About 310 million years ago, these plants were common in the coastal swamps that produced Iowa's coal deposits (Pennsylvanian).
(these plants; were; common; L:in the coastal swamps; T:About 310 million years ago) (the coastal swamps; produced; Iowa's coal deposits)
these plants the coastal swamps
were produced
common L:in the coastal swamps T:About 310 million years ago
Iowa's coal deposits