Publication: Multivariate hierarchical analyses of Early Jurassic
Ostracoda assemblages
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Publication Date
2009
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Taylor & Francis
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Abstract
Palaeobiogeographic patterns of Early Jurassic ostracods from the northern and southern
hemispheres (96 sections located in Europe, North Africa, Western Australia and North
and South America) based on 243 species-level records document global patterns of distribution
that can be compared to those previously published on ostracods from the European
Epicontinental Sea and Tethyan and South Panthalassa areas. All described
records of ostracods from both hemispheres spanning the Hettangian to Early Toarcian
have been compiled and verified, and their patterns of origin and distribution have been
interpreted. Jaccard coefficient of similarity was used to asses similarities among European,
American and Tethyan ostracod shelf faunas. The numerical analysis shows a progressive
longitudinal gradient in provincialism through the Early Jurassic, consistent
with the northward drift of Tethyan ostracod faunas towards the European Epicontinental
Sea and the southward movement of European taxa into Tethys and Panthalassa
oceans. The spread of cosmopolitan species and extinction of endemic species, allied to
the disappearance of geographical barriers, warmer climate conditions and rising sea
levels can explain the reduction in ostracod diversity and the east-west provincialism
throughout the Early Jurassic. Interchange between hemispheres, including bipolar distributions,
are recognized from the Sinemurian time, pointing out that for most of the
studied period, the climate worldwide was warm and tropical.