Origin and Radiation of the Earliest Vascular Land Plants
Philippe Steemans,1*
Alain Le Hérissé,2
John Melvin,3
Merrell A. Miller,3
Florentin Paris,4
Jacques Verniers,5
Charles H. Wellman6*
Colonization of the land by plants most likely occurred in a
stepwise fashion starting in the Mid-Ordovician. The earliest
flora of bryophyte-like plants appears to have been cosmopolitan
and dominated the planet, relatively unchanged, for some 30
million years. It is represented by fossilized dispersed cryptospores
and fragmentary plant remains. In the Early Silurian, cryptospore
abundance and diversity diminished abruptly as trilete spores
appeared, became abundant, and underwent rapid diversification.
This change coincides approximately with the appearance of vascular
plant megafossils and probably represents the origin and adaptive
radiation of vascular plants. We have obtained a diverse trilete
spore occurrence from the Late Ordovician that suggests that
vascular plants originated and diversified earlier than previously
hypothesized, in Gondwana, before migrating elsewhere and secondarily
diversifying.
2 Université de Brest, UMR 6538 du CNRS, Institut Universitaire Européen de la Mer, 6 Avenue le Gorgeu, 29238 Brest-cedex 3, France.
3 Saudi Aramco, Dhahran, 31311, Saudi Arabia.
4 Université de Rennes 1, UMR 6118 du CNRS, 35042 Rennes-cedex, France.
5 Research Unit Palaeontology, Ghent University, Krijgslaan 281/S8, B-9000 Ghent, Belgium.
6 Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: c.wellman{at}sheffield.ac.uk
