Psilophyton szaferi sp. nor. from the Lower Devonian of the Holy Cross Mountains. Poland

Abstract

Philophyton szaferi sp. nov. belonging to the Trimerophytina was found in the Lower Devonian (Emsian) in the bore-hole Modrzewie 2A near Bostów in the Holy Cross Mountains (Gory Świętokrzyskie). The axes are sterile and fertile. their branching is dichotomous, unequally dichotomous and unequally dochotomous where the wider branch tends to form the main axis. The majority of axes branch in one plane, some in different planes; they show on their surface irregularly distributed enations in the form of rounded swellings. Some of them continue downwards as protruding ridges forming a characteristic longitudinal pattern. The apices of sterile axes are forking. Fertile axes end in clusters of fusiform. upright sporangia, arranged in pairs. The vascular strand shows protoxylem inside and metaxylem outside. Tracheids possess scalariform thickenings and what appear to be small pits between them. The systematic position of the plant and its position in the evolutionary sequence leading to megaphyllous leaves is discussed.