New data on the morphology and anatomy of the Devonian zosterophyll Serrulacaulis Hueber and Banks from Venezuela

Abstract

The first South American record of the zosterophyll Serrulacaulis Hueber and Banks from the Middle or lower Upper Devonian Campo Chico Formation, western Venezuela, has yielded new insight into the morphology and anatomy of this plant. The emergences are demonstrated to the modified triangular prisms arranged in two rows in a step-like fashion on opposing sides of the axis, contrasting with the more or less conical shape originally described. Furthermore the axis is interpreted as more or less terete in transverse section instead of the original oval. Models of compression are put forward to explain the orientation and appearances of the compression fossils. This new interpretation is confirmed by observations on material from the type locality in New York State. Fragments of permineralized xylem show it to be composed of tracheids of the G-type. An emended diagnosis of Serrulacaulis is proposed.