Phycosiphon incertum Fischer-Ooster, 1858

Description.This ichnotaxon is observed as small, dark, contorted burrows surrounded by a poorly definedlight halo (Fig. 3E). Diameter is 0.2–0.5 cm.

Diagnosis.—Small, oblique or parallel to bedding, spreiten-filled burrow systems comprised of protrusive U-shaped lobes with dark, fine-grained cores and light, coarse-grained mantles (Wetzel & Bromley, 1994; Głuszek, 1998; Uchman, 1998).

Horizontal to subhorizontal elongated lobes encircled partially by a thin, commonly winding marginal tunnel. The lobes are 2–3 mm wide, up to 16 mm long. The marginal tunnel is about 3 mm wide and filled with lighter material than the surrounding rock.

This is a typical deposit feeder trace fossil. For its taxonomy see Wetzel and Bromley (1994). Morphological problems were studied by Naruse and Nifuku (2008) and Bednarz and McIlroy (2009).

Remarks-The burrows resemble Furculosus carpathicus Roniewicz and Pienkowski 1977 but this forms tighter fork-like loops, has a larger burrow diameter, and a greater 3-dimensional continuity.