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.

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).

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).

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.