The graptolite nema: problem to all our solutions

Abstract

AbstractLack of understanding of the graptolite nema and virgula is probably the main cause of the general failure to arrive at a general mode of life theory for planktonic species. The nema and virgula are shown to be different structures. The nema may have had a rhabdosome rotational function at early growth stages; the primary function of the virgula may have been rhabdosomal rotation, whilst a secondary function was as a stipe growth guide. Rotational function would be inapplicable for pseudovirgulae and in synrhabdosomes.