(?vestimentiferan)
‘Ellef Ringnes tubes’
(Fig. 11A, B, D, E)
1989 serpulid worm tubes Beauchamp, Harrison, Nassichuk, Krouse, & Eliuk: 54, fig. 2.
1992 serpulid worm tubes Beauchamp & Savard: 438, figs 2b, 5b.
2013 tubeworms Williscroft: 20, fig. 5c, d.
2017 vestimentiferan worm tubes Williscroft, Grasby, Beauchamp, Little, Dewing, Birgel, Poulton, & Hryniewicz: 797, fig. 8l, m.
Material. NRC C-581891 QQA 10-22, clustered broken fragments of large tubes, mostly in various orientations however some tubes are aligned parallel to each other. NRC C-541891 CPPL, tubes observed in thin section. Provided by S. E. Grasby.
Occurrence. Ellef Ringnes Island seep carbonates, Arctic, Canada. Christopher Formation, Lower Albian, Cretaceous (Beauchamp et al. 1989; Beauchamp & Savard 1992; Williscroft 2013).
Description. Carbonate tubes are non-branching, do not appear attached to other tubes, and are not agglutinated (Fig. 11A, B). They are 2.0–10.0 mm in diameter, more or less straight, and have smooth walls. In thin section, the tubes show very thick, concentrically multi-layered walls (Fig. 11D, E) that are very likely organic due to the presence of breaks in the tube wall that reveal potential torn misaligned layers that have curved slightly away from each other (Fig. 11D, E). The round cross sections suggest that the tubes are likely to originally have been rigid and inflexible.
Remarks. These tubes were previously considered to have been made by serpulids (Beauchamp & Savard 1992; Williscroft 2013), but have more recently been interpreted as vestimentiferan worm tubes (Williscroft et al. 2017). Evidence of an originally calcareous tube wall such as chevron-like layering is absent, while torn fibres point to the tubes having been originally organic in composition. The thick tube walls and neat, well-consolidated multi-layering are very characteristic of vestimentiferan tubes, and the size of these tubes and their hardness support this interpretation. However, these tubes only group among modern siboglinid tubes when more homoplasy is permitted within the cladistic analysis (Fig. 23B). For the above reasons, we tentatively suggest that the large tubes from Ellef Ringnes Island are likely the anterior sections of vestimentiferan tubes.