The Cambrian Burgess Shale–type fossil Lagerstätten play a crutial role in revealing the origin and early evolution of arthropods. Tuzoiidae, one of the important bivalved arthropod groups, occupied a very important ecological niche in the Cambrian marine ecosystem. Here we describe a new taxon, Duplapex anima gen. et. sp. nov., in the family Tuzoiidae, on the basis of four exceptionally preserved specimens from the early Cambrian (Stage 3) Qingjiang biota of Hubei, South China. Duplapex is characterized by an ornament bivalved carapace, the ventral notch (vno) and doublure spine (dsp) of the valve, a pair of compound eyes connected by the fleshy annulated eye stalks. Despite having an unusual morphology for the group, the new taxon is recognized as a tuzoiid arthropod and indicates that these problematic euarthropods possessed a greater degree of morphological disparity than previously considered. D. anima, as well as the new reported Tuzoia. sp. from the Fandian biota, represent the oldest occurrence of Tuzoiidae, extending its stratigraphic range to Cambrian stage 3 and expanding the palaeobiographic distribution of the group to the northern border of Yangtze Platform.Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

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Radiodonta, an extinct stem-euarthropod group, has been considered as the largest predator of Cambrian marine ecosystems. As one of the radiodont-bearing Konservat-Lagerstätten, the Guanshan biota (South China, Cambrian Stage 4) has yielded a diverse assemblage of soft-bodied and biomineralized taxa that are exclusive to this exceptional deposit. “Anomalocaris” kunmingensis, the most abundant radiodont in the Guanshan biota, was originally assigned to Anomalocaris within the Anomalocarididae. Despite this taxon being formally assigned to the family Amplectobeluidae more recently, its generic assignment remains uncertain. Here, we present new materials of “Anomalocaris” kunmingensis from the Guanshan biota, and reveal that the frontal appendages possess two enlarged endites; all endites bear one posterior auxiliary spine and up to four anterior auxiliary spines; three robust dorsal spines and one terminal spine protrude from the distal part. These new observations, allied with anatomical features illustrated by previous studies, allow us to assign this taxon to a new genus, Guanshancaris gen. nov. Brachiopod shell bearing embayed injury and incomplete trilobites, associated with frontal appendages in our specimens, to some extent confirm Guanshancaris as a possible durophagous predator. The distribution of amplectobeluids demonstrates that this group is restricted to Cambrian Stage 3 to Drumian, and occurs across South China and Laurentia within the tropics/subtropics belt. Moreover, the amount and abundance of amplectobeluids evidently decreases after the Early–Middle Cambrian boundary, which indicates its possible preference for shallow water, referring to its paleoenvironmental distribution and may be influenced by geochemical, tectonic, and climatic variation.