Archaeopteris is the earliest known modern tree

Archaeopteris is an extinct plant which is of botanical interest for two reasons. It was the main component of the earliest forests until its extinction around the Devonian/Carboniferous boundary1,3, and phylogenetically, it is the free-sporing taxon that shares the most characteristics with the seed plants4,5. Here we describe the largest group of anatomically preserved Archaeopteris remains ever found, from the Famennian marine beds of south-eastern Morocco6, and provide the first evidence that, in terms of development and branching strategies, these 370-million-year-old plants were the earliest known modern trees. This modernization involved the evolution of four characteristics: a lateral branching syndrome similar to the axillary branching of early seed plants; adventitious latent primordia similar to those produced by living trees, which eventually develop into roots on stem cuttings; nodal zones as important sites for the subsequent development of lateral organs; and wood anatomy strategies that minimize the mechanical stresses caused by perennial branch growth.