Abstract

The Lower Cambrian Shuigoukou Formation of Xichuan, Henan province, China, yielded phosphatized instars belonging to the protolenid Ichangia ichangensis Chang, 1957, and two undetermined taxa. With relatively simple body plans, the three larval forms resemble each other to some extent, and protaspides of I. ichangensis show general similarities to those of the ellipsocephalid Palaeolenus lantenoisi Mansuy. However, their early ontogenetic processes exhibit subtle yet distinct differences. One group of unassigned protaspides possesses a sagittal glabellar furrow and protomarginal spines with branching extremities. The other unassigned protaspides bear especially long genal and protomarginal spines. The detailed preservation of these larvae reveals delicate structural variations that help provide a framework for evaluating relationships among Early Cambrian trilobites.

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