Venation pattern in the sphenophyll Trizygia speciosa Royle from the Raniganj Formation

Abstract

There has been a running controversy about the independent taxonomic status of the genus Trizygia vis-a·vis Sphenophyllum. The basic organization of the foliage shoot in both genera is apparently similar, except for the trizygoid leaf whorls in the former. The trizygoid leaf whorls are, however, not unknown in Sphenophyllum. The two genera cannot be compared at the level of the anatomy of the axes or the organization of the fertile shoot as this information is not available for Trizygia. The venation pattern in leaves of Trizygia has been analysed in detail with a view to comparing it with that of Sphenophyllum, when that information is forthcoming. The parameters chosen for analysis include length, width and area-index of leaves and number of dichotomies, ultimates and dichotomy levels.