Aarabia, a new Early Devonian vascular plant from Africa (Morocco)

Abstract

Aarabia brevicaulis Meyer-Berthaud and Gerrienne, gen. et sp. nov. is described from the Early Emsian of Central Morocco. The preserved parts of the aerial system are interpreted as erect shoots bearing branches in a planar-alternate arrangement. Branching is pseudomonopodial in all orders of axes. Distinction is made between short and long branches. Short branches consist of a foreshortened axis dichotomising in two terminal segments recurved abaxially and adaxially towards the axis of previous order. Arrangement of short laterals on main stem is unpredictable. It is typically proximal on long branches. Long branches of all orders are characterised by short internodes proximally, that increase in length distally. Fertile branches display few anisotomous divisions and bear a small number of non-paired elongated sporangia. Associated large spores in the vicinity of the fertile appendages suggest that the plant might have been heterosporous. Aarabia is compared to Early Devonian euphyllophytes. A preliminary cladistic analysis places it as sister-group of the Euphyllophytina.