The ichnotaxonomic status of Plangtichnus and Treptichnus

A new ichnospecies, Treptichnus pollardi, is described from Carboniferous lacustrine rocks of the Paganzo Basin, northwestern Argentina. Accordingly, the ichnotaxonomic status of the ichnogenera Plangtichnus and Treptichnus is reviewed. Because these ichnotaxa represent different parts of the same 3D zigzag structure, they are considered to be synonymous. Considering historical usage, Plangtichnus is regarded as a nomen oblitum and Treptichnus as a nomen conservandum. Four Treptichnus ichnospecies have been recognized in the stratigraphic record: T. bifurcus, T. triplex, T. lublinensis, and T. pollardi  isp. nov. Treptichnus pollardi differs from the ichnospecies described hithertoo by the absence of segment projections and the presence of shafts vertical to the zigzag trace, expressed at the bedding plane by pits either at the angle of juncture between burrow segments or within burrow segments. It is also distinguished from T. lublinensis and T. triplex by its thinner burrow segments.