The euphyllophytes of a new Givetian plant assemblage from the eastern Anti-Atlas, Morocco

Abstract

The Middle Devonian is a transitional period for the first vascular plants, which acquire modern vegetative and reproductive structures, diversify considerably and, within the euphyllophytes, evolve the first representatives of modern plant groups, the monilophytes and lignophytes. However, the dynamics of this diversification across the different paleocontinents remains obscure, particularly within Gondwana. The upper Givetian locality of Oum el Jerane, in southeastern Morocco, has yielded a new assemblage of anatomically preserved plant remains whose description contributes to a better understanding of the floras of the northern margin of Gondwana during the Middle Devonian. The euphyllophytes include one iridopterid, Arachnoxylon minor, two cladoxylopsids, one of which represents the new genus Jerana, and two aneurophytales affiliated with the genus Triloboxylon. The cladoxylopsid remains from Oum el Jerane correspond to relatively small plants compared to the well-known coeval cladoxylopsids of Laurussia. Compared to the taxonomic composition of the four phytochoria recently defined for the Middle Devonian, the Oum el Jerane plant assemblage corresponds to the ‘subtropical’ phytochorion, which is close to the ‘Laurussia’ phytochorion, but which would correspond to drier environmental conditions.