There was a major diversification known as the Ordovician Radiation, in the period immediately following the Cambrian. This event is unique in taxonomic, ecologic and biogeographic aspects.While all of the phyla but one were established during the Cambrian explosion, taxonomic increases during the Ordovician were manifest at lower taxonomic levels although ordinal level diversity doubled. Marin...

Lobopodians, a nonmonophyletic assemblage of worm-shaped soft-bodied animals most closely related to arthropods, show two major morphotypes: long-legged and short-legged forms. The morphotype with stubby, conical legs has a long evolutionary history, from the early Cambrian through the Carboniferous, including the living onychophorans and tardigrades. Species with tubular lobopods exceeding the...

Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnidarian jellyfish fossils from the Middle Cambrian (approximately 505 million years old) Marjum Form...

This paper completes the project of constructing combinatorial models (called frameworks) for the exchange graph and g-vector fan associated to any exchange matrix B whose Cartan companion is of finite or affine type, using the combinatorics and geometry of Coxeter-sortable elements and Cambrian lattices/fans. Specifically, we construct a framework in the unique non-acyclic affine case, the cyc...

The Gucheng region is oil and gas accumulation area of Tarim Basin，dominated by beach controlled lithologic reservoirs，which has superior conditions broad exploration prospects. lower Paleozoic strata in the are Carboniferous, Ordovician, Cambrian systems from top to bottom. Silurian, Devonian, Permian missing. Ordovician – main target layers area. There four reservoirs: group, Yingshan Penglai...

Sixty-four surface samples from the Lower Palaeozoic rock units (mainly Lalun,Abastu and Abarsaj formations) near Kholin-Darreh village in the Fazel Abad area,southeastern the Caspian Sea, Northern Iran, were analyzed to determine their agerelationships. The samples of Lalun Formation were barren, but those of Abastu andAbarsaj formations contained well-preserved and abundant palynomorph entiti...

cambrian sedimentary facies are exposed throughout north part of kerman region. trilobites’ faunas are the most common invertebrate fossils within the cambrian strata. the section is made of 217 m of sandstone, shale, limestone and dolomite. in this study, 153 trilobite samples including seven species and genera were identified from the dahu section 12 km. east of zarand. this trilobite’s assem...

Here we report exceptionally preserved non-biomineralized compound eyes of a non-trilobite arthropod Cindarella eucalla from the lower Cambrian Chengjiang Lagerstätte, China. The specimen represents the oldest microanatomical evidence confirming the occurrence of highly developed vision in the early Cambrian, over 2,000 ommatidia in each eye. Moreover, a quantitative analysis of the distributio...