Exceptional preservation in cherts reveals complex cuticular architecture in one of the earliest Cambrian ecdysozoans

Ecdysozoans, animals characterized by a periodically moulted cuticle, became major components of Cambrian marine ecosystems, yet the structural organization of their earliest non-mineralized cuticles remains poorly documented. Here we report Spinosoma reticulatus gen. et sp. nov., a millimeter-scale ecdysozoan from Fortunian cherts on two paleogeographic blocks: the Liuchapo Formation, South China, and the Yurtus Formation, Tarim Block, dating to ca. 538 Ma. This occurrence represents one of the earliest Cambrian ecdysozoan body-fossil records and may predate the classic Kuanchuanpu scalidophoran assemblages. The material preserves a terminal mouth with large circumoral spines and abundant cuticular fragments. Its cuticle comprises a fibrous mesh, short upright plate-like structures, and hollow ridged spines. Morphological and Raman data support an ecdysozoan affinity, whereas scalidophoran placement remains tentative. Spinosoma reveals a previously undocumented cuticular architecture, suggesting that early ecdysozoan ecological breadth and integument diversity are underestimated in the earliest phase of the Cambrian Explosion.