Phylum Annelida Lamarck, 1809 Family incertae sedis ‘Rocky Knob tubes’ (Fig. 1) 2008 worm tubes Campbell, Francis, Collins, Gregory, Nelson, Greinert, & Aharon: 90, fig. 4b, c. 2010 worm tubes Saether, Little, & Campbell: 510, fig. 3c. 2011? Siboglinidae Saether: 73, fig. 5.1e–i. Material. RK-5, block of many large-diameter tubes, mostly in the same orientation. RK-15B-6, block of small-diameter tubes mostly in the same orientation. RNT1, many similar-sized tubes, mostly in the same orientation. RNT2, dense aggregation of small-diameter tubes in a range of orientations. 12-RK, small and larger diameter tubes, mostly in the same orientation. Donated by K. A. Campbell and collected by C. T. S. Little. Occurrence. Rocky Knob, northern Hawke’s Bay area, east coast of North Island, New Zealand (~ 38 º 19’S, 177 º 56’E). Seep carbonates occurring as isolated lenses in mudstone, Bexhaven Limestone Formation, Tolaga Group, Middle Miocene (Campbell et al. 2008; Saether et al. 2010; Saether 2011). Description. Carbonate tubes mostly straight and exhibiting a wide range of diameters, from 1.0 to 7.9 mm, preserved in clusters mostly of similar-sized tubes (Fig. 1A, B). In some clusters, tubes are preserved in the same orientation (Fig. 1B). The tubes are non-branching, large-diameter fragments taper somewhat (Fig. 1A), and some tube walls appear to be touching others (Fig. 1B, F). Tube walls are mostly smooth (Fig. 1C); however, one tube exhibits small round textures on its surface (Fig. 1D) while another small-diameter tube bears fine, long, continuous longitudinal wrinkles (Fig. 1B). Tube walls appear to have been originally fibrous as in places torn fibres are preserved (Fig. 1E), and some of the tubes also seem to have been originally flexible due to the occurrence of irregular tube cross-sections (Fig. 1F). The tubes show pronounced organic content (Fig. 1G; Supplementary File 1, Table S9). The tubes also appear originally to have been multi-layered (Fig. 1E, G, H), with delamination occurring between some layers (Fig. 1H). Some tube sections show well-consolidated lamination that is many layers thick (Fig. 1G, H). Remarks. Tubes from Rocky Knob have previously been tentatively ascribed to siboglinids (Saether 2011). However, cluster and cladistic analyses (Figs 22, 24) failed to place these tubes among the siboglinids or any other annelid families included in the analyses. Noting their similarity to vestimentiferan tubes, we therefore assign these tubes to the annelids only, as more information would be required to assign them to siboglinids. The abundance of these tubes at this ancient seep, large diameter range, generally smooth organic tube walls, and the thick, neatly multi-layered tube wall appearance in some of the specimens do suggest a vestimentiferan affinity. The round structures (Fig. 1D) present on the surface of a large-diameter tube may constitute the circular bases of aragonite botryoids (Fig. 1F).

Published as part of Georgieva, Magdalena N., Little, Crispin T. S., Watson, Jonathan S., Sephton, Mark A., Ball, Alexander D. & Glover, Adrian G., 2019, Identification of fossil worm tubes from Phanerozoic hydrothermal vents and cold seeps, pp. 287-329 in Journal of Systematic Palaeontology 17 (4) on page 291, DOI: 10.1080/14772019.2017.1412362, http://zenodo.org/record/10883381