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Sphenothallus Hall, 1847 from Cambrian of Skryje–Týřovice Basin (Barrandian area, Czech Republic)

Fatka O., Kraft P.

Annales Societatis Geologorum Poloniae

2013

Vol. 83, No. 4

309--315

Two conical tubules from shales of the Skryje Member (Buchava Formation) at the Skryje–Luh and Týřovice–“Pod hruškou” localities, two of the key outcrops of this stratigraphic unit in the Skryje–Týřovice Basin (Barrandian area, Czech Republic), are described. One specimen consists of a small, compressed tubule with a very low expansion angle and wide and flat thickenings. The second, larger specimen exhibits indications of very narrow thickenings of a more abruptly expanding shell. Both specimens are assigned to the genus Sphenothallus Hall, but the latter only provisionally. Sphenothallus shows a worldwide distribution with numerous species, ranging from Cambrian to Permian in age. However, reported occurrences in the Cambrian are relatively sparse, in the form of rare specimens from the lower to middle Cambrian strata of Laurentia, Eastern Gondwana and European peri-Gondwana. According to accepted palaeogeographical reconstructions, Cambrian Sphenothallus occurred in low as well as in higher palaeolatitudes.

Arachnostega Bertling, 1992 in the Drumian (Cambrian) sediments of the Tepla-Barrandian region (Czech Republic)

Fatka O., Mikulas R., Szabad M., Micka V., Valent M.

Acta Geologica Polonica

2011

Vol. 61, no. 4

367-381

The presence of the ichnospecies Arachnostega gastrochaenae Bertling, 1992 is documented from the Cambrian for the first time. It occurs in several stratigraphical levels of the "middle" Cambrian sediments in the Pribram-Jince and Skryje-Tyrovice basins of the Tepla-Barrandian region in the Czech Republic. Simple tunnels as well as the complicated morphologies of Arachnostega were observed on internal moulds of trilobite exoskeletons and hyolith conchs and represent the oldest record of this ichnogenus. The Cambrian occurrences of Arachnostega on skeletal body fossils evoke the connection between the Arachnostega-type feeding strategy and the sudden appearance of numerous skeletal animals. The development of the Arachnostega-type behaviour can be considered a feature of the "Cambrian substrate revolution".