Silurian Ostracodes Research Articles

Silurian ostracods from the Nyalam region, southern Tibet, China and their implications on palaeoenvironment and palaeobiogeography

The overall occurrence, stratigraphical distribution, palaeoenvironmental and palaeobiogeographical significances of the ostracod faunas from the Silurian Pulu Formation in the Yalai West II section, Nyalam region, southern Tibet, China, are documented for the first time. Thirty-two species belonging to 19 genera are identified and figured herein. The ostracod fauna in the Pulu Formation indicates an age of the late Llandovery–Pridoli. The ostracods belong to a podocope-rich association, which suggests an offshore environment for the Yalai West II section. The ostracods of the Pulu Formation have strong affinities with the South China taxa and also share some similarities with those from Baltica. This implies that ostracods could probably benefit from sea-level changes to facilitate faunal exchanges between peri-Gondwana and Baltica. Geographical isolation and global sea-level changes are proposed as the primary factors controlling the palaeobiogeographical distribution of ostracods during the Silurian.

Late Silurian and Devonian ostracods of the Istanbul Zone (Western Pontides) and the Taurides: palaeogeographical implications

Non-metamorphic Palaeozoic sedimentary successions without major breaks exist in the Istanbul Zone of the Western Pontides (northern Turkey) and in the Taurides (southern Turkey). Based on different proxies, a Gondwanan affinity has been determined for the Taurides; however, the palaeogeographical position of the Istanbul Zone is still controversial. The aim of this paper is to discuss possible contributions of late Silurian and Devonian ostracods to the palaeogeographical assignment of the Western Pontides (Istanbul Zone). Furthermore, ostracods of the Taurides have also been evaluated in terms of the palaeogeographical setting of this terrane. Late Silurian ostracods of the Istanbul Zone (Western Pontides) show close similarities at the species level with the assemblage from the upper Silurian (Ludlow) rocks of Baltica. This Laurussian affinity indicates a palaeogeographical setting to the north of the Rheic Ocean for the Pontides during the late Silurian. The Devonian ostracod assemblages of both the Taurides and the Istanbul Zone have an affinity to both Laurussia and Gondwana. Therefore, a faunal link should exist during this long period between Laurussia and Gondwana. The faunal link between the two palaeocontinents can be explained on the one hand by a narrow ocean with shallow pathways. On the other hand, a wider ocean with long-shore currents, with broad and shallow shelf areas and/or islands functioning as stepping stones would also allow a faunal link for benthic ostracods.

Early Silurian carbonate platform ostracods from Iran: A peri-Gondwanan fauna with strong Laurentian affinities

Early Silurian (Aeronian) carbonate platform deposits of the lower Niur Formation of east central Iran yield an ostracod fauna of fourteen species dominated by podocopes with rare palaeocopes and binodicopes. The podocope-rich fauna is unusual in that Early Palaeozoic carbonate platforms are typically dominated by palaeocopes. Despite its mid-palaeolatitude peri-Gondwanan setting and isolation from low palaeolatitudes, the ostracod assemblage of the lower Niur Formation shows striking affinities to species-level with Late Ordovician and Early Silurian ostracod faunas of palaeo-equatorial Laurentia. Biogeographically the lower Niur Formation ostracod fauna also shows species- and genus-links with Late Ordovician and Early Silurian faunas of low-palaeolatitude (0°–30°S) Baltica and mid palaeolatitude peri-Gondwanan Uzbekistan, dispelling the notion of strict endemism for Early Silurian ostracods. Two new species Bulbosclerites jamshidis sp. nov. and Steusloffina fravashi sp. nov. are described.

The Silurian Ostracodes established by Steusloff 1895

The Silurian Ostracodes established by Steusloff 1895

Silurische Ostrakoden Deutschlands

Silurische Ostrakoden Deutschlands

Reconstruction and use of the Succession of the Baltic Silurian Ostracodes

Reconstruction and use of the Succession of the Baltic Silurian Ostracodes

Silurian Myodocopes: Pioneer pelagic ostracods and the chronology of an ecological shift

Abstract. Analysis of all relevant palaeontological and global geological data strongly supports the notion that representatives of Silurian myodocope ostracods had pelagic lifestyles and habitats and that they may well be, within the Ostracoda, pioneer colonisers of such environments. Morphological evidence (from fossil and Recent myodocopes) combined with facies distributional and concomitant faunal evidence (from the Silurian of, for example, Britain, France, Czechoslovakia, Sardinia, Australia and China) endorses the idea that myodocope ostracods may have undergone a benthic to pelagic ecological shift during mid Silurian times.Lower Silurian myodocopes lived, with benthic associates, on well oxygenated shelves. Upper Silurian ostracods lived, typically with low diversity, largely pelagic faunas in outer shelf topographic lows or off-shelf basin slopes, and are characteristically associated with deposits which are in part suggestive of lowered oxygen levels or even anoxic conditions. A pre-adaptation for swimming may have allowed Silurian myodocopes to respond to environmental forcing (negative oxygen levels; positive trophic and nutrient incentives; rises in sea levels) by migrating, through time, up the water column.