Diaphragmus
Diaphragmus is an extinct genus of brachiopod belonging to the order Productida and family Linoproductidae. Specimens have been found in Carboniferous beds in North America. Classification
Leighton & Maples (2002) conducted multiple phylogenetic analyses which are strongly in agreement that the four subfamilies Buxtoniinae, Echinoconchinae, Pustulinae and Juresaniinae form the family Echinoconchidae. The results of their phylogenetic analyses are displayed in the cladogram below:

Species
D. elegans Norwood and Pratten
D. nivosus Gordon 1975

References 

Paleozoic animals
Productida