The Anastrophic Burial of Bivalves and its Paleoecological Significance

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access ABSTRACT The eight bivalve life habit groups-(1) epifaunal suspension feeders, (2) borers, (3) deep-burrowing siphonate suspension feeders, (4) infaunal nonsiphonate suspension feeders, (5) infaunal mucus tube feeders, (6) shallow-burrowing siphonate suspension feeders, (7) labial palp deposit feeders, and (8) infaunal siphonate deposit feeders-are distinct with regard to escape potentials. Escape potentials (i.e., the maximum depth of burial from which the members of an animal group or taxon are able to dig out and successfully reestablish themselves in normal feeding position) have been determined through laboratory experiments for 25 species of bivalves. Escape potentials range from < 5 cm to > 50 cm. Major factors controlling escape potentials are bivalve life habits, degree of mantle fusion and siphon formation, and sediment type. Examination of sedimentary structures formed by escaping bivalves has revealed that, while all species produce what appears in vertical section to be a nested series of inverted cones, horizontal sections show a cross-sectional outline of the bivalve shell. X-ray photography shows that some bivalves have escape orientations (anterior uppermost) distinctly different from normal feeding orientations (posterior uppermost). The escape potentials of the various bivalve life habit groups are a selective factor in the formation of modern and fossil communities, bias fossil assemblages, and probably were important in evolutionary radiations. Because of their escape burrows, escape behavior, and distribution, bivalves are excellent indicators of sedimentary environments and rates of sedimentation.