Anatomy and branching of Arthropitys bistriata (Cotta) Goeppert — New observations from the Permian petrified forest of Chemnitz, Germany

摘要

Sizable permineralized calamitean trunks from the Permian petrified forest of Chemnitz, Germany, enabled us to recognize two different branching patterns and wood anatomies for material currently classified as Arthropitys bistriata. This resulted in re-evaluation of the generitype of the widely distributed organ genus Arthropitys Goeppert 1864. As a result, a mosaic of anatomical and morphological characteristics has been recognized that permit A. bistriata to be characterized in much more detail than previously possible. The first type of calamite previously included in A. bistriata is characterized by whorls of branches at every 5th to 9th node and simple scalariform thickenings in tracheid walls of the secondary xylem. Additionally it shows irregularly positioned woody adventitious shoots that also carried whorls of leafy branches. The second type shows reticulated thickenings and multiseriate pitting in secondary xylem tracheid walls and regular branching at every node. Branches alternate in successive nodes and, therefore, lie on the top of each other at every second node. Comparison with the type material suggests the two calamite forms need to he split taxonomically as follows. The first type of calamite is regarded as A. bistriata and emended herein, the second type is separated and introduced as Arthropitys sterzelii sp. nov.The secondary tissues of both species are characterized by a high portion of parenchyma (around 454 Sometimes irregular growth rings were recognized that may reflect some kind of seasonality and/or environmental influence. We suspect the leafy branches, which were free of any secondary growth in both species, were probably grown and abscised seasonally. Comparisons are made with both different calamitean species and other preservational forms.