Leptichnus tortus isp. nov., a new cheilostome etching and comments on other bryozoan-produced trace fossils

Leptichnus tortus isp. nov., a new cheilostome etching and comments on other bryozoan-produced trace fossils - A new etching trace Leptichnus tortus isp. nov. is described for small groupings of relatively widely spaced pits spirally arranged around a central, larger pit. The inclusion of this new ichnospecies within Leptichnus forces the generic diagnosis to be amended to take into account the latter character. Smaller isolated pits can be locally present, mostly near the central pit. The new ichnotaxon is presently reported from Upper Pleistocene sediments from the Ionian Sea and incipient formation of comparable traces has been commonly observed in thanatocoenoses from the Eastern Sicilian shelf. The producers are setoselliniform bryozoans belonging to Setosella vulnerata and Setosellina capriensis whose traces show no differences. Pit size and shape vary according to the development of basal lacunae and of local dissolution affecting the underlying substratum, and to substratum morphology, its mineralogical composition and above all its structure. The placement of Lepthichnus within ichnotaxonomy (Fixichnia and Domichnia) is discussed. Confusion and ambiguity in treating boring bryozoans within zoological and ichnological taxonomies are discussed.