First evidence of arthropod herbivory in calamitalean stems from the Pennsylvanian of Germany

摘要

Arthropod borings are commonly described from pteridophyte and gymnosperm wood in the late Palaeozoic,but they are almost unknown from calamitalean stems.In this paper,a new type of boring in calamitalean stems from two German localities is reported.These are the mine dumps of Pl?tz near Halle (Saale),Saale Basin,(Wettin Subformation,Latest Pennsylvanian,Gzhelian,Stephanian C) and the Piesberg quarry near Osnabrück,Subvariscan Foreland Basin,(Osnabrück Formation,Middle Pennsylvanian,latest Moscovian,Asturian/Westphalian D).Most borings were found in marginal parenchyma of the internodes.They run longitudinally through the pith.The borings are preserved as three-dimensional casts that protrude on the surface of considerably compressed pith casts.This unique preservation of the boring casts required special taphonomic conditions,such as rapid burial coupled with different sediment infilling of the borings and the pith cavity,as well as anoxic conditions to prevent decomposition of the non-resistant parenchyma.Most borings are between 3 to 5 mm wide and contain two classes of invertebrate coprolites: the smaller coprolites are sub-spheroidal in shape and measure (37 to 74) x (37 to 63) μm in diameter.The larger coprolites are also sub-spheroidal and range between (88 to158) x (68 to 123) μm in diameter.The coprolites,the morphology of the borings,as well as the feeding strategy of the arthropods,suggest that the tunnel system was most likely produced by small millipedes (Myriapoda) and probably also visited by oribatid mites.