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 : 295-296

?Family Siboglinidae Caullery, 1914

‘West Fork Satsop River tubes’

( Fig. 4 )

Material. JLG459C, WFSR-3B, several wavy tubes. WFSR-3A-1, several tubes observed in thin section. Donated by J. L. Goedert.

Occurrence. West Fork Satsop River, Grays Harbor County, Washington State, USA (~ 47 º 16 ' N, 123 º 33 ' W). Float seep limestone blocks. Lincoln Creek Formation, Oligocene ( Campbell & Bottjer 1993; Kiel & Amano 2013).

Description. Carbonate tubes up to 2.4 mm in diameter, somewhat sinuous, non-branching, and not appearing to have been agglutinated or to taper in the observed fragments ( Fig. 4A, B ). Tubes appear inflexible and unattached, and the tube walls are free of ornamentation. In thin section, the tube walls are brown, of variable thickness but finely multi-layered ( Fig. 4C, D ). An originally organic composition of the tube walls is also supported by confocal microscopy ( Fig. 25 ), and breaks in the tube wall can be observed showing potential frayed fibre endings ( Fig. 4D ).

Remarks. These tubes were resolved only within the cladistic analysis that allowed for more homoplasy ( Fig. 23B ), in which they fall among siboglinids. The fibrous organic composition and concentrically multi-layered walls are, however, also consistent with the tubes of chaetopterids, although the smooth walls and sinuosity of these tubes suggest that they are possibly more likely to have been made by siboglinids. We therefore tentatively suggest a siboglinid affinity.

Figures

Figure 4. ‘West Fork Satsop River tubes’, Oligocene, Washington State, USA. A, B, WFSR-3B and WFSR JLG 459C, respectively, tubes in hand specimen showing wavy nature and smooth tube walls. C, D, WFSR 3A-1; C, transverse section of tube showing multilayered brown walls of varying thickness; D, detail of tube wall where a potential preserved fibrous tear occurs, revealing frayed fibre endings (white arrow). Scale bars: A = 10 mm; B = 5 mm; C = 300 µm; D = 100 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.

Figure 25. Results of confocal laser-scanning microscopy (CLSM) of recently mineralized and ancient fossil annelid tubes (see online edition for colour version). Tubes are imaged in auto-fluorescence mode, where areas of fluorescence likely reflect the presence of organic matter. A, detail of mineralized Escarpia southwardae (Siboglinidae) tube transverse section. B, fossil tube from Upper Waiau River, New Zealand (UWT3-4), detail of transverse section. C, fossil tube from West Fork Satsop River, Washington State, USA (WFSR 1A), detail of transverse section. D, fossil tubes from Bexhaven, New Zealand (BXG), detail of two near-transverse sections. Scale bars: A = 100 µm; B–D = 200 µm.