When these ferns and other plants died they would become submerged in water and mud before they could decompose.
(these ferns and other plants; died; ) (they; would become; submerged in water and mud; T:before they could decompose; T:When these ferns and other plants died) (they; submerged; in water and mud) (they; could decompose; )
these ferns and other plants they they they
died would become submerged could decompose
submerged in water and mud T:before they could decompose T:When these ferns and other plants died
in water and mud