The coal balls of the Carboniferous, which contain well-preserved material from the lowland coal swamps, are also products of this type of fossilization.
(The coal balls of the Carboniferous; contain; well-preserved material; from the lowland coal swamps) (The coal balls of the Carboniferous; are also; products of this type of fossilization)
The coal balls of the Carboniferous The coal balls of the Carboniferous
contain are also
well-preserved material from the lowland coal swamps
products of this type of fossilization