Middle Cambrian chancelloriids from the Argentine Precordillera

We report, for the first time, and systematically describe chancelloriid from the region, including Chancelloria bella, Allonnia cf. tintinopsis, Al. cf. erromenosa, Al. tripodophora, Archiasterella cf. coriacea, Ar. cf. hirundo, Ar. cf. tetraspina, and Ar. cf. fletchergrully, along with previously reported chancelloriid species (Chancelloria cruceana, C. eros, and Archiasterella sp.). The current chancelloriid fauna is similar in taxonomic composition to the Cambrian Burgess Shale-type biotas and to those of China and South Australia. Based on the sclerite construction, we found that the different articulatory facet types may be used to distinguish Allonnia from Archiasterella, and the number of rays is closely related with the arrangement of sclerite rays. The chancelloriid fauna is found stratigraphically between the Glossopleura trilobite zone of the restricted-shelf facies and the Oryctocephalus trilobite zone of the open-shelf facies, spanning the Wuliuan Stage (Delmaran/Topazan) of the Miaolingian Series, middle Cambrian. This study is significant for better understanding the diversity of this enigmatic and cosmopolitan group in the middle Cambrian warm platform of the Precordillera. (C) 2021 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.

Automated summary

This study reports and describes a chancelloriid fauna for the first time, which exhibits taxonomic composition similar to other Cambrian species in different regions. Based on the construction of sclerites, different articulatory facet types can be used to distinguish between chancelloriid species, and the number of rays is closely related to the arrangement of sclerite rays. This study is significant for understanding the diversity of chancelloriid fauna in the middle Cambrian platform of the Precordillera.