Pyritonema arctica Wisshak 2017, isp. nov.

• Main Author: Wisshak, Max
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2017
• Subjects: Biodiversity; Taxonomy; Animalia; Porifera; Hexactinellida; Lyssacinosida; Pyritonema; Pyritonema arctica; Jan Mayen; Svalbard
• Online Access: https://doi.org/10.5281/zenodo.3853717; http://treatment.plazi.org/id/8878B758BA489F684E362623FC03FC4C

Pyrodendrina arctica isp. nov. urn:lsid:zoobank.org:act: A41E7E41-748C-4DE6-B32F-6383C3852036 Fig. 24 ‘Sponge form VI’ – (?) Wisshak et al. 2005a: 991, fig. 7F. ‘Microsponge-form 6’ – (?) Wisshak 2006: 86, fig. 28H. Diagnosis Prostrate galleries with a high degree of anastomosis and a decrease in diameter toward the periphery. From the central node of trace, ramifying, sub-vertical tunnels with tapering terminations extend deeper into the substrate. Etymology Latinised from the geographic name Arctica, making reference to the known occurrence of this trace being limited to the polar waters off Svalbard and Jan Mayen (as well as one uncertain record from coldtemperate waters off Sweden). Type material, locality and horizon The holotype (Fig. 24 A–B) and one paratype (Fig. 24 C–D), together with several further specimens, are cast in epoxy resin from a subfossil (possibly Late Pleistocene to probably Holocene) shell of the bivalve Chlamys islandica (O.F. Müller, 1776), sampled in 75 to 85 m water depth at Sørkappbanken, SW Svalbard Shelf (76°23′ N, 15°57′ E; station 15/161-AGT of the ARK VI/1-4 Expedition of the RV Polarstern in 1989; see Krause et al. 1991 for details). Deposited in the trace fossil collection of the Senckenberg Institute in Frankfurt, Germany (SMF XXX 864, including the holotype, and SMF XXX 865, including the paratype). Description This species describes relatively large dendrinids with a basal network of anastomosing galleries, running closely parallel to the substrate surface and emerging from an indistinct central cavity (Fig. 24 A–E). At least near the centre of the trace, vertically-oriented tunnels reach deeper into the substrate (e.g., Fig. 24 A–B), with rapidly ramifying, tapering, and pointed terminations. The overall appearance of the trace in side view resembles a blazing campfire – in accordance with the ichnogenus name (Fig. 24A). Measured complete specimens range from 1067 to 2936 µm in maximum diameter (mean = 1779 ± 564 µm; n = 180), at a width of 824 to 2301 µm (mean = 1405 ± ...