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Early-Middle Devonian brachiopod provincialism and bioregionalization at high latitudes; a case study from southwestern Gondwana

Cameron R. Penn-Clarke and David A. T. Harper
Early-Middle Devonian brachiopod provincialism and bioregionalization at high latitudes; a case study from southwestern Gondwana
Geological Society of America Bulletin (August 2020) Pre-Issue Publication


The paleobiogeography of Early-Middle Devonian (Pragian-Eifelian) brachiopods from West Gondwana was assessed to determine any potential controls (regional climatic differences or global eustasy) that may have driven bioregionalization. The Pragian-Eifelian interval of West Gondwana was examined because work by previous authors suggested that this was a period when regionally extensive areas of provincialism among marine invertebrates were present and most pronounced. Factors of particular interest in this study were the controls over brachiopod bioregionalization at high (60 degrees -90 degrees ) southern latitudes, which the Malvinokaffric Realm is thought to have entirely occupied. A large presence-absence data matrix was compiled consisting of the occurrences of 206 genera from 17 localities across West Gondwana, and an array of multivariate methods (cluster analysis, nonmetric multidimensional scaling, and network analysis) was employed to assess regional bioregionalization trends. The results of our study suggest that regional climatic differences brought on by latitudinal effects were the determining driver for bioregionalism of brachiopods during the Pragian-Eifelian, and these trends were coincident with a global cooling period during the Early-Middle Devonian. Our study further suggests that of the three regional paleobiogeographic realms thought to be present in West Gondwana during the Early-Middle Devonian (Eastern Americas, Old World, and Malvinokaffric), only the Malvinokaffric Realm is valid as a single biogeographic area. Its area, however, is reduced; it is interpreted to have been a second-order biogeographic area and not a first-order area as suggested by previous authors. Given these factors, we suggest a new demonym for this area, the "Malvinoxhosan," given the racially charged connotations of "Malvinokaffric." We present a new biogeographic framework for West Gondwana that is free of preconceived biogeographic area and rank biases, with the understanding that a more globally expansive study should be undertaken to elucidate these areas and their rank within the correct hierarchy. Two first-order paleobiogeographic areas are recognized in West Gondwana and are named according to their latitudinal extent, namely, the high-latitude (60 degrees S-90 degrees S) and temperate-latitude (30 degrees S-60 degrees S) bioregions. The temperate-latitude bioregion consists of a single second-order paleobiogeographic area, the "Colombian-West African" bioregion. Two second-order bioregions are present in the high-latitude bioregion, namely, the Amazonian and Malvinoxhosan bioregions. Here, the Amazonian ( approximately 50 degrees S-70 degrees S), compositionally, was an intermediate region between the Colombian-West African ( approximately 30 degrees S-50 degrees S) and Malvinoxhosan (70 degrees S-90 degrees S) end members. Latitudinal effects may also have been responsible for dividing the Malvinoxhosan bioregion into two tentative third-order paleobiogeographic areas, namely, the Andeo-South African ( approximately 70 degrees S-80 degrees S) and the Parana ( approximately 80 degrees S-90 degrees S) bioregions.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: Pre-Issue Publication
Title: Early-Middle Devonian brachiopod provincialism and bioregionalization at high latitudes; a case study from southwestern Gondwana
Affiliation: Council for Geoscience, Cape Town, South Africa
Published: 20200819
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 233
Accession Number: 2021-004955
Categories: Invertebrate paleontologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
Secondary Affiliation: Durham University, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202102
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