Revision of the supposed Triassic, in fact Silurian genus Triadophyllum; Weissermel, 1925 (Anthozoa, Rugosa)

The only existing type specimen of Triadophyllum posthumum Weissermel, 1925 is not a Middle Triassic (middle Anisian, Pelsonian) Scleractinia, but a Silurian Rugosa collected from a Pleistocene erratic boulder of Baltoscandian origin. First serial cross sections demonstrate a synonymy of Triadophyllum Weissermel, 1925 with the worldwide distributed ahermatypic genus Palaeocyathus Foerste, 1888 (including also Enterolasma Simpson, 1900) known from Llandoverian/Wenlockian – Eifelian times. The species Palaeocyathus posthumus as well as the genus are still unknown in the classical Silurian sequences of Gotland and Estonia, which may be the possible origin of the glacial drift. At present, a more precise age determination within the Llandoverian, Wenlockian, or Ludlovian can not be achieved. The nearest certain occurrence of the genus is the early Wenlockian Palaeocyathus conicus (Bul'vanker, 1952) of Podolia (Ukraine), situated likewise on the southwestern margin of the ancient Baltoscandian shield; other records such as the Ludlovian Palaeocyathus bohemicus (Počta, 1902) from the Barrandian (Czech Republic) and Palaeocyathus radiatus (Münster, 1839) from Upper Franconia (Saxothuringia, Germany) are more distant on Gondwana-derived terranes.