Micrina

Micrina is an extinct genus of tommotiids with affinities to brachiopods.
Micrina can be considered a stem group brachiopod based on its larval shell
Its microstructure is very brachiopod like and its adult morphology is similarly bivalved, even though it was once thought to be halkieriid-like.
Micrina is quite similar to Mickwitzia in terms of shell microstructure. The two genera are evidently closely related.