Micrina

Isolated Micrina sellate sclerites with paired muscle scars and mitral apophyses interpreted as muscle platforms support a reconstructed bivalved body and stem-brachiopod model; articulation, valve homology and direct ancestry are not preserved.

Micrina material from four localities in three broadly synchronous late Atdabanian carbonate units supports a conservative Cambrian Stage 3 study-sample envelope of 521–514.5 Ma, not a global genus range, a brachiopod origin date or a direct-ancestor sequence.

Micrina is retained as a tommotiid genus represented by isolated mitral and sellate sclerites; sellate paired muscle scars and mitral apophyses interpreted as muscle platforms inform a reconstructed bivalved arrangement, while valve homology and phylogenetic placement remain comparative hypotheses rather than preserved articulation.

The represented Micrina material includes the Lower Cambrian Wilkawillina Limestone of the Arrowie Basin, South Australia, among four localities in three broadly synchronous carbonate units; these named collections do not establish a complete geographic distribution or an origin centre.

The reconstructed Micrina body is interpreted as sessile in an Early Cambrian marine carbonate setting, but diet, locomotion, guild and whole-body dimensions are not directly preserved by the isolated sclerites.

Micrina sellate phosphatic sclerites preserve paired muscle scars, whereas mitral sclerites bear apophyses interpreted as muscle platforms; their near-bilateral bivalved assembly is a reconstruction, not a fossil preserving both articulated valves.