Occurrence of bioglyphs on Ocypode crab burrows in a modern sandy beach and its palaeoenvironmental implications

The ichnological term “bioglyph” covers biogenic sculpture on burrow walls. Bioglyphs in the burrows of ocypodid crabs were studied in a modern unconsolidated sandy substrate (looseground) on Irino Coast, southwestern Japan. They are seen exclusively on sides and roof of the burrow, and are characteristically seen near the distal end of the burrow. Moist sandy substrate where sand particles are bound together by surface tension of interstitially suspended water might allow the production of such bioglyphs.Although bioglyphs are only partially developed in such burrows, those interpreted to have formed in semi-consolidated substrates (firmground) are known to be sculptured over the entire burrow surface. Such difference in the modes of bioglyph occurrence can be used as a criterion to reconstruct the substrate consistency in the rock record.