?Phylum Annelida Lamarck, 1809

Family incertae sedis

‘Sibay tubes’

(Fig. 17)

1999c Indeterminate annelid? tube Little, Maslennikov, Morris, & Gubanov: 1061, figs 4, 5.

Material. NHMUK VF71, cluster of tubes. Collected by C. T. S. Little.

Occurrence. Sibay massive sulphide deposit, southern Ural Mountains, Russia (52 º 41.66 ' N, 58 º 38.15 ' E). Middle-Lower Devonian (Little et al. 1999c; Shpanskaya et al. 1999).

Description. Pyritic tubes 0.3–7.0 mm in diameter, nontapering, sometimes gently curved and with smooth walls (Fig. 17A, B) (Little et al. 1999c). The tube walls were originally described to be formed of fine-grained pyrite which is occasionally colloform (Little et al. 1999c). In thin sections examined during the present study, the tube walls appear thick and may be multi-layered (Fig. 17C), and some also appear to be comprised of framboidal pyrite (Fig. 17D).

Remarks. These tubes exhibit few distinguishing characteristics, which led to their previous diagnosis as indeterminate?annelid tubes (Little et al. 1999c). As we were unable to find further characters, the tubes were largely unresolved within cluster and cladistic analyses (Figs 22, 24). The indeterminate status of the tubes is therefore maintained. They are tentatively suggested to be annelid tubes due to their smooth, thick and possibly multi-layered walls, and as they do not closely resemble the tubes of other Palaeozoic tubicolous animals.