Ephedra-like Cones from Serra do Tucano formation (Lower Cretaceous), Takutu Basin, Roraima

Abstract

The fossilized parts of several plants are described from the Lower Cretaceous of the Serra do Tucano Formation, Brazil. These include ovulate cones with whorls/decussate bracts involving one terminal female reproductive unit sometimes attached to an incomplete shoot with striated axes and nodes with unequivocal ephedroid affinity. A new genus, Paraephedra, is proposed to accommodate three different ovulate structures. Paraephedra amazonensis is interpreted as a terminally attached single ovule/seed surrounded by whorls/decussate bracts that cover the ovule almost completely. Paraephedra sp. 1 is interpreted as a single ovoid to elongate-ovoid ovule/seed surrounded by one to two connate bracts extending to just below the middle of the ovule. Paraephedra sp. 2 is interpreted as a terminally attached single ovule/seed surrounded by one to two pairs of decussate bracts that cover the ovule almost completely. Although the general morphology of Paraephedra bears a strong resemblance to Ephedra L., the expected micropylar tube is missing (or has not been confirmed), thus preventing its classification in the Ephedrales/Ephedraceae. The association of these Ephedra-like reproductive structures with other taxa previously recognized from the Serra do Tucano Formation support the hypothesis that the Takutu Basin region was under an arid/semi-arid climate regime during the Barremian–Albian interval.