On tile anatomy of Dadoxylon arberi Seward with some remarks on the phylogenetical tendencies of its tracheid pits

07 January 2015

A well preserved specimen of Dadoxylon arberi Seward has been discovered in the Beaufort Series (Upper Karroo System) of the Empangeni district in Natal, South Africa. The species is characterized by the tracheid pits which are araucaroid in the multiseriate condition, but which are more often circular and separately arranged or appear in stellate groups. The cross field pits tend to be aligned in horizontal pairs. Dadoxylon arberi shows a relationship with several species of the recent Araucariaceae. Its resemblance to other Gondwana woods from other Southern Hemisphere countries suggests a great uniformity in the elements of the coniferous flora of that time. It is suggested that Dadoxylon arberi represents an intermediate form between the Araucariaceae and Podocarpaceae. The reduction in the seriation of the tracheid pits and a drifting thereof seems to stand in close correlation with the formation of annual rings.