New morphological and anatomical data derived from a rare Early Devonian French flora

Abstract

The Pragian–Emsian interval was a period of remarkable morphological and anatomical diversification among various early land plant groups. Nonetheless, evidence documenting this crucial event remains limited, especially given the scarcity of permineralized material, such as in the Ardenno-Rhenish region located on the southeastern shelf of Laurussia. Here, we reinvestigate an Emsian flora from Matringhem (northern France), to both revise the originally described adpression assemblage and examine the permineralized content. Additionally, a newly sampled nearby locality (La Grande Pièce Quarry) yielded plant macrofossils, providing further material to document plant diversity in this area. The adpression assemblages demonstrated the predominance of basal euphyllophytes, with interestingly, isolated vegetative and fertile remains attributed to Psilophyton burnotense. This differs with the permineralized flora found to be entirely composed of axes with anatomical characteristics encountered among zosterophylls. A discrepancy between both types of fossil records is common in Early Devonian plant assemblages and might reflect a sampling/identification bias or divergent taphonomic pathways. Nevertheless, a comparison between several other permineralized floras showed that zosterophyll-dominated records are indeed more reminiscent of Pragian to early Emsian assemblages, in contrast to euphyllophyte-dominated middle to late Emsian floras, further suggesting an early Emsian age for these localities.