Siboglinidae Caullery, 1914

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, Journal of Systematic Palaeontology 17 (4), pp. 287-329 : 304

?Family Siboglinidae Caullery, 1914

(?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.

Figures

Figure 11. Tubes from the Albian Christopher Formation, Canada. A, B, D, E, ‘Ellef Ringnes tubes’; A, NRC C-581891 QQA-10-22, tubes in hand specimen; B, NRC C-581891 QQA-10-22, sections of tubes; D, NRC C-541891CPPL, detail of a transverse section of a tube showing thick, multi-layered tube walls, with some possible misaligned torn fibres (white arrow); E, NRC C-541891CPPL, detail of a transverse section of a tube showing a break in the tube wall where it appears broken fibres have curved slightly and misaligned (white arrow). C, F, G, ‘Prince Patrick tubes’; C, NRC C-453952 1–4, tubes in hand specimen; F, NRC C-453961PPL, transverse section of a tube exhibiting thick, multi-layered tube walls; G, NRC C-453989PPL, longitudinal section of a tube with thinner walls containing round pellets. Scale bars: A–C = 10 mm; D, F, G = 1 mm; E = 500 µm.

Figure 23. Strict consensus cladograms constructed using a total of 64 modern and fossil annelid taxa and 48 mostly morphological tube characters. Analyses were performed using implied character weighting, with the concavity constant set as default (k = 3; A), and also set to downweight homoplastic characters less (k = 4; B). Numbers on nodes represent groups present/contradicted support values. Modern taxa are coloured according to taxonomic groups; fossil taxa are in grey. A, consensus of 271 most parsimonious trees (best score = 15.387, consistency index = 0.195, retention index = 0.264); B, consensus of 60 most parsimonious trees (best score = 13.568, consistency index = 0.232, retention index = 0.569). Symbols/colours indicate taxonomic affinities.