The plant-fossil materials that make up the coal beds of Illinois are the remains of primitive trees and plants that lived in swamps during the Pennsylvanian Period (290 to 323 million years ago) or Coal Age.
(The plant-fossil materials; make up; the coal beds of Illinois) (The plant-fossil materials that make up the coal beds of Illinois; are; the remains of primitive trees and plants) (primitive trees and plants; lived; L:in swamps; T:during the Pennsylvanian Period (290 to 323 million years ago) or Coal Age)
The plant-fossil materials The plant-fossil materials that make up the coal beds of Illinois primitive trees and plants
make up are lived
the coal beds of Illinois
the remains of primitive trees and plants
L:in swamps T:during the Pennsylvanian Period (290 to 323 million years ago) or Coal Age