Summary:

Hitherto, large crinoid pluricolumnals and attachment structures, commonly c. 30–60+ mm in diameter, from the Mississippian of Salthill Quarry in Lancashire, England, have been left in open nomenclature. The columnal morphospecies Bystrowicrinus (col.) westheadi sp. nov. is erected for these pluricolumnals, representing the dististele and attachment structure of a xenomorphic crinoid stem of a cladid or camerate. The column is homeomorphic or irregularly heteromorphic, with a circular, elliptical or pentagonal section, a relatively small pentastellate lumen, radially symplectial articulation and distal radicular attachment. The mesistele-dististele transition involves an abrupt increase in diameter. No large thecae known from this site could obviously be associated with such a dististele. The large column grew to such a diameter over a period of years, indicated by numerous, densely packed growth lines. Attachment was by both robust, unbranched radices and the weight of the large, inflexible column. Nutrient absorption and gaseous exchange would have occurred through the ectoderm.

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