Arenicolites is a U-shaped ichnotaxon (trace fossil)[1] dating from Ediacaran times onwards in South Australia. The trace shown by this fossil, is a pair of closely spaced circles on a bedding plane. In vertical section the traces are U- or J-shaped. They appear to be burrows made by a kind of worm.[2]
References
^Gevers, T.W.; Frakes, L.A.; Edwards, L.N.; Marzolf, J.E. (1971). "Trace Fossils in the Lower Beacon Sediments (Devonian), Darwin Mountains, Southern Victoria Land, Antarctica". Journal of Paleontology. 45 (1): 81–94. JSTOR1302754.