Comparative analysis of living and death bivalve assemblages on the Kawarazu Shore, Ehime Prefecture, west Japan

Abstract

KAZUSHIGE TANABE, TOORU FUJIKI and TAKASHI KATSUTA (Faculty of Science, Ehime University), 1986. Comparative analysis of living and death bivalve assemblages on the Kawarazu Shore, Ehime Prefecture, west Japan (Bull. Jap. Assoc. Benthology), 30 :
Mode of occurrence and distributional patterns of living and dead shell assemblages of some infaunal bivalve species in the intertidal zone of the Kawarazu Shore, Ehime Prefecture, west Japan, were analyzed quantitatively. The results show that community or population ecological properties of living species (e.g.spatial distribution and population density) are not preserved directly in the death assemblage. The degree of modification in the early process of fossilization differs from species to species and/or area to area. Death assemblage consisting of conjoined valves, however, retain more reliable data of living community than those of detached valves. The articulation ratio of dead shells is influenced by biological (inhabiting depth, shell and ligament strength, tooth structure etc.) and physical (substratum type and bottom currents) factors. This work suggests that consideration of life habits and functional morphology of individual species is needed to obtain reliable palaeoecological information from fossil assemblages, as well as the numerical analysis of species composition.