Hyoliths were among the earliest biomineralizingmetazoans in Palaeozoic marine environments. They havebeen known for two centuries and widely assigned tolophotrochozoans. However, their origin and relationshipswith modern lophotrochozoan clades have been a longstand-ing palaeontological controversy. Here, we provide broadmicrostructural data from hyolith conchs and opercula fromthe lower Cambrian Xinji Formation of North China, includ-ing two hyolithid genera and four orthothecid genera as wellas unidentified opercula. Results show that most hyolithconchs contain a distinct aragonitic lamellar layer that is com-posed of foliated aragonite, except in the orthothecid Newtaxon 1 that has a crossed foliated lamellar microstructure.Opercula are mostly composed of foliated aragonite andoccasionally foliated calcite. These blade or lath-likemicrostructural fabrics coincide well with biomineralizationof Cambrian molluscs rather than lophophorates, as exempli-fied by the Cambrian members of the tommotiid-brachiopodlinage. Accordingly, we propose that hyoliths and molluscsmight have inherited their biomineralized skeletons from anon-mineralized or weakly mineralized common ancestorrather than as a result of convergence. Consequently, fromthe view of biomineralization, the homologous shellmicrostructures in Cambrian hyoliths and molluscs stronglystrengthen the phylogenetic links between the two groups.