Pliocene ostracods (Crustacea) from the Togakushi area, central Japan; palaeobiogeography of trans-Arctic taxa and Japan Sea endemic species

Hirokazu Ozawa,Hideaki Nagamori,Tomotaka Tanabe

doi:10.1144/jm.27.2.161

Hirokazu Ozawa, Hideaki Nagamori + Show 1 more

Open Access

https://doi.org/10.1144/jm.27.2.161

Copy DOI

Abstract

Abstract. Pliocene strata (4–3 Ma) in the Togakushi area, central Japan, yield significant ostracods, which allow investigation of the origins of high-latitude (Arctic–Atlantic) taxa and the Japan Sea endemic species, together with their post-Miocene history of extinction-speciation and migration. Three types of extinct species are found here: (1) cryophilic species in common with, or closely related to, species in Plio-Pleistocene assemblages described from the Japan Sea; (2) species closely related to, or comparable with, species that characterize Miocene Japan; and (3) species endemic to the Pliocene Japan Sea. Type (1) contains species closely related to high-latitude species known from the Arctic and northern Atlantic Oceans. Their presence suggests migration from the northwestern Pacific to the northern Atlantic through the Arctic seas since the Late Pliocene after the opening of the Bering Strait. Both Types (2) and (3) contain genera originating in the south, which show high specific diversity in regions affected by the modern warm Kuroshio Current. Ancestral ostracods of Types (2) and (3) invaded the Japan Sea from the Pacific from the Middle Miocene, and diversified to produce closely related species in the semi land-locked Japan Sea until the Early Pliocene. Two new species Aurila togakushiensis sp. nov. and Aurila shigaramiensis sp. nov. are described.

Highlights

Key insights for modelling the potential impact of future environmental fluctuations on the world’s biota are provided by examining the effects of environmental change on biodiversity from the geological past (e.g. Thomas & Gooday, 1996; Cronin et al, 1999)
Predictions of migration and extinction-speciation in response to possible future environmental fluctuations can be obtained from studies on biotic responses of past shallow-sea benthic faunas to environmental change caused by geological events in the Late Cenozoic (Cronin & Raymo, 1997; Boomer et al, 2003; Amano, 2005; Whatley et al, 2005)
This formation yielded significant ostracods containing three types of extinct species to investigate the origins of endemic species in the Japan Sea and high-latitude

Summary

Introduction

Key insights for modelling the potential impact of future environmental fluctuations on the world’s biota are provided by examining the effects of environmental change on biodiversity from the geological past (e.g. Thomas & Gooday, 1996; Cronin et al, 1999). Predictions of migration and extinction-speciation in response to possible future environmental fluctuations can be obtained from studies on biotic responses of past shallow-sea benthic faunas to environmental change caused by geological events in the Late Cenozoic (Cronin & Raymo, 1997; Boomer et al, 2003; Amano, 2005; Whatley et al, 2005). Species compositions of the shallow-marine benthic fauna, marginal seas surrounded by land, are influenced most strongly by both marine and continental environmental changes. Both species compositions and environments changed more rapidly in the Late Cenozoic than at any other time. Such events included the Japan Sea developing during back-arc spreading (20–15 Ma), the closure of the southern strait of the Japan Sea (10–3 Ma) and the opening of the Bering Strait in the North

Objectives

Methods

Discussion

Conclusion