and Squidward taught Primitive Sponge and Primitive Star how to Jellyfishing. In that time the language, houses, writing and other things don't existed.
- Basic Prehistoric Era came before Advanced Prehistoric Era.