The Most Extensive Devonian Fossil Forest with Small Lycopsid Trees Bearing the Earliest Stigmarian Roots

Since the Late Paleozoic, forests have become distributed worldwide and significantly changed the Earth’s climate and landscapes, but the record of forests is rare in the Devonian (419–359 Ma in age) when they first appeared. From the Upper Devonian (Famennian with the age of 372–359 Ma) of Xinhang, Anhui, China, we report a very large in situ forest, which includes locally dense stands of lycopsid plants. The Xinhang forest is monospecific with a small tree lycopsid Guangdedendron gen. nov., probably dioecious with monocarpic reproduction. The plant shows the earliest stigmarian rooting system typical of giant tree lycopsids dominating Carboniferous forests. It colonizes coastal clastic wetlands that were influenced by floods. This significantly increases the paleogeographical coverage of in situ Devonian forests, and contributes to our understanding of atmospheric CO2 decline and coastal consolidation. •The earliest forests in the Devonian can be very large and potentially abundant•Devonian Xinhang forest consists of dense and new tree lycopsid Guangdedendron•Guangdedendron may be monocarpic and dioecious, showing the earliest stigmarian root•Devonian forests could contribute greatly to CO2 decline and coastal consolidation Wang et al. report the largest Devonian forest (also the oldest forest of Asia) with the earliest rooting system characterizing giant lycopsid trees distributed worldwide in the Carboniferous. It indicates that the earliest forests can be abundant, and have more impact on the rapid drop of atmospheric CO2 and on the stabilization of coastal lines.