We generalize the brick polytope of V. Pilaud and F. Santos to spherical subword complexes for finite Coxeter groups. This construction provides polytopal realizations for a certain class of subword complexes containing all cluster complexes of finite types. For the latter, the brick polytopes turn out to coincide with the known realizations of generalized associahedra, thus opening new perspec...

The sudden appearance of fossils that marks the so-called 'Cambrian explosion' has intrigued and exercised biologists since Darwin's time. In On the Origin of Species, Darwin made it clear that he believed that ancestral forms 'lived long before' their first fossil representatives. While he considered such an invisible record necessary to explain the level of complexity already seen in the foss...

Late Cambrian to early Ordovician trilobites, the family Olenidae, were tolerant of oxygen-poor, sulfur-rich sea floor conditions, and a case is made that they were chemoautotrophic symbionts. Olenids were uniquely adapted to this habitat in the Lower Paleozoic, which was widespread in the Late Cambrian over Scandinavia. This life habit explains distinctive aspects of olenid morphology: wide th...

Article history: Soft-bodied Cambrian arth Received 15 August 2007 Received in revised form 27 March 2008 Accepted 3 April 2008

The Precambrian genesis plus Cambrian explosion scenario also implies a perplexing view of a major evolutionary radiation: a long period of cryptic speciation with increasing developmental complexity and anatomical sophistication, yet without substantial behavioural or ecological modification or diversification, followed by a sudden increase in morphological and ecological innovation. Page 1046...

Abstract The Sichuan Basin was a part of the Yangtze Carbonate Platform (YCP) during Cambrian–Ordovician, and marine carbonates were deposited in basin this interval. Although previous studies have evaluated paleogeography, paleoclimate paleoecology basin, they primarily focused on biological evolution basin; however, analysis paleogeography is lacking. This study integrated outcrop sedimentolo...

ECOS III The slender, spine-shaped, apatitic protoconodonts appear in the fossil record near the Precambrian-Cambrian boundary and persist through the Cambrian . Recent work (Szaniawski 1 982, J. Paleont. 56) suggests that protoconodont elements were homologous to the grasping spines of modern chaetognaths . Paraconodonts are similar to protoconodonts in their mode of growth by basal accretion ...

Echinoderms possess a skeleton with a unique and distinctive meshlike microstructure called stereom that is underpinned by a specific family of genes. Stereom is thus considered the major echinoderm synapomorphy and is recognized already in some Cambrian echinoderm clades. However, data on the skeletal microstructures of early echinoderms are still sparse and come only from isolated ossicles of...

The Meishucun Section (Yunnan Province, South China) is considered to be an important Precambrian–Cambrian boundary section, primarily because of its rich small shelly fossil record. In this article, we report the results of a sulphur isotope study of phosphate-bound sulphate from the Meishucun Section and several correlative sections in South China. Forty clastic, granular phosphorites from Me...