The last decade has witnessed a resurgence in the study of the evolution of plant development, combining investigations in systematics, developmental morphology, molecular developmental genetics, and molecular evolution. The integration of phylogenetic studies, structural analyses of fossil and extant taxa, and molecular developmental genetic information… (More)
Fig. 2. Evolution of roots. (A) In the absence of integration of fossil taxa into a phylogeny, it might be concluded that the roots of all extant plants are homologous, but this is an artifact because key fossil taxa appear to lack roots. (B) When key fossil taxa are integrated into the phylogeny for analysis of root evolution, it is apparent that there have been two evolutionary origins of roots. One origin is in the Lycophyta, perhaps from telomic systems that grow into substrate, as found in Zosterophyllum. Another independent origin is observed in the common ancestor of extant euphyllophytes.