The distribution of all known Cambrian echinoderm taxa, encompassing both articulated specimens and taxonomically diagnostic isolated ossicles, is documented for the first time. The database described by 2011 comprises 188 species recorded from 65 formations from around the world. Formations that have yielded articulated echinoderms are unequally distributed in space and time. Only Laurentia and West Gondwana provide reasonably complete records at the resolution of Stage. The review of the biogeographical distributions of the eight major echinoderm clades shows that faunas from Laurentia and Northeast Gondwana (China and Korea) are distinct from those of West Gondwana and Southeast Gondwana (Australia); other regions are too poorly sampled to make firm palaeobiogeographical statements. Analysis of alpha diversity (species per formation) shows that diversity rose initially to Cambrian Stage 5, declined into Guzhangian and Paibian before returning to Stage 5 levels by the end of the Cambrian. This pattern is replicated in Laurentia and West Gondwana. We show that taxonomically diagnostic ossicles found in isolation typically occur significantly earlier than the first articulated specimens of the same taxa and provide important information on the first occurrence and palaeobiogeographical distribution of key taxa, and of the phylum as a whole.Supplementary material:Articulated Cambrian echinoderms and Isolated plates of Cambrian echinoderms are provided at:http://www.geolsoc.org.uk/SUP18668

No abstract

Central Europe consists of a complex mosaic of more or less independent terranes with varying tectonometamorphic histories, usually also of different lithological compositions and protolith, and thus it is reasonable to suppose that the majority of these blocks have experienced somewhat different palaeogeographical evolution. The present terrane juxtaposition has been interpreted in general as a result of the Variscan collision of peri-Gondwanan and peri-Baltic derived terranes, with Gondwana on one side and Baltica and/or Laurentia on the other side. However, reconstruction of the pre-Variscan development and mutual palaeogeographical relationships remains a major challenge of interpretation.

O. 2005 03 15: Middle Cambrian pterobranchs and the Question: What is a graptolite? Lethaia, Vol. 38, pp. 73-85. Oslo. ISSN 0024-1164.The presence of distinct fusellar structure is taken as evidence to include a number of fossils from the Middle Cambrian to the Lower Ordovician of North America and Europe with the Pterobranchia. The dome of the pterobranchs and the prosicula of the planktic graptolites are contrasted and evidence is given for the re-assignment of a number of well known dendroid graptolites to the pterobranchs. A non-destructive method is described to reveal fusellar development of delicate hemichordate exoskeletons from shales.

The Brunovistulian terrane represents a microcontinent of enigmatic Proterozoic provenance that was located at the southern margin of Baltica in the early Paleozoic. During the Variscan orogeny, it represented the lower plate at the southern margin of Laurussia, involved in the collision with the Armorican terrane assemblage. In this respect, it resembles the Avalonian terrane in the west and the Istanbul Zone in the east. There is a growing evidence about the presence of a Devonian back-arc at the margin of the Brunovistulian terrane. The early Variscan phase was characterized by the formation of Devonian extensional basins with the within-plate volcanic activity and formation of narrow segments of oceanic crust. The oldest Viséan flysch of the Rheic/Rhenohercynian remnant basin (Protivanov, Andelska Hora and Horní Benesov formations) forms the highest allochthonous units and contains, together with slices of Silurian Bohemian facies, clastic micas from early Paleozoic crystalline rocks that are presumably derived from terranes of Armorican affinity although provenance from an active Brunovistulian margin cannot be fully excluded either. The development of the Moravo-Silesian late Paleozoic basin was terminated by coal-bearing paralic and limnic sediments. The progressive Carboniferous stacking of nappes and their impingement on the Laurussian foreland led to crustal thickening and shortening and a number of distinct deformational and folding events. The postorogenic extension led to the formation of the terminal Carboniferous-early Permian Boskovice Graben located in the eastern part of the Brunovistulian terrane, in front of the crystalline nappes. The highest, allochthonous westernmost flysch units, locally with the basal slices of the Devonian and Silurian rocks thrusted over the Silesicum in the NW part of the Brunovistulian terrane, may share a similar tectonic position with the Giessen-Harz nappes. The Silesicum represents the outermost margin of the Brunovistulian terrane with many features in common with the Northern Phyllite Zone at the Avalonia-Armorica interface in Germany.

The Teplµ-Barrandian unit (TBU) of the Bohemian Massif was a part of the Avalonian-Cadomian belt at the northern margin of Gondwana during Neoproterozoic and Early Cambrian times. New detrital zircon ages and geochemical compositions of Late Neoproterozoic siliciclastic sediments confirm a deposition of the volcano-sedimentary successions of the TBU in a back-arc basin. A change in the geotectonic regime from convergence to transtension was completed by the time of the Precambrian-Cambrian boundary. The accumulation of around 2,500 m Lower Cambrian continental siliciclastics in a Basin-and-Range-type setting was accompanied by magmatism, which shows within-plate features in a few cases, but is predominantly derived from anatectic melts displaying the inherited island arc signature of their Cadomian source rocks. The geochemistry of clastic sediments suggests a deposition in a rift or strike-sliprelated basin, respectively. A marine transgression during Middle Cambrian times indicates markedly thinned crust after the Cadomian orogeny. Upper Cambrian magmatism is represented by 1,500 m of subaerial andesites and rhyolites demonstrating several geochemical characteristics of an intra-plate setting. Zircons from a rhyolite give a U-Pb-SHRIMP age of 499€4 Ma. The Cambrian sedimentary and magmatic succession of the TBU records the beginning of an important rifting event at the northern margin of Gondwana.

The preservation of digestive structures of trilobites is extremely rare. Here we describe two new examples of trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic), which display remains of the digestive system. The first specimen, assigned to <i>Selenopeltis buchi </i>(Barrande, 1846), exhibits cavities under the posterior part of the glabella and the axis of most thoracic segments. These cavities are interpreted as remains of metamerically paired digestive caeca and constitute the first example of preserved digestive structures in the order Odontopleurida. The second specimen belongs to <i>Birmanites ingens </i>(Barrande, 1852) and displays a tube-like structure, filled with a finely-grained material, that runs under the axial lobe of the entire trunk. We interpret this structure as a gut infilling similar to that repeatedly observed in the Moroccan <i>Basilicus calzadai</i>. These specimens confirm that the depositional environment of the Letná Formation was locally favourable to soft-tissue preservation. They also further document the presence of two different types of digestive systems in trilobites. The possibility that different processes might have been involved in the preservation of different parts of the trilobite gut is discussed, and several criteria to differentiate genuine gut remains from scavenger burrows are proposed

No abstract