Sprecher
Beschreibung
Before land plants came to dominate terrestrial habitats, metre-tall, columnar organisms of unknown systematic classification – known by the generic name Prototaxites – were the largest land-dwelling organisms during the Early and Middle Devonian. The size and biomass of these organisms suggest that Prototaxites provided a potentially rich food source for arthropods and other terrestrial organisms capable of utilising their robust tissue.
Our study of three silicified Prototaxites stem fragments revealed a complex system of tunnels, some of which feature chamber-like expansions and are filled with coprolites of two morphotypes: both are characterised by a prismatic shape with a hexagonal cross-section and differ only in size and shape. The partial healing of the feeding tunnels, similar to that recognised in modern fungi, proves that the tunnels were formed during the organism’s lifetime.
The fact that hexagonal coprolites are now found exclusively in insects, which possess six rectal pads for shaping and compressing faecal matter, suggests that insects adapted to an endophagous lifestyle already existed in the Early Devonian. The simultaneous presence of smaller, elongated coprolites in the same feeding tunnels points to coprophagy – the earliest evidence to date of this behaviour in terrestrial land-dwelling organisms.
The new discovered feeding tunnels in Prototaxites at various early Devonian sites in Germany indicate that insects appeared much earlier in early terrestrial habitats, a finding that is consistent with the predictions of molecular phylogenetic studies on the emergence of the Pterygota.