The renowned soft-bodied faunas of the Cambrian period, which include the Burgess Shale, disappear from the fossil record in the late Middle Cambrian, after which the Palaeozoic fauna dominates. The disappearance of faunas of Burgess Shale type curtails the stratigraphic record of a number of iconic Cambrian taxa. One possible explanation for this loss is a major extinction, but more probably it reflects the absence of preservation of similar soft-bodied faunas in later periods. Here we report the discovery of numerous diverse soft-bodied assemblages in the Lower and Upper Fezouata Formations (Lower Ordovician) of Morocco, which include a range of remarkable stem-group morphologies normally considered characteristic of the Cambrian. It is clear that biotas of Burgess Shale type persisted after the Cambrian and are preserved where suitable facies occur. The Fezouata biota provides a link between the Burgess Shale communities and the early stages of the Great Ordovician Biodiversification Event.

Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of the early evolution of metazoans. Here, we present the discovery of 505–million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.

A new marine fossil assemblage from the Early Triassic shows unexpected phyletic diversity and functional complexity.

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The relationships of the sponge classes are controversial, particularly between the calcareous and siliceous sponges. Specimens of the putative calcarean Eiffelia globosa Walcott from the Burgess Shale show the presence of diagnostic hexactinellid spicules integrated into the skeletal mesh. The arrangement of these spicules in Eiffelia is shown to be precisely equivalent to that of early protospongioid hexactinellids, and sponge growth occurred through an identical pattern to produce identical skeletal body morphology. The difference in spicule composition of the classes is interpreted through the observation of taphonomic features of Eiffelia that suggest the presence of at least two mineralogically distinct layers within the spicules. These results support molecular analyses that identify the calcarean-silicisponge transition as the earliest major sponge branch and suggest that the heteractinids were paraphyletic with respect to the Hexactinellida.Cambrian ͉ evolution ͉ Porifera ͉ stem group

Biological materials are a rewarding area of modern materials science, yielding both evolutionary insights and inspiration for biomimetic research. In particular, biocomposite structures are valuable sources of novel structures with unusual chemical properties, and they are very informative for the mechanisms of biomineralization. Here we describe a unique biocomposite of amorphous silica, crystalline aragonite, and chitin from species of the order Verongida, a group of marine sponges. The structures have been analyzed with a diverse suite of techniques, revealing a chitinous template for siliceous overgrowth containing aragonite-based crystal aggregates. Sponge chitin is an example of a specific template where two minerals in amorphous and crystalline forms are formed together with an organic molecule.

The Sirius Passet Biota of the Buen Formation in North Greenland is one of the key Burgess Shale‐type faunas, as it represents the only diverse early Cambrian (Stage 2, Series 3) biota from Laurentia. The sponges are one of the major components of the fauna, although they appear to be much less abundant than arthropods, based on the available collections. At least 13 species are described here, including the new taxa Hamptonia limatula sp. nov., Lenica perversa sp. nov., Saetaspongia procera sp. nov., Constellatispongia canismajorii gen. et sp. nov. and Crassicoactum cucumis gen. et sp. nov. An additional new species, Ratcliffespongia freuchenensis sp. nov., is described from the upper part of the Buen Formation. The assemblage is dominated by a major lineage of protomonaxonids, together with rarer reticulosans and demosponges. Some taxa, such as the anthaspidellid lithistid Fieldospongia bellilineata, were previously known only from Laurentian faunas; others, such as Saetospongia densa, Solactiniella cf. plumata and Lenica unica, were previously recognized from South China and/or Siberia. The described assemblage confirms the cosmopolitan distribution of Cambrian sponges generally, and suggests that the differences between Laurentian and Chinese assemblages are due more to a taxonomic overturn during Cambrian Series 2, Stage 4, than to the geographical separation. Furthermore, crown‐group demosponges appear to have occupied shallow‐water (perhaps dominantly platform) environments at this time, and may have been much more diversified and widespread than is currently recognized during the early Cambrian.