Eine mutmaßliche Armleuchteralge aus einem silurischen Geschiebe [A Presumable Charophyte in an Silurian Geschiebe (glacial erratic boulder)

The oldest known charophytes were described from Upper Silurian beds of the lsle of Gotland (C0NKIN & C0NKIN 1992) and from Podolia (ISTCHENK0 & SAIDAK0VSKY 1975, ISTCHENK0 ISTCHENK0 1982); the record from Turkestan, however, has not been adaequately documented (HACQUAERT 1932). The material from Gotland and Podolia shows not only gyrogonites but also vegetative parts of the plant, few being in contact with the gyrogonites. The vegetative parts are preserved as fragments only without or limited information about the general construction of the plant. However, a geschiebe (glacial erratic boulder) from Northern Germany does not only yield charophyte fragments but also a piece of a stem mit preserved whorls (fig. 1 ). lt is the oldest record of this kind and dates from the Upper Silurian which could be precisely determined by the assocated ostracod fauna . In recent charophytes, the internodal cells are elongate and the whorls extend from very short nodal cells (for example TAPPAN 1980). The recorded Silurian species, Primochara ? equisetiformis sp.n .• has relatively short internodal cells and the whorls therefore, are closely spaced to each other. The new finding documents that the construction of Recent charophytes remained principally unchanged for more than 400 million years