Mid-Devonian Archaeopteris roots signal revolutionary change in earliest fossil forests

The origin of trees and forests in the Mid Devonian (393–383 Ma) was a turning point in Earth history, marking permanent changes to terrestrial ecology, geochemical cycles, atmospheric CO2 levels, and climate. However, how all these factors interrelate remains largely unknown. From a fossil soil (palaeosol) in the Catskill region near Cairo NY, USA, we report evidence of the oldest forest (mid Givetian) yet identified worldwide. Similar to the famous site at Gilboa, NY, we find treefern-like Eospermatopteris (Cladoxylopsida). However, the environment at Cairo appears to have been periodically drier. Along with a single enigmatic root system potentially belonging to a very early rhizomorphic lycopsid, we see spectacularly extensive root systems here assigned to the lignophyte group containing the genus Archaeopteris. This group appears pivotal to the subsequent evolutionary history of forests due to possession of multiple advanced features and likely relationship to subsequently dominant seed plants. Here we show that Archaeopteris had a highly advanced root system essentially comparable to modern seed plants. This suggests a unique ecological role for the group involving greatly expanded energy and resource utilization, with consequent influence on global processes much greater than expected from tree size or rooting depth alone

A New, High‐Precision CA-ID-TIMS Date for the ‘Kalkberg’ K‐Bentonite (Judds Falls Bentonite)

The numerical calibration of the base of the Devonian is poorly constrained due to several factors. Few precise radioisotopic age determinations are available from the late Silurian and Early Devonian, and the limited published data carry large error bars from older analytical methodologies. Volcanic ashfalls suitable for dating occur in the Lower Devonian of the Appalachian Basin, but have not been precisely correlated into the global chronostratigraphical scheme because of limited bio‐ and lithostratigraphical information. Here, we report a new U‐Pb zircon radioisotopic age determination of 417.61 ± 0.12(0.23)[0.50] Ma and improved chronostratigraphical context, including revised biostratigraphy, for an ash bed in the New Scotland Formation, Helderberg Group, from the Lochkovian Stage that was previously identified as the Kalkberg K‐bentonite. This new information helps to integrate the classic New York Appalachian Basin succession into global Siluro‐Devonian stratigraphy, refine the calibration of the Silurian–Devonian boundary and more precisely estimate the duration of both time periods