Dictyoporus Mägdefrau, 1937

Wisshak, Max, 2017, Taming an ichnotaxonomical Pandora’s box: revision of dendritic and rosetted microborings (ichnofamily: Dendrinidae), European Journal of Taxonomy 390, pp. 1-99 : 43-44

Dictyoporus Mägdefrau, 1937

Cicatricula Palmer & Palmer, 1977: 186.

Dendrorete Tavernier et al., 1992: 304.

Type ichnospecies

Dictyoporus nodosus Mägdefrau, 1937 , by monotypy.

Original diagnosis

n/a

Emended diagnosis

Radiating, reticulate system of etched channels or prostrate tubular borings at or immediately beneath the surface of calcareous substrates. High degree of anastomosis, leaving only a few peripheral branches blind ending.

Original description

Distinctly net-shaped cavity system in belemnite rostra without external opening. [Translated from German]

Remarks

A reinvestigation of the holotype of the type species and a wealth of new material from other localities exposing Upper Cretaceous strata in northern Germany revealed a considerable morphological variability between specimens, as well as within one and the same trace of D. nodosus . This variability concerns the degree of anastomosis, the mesh size, and – most importantly – the occurrence and co-occurrence of shallow open channels and prostrate endolithic tunnels. While the distinction between open and closed galleries is possible in well-preserved material, it is often altered even by slight erosion or diagenetic pressure dissolution, complicating a confident discrimination. As a consequence, a morphological and ichnotaxonomical distinction of D. nodosus from several other ichnotaxa cannot be maintained and herein leads to a widening of the ichnogenus diagnosis and a number of synonymisations.At the ichnogenus level, this concerns the ichnogenus Cicatricula Palmer & Palmer, 1977, which was only distinguished from Dictyoporus by its preservation as open channels, while its most conspicuous feature, the high degree of anastomosis, was not part of the original ichnogenus diagnosis. However, that feature in particular and the flat and widened branching points strongly support an inclusion within Dictyoporus . Elias (1980) made the case that both Cicatricula and Calcideletrix should be considered as synonyms of Dictyoporus that run at and below the substrate surface, respectively. However, Calcideletrix is clearly distinguished from Dictyoporus based on other, more distinct, morphological characters (i.e., almost complete lack of anastomoses, regular rhizoidal connections to substrate surface, etc.), and a synonymisation with Dictyoporus is thus not recommended. Another potential junior synonym is Repentella Müller, 1968, the description and illustrations of which suggest the presence of tunnels with anastomoses similar to those in Dictyoporus . However, reinvestigation of the type material clearly showed that they are merely moulds of epiliths and not trace fossils. The morphology of Dendrorete Tavernier, Campbell & Golubic, 1992 also corresponds closely to that of Dictyoporus and the former ichnogenus is herein regarded as another junior synonym. Its type ichnospecies is the only ichnospecies that is morphologically clearly distinct from D. nodosus and is thus retained as a new combination.