237 / 2025-04-15 17:20:32

A new lobopod (Genus, Collinsium) from the early Cambrian Chengjiang Biota, South China

new lobopod, Collinsium,early cambrian,Chengjiang biota,Chiungchussi Formation

Theme 3: Earth-Life Co-evolution Through Time > Session 3a: Precambrian Earth and Life Co-evolution

Lobopodians are a rare extinct group of vermiform animal, with metameric appendages, that exhibit rich morphological diversity during the Paleozoic. They are especially diverse during the Cambrian Series 2, Stage 3-4, and are crucial to understanding the origin of panarthropods. Here we report a new lobopod specimen collected in the northwest of the Guanshan Reservoir, Chenggong district of Kunming, Yunnan Province. The specimen is preserved in yellowish green mudstone, and the associated arthropods, such as Leanchoilia, Naraoia, Chuandianella, and Yunnanocephalus, suggest that the new material is from the Cambrian (Series 2, Stage 3) Yu’anshan Member of the Chiungchussi Formation.The body of the specimen is approximately 2.1 cm long, with key taxonomic features similar to Collinsium ciliosum previously reported from the Xiaoshiba Biota. There are continuous annulations found at the surface of the body, and about 15 sets of spiny dorsal sclerites, each comprising an elongate median spine and a pair of slightly shorter lateral spines. The sclerite sets of the body surface carry different lengths and spacing, with the spacing and the length of the sclerites decreasing towards the anterior and posterior ends of the body, respectively.The anterior appendages are slender with double rows of long setiform spines, whereas the posterior rod-like appendages have annuli at the surface. The streamlined dark line running the length of the body is interpreted as the digestive tract. Roughly, the ratio of the largest dorsal sclerites length to trunk width in the middle of the carapace is about 5:3; the ratio of dorsal sclerite length to width is about 6:1.The discovery of new material of Collinsium in the Guanshan area of Chenggong traces the origin of this taxon from the Xiaoshiba Biota in the Tsanglongpu Formation back to the Chengjiang biota in the Chiungchussi Formation, and is the first report of this taxon from the Chengjiang Biota. This discovery extends the temporal and spatial distribution of this group of lobopodians and provides new data for the study of the phenotypic relationships.