XVI International Botanical Congess

Mid Devonian aneurophyte progymnosperms, cladoxylalean ferns, cormose lycopods, and other groups produce dense multi-tiered, but patchy vegetation with deep rooting that stabilize floodplains. Archaeopterid progymnosperms appear near the end of Mid Devonian and quickly dominate most areas by expansion of vegetation cover and loss of aneurophytes. Archaeopteris has a wide range of tolerances within a landscape and is widespread, ranging from paleo-equatorial to paleo-boreal latitudes and from seasonally dry to wet habitats, but is species-poor. Cormose lycopod trees occupy permanent wetlands while zygopterid ferns cover ephemeral wetlands. Pioneer habitats have early gymnosperms. Fire becomes a factor in maintenance and/or succession of communities by Latest Devonian.