A new small soft-bodied non-trilobite artiopod from the Cambrian Stage 4 Guanshan Biota

Abstract

We describe an extraordinarily preserved non-trilobite artiopod Bailongia longicaudata gen. et sp. nov. from the Cambrian Stage 4 Guanshan Biota in Yiliang, Kunming of the Yunnan Province in China. Its exoskeleton consists of a large semi-elliptical cephalon with paired lateral posterior eyes, nine tapering homonomous tergites and a long slender tailspine. Appendages include paired small antennae, at least three pairs of post-antennal cephalic limbs, and trunk biramous limbs consisting of an endopod and an exopod with lamellae. B. longicaudata does not conform to any taxon within Artiopoda, although the eyes invite comparisons with Xandarella spectaculum, Sinoburius lunaris and Phytophilaspis. Parsimony analyses indicate Bailongia is a member of Artiopoda and cannot be readily accommodated within any of the major artiopod clades.

Multiple origins of dorsal ecdysial sutures in trilobites and their relatives

“…Such ventral head structures are unknown from other fossil arthropods, or even extant arthropods (Edgecombe, 2020), e.g. radiodonts (Potin and Daley 2023), fuxianhuiids (Yang et al, 2018), Cambrian bivalved arthropods (Zhang et al, 2023), megacheirans (Liu et al, 2020), artiopodans excluding Acanthomeridion (Ortega Hernández et al, 2013; Jiao et al, 2022), chelicerates and mandibulates (Brusca et al, 2016). One ecological interpretation is that Acanthomeridion may have used its head to plough through the sediment, using endopodites bearing long endites to catch food items, while the large ventral plates and hypostome protected the non-biomineralized structures and directed sediment.…”

Multiple origins of cephalic sutures in trilobites and their relatives

“…Such ventral head structures are unknown from other fossil arthropods, or even extant arthropods (Edgecombe, 2020 ), e.g. radiodonts (Potin and Daley 2023 ), fuxianhuiids (Yang et al, 2018 ), Cambrian bivalved arthropods (Zhang et al, 2023 ), megacheirans (Liu et al, 2020 ), artiopodans excluding Acanthomeridion Jiao et al, 2022 ), chelicerates and mandibulates (Brusca et al, 2016 ). One ecological interpretation is that Acanthomeridion may have used its head to plough through the sediment, using endopodites bearing long endites to catch food items, while the large ventral plates and hypostome protected the non-biomineralized structures and directed sediment.…”

“…In Sinoburius lunaris, the first two post-antennal appendages have reduced endopodites with elongated exopodites (Chen et al, 2019 ), and in Pygmaclypeatus daziensis the exopodite is significantly reduced in the cephalic appendages (Schmidt et al, 2022 ). Recently, the head of Retifacies abnormalis was interpreted to develop three pairs of uniramous post-antennal appendages and following by one biramous appendage pair (Zhang et al, 2022 ). It would be unclear the function of an appendage with both distal elements being significantly reduced until more clear appendages are found.…”