Sphenopsids of the Permian (I): The largest known anatomically preserved calamite, an exceptional find from the petrified forest of Chemnitz, Germany

The stem anatomy and internal organisation of a newly collected sphenophyte trunk is studied from the type locality of Arthropitys, the Lower Permian petrified forest of Chemnitz, Germany. The trunk was found nearly in situ, still standing upright, and embedded in coarse-grained pyroclastics of the Zeisigwald Tuff Horizon (Leukersdorf Formation, Erzgebirge Basin). This specimen – the basal portion of a huge woody tree measuring up to 60 cm in diameter – represents the largest anatomically preserved calamite trunk ever found. On the basis of current investigation the exceptional find has been attributed to Arthropitys ezonata Goeppert, which is more completely characterised and emended herein. This species is characterised by its rather homogeneous loose wood without clearly distinct interfascicular rays and fascicular wedges. For the first time we are able to show details of the primary body of this poorly understood species such as vascular strands and pith parenchyma. Comparisons are made with the generitype Arthropitys bistriata (Cotta) Goeppert and other species of the genus Arthropitys.