Kauffman, E.G., and Steidtmann, J.R., 1981, Are these the oldest metazoan trace fossils?: Journal of Paleontology, v. 55, p. 923-947.
Kauffman, E.G., and Steidtmann, J.R.
Journal of Paleontology, v. 55, p. 923-947.
Trace Fossil, Paleontology, Nankoweap Fm(Nankoweap Group) - Grand Canyon Supergroup - Middle Proterozoic,