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Thylacocephalans are enigmatic euarthropods, known at least from the Silurian to the Cretaceous. Despite remaining uncertainties concerning their anatomy, key features can be recognised such as a shield enveloping most of the body, hypertrophied compound eyes, three pairs of raptorial appendages and a posterior trunk consisting of eight up to 22 segments bearing appendages and eight pairs of gills. Well-known for its euarthropod diversity, the La Voulte-sur-Rhône Lagerstätte (Callovian, Middle Jurassic, France) has provided many remains of four thylacocephalan species so far: Dollocaris ingens, Kilianicaris lerichei, Paraostenia voultensis and Clausocaris ribeti. In this paper, we study the type material as well as undescribed material. The re-description of La Voulte thylacocephalans reveals an unexpected diversity, with the description of two new species, Austriocaris secretanae sp. nov. and Paraclausocaris harpa gen. et sp. nov., and of specimens of Mayrocaris, a taxon originally described from Solnhofen Lagerstätten. We also reassign Clausocaris ribeti to Ostenocaris. The reappraisal of La Voulte thylacocephalans also provides important insight into the palaeobiology of Thylacocephala. New key anatomical features are described, such as an oval structure or a putative statocyst, which indicate a nektonic or nektobenthic lifestyle. Finally, we document a juvenile stage for Paraostenia voultensis.
26 samples were processed for a taxonomic study of ostracods from the Upper Permian (Changhsingian) - Lower Triassic (Griesbachian) interval of the Dajiang section, Guizhou Province, South China. 112 species belonging to 27 genera are recognized. Five new species are described: Acratia candyae sp. nov, Bairdia adelineae sp. nov., Bairdia? huberti sp. nov., Bairdia jeromei sp. nov., Orthobairdia jeanlouisi sp. nov. The unexpected survival faunas associated with microbial formations in the aftermath of the end-Permian extinction are documented for the first time. Ostracod biodiversity variations and palaeo-environmental modifications associated with microbial growth through the Permian-Triassic boundary (PTB) are discussed.
The present study evaluates the significance of Triassic ostracods from the Romanian Black Sea shelf as part of a project for the understanding of the palaeoceanographical evolution of the offshore extension of the North Dobrogean Orogen. The drill core CM31, sampled from the borehole 817 Lebăda Vest drilled on the western Romanian portion of the Black Sea shelf, contains sediments of Rhaetian, Late Triassic age. The taxonomy of ostracods obtained is discussed and adds to the scientific understanding of marine ostracods during the Rhaetian stage. We document 72 species, of which seven are new: Histriabairdia pontuseuxinusensis Forel gen. et sp. nov., Bairdiacypris argonautaii Forel sp. nov., Ceratobairdia? akhilleusi Forel sp. nov., Isobythocypris atalantella Forel sp. nov., Petasobairdia amazonella Forel sp. nov., Paracypris ovidi Forel sp. nov. and Pseudomacrocypris? kerabani Forel sp. nov. Histriabairdia Forel gen. nov. is introduced to accommodate species of the Triassic–Jurassic interval previously attributed to the modern genus Anchistrocheles. These assemblages point to an outer shelf environmental with relatively normal marine oxygenation. The oldest occurrence of Pokornyopsis, found in this material, indicates that this forerunner of modern troglobitic ostracods may not have been troglobitic in the Triassic.
The impact of the late Devonian Hangenberg Event on ostracods is quantified for the first time from newly acquired data from the Blue Snake section, Guizhou Province, South China. Ninety–eight species belonging to 31 genera are identified and figured. Four new species are described: Clavofabella? lanshella sp. nov., Sansabella gelaohensis sp. nov., Cytherellina caerulea sp. nov., Sulcella baisuzhena sp. nov. The ostracod associations from the Blue Snake section document a significant drop in specific diversity as well as major changes in taxonomic composition through the Hangenberg Event. We here report the reduction of the proportion of Palaeocopida and the increase in that of Podocopida between the latest Famennian and the Tournaisian. The specific extinction and renewal rates are estimated at 44% and 62%, respectively. The main factor of the post–crisis renewal of ostracod faunas in the Blue Snake section appears to be the progressive diversification of the family Bairdiidae and was probably related to palaeoenvironmental changes. The characteristics of associations point to an increase of the water depth over the studied area, from a near–shore shallow environment during the latest Famennian to a deeper and more open offshore environment during the Tournaisian.
Middle Permian (Guadalupian) ostracods are described from the Williams Ranch Member of the Cutoff Formation (Roadian) and the McKittrick Canyon Member of the Bell Canyon Formation (Capitanian) from two sections exposed in Culberson County, Guadalupe Mountains, West Texas. Their taxonomy is discussed and adds to the scientific understanding of marine ostracod biodiversity and palaeobiogeography during the Middle Permian. Ostracod assemblages are represented by 51 species of 26 genera and 15 families. Eleven species are newly described: Healdia mckittrickensis Crasquin sp. nov., Healdia cutoffella Crasquin sp. nov., Aurikirkbya guadalupensis Crasquin sp. nov., Hollinella (Hollinella) williamsranchensis Crasquin sp. nov., Geisina culbersonensis Crasquin sp. nov., Paraparchites pecosensis Crasquin sp. nov., Bairdia elcapitanensis Forel sp. nov., Ceratobairdia mescaleroella Forel sp. nov., Ceratobairdia sexagintaduella Forel sp. nov., Ceratobairdia pratti Forel sp. nov., and Denticupachydomella bellcanyonensis Forel sp. nov. The diagnosis of the genus Denticupachydomella is emended. The palaeobiogeographic distribution of the species is analyzed and exemplifies the taxon exchanges between Tethyan and Panthalassic localities in the Permian. The eastern margin of the Palaeo-Tethyan realm is shown to have played a major role in radiation of taxa in the Permian.
Late Holocene ostracods were recovered from marine sediments of the Chao Phraya delta at a whale-fall excavation site located fifteen kilometers on land in the Am Pang Subdistrict, Ban Paew District, Samut Sakhon Province, north of the Gulf of Thailand. Thirteen species belonging to seven genera are identified. The deposition environment of the succession is for the first time characterized. The ostracod assemblages suggest that the entire succession associated with the whale-fall deposited in a shallow marine environment such as estuary, bay, inner shelf, subtidal, under less than 20 meters water-depth, in brackish to normal salinity with high mud content and turbidity, on a muddy substrate. This analysis is an important step toward the first in-depth study of ostracods associated with modern and fossil shallow-water whale-falls.