Genus Micrina (small shelly problematics) from the Lower Cambrian of South Australia: morphology, microstructures, and possible relation to halkieriids

Genus Micrina Laurie, 1986 of the family Tannuolinidae from the Botomian (Lower Cambrian) of South Australia is redescribed. The family is tentatively referred to the problematic order Coeloscleritophora. The genus includes two species, of which M. pusilla is new. These fossils consist of two sclerites that differ considerably in shape but are identical in microomamentation and microstructure. The original organic composition of skeletal integuments is inferred. The similarity of micrins to halkieriids, the other widespread Early Cambrian fossils, is discussed.