Published online by Cambridge University Press: 06 July 2012
Detached petioles and their branches are described under the name Lyginorachis arberi sp. nov. In their anatomy they resemble the petioles of Rhetinangium arberi Gordon, a presumed Pteridosperm. Two specimens show preparation for dichotomy. Others are interpreted as rachides probably formed by dichotomy of petioles. In cross section such rachides show the presence of pinna-traces arising alternately and marginally from the V-shaped vascular bundle. The pinna bundles are also V-shaped but have only three corrugations in section. Cylindrical pinnules are borne on the pinnæ.
L. kidstoni sp. nov. is a smaller petiole with a less corrugated and C-shaped vascular bundle. Both species are associated with seeds of Genomosperma.