Dictyoporus nodosus Magdefrau 1937
Creators: name: Wisshak, Max
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Dendrinidae
Dictyoporus
Dictyoporus nodosus

description: Dictyoporus nodosus Mägdefrau, 1937
Fig. 15
Dictyoporus nodosus Mägdefrau, 1937: 55, pl. IV, fig. 10.
Cliona fenestralis Elias, 1957: 383, pl. 40, fig. 2.
Cicatricula retiformis Palmer & Palmer, 1977: 185, fig. 6.
Dictyoporus garsonensis Elias, 1980: 273, figs 1–3.
Dictyoporus nodosus – Häntzschel 1962: W230, fig. 144-5 (reproduced from Mägdefrau 1937); 1975: W127, fig. 78-5 (reproduced from Mägdefrau 1937). — (?) Pugaczewska 1965: 75, pl. I, fig. 1; 1970: 427, pl. I, fig. 1. — Nadjin 1969: 155, pl. IV, fig. 10 (reproduced from Mägdefrau 1937). — Plewes 1996: 191, pl. 36, figs 1–7. — Buatois et al. 2017: 161, fig. 75D (holotype). — Breton et al. 2017: 46, fig. 3D.
Without name – Lindström 1979: 154, fig. 2A–C. — Girod & Rösner 2013: 282, fig. 15c.
Calcideletrix breviramosa – Ghare 1982: 132, pl. 1, fig. 6. — (?) Košt’ák 2004: 32, fig. 12 (poor illustration).
Calcidelatrix flexuosa – Plewes 1996 (partim): 186, pl. 33, figs 3, 5, pl. 34, figs 5–6. — (?) Košt’ák 2004: 32, fig. 11 (poor illustration).
Dendroid-Form A – Bundschuh 2000: 63, pl. 8, figs 5–8.
Dendroid-Form C – Bundschuh 2000: 66, pl. 9, figs 3–5.
Original diagnosis
n/a
Emended diagnosis
Overall shape as well as gallery diameter and mesh-size varies but generally decreases towards the periphery of the trace. Branching points flattened parallel to the substrate surface and with rounded outline. Peripheral branches taper to pointed ends and have a jagged appearance. Galleries either developed as open channels and/or prostrate tunnels with few rhizoidal connections to the substrate surface.
Original description
Channels 0.06–0.08 mm in diameter, with swellings at branching or crossing points. [Translated from German]
Supplementary description
The morphology of this ichnospecies is quite variable and partly dependent on the ontogeny of the trace or the type of substrate. All of this variability is evident in the Upper Cretaceous material alone and concerns the overall shape of the traces, ranging from radial symmetrical and circular to oval specimens (Fig. 15C) to more irregular outlines with little discernible centre (Fig. 15 A–B, D–F). It also concerns the degree and the mesh size of the anastomoses, with a general trend towards smaller size at the periphery of the trace, which often goes along with a decrease in gallery diameter (Fig. 15 C–F). Most conspicuously, the variability is expressed in the preservation of the galleries as open surficial etchings vs true endolithic tunnels, including the combination of both orientations within one and the same trace, either laterally grading into each other (Fig. 15D) or developed as multiple tiers (Fig. 15 E–F). Published data on the diameter of the trace range from 0.5 to 14 mm (Elias 1957, for junior synonym Cliona fenestralis; Palmer & Palmer 1977, for junior synonym Cicatricula retiformis; Bundschuh 2000 for synonyms ‘Dendroid-Form A’ and ‘Dendroid-Form D’), and tunnel diameters were specified to range from 60 to 80 µm (Mägdefrau 1937; Plewes 1996).
Type material, locality and horizon
The holotype (Fig. 15 A–B) is preserved in a Belemnitella mucronata (Schlotheim, 1813) rostrum from the Upper Cretaceous of Misburg near Hannover, Germany, deposited in the collections of the Institut für Geowissenschaften und Geographie, Halle, Germany (MLU.Mäg1937.IV.10).
Remarks
As noted above, the considerable morphological range of D. nodosus questions the validity of a number of other ichnotaxa characterised by strongly anastomosing networks of channels or shallow tunnels. As a consequence, a number of ichnospecies are herein lumped within D. nodosus as subjective junior synonyms. This concerns Cliona fenestralis, established by Elias (1957) as a sponge biotaxon, based on a single natural cast in a Carboniferous brachiopod. The holotype is currently lost but the morphological resemblance to D. nodosus is evident from the original illustration alone (reproduced in Fig. 15G). The second junior synonym is Cicatricula retiformis, reported by Palmer & Palmer (1977) from an Ordovician hardground (Fig. 15H). Its preservation as an anastomosing network of open channels does not merit retaining a separate ichnospecies, let alone ichnogenus. The third junior synonym is Dictyoporus garsonensis, established by Elias (1980) based on traces in an Upper Ordovician rugose solitary coral and characterised as a combination of larger, surficial to epilithic anastomoses grading into smaller, endolithic tunnels in the periphery of the trace (Fig. 15I). Reinvestigation of the holotype showed that the diagenetic alteration and state of preservation render such a distinction problematic, and the body fossil preservation of epilithic algae thalli (according to Elias the part of the trace shown at the top of Fig. 15I) is herein questioned. These features more likely present mineralised infills of either shallow etched channels or exposed parts of endolithic tunnels, and both of these features are well within the morphological range of D. nodosus. The trace also appears to be very common in Silurian skeletal carbonates, such as reported by Bundschuh (2000) under the informal names Dendroid-Form A and C, with the two forms again illustrating the morphological variability of D. nodosus, which agrees with the appearance of this trace in epoxy casts of Cretaceous specimens.
description: Published as part of Wisshak, Max, 2017, Taming an ichnotaxonomical Pandora's box: revision of dendritic and rosetted microborings (ichnofamily: Dendrinidae), pp. 1-99 in European Journal of Taxonomy 390 (390) on pages 44-46, DOI: 10.5852/ejt.2017.390, http://zenodo.org/record/3839858