Annelida Lamarck, 1809

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 : 8-10

Phylum Annelida Lamarck, 1809

Family incertae sedis

‘Sassenfjorden area tubes’

( Fig. 14 )

2011 ‘vestimentiferan’ worm tubes Hammer et al. 21, fig. 5d.

2012 worm tubes Hryniewicz, Hammer et al. 118, fig. 5a.

Material. Svalbard 2007-03, long tube with yellowish wall. PMO 2009-01, single tube with dark black wall. PMO 2009-03: single tube with longitudinal wrinkles. 171.002D, 170.996, 171.027, selection of thin sections of different tubes. Donated by K. Hryniewicz.

Occurrence. Sassenfjorden area, Svalbard. Seep carbonates in shale and shale and siltstone, Slottsmøya Member, upper Agardhfjellet Formation, Volgian–Ryazanian (latest Jurassic–earliest Cretaceous) ( Hammer et al. 2011; Hryniewicz et al. 2012, 2015; Vinn et al. 2014).

Description. Carbonate tube sections measuring 2.9– 5.7 mm in diameter, all fairly straight, and not attached to other tubes. The long tube appears unornamented ( Fig. 14A ) and the tube with a black wall is smooth and shows no ornamentation apart from a possible small collar ( Fig. 14B ), while the remaining tube fragment bears what may be faint longitudinal wrinkles ( Fig. 14C ). In thin section, some of the tubes exhibit thick, neatly multi-layered walls ( Fig. 14D, E ). Curving delaminated layers can also be observed in some of the tube sections ( Fig. 14F ), suggesting that they were originally organic in composition. A subset of tubes exhibit diffuse (poorly preserved?) tube walls ( Fig. 14G ).

Remarks. Non-serpulid, originally organic-walled tubes from the Sassenfjorden area were suggested to have been made by siboglinids ( Hammer et al. 2011; Hryniewicz et al. 2015). However, the tubes examined do not clearly group with the tubes of modern annelid families included in cladistic and cluster analyses ( Figs 22 , 24 ). The tube sections with thick, neatly multi-layered walls that were observed within this study were possibly made by vestimentiferans, in which this tube structure is widely observed. However, the broad morphology of this tube is presently unknown, and tubes from this deposit in general warrant further investigation as several different tube types are present. Hence, these tubes are broadly ascribed to the annelids.

Figures

Figure 14. ‘Sassenfjorden area tubes’, Volgian–Ryazanian, Svalbard. A–C, hand specimens of tubes; A, Svalbard 2007-03, long tube with poorly preserved walls; B, PMO 2009-01, smooth-walled tube possibly with a small collar; C, PMO 2009-03, tube with possible longitudinal wrinkles. D, E, 171.002D, near-transverse sections of tubes with thick, neatly-multi-layered walls. F, 170.996, detail from transverse section of a tube where the tube exhibits curving layers that have separated. G, 171.027, tube with poorly preserved walls. Scale bars: A = 10 mm; B = 2 mm; C = 5 mm; D, E = 300 µm; F = 100 µm; G = 200 µm.

Figure 22. Strict consensus cladogram of the three most parsimonious trees of tubes built by a total of 43 modern annelid taxa (best score = 14.344, consistency index = 0.308, retention index = 0.629). The analysis was based on the 48 mostly morphological tube characters and was performed using implied character weighting (k = 3). Numbers on nodes represent groups present/contradicted support values. Symbols/colours indicate taxonomic affinities.

Figure 24. Fourier transform infrared (FTIR) spectroscopy spectra of the organic tubes of vent and seep annelids. Spectra are offset on the absorbance axis, and key spectral absorbance peaks are labelled with the types of chemical bonds they represent: -NH, nitrogenhydrogen; -CH, carbon-hydrogen; -OH, oxygen-hydrogen. The regions of the tube analysed are as follows: Tevnia jerichonana (anterior, inner tube wall); Zenkevitchiana longissimi (middle, outer tube wall); Lamellibrachia anaximandri (posterior, outer tube wall); Sclerolinum contortum (anterior, outer tube wall); Alvinella sp. (middle); Spiochaetopterus izuensis (middle, outer tube wall).