Diagnosis.—Horizontal to subhorizontal, cylindrical to U-shaped burrows with dichotomously branched tunnels forming bundles (Fillion & Pickerill, 1990; Knaust, 2007).
Diagnosis. Horizontally bundled burrows preserved outwardly as convex hyporeliefs. Overall, the pattern is reniform, fasciculate, flabellate, broomlike, ungulate, linear, falcate, or circular. Most forms consist of a single or a few main branches showing a spreite structure that
give rise distally to numerous free branches. In other forms, the spreiten are lacking and branching tends to be secondary or more random. Individual branches are terete and finally annulate or smooth (after Han and Pickerill, 1994, based on Osgood, 1970, and Fillion and Pickerill, 1990).
Remarks. Seilacher (2007) confined Phycodes to tightly spaced bundles. Phycodes is regarded as a feeding structure produced by unknown organisms. In the Paleozoic, it is known mostly from shallow-marine sediments.For discussion of this ichnogenus, see Osgood (1970), Fillion and Pickerill (1990), Han and Pickerill (1994), and Seilacher (2000).