Northern and Southern Hemispheres ostracod palaeobiogeography during the Early Jurassic: Possible migration routes

摘要

The purpose of this paper is to review the palaeobiogeographical distribution of Early Jurassic ostracod species worldwide, to establishing possible migration pathways between the North and South Hemispheres in direction and timing and, in particular, to examine the existence of a seaway through Central America ("the Hispanic Corridor"), from at least the Pliensbachian?-Toarcian. A detailed taxonomic revision of over 270 Early Jurassic ostracod species from Europe, North Africa, South America, Asia and Australia (a revision of every figured specimen and/or taxon included in each list of synonymous taxa) has been undertaken. Each assemblage was subjected to a quantitative analysis (this metric was calculated using the Dice Similarity index) in order to ascertain the degree of similarity between ostracod assemblages from both hemispheres. The obtained results indicate that there is a clear differentiation between Australian and Argentinean ostracod assemblages in relation to European ostracod assemblages. The Australian faunas are similar to western Tethyan and central European assemblages, probably indicating a communication route along the western Tethys, aided by the action of western currents. Moreover the Argentinian ostracod assemblages exhibit a high degree of similarity with North-Western European (Portugal, Grand Banks, the Fasnet Basin, and Wales) and North African assemblages. Through the detailed analysis of ostracod spatial and temporal distribution (the coeval occurrence of taxa in Argentina and Western Europe and the differences between Australian and Argentinian faunas) and the pattern of ocean currents derived from climate models simulations, it would infer the existence of "the Hispanic Corridor". (c) 2005 Elsevier B.V. All rights reserved.