Entobia is a trace fossil in a hard substrate (typically a shell, rock or hardground made of calcium carbonate) formed by clionaid sponges as a branching network of galleries, often with regular enlargements termed chambers. Apertural canals connect the outer surface of the substrate to the chambers and galleries so the sponge can channel water through its tissues for filter feeding (Bromley, 1970). The fossil ranges from the Devonian to the Recent (Taylor and Wilson, 2003; Tapanila, 2006).
- Bromley, R.G. (1970). "Borings as trace fossils and Entobia cretacea Portlock, as an example". Geological Journal, Special Issue 3: 49–90.
- Tapanila, L. (2006). "Devonian Entobia borings from Nevada, with a revision of Topsentopsis". Journal of Paleontology 80: 760–767. doi:10.1666/0022-3360(2006)80[760:DEBFNW]2.0.CO;2.
- Taylor, P.D., Wilson. M.A. (2003). "Palaeoecology and evolution of marine hard substrate communities". Earth-Science Reviews 62: 1–103. doi:10.1016/S0012-8252(02)00131-9.