Ostracoda from Lee Point on Shoal Bay, Northern Australia: part 3, podocopina (cytheracea)

The littoral environments present in Shoal Bay, Northern Territory (Australia) show a high diversity of ostracods cyther&aacute;ceos (51 genera and 97 species). Probably this diversity is due to three factors: (1) marine environments warm and well oxygenated leading to a high level of biological productivity, (2) shallow marine environments favorable for the accumulation of material conch&iacute;fero post mortem, and (3) a location central in the way of dispersal on the continental shelf between the regions of the Pacific and Southeast Asia. A particular feature of this fauna Cytherscea is that some genres, such as Alocopocythere, can be traced back to the Cretaceous when it first appeared in the shallow waters of the Tethys. In this overlay component of the ancient ostracods are the dominant fauna in partnerships of the modern Indo / Pacific, such as gender Keiji. While the Cytheracea ostracods are the dominant groups, especially the Cypridacea marine Bairdiacea and Plstycopina, are well represented and are quite different (fide Whatley et al., 1995, 1996). We describe here a new genre, Paraxestoleberis, and 15 new species: Dentiby&iacute;here multituberosa, Dampiercythere papillolineata, Neocy&iacute;heromorpha papilloporosa, Loxoconcha catas&iacute;eros, Semicyrherura gamma, Callistocy&iacute;here cookei, Loxocorniculum koolpionyahensis, Ke&uacute;ia interim, K. profundosculpia, K. parademissa, Quasibradleya leepoin&iacute;ensis, Actinocy&iacute;hereis gippsi, Henryhowella sinespinosa, Pon&iacute;icocy&iacute;hereis spatulospinosa and Paraxestoleberis posteroacuminata. Due to the limited material obtained, 16 species are kept in open nomenclature: Bythoceratina sp. Corallicy&iacute;here sp. Venericythere sp. Tanella sp. Loxocorniculum sp. 1 L. sp. 2, Gambiella sp. Javanella sp. Paradoxostoma sp. Neomonoceratina sp., Bradley (sl) sp. Echinocytbereis (sl) sp. Pla&iacute;ycy&iacute;hereis? sp. Alocopocy&iacute;here sp. Xestoleberis sp. and Paraxestoleberis sp. The remaining 66 species have been described previously in other areas.<br /

Multivariate hierarchical analyses of Early Jurassic Ostracoda assemblages

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.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu