岡山県前島の古第三系前島層から産出したミョウガガイ科が卓越する蔓脚類化石群とその進化古生態学的意義

概要

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Scalpellid-dominated barnacle assemblages are discovered from the Paleogene Maejima Formation in Maejima Island, Okayama Prefecture. The barnacle assemblages consist of one species belonging to the Scalpellidae and four species of the Balanomorpha. Tidal- and wave-dominated shallow marine depositional environments are inferred for the Maejima Formation. Nearly all the barnacle shells, which are composed of many shell plates, are disarticulated by water current. In addition, relative abundances of the sampled shell plates of each species are inferred to have been highly biased. Although the species compositions of the barnacle assemblages are disturbed by these taphonomic agents, the dominance of scalpellids is conspicuous quantitatively, and probably reflects the original composition. The unusual Paleogene barnacle assemblages dominated by scalpellids may document a transitional stage in the radiation within shallow marine barnacles.
2004-12-31