First Grammatopteris tree ferns from the Southern Hemisphere – new insights in the evolution of the Osmundaceae from the Permian of Brazil

Abstract

The stem anatomy and organization of new anatomically preserved Grammatopteris fern specimens are described from the Permian of the Maranhão Basin (NE Brazil). Grammatopteris freitasii nov. sp. is established to accommodate the newly collected material, which is preserved as silicified permineralization. On the basis of their anatomical details, Grammatopteris rigollotii, the type species originally described from the Permian of Autun, France, and Grammatopteris baldaufii, another species originally described from the Permian of Chemnitz, Germany, are re-examined and discussed. The generic diagnosis of Grammatopteris is emended. Furthermore, all species of the genus Grammatopteris are compared with Rastropteris pingquanensis (Galtier, Wang, Li and Hilton), a recently introduced type of fern from the Lower Permian of China. The Grammatopteris ferns are interpreted as showing a growth habit of small to medium-sized erect trees. Their trunks are 4–35 cm in diameter and possess an exarch maturated solid protostele surrounded by a dense mantle of petiole bases and more downwards completely clothed in a root mantle. Stem cortex contains different types of sclerotic tissue. Leaf trace vascular tissue developes from oval-shaped to tangentially elongated, typically bar-shaped strand. Grammatopteris ferns are thought to be of considerable importance or a link in the origin and early development of Osmundaceae.