Nododendrina incomposita ( Mägdefrau, 1937 ) Wisshak, 2017

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 : 56-58

Nododendrina incomposita ( Mägdefrau, 1937) comb. nov.

Fig. 20

Dendrina incomposita Mägdefrau, 1937: 56 , pl. IV, fig. 2.

Dendrina minor Mägdefrau, 1937: 56 , pl. IV, fig. 3.

Hyellomorpha microdendritica Vogel et al., 1987: 275 , fig. 8.

Dendrina incomposita – Nadjin 1969: 138, pl. IV, fig. 2 (reproduced from Mägdefrau 1937).

Dendrina minor – Nadjin 1969: 138, pl. IV, fig. 3 (reproduced from Mägdefrau 1937).

Hyellomorpha – Vogel 1987: fig. 7.

Hyellomorpha microdendritica – Schnick 1992: 112, pl. 1–2.

Globodendrina monile – Plewes 1993 et al. (partim?): fig. 1B .

Original diagnosis

n/a

Emended diagnosis

Prostrate branches diverge from a small and irregularly shaped central node, ramify at various angles, and exhibit an irregular surface texture. Density of branching varies and anastomosis or complete fusion is common.

Original description

Cavity system 0.18 to 0.3 mm in total diameter, with ramifications less regular than in D. belemniticola . [Translated from German]

Supplementary description

Vogel et al. (1987) gave the following detailed description in their diagnosis of the junior synonym Hyellomorpha microdendritica from the Devonian: “Rosette-shaped, repeatedly branched systems, up to 0.5 mm (0.24 ± 0.078 [49]). Branches diverge radially, parallel to and immediately beneath the substrate surface, from a small central node (at the presumed point of entry). Anastomoses are common. The central node, approximately isodiametric 20–80 µm (50.26 ± 19.8 [16]) in diameter, represents the deepest penetrating part of the system. Branches diverge in straight line at angles ranging from 50° to 120° (76 ± 17 [21]), or are slightly curved, or change direction abruptly. The density of branching varies within samples. Branches are circular in cross section, with a diameter of 8–19 µm (11.2 ± 2.8 [63]), at their distal ends swollen to a diameter of 10–30 µm (17.9 ± 5.3 [55]). The surfaces are smooth (except for substrate imprints).”

Type material, locality and horizon

Several dozen type specimens ( Fig. 20A ) of N. incomposita are preserved in a brachiopod shell from the Lower Maastrichtian (Upper Cretaceous) of Rügen, Germany, deposited in the collections of the Institut für Geowissenschaften und Geographie, Halle, Germany ( MLU. Mäg1937. IV.2). One of these specimens (indicated by an arrow in Fig. 20A ) is hereby selected as the lectotype, rendering the other specimens in the brachiopod paralectotypes. The lectotype is selected on the basis of it being the most typical and best preserved specimen in the type sample, and the best visible specimen in Mägdefrau’s original figure ( Mägdefrau 1937: pl. IV, fig. 2 upper left).

Remarks

Mägdefrau’s (1937) Dendrina minor is in the size range of N. microdendritica and shows a very similar silhouette in reflective and transmitted light microscopy ( Fig. 20 J–K) rendering it a most probable junior synonym (by page priority). However, it was not possible to observe the central node in the type material and the synonymisation should thus be confirmed as soon as topotypic material is available for epoxy casting.

According to Schnick (1992: pl. 2), the trace forms in three ontogenetic stages, starting with the development of the central node, followed by the lateral development of the prostrate plexus, and consecutive fusion of the plexus around the central node. The first two phases of this ontogenetic series closely resemble the development of N. europaea , as illustrated (as Semidendrina pulchra ) by Wisshak (2006: fig. 24) and Bromley et al. (2007: fig. 32.4). This circumstance complicates the distinction of immature N. microdendritica from the latter ichnospecies, which is, however, larger in diameter and its plexus always emerges to only one side from the node, whereas this limitation does not apply to N. microdendritica or N. nodosa . The latter ichnospecies is much larger and exhibits a lower degree of fusion of the prostrate galleries.

Figures

Fig. 20. Nododendrina incomposita (Mägdefrau, 1937) comb. nov. A. Lectotype (arrow) and several paralectotypes in a brachiopod shell from the upper Maastrichtian of Rügen, Germany. B. Topotypic shell of the brachiopod Chatwinothyris Sahni, 1925 with several specimens in various ontogenetic stages. C. Mirror-symmetrical SEM image of epoxy cast of the same shell. D–G. SEM close-ups of various specimens from the same shell, illustrating an ontogenetic series. H–I. Cluster of traces and close-up of holotype of junior synonym Hyellomorpha microdendritica Vogel et al., 1987, in a cast of the brachiopod Mediospirifer Bublichenko, 1959 from the Devonian at Lake Erie, New York, USA. J–K. Reflective and transmitted light micrographs of syntypes of the junior synonym Dendrina minor Mägdefrau, 1937 in an Ordovician trilobite fragment from erratics found near Köthen, Germany.

Fig. 1 (page 7). Morphological characters of dendrinid microborings with respect to overall shape and symmetry of the trace, its vertical profile, openings to the substrate surface, orientation of entrance tunnel (where present), branching pattern and surface texture (in order of decreasing relevance as ichnotaxobase).