Dictyoporus balani ( Tavernier, Campbell & Golubic, 1992 ) 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 : 47-48

Dictyoporus balani ( Tavernier, Campbell & Golubic, 1992) comb. nov.

Fig. 16

Dendrorete balani Tavernier, Campbell & Golubic, 1992: 304 , figs 2–3.

Without name – Rooney & Perkins 1972: 1146, figs 12, 14.

Dendrorete balani – Tavernier & Golubic 1993: 409, fig. 2. — (?) Blissett & Pickerill 2007: 82, fig. 3 (dubious illustration).

Original diagnosis

Shallow, radiating to prostrate boring networks spread beneath the shell surface of the barnacle Balanus sp. Individual systems range from 1 to 4 mm in diameter and penetrate 100–200 µm into the shell. They consist of tubular, branched and anastomosing tunnels. The tunnels spread immediately below, and parallel to the substrate surface, they branch repeatedly and fuse at contact, forming twodimensional networks. At the periphery of the system, long and shallow “exploratory” tunnels penetrate the substrate and branch. Branching is subdichotomous or lateral, diverging at angles of 82° ± 19° (50). The branches behind the expansion front arch deeper into the substrate and anastomose. The average mesh size of the resulting reticulum is 257 ± 63 (16) µm. Pointed lateral branches that originate along the interconnecting tunnels give the network a spiny appearance, and ultimately subdivide the network. As a consequence, the density of the net in the older parts increases by secondary branching (mesh size 103 ± 28 (26) µm). In addition, the tunnels send out at intervals finer tubular connections (10 ± 2.5 (18) µm) to the substrate surface. The main tunnels are circular or ellipsoidal in cross-section, with the longer axis oriented upright, i.e., perpendicular to the substrate surface. They are 20–50 µm in diameter (M ± s (n) = 35.5 ± 8.5 (78) µm), appear knobby, and are occasionally widened at branch points. The boring starts from a single point of entry and spreads initially in a radiating fashion. When cast in resin, these young diverging tunnels resemble the surface roots of some tropical trees. In later stages the network becomes prostrate, and the radiating pattern is masked by anastomosing cross-connections. Thus, a mature boring system of Dendrorete balani is organized in three concentric zones. The peripheral (youngest) one is the zone of lateral spreading of the boring system with straight, shallow “exploratory” tunnels. In the second zone behind, these tunnels interconnect to form a flat horizontal reticulum. Branches oriented toward the interior that form deeper arches are more common in the third (oldest) zone resulting in a three-dimensional reticulum.

Emended diagnosis

Tunnels branch sub-dichotomously or laterally, occasionally widened at branch points, circular or ellipsoidal in cross-section, with the longer axis oriented perpendicular to the substrate surface, sending out finer tubular connections at intervals to the substrate surface. A mature boring system is organised in three concentric zones, a peripheral zone of lateral spreading with straight, shallow tunnels, a second zone behind with tunnels interconnecting to form a prostrate reticulum and branches more commonly forming deeper arches of a three-dimensional reticulum in the central zone.

Original description

n/a, but see detailed original diagnosis.

Type material, locality and horizon

Holotype ( Fig. 16 A–B) in resin-cast of a Balanus fragment from the Purisima Formation, Pliocene, sampled at the base of a sea cliff at Capitola State Beach, Capitola, CA, USA. It is supposedly deposited in the Harvard University Paleobotanical Collection ( HU-62706 ), but is at present not traceable in this collection.

Remarks

Originally established within the ichnogenus Dendrorete, which is herein regarded as a junior synonym of Dictyoporus (see above).

Dictyoporus balani is clearly distinguished from D. nodosus by the more distinct ontogenetic zones, including deeper arches in the central (oldest) part of the trace, a higher number of rhizoidal connections to the substrate surface, a generally smaller trace and tunnel diameter, and by its mesh-size decreasing in the centre due to secondary interconnecting tunnels. In contrast to D. nodosus , this ichnospecies always consists of endolithic tunnels only.

Figures

Fig. 16. Dictyoporus balani (Tavernier, Campbell & Golubic, 1992) comb. nov. A. SEM of holotype (lower right corner) in an epoxy cast of a Pliocene Balanus shell (reproduced from Tavernier et al. 1992: fig. 1A). B. Close-up of holotype (reproduced from Tavernier et al. 1992: fig. 1D). C. Prostrate peripheral reticulum with rhizoidal connections to the substrate surface (reproduced from Tavernier et al. 1992: fig. 2B).