New Early Cambrian bivalved arthropods from southern France

International audienceThe Lower Cambrian Pardailhan Formation of the Montagne Noire (Southern France) has yielded a diverse fossil assemblage including bivalved arthropods (the bradoriids Monceretia erisylvia gen. et sp. nov., Cambria danvizcainia sp. nov. and Matthoria? sp., together with Isoxys sp.) associated with trilobites, hyolithids, inarticulate brachiopods, sponge spicules, ichnofossils and chancelloriid sclerites. This assemblage provides new evidence about the biodiversity of Early Cambrian marine communities in palaeocontinentalGondwana. The bradoriids are Cambriidae, a familywith widespread distribution in offshore shelf marine environments during Early Cambrian times. The present study confirms the presence of cambriids within a subtropical latitudinal belt that encompasses Laurentia, Siberia and the Gondwanan margins from Southern France to South China. Although knowledge of the distribution of fossil cambriids is patchy, at the generic level they appear to be provincial, with Petrianna from Laurentia, Shangsiella and Auriculatella from South China, Cambria from Siberia and Gondwana (Armorica), and Monceretia gen nov. from Gondwana (Armorica). The presence of Isoxys in the Montagne-Noire confirms the cosmopolitan distribution of this genus in the Early and Middle Cambrian tropics. Cambriid bradoriids occupy a biostratigraphically narrow time interval, probably equating to part of the Atdabanian and Botomian stages of Russian terminology. Their presence in the Pardailhan Formation supports the notion of a Botomian age, determined from archaeocyathan evidence. The North American bradoriid genus Matthoria, also possibly present in the Pardailhan Formation, is reassigned to the Cambriidae

The Cabrières Biota (France) provides insights into Ordovician polar ecosystems

Early Palaeozoic sites with soft-tissue preservation are predominantly found in Cambrian rocks and tend to capture past tropical and temperate ecosystems. In this study, we describe the diversity and preservation of the Cabrières Biota, a newly discovered Early Ordovician Lagerstätte from Montagne Noire, southern France. The Cabrières Biota showcases a diverse polar assemblage of both biomineralized and soft-bodied organisms predominantly preserved in iron oxides. Echinoderms are extremely scarce, while sponges and algae are abundantly represented. Non-biomineralized arthropod fragments are also preserved, along with faunal elements reminiscent of Cambrian Burgess Shale-type ecosystems, such as armoured lobopodians. The taxonomic diversity observed in the Cabrières Biota mixes Early Ordovician Lagerstätten taxa with Cambrian forms. By potentially being the closest Lagerstätte to the South Pole, the Cabrières Biota probably served as a biotic refuge amid the high-water temperatures of the Early Ordovician, and shows comparable ecological structuring to modern polar communities.</p

The Cabrières Biota (France) provides insights into Ordovician polar ecosystems

Early Palaeozoic sites with soft-tissue preservation are predominantly found in Cambrian rocks and tend to capture past tropical and temperate ecosystems. In this study, we describe the diversity and preservation of the Cabrières Biota, a newly discovered Early Ordovician Lagerstätte from Montagne Noire, southern France. The Cabrières Biota showcases a diverse polar assemblage of both biomineralized and soft-bodied organisms predominantly preserved in iron oxides. Echinoderms are extremely scarce, while sponges and algae are abundantly represented. Non-biomineralized arthropod fragments are also preserved, along with faunal elements reminiscent of Cambrian Burgess Shale-type ecosystems, such as armoured lobopodians. The taxonomic diversity observed in the Cabrières Biota mixes Early Ordovician Lagerstätten taxa with Cambrian forms. By potentially being the closest Lagerstätte to the South Pole, the Cabrières Biota probably served as a biotic refuge amid the high-water temperatures of the Early Ordovician, and shows comparable ecological structuring to modern polar communities