Sprecher
Beschreibung
The affinities of Prototaxites are currently strongly debated. A further question is why Prototaxites is found together with Pachytheca in Silurian/earliest Devonian sediments from their earliest records. The small number of large, trunk-like, Emsian and younger Prototaxites share similar anatomy with the more numerus older fragments. All comprise aggregations of tubes that show similarities with fungal anatomy, an interpretation reinforced by their frequent occurrence with fragmentary hymenial tissues and geochemical evidence of heterotrophic nutrition. By contrast Pachytheca comprises spherical colonies of septate filaments that radiated from the central interweaving mass though a presumed mucilaginous matrix, with geochemistry indicative of autotrophy.
The above data were largely obtained from carbonized fossils. Both taxa are very rare in the Rhynie chert. Nevertheless, of the pachythecas studied here, three were juvenile enclosed in a partial hymenial layer, the fourth being positioned close to sterile P. taiti, hymenial layers and potential cords. Considering Prototaxites, in addition to the above, there are two examples of P. taiti recorded in an assemblage of presumed drifted plant and microbial remains.
We found no evidence for organic connection in this allochthonous material, but the consistent association of the two taxa is strongly suggestive that they originally colonised the same catchment region, and this was very rare in an area dominated by hot springs. Pachytheca being spherical could have rolled through pools, only becoming trapped among accumulations of shed ephemeral fertile material of Prototaxites. The origin of the fragments of typical Prototaxites escapes us.