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The δ13Corg values and their variations in conodont elements of the latest Famennian-Tournaisian species Polygnathus parapetus Druce are considered. The conodonts studied come from the latest Famennian-Tournaisian interval of the Kamenka River section (Timan-Pechora Basin). The carbon isotope composition of conodont elements had an average value of -25.2‰, suggesting a low trophic level of this species. During the latest Famennian (praesulcata conodont Zone) δ13Corg shifted to more negative values (up to -30.4‰), which may be attributed to changes in the global carbon cycle and local influx of organic matter of terrestrial origin during the terminal Famennian regression. [ABSTRACT FROM AUTHOR]

Diverse skeletal assemblage has been discovered in the Ediacaran/Cambrian strata of the Codos locality in NE Spain (Aragón, Cadenas Ibéricas). This assemblage includes at least seven genera, only three of which can be ascribed to known taxa. All the fossils are preserved in phosphate but their original microstructures are traceable by both elementary composition and microstructural features that are indicative for primary aragonite and high-magnesium calcite biomineralogies. Already these early skeletal fossils show sophisticated microstructures represented by heterogeneous multilayered composites to satisfy the requirements for better protection against both chemical dissolution and mechanical predator deterioration. The most common and best-preserved fossil, which is tubicolous Codositubulus grioensis gen. et sp. nov., is described here. The composition of the fossil assemblage and its stratigraphic position are indicative for the lowermost Terreneuvian (lower Cambrian) or even pre-Terreneuvian age of this fauna. [ABSTRACT FROM AUTHOR]

A new upper Tournaisian (Lower Carboniferous) siphonodellid conodont species Siphonodella carinata n. sp. is described. The material comes from the shallow-water carbonate sediments of the Pechora Swell (Timan-Pechora region or NE of European Russia). The co-occurrence of conodonts Hindeodus cristulus (Youngquist & Miller), Bispathodus stabilis (Branson & Mehl) Morphotype 1, Polygnathus longiposticus Branson & Mehl and Pseudopolygnathus nodomarginatus (Branson) suggests the late Tournaisian (Lower Siphonodella crenulata Zone) age of the deposits. Morphologically the new species is similar to Siphonodella semichatovae Kononova & Lipnjagov and S. ludmilae Zhuravlev & Plotitsyn, but differs in possessing three rostral ridges at the late stages of ontogeny and Class III symmetry. The presence of the shallow-water siphonodellids Siphonodella bella Kononova & Migdisova and S. quasinuda Gagiev, Kononova & Pazuhin in the upper part of the Tournaisian is detected for the first time. [ABSTRACT FROM AUTHOR]

Detailed analysis of the distribution of archaeocyaths in five lower Cambrian sections in South China has resulted in the erection of four new archaeocyathan zones and one new archaeocyathan bed. Listed in order of ascending age, these are: the Dailycyathus xiuqiensis Zone; the Dictyocyathus shaanxiensis Zone; the Spirillicyathus duplex Range Zone; the Sibirecyathus meitanensis Range Zone; and the Archaeocyathus yanjiaoensis beds. These new subdivisions permit a correlation of lower Cambrian strata both within the area of the Yangtze Platform (South China) as well as between this region and Siberia, Australia, Western Europe and North America. Within the Yangtze Platform area, archaeocyaths of the Dailycyathus xiuqiensis and Dictyocyathus shaanxiensis zones co-occur with trilobites of the middle and upper Eoredlichia Trilobite Zone of the Qiongzhusian Stage. The Spirillicyathus duplex and the Sibirecyathus meitanensis Range Zone correspond to the Malungia, Yiliangella–Yunnanaspis and Drepanuroides Trilobite zones of the basal and middle Canglangpuan Stage, respectively. Finally, the Archaeocyathus yanjiaoensis beds belong to the Palaeolenus fengyangensis Trilobite Zone of the upper Canglangpuan Stage. Global correlations based on archaeocyath assemblage zones suggest that: (1) the middle–upper Qiongzhusian of South China correlates with the middle Atdabanian Stage of the Siberian Platform, the Warriootacyathus wilkawillinensis Archaeocyath Zone in South Australia, the middle Issendalenian Stage of Morocco and the lower Ovetian Stage in Spain; (2) the lowermost Canglangpuan Stage of South China correlates with the uppermost Atdabanian of the Siberian Platform, the Spirillicyathus tenuis – Jugalicyathus tardus archaeocyath zones in South Australia, the uppermost Issendalenian – lower Banian stages of Morocco, the middle Ovetian Stage of Spain and the middle Montezuman Stage of North America; (3) the middle Canglangpuan Stage approximates the lowermost Botoman Stage of the Siberian Platform, middle Banian Stage of Morocco, the uppermost Ovetian – lowermost Marianian stages of Spain and the upper Montezuman Stage of North America; (4) the uppermost Canglangpuan Stage is equivalent of the middle Toyonian Stage of the Siberian Platform, Archaeocyathus abacus beds in Australia, the middle Bilbilian Stage in Spain and the middle Dyeran Stage (Bolbolenellus euryparia Trilobite Zone) in North America. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms that sustain high biodiversity and regulate community structure remains a major challenge as past ecological interactions cannot be reconstructed with precision. Here we reveal the dynamics of the earliest diverse skeletal metazoan communities known, the early Cambrian (Tommotian–Atdabanian) archaeocyathan sponge reefs, over a period of 20 million years from their first appearance ~ 535 million years ago (Ma) until the first mass extinction event ~ 512 Ma. Archaeocyaths were restricted to the Siberian Platform until ~ 520 Ma, and so these data provide unique insight into a single, evolving isolated species pool. Systematic and statistical analyses, including α -diversity, evenness, Jaccard similarity, species abundance distributions, and Spearman statistics coefficient were undertaken for 58 sampling units representing 6121 individuals of 84 archaeocyath species from the Siberian Platform. These statistical results indicate an overall similarity to analyses of species co-occurrence in modern tropical coral reefs and rainforest communities. We show a prevalence of niche-assembly mechanisms throughout the entire Tommotian–Atdabanian interval. By the late Atdabanian, however, these earliest metazoan reefs showed the addition of community assembly processes, which can be attributed to neutral behaviour. [ABSTRACT FROM AUTHOR]