Family Siboglinidae Caullery, 1914

(vestimentiferan)

‘Figueroa tubes’

(Fig. 15 A–F, H, I)

1999b Vestimentiferan tube worm Little et al.: 168, fig. 2b–d.

2004 Vestimentiferan tube indeterminate Little et al.: 545, figs 7.3, 8.1–8.7, 11.5

Material. FF-10, FFC-00, FFC-12, FFC-18, FFC-19, FFC-37, blocks of vent sulphides containing fossilized tube fragments, tubes often occurring singly. Collected by C. T. S. Little.

Occurrence. Figueroa massive sulphide deposit, San Rafael Mountains, southern California, USA. Franciscan Complex, Pliensbachian, Lower Jurassic (Little et al. 1999a, 2004).

Description. Pyritic tubes are 0.3–6.9 mm in diameter, appear to have been originally rigid as they do not exhibit folds or depressions in their walls, and are fairly straight (Fig. 15A). One long tube fragment appears to taper along its length (Fig. 15A). Tubes possess collars (Fig. 15B–D) which are large and flaring in some cases (Fig. 15B, D), some tubes showing several collars in short succession (Fig. 15B), the collars sometimes oriented obliquely (Fig. 15C). The tube walls are ornamented with fine, bifurcating longitudinal and irregular transverse wrinkles (Fig. 15A–C, E, F). In section, tube walls are preserved by colloform and framboidal pyrite, and it is unclear whether tubes were originally multi-layered (Fig. 15H, I).

Remarks. These tubes group with siboglinids in both PCA and cladistic analyses (Figs 22, 24). The presence of large, flaring collars suggests that they are unlikely to have been made by chaetopterids. Serpulids and vestimentiferans both produce collars which are large and flaring; however, the pattern of fine longitudinal and irregular transverse wrinkles on tube surfaces suggests that the tubes are more likely to have been made by vestimentiferans, as fine longitudinal wrinkles are not commonly observed in serpulid tubes. The ornamentation of the Figueroa tubes also greatly resembles that of Ridgeia piscesae tubes (Fig. 15G). Therefore, we infer that the most likely constructors of the Figueroa tubes were vestimentiferans.