Cambrian trees are oriented and labeled trees which fulfill local conditions around each node generalizing the conditions for classical binary search trees. Based on the bijective correspondence between signed permutations and leveled Cambrian trees, we define the Cambrian Hopf algebra generalizing J.-L. Loday and M. Ronco’s algebra on binary trees. We describe combinatorially the products and ...

The Cambrian appearance of fossils representing diverse phyla has long inspired hypotheses about possible genetic or environmental catalysts of early animal evolution. Only recently, however, have data begun to emerge that can resolve the sequence of genetic and morphological innovations, environmental events, and ecological interactions that collectively shaped Cambrian evolution. Assembly of ...

. Figure 1. Cambrian lobopodian diversity. (A) Aysheaia pedunculata, middle Cambrian Burgess Shale (NMNH-83942). (B) Claws of Aysheaia pedunculata (NMNH-365608). (C) Hallucigenia sparsa, middle Cambrian Burgess Shale (NMNH198658; courtesy of M. Smith, University of Cambridge. Nature 523, 75–78). (D) Microdictyon sinicum, early Cambrian Chengjiang (ELRC-30060; courtesy of G. Edgecombe, Natural H...

Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian 'explosion'. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive ...

The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biologi...

A well-preserved Cambrian section in the Zanskar Valley of northern India has previously been interpreted to record the transition from a passive to an active tectonic margin related to Cambrian–Ordovician orogenesis. This interpretation has been used to support the tectonostratigraphic interpretation of other successions across the Tethyan Himalaya. Our detailed paleoenvironmental analysis sig...

a r t i c l e i n f o The Early–Middle Cambrian Pioche Shale of Lincoln County, Nevada preserves a diverse array of soft-bodied ecdysozoans that are well-known from the Burgess Shale soft-bodied fauna of British Columbia, Canada. At Pioche certain genera occur both above and below the Middle Cambrian boundary, allowing a comparison of the nature of their preservation across this interval. In or...

The oldest annelid fossils are polychaetes from the Cambrian Period. They are representatives of the annelid stem group and thus vital in any discussion of how we polarize the evolution of the crown group. Here, we describe a fossil polychaete from the Early Cambrian Sirius Passet fauna, Pygocirrus butyricampum gen. et sp. nov., with structures identified as pygidial cirri, which are recorded f...

Whilst the "Cambrian Explosion" continues to attract much attention from a wide range of earth and life scientists, the detailed patterns exhibited by the terminal Proterozoic-Early Cambrian biotas remain unclear, for reasons of systematics, biostratigraphy and biogeography. In particular, recent changes in absolute dating of the Cambrian have refined the period of time that the fossil record m...

SYNOPSIS. The Cambrian radiation is that key episode in the history of life when a large number of animal phyla appeared in the fossil record over a geologically short period of time. Over the last 20 years, scientific understanding of this radiation has increased significantly. Still, fundamental questions remain about the timing of the radiation and also the tempo of evolution. Trilobites are...