Ostracod crustaceans are the most abundant fossil arthropods and are characterized by a long stratigraphic range. However, their soft parts are very rarely preserved, and the presence of ostracods in rocks older than the Silurian period [1-5] was hitherto based on the occurrence of their supposed shells. Pyritized ostracods that preserve limbs and in situ embryos, including an egg within an ova...

The genus Granulina (type species Plasmoporella granulosa Bondarenko, 1958, by original designation) was established by Leleshus (1975: 7) for a distinctive heliolitoid genus from the Upper Ordovician of Kazakhstan and Tajikistan. However, the name Granulina Jousseaume, 1888 (p. 191), which designates a genus of a living molluscs (Gastropoda: Neogastropoda: Marginellidae: Granulininae), has pri...

The occurrence of the blue-green alga Girvanella, reported for the first time in the Ordovician rocks of South America (Precordilleran Ar­ gentina), allows the completion of the pattern of horizontal distribution of this organism in relation to the palaeobiogeography of the Lower Ordovi­ cian.

The Late Ordovician mass extinction was linked to climate cooling and glaciation of Gondwana during the terminal Ordovician Hirnantian Age (444.7–443.4 Ma). Extinction patterns have been well described for many marine taxa, but much less is known about marine microbial communities through this interval. To elucidate the structure of microbial communities in tropical marine basins through the La...

We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages. The temporal window within whi...

Abstrac.t-Based on the intensity and rates of various kinds of intense ionizing radiation events such as supernovae and gamma-ray bursts, it is likely that the Earth has been subjected to one or more events of potential mass extinction level intensity during the Phanerozoic. These induce changes in atmospheric chemistry so that the level of Solar ultraviolet-B radiation reaching the surface and...

The Ordovician System, cropping out in southern and west-central Jordan, consists entirely of a 750 m thick clastic sequence that can be subdivided into six formations. The lower Disi Formation starts conformably above the Late Cambrian Umm Ishrin Formation. According to Cruziana furcifera occurring in the upper third of the Disi Formation, an Early Ordovician age is con®rmed. The Disi Formatio...

We present new geologic maps of the Lake Champlain region of west-central Vermont and east-central New York State. This region contains a shallow-crustal section of an Ordovician foreland basin and a far-traveled thrust system that transported the Upper Cambrian–Lower Ordovician platform-sequence, allochthonous risefacies pelites and arenites and Middle Ordovician basinal shales and flysch. Ear...