Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Prokop, Petr

Remarks on palaeobiology of juvenile scyphocrinitids and marhoumacrinids (Crinoidea, Camerata) in the Bohemian uppermost Sillurian and lowermost Devonian

Journal of the Czech Geological Society, volume 46 (2001), issue 3-4, 259 - 268

Numerous crinoid cirriferous holdfasts have been discovered attached practically exclusively to the concavity within inner side of collars of plate loboliths and cirrus loboliths (including a problematical small bulbous structure which may be interpreted as a juvenile lobolith) in the weathered limestones of uppermost Silurian and partly lowermost Devonian age of the Barrandian area (Bohemia, Czech Republic). All those remains come from the so-called "lobolith hillside" locality near Praha-Řeporyje. The holdfasts are photographed here and interpreted as juvenile roots of the float-bearing crinoids, particularly genera Scyphocrinites and Carolicrinus. Both genera, superfically very similar, co-existed in the uppermost Silurian of Bohemia (there are still no certain specimens of Carolicrinus in the Devonian). They have structurally different crowns suggesting different ontogenies as well as phylogenies (and very probably different types of floats, i.e. cirrus lobolith and plate lobolith). The authors have found no evidence of previously supposed cosmopolitan distribution of particular float-bearing species, rather that of more or less restricted colonies of different species and even genera. It is concluded that in the float-bearing crinoids their possible short swimming larval phase was responsible for the limited palaeogeographical distribution of adults. According to the material at authors' disposal, there seems to be evidence of limited active swimming as well as active settlement behaviour in larvae of float-bearing crinoids from Bohemia, and a striking probability that juveniles remained attached to particular adults until small floats attained a functional size (supporting a hypothesis proposed by Strimple 1963).