Relationship between embaymental associations and relict species : Molluscan fauna from the Pliocene Joshita Formation in the northern part of Nagano Prefecture

Abstract

Five Miocene relict species were found in the Pliocene embaymental fauna including many boreal species from the Joshita Formation in the northern part of Nagano Prefecture. The occurrences of these species are confined to the upper sublittoral Anadara-Neogenella association. The upper sublittoral zone of cold-water embayment acts as one of the ecological refuges due to the high primary production rate and the lower predation pressure than in the warmer seas.