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Journal Articles New Phytologist Year : 2018

Putative Late Ordovician land plants

Abstract

The colonization of early terrestrial ecosystems by embryophytes (i.e. land plants) irreversibly changed global biogeochemical cycles (Berner & Kothavala, 2001; Berner et al., 2007; Song et al., 2012). However, when and how the process of plant terrestrialization took place is still intensely debated (Kenrick & Crane, 1997; Kenrick et al., 2012; Edwards et al., 2014; Edwards & Kenrick, 2015). Current knowledge suggests that the earliest land plants evolved from charophycean green algae (Karol et al., 2001) most probably during Early-Middle Ordovician times (Rubinstein et al., 2010; and references cited therein). They were represented by small nonvascular bryophyte-like organisms (Edwards & Wellman, 2001; Wellman et al., 2003; Kenrick et al., 2012). The oldest fossil evidence from dispersed spores of presumable bryophytic nature is known from a Middle Ordovician locality (c. 470 million years ago (Ma), Rubinstein et al., 2010; Fig. 1) from Argentina (Gondwana palaeocontinent). The dispersed spore fossil record also suggests that the first radiation of vascular plants probably occurred during Late Ordovician times (c. 450 Ma, Steemans et al., 2009). However, unequivocal macrofossils of vascular plants appear much later, during mid-Silurian (c. 430 Ma, Edwards et al., 1992). This macrofossil evidence comes from the fossil-genus Cooksonia, an early polysporangiophyte (i.e. a plant with bifurcating axes and more than one sporangium), which is considered the earliest vascular land plant (Edwards et al., 1992; Fig. 1). Further advances in knowledge about the origin and early dispersion of polysporangiophytes are needed for a better understanding of the initial plant diversification. Unfortunately, unravelling the initial steps of polysporangiophyte evolution is hindered by gaps in the fossil record of the earliest plants as well as by limitations of inference based on molecular clocks (Kenrick et al., 2012; Edwards & Kenrick, 2015).
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Dates and versions

hal-01910099 , version 1 (21-09-2022)

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Mariusz Salamon, Philippe Gerrienne, Philippe Steemans, Przemysław Gorzelak, Paweł Filipiak, et al.. Putative Late Ordovician land plants. New Phytologist, 2018, 218 (4), pp.1305 - 1309. ⟨10.1111/nph.15091⟩. ⟨hal-01910099⟩
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