On the doctrine of ichnotaxonomic conservatism: the differences between ichnotaxa and biotaxa

摘要

Abstract: If the aim of ichnotaxonomy is to develop a practical and biologically realistic system of delimiting and naming trace fossils, it is important to keep five precepts, or guiding principles, clearly in view:(1)ichnotaxonomy(in general representing behavioral records)and biologic taxonomy(rep-resenting evolutionary products such as species and clades)are never equivalent;(2)ichnogenera stand for major structural themes of preserved behavioral patterns or patterns of substrate modifica-tion(defined using exclusive, essential characters or primary ichnotaxobases);(3)ichnospecies stand for(intergrading or discontinuous)variations on these major themes(defined using characters or ichnotaxobases of secondary rank);(4)just enough ichnotaxa should be delimited and named to fill out the possibilities of character space(resulting in a nomenclatural system that is both realistic and neither over-divided nor impoverished - the 'middle path' of naming trace fossils); and(5)descrip-tions and interpretations of ichnotaxa must be kept absolutely separate(to the point of isolating them in different sections of publications). Most ichnologists already follow these guidelines; losing sight of them, however, has resulted in blurring of ichnotaxa and evolutionary units, excessive lumping or splitting that obscures actual diversity, and a reputation for a largely arbitrary system of delimitation and naming of trace fossils.