Early seed plant radiation: an ecological hypothesis

Abstract

The earliest steps of seed plant evolution have been extensively studied during the past 25 years. There is a growing body of evidence indicating that the first major spermatophyte radiation occurred during the Late Devonian. At least fourteen Late Devonian species are now recognized, and our knowledge of the diversity of those early seed plants has dramatically increased. Five morphotypes of seeds have been defined, mostly based on cupule morphology and on the number and degree of fusion of the integumentary lobes. In this paper, we critically discuss the abundant environmental information in order to characterize the environment in which this radiation occurred. Sedimentological information indicates that seed plants evolved in disturbed environments. It is suggested that early seed plants thrived in the shade of the dominating Archaeopteris, and that their evolution was canalized by this strong biotic pressure. We also confirm the previous suggestion that the variability of seed morphotypes can be explained by the weak abiotic selective pressure that existed in the Archaeopteris understory.

Characterization of the placoderm (Gnathostomata) assemblage from the tetrapod‐bearing locality of Strud (Belgium, upper Famennian)

“…Kenrick and Fairon‐Demaret () and then Cressler et al . () and Prestianni and Gerrienne () noticed that the localities of the Belgian Evieux Formation, including Strud, display plant assemblages that are very similar to those from the North American sites, especially Red Hill. Both sites were located along the southern margin of the Euramerica and date from the same VCo palynozone ( sensu Streel et al .…”

Early evolution of life cycles in embryophytes: A focus on the fossil evidence of gametophyte/sporophyte size and morphological complexity

“…The megagametophyte of the late Devonian early seed plant Elkinsia polymorpha is endosporic (Rothwell & Serbet, 1992). All other Devonian early seed plants (Prestianni, 2005; Prestianni & Gerrienne, 2010) are likely to have had a comparable type of female gametophyte. As noticed by Gerrienne et al (2006), the Middle Devonian proto‐ovule Runcaria Stockmans (Gerrienne et al, 2004; Gerrienne & Meyer‐Berthaud, 2007) presumably already possessed a heteromorphic alternation of generations with a reduced endosporic megagametophyte.…”

Buried deep beyond the veil of extinction: Euphyllophyte relationships at the base of the spermatophyte clade

“…Because seed plants arose early in the history of plant life (no later than the Givetian, ca. 385 Myr ago; Prestianni and Gerrienne, ) and their closest hypothesized relatives among seed‐free plants are all extinct Devonian plants, the key to the origin and early evolution of seed plants lies in the fossil record.…”