Simplify the following text for a Grade 12 native English-speaking person.
Original: It is known from partial skulls and skeletons from at least four individuals of differing biological ages , found in Tithonian ( Late Jurassic ) rocks of the Morrison Formation in Colorado .
Simplified: It is known from partial skulls and skeletons from at least four individuals of differing biological ages , found in rocks of the Morrison Formation in Colorado .