Hoeh, W.R., K.S. Frazer, E. Naranjo-Garcia & R.J. Trdan. 1995. A phylogenetic perspective on the evolution of simultaneous hermaphroditism in a freshwater mussel clade (Bivalvia: Unionidae: Utterbackia). Malacological Review 28: 25-42.
(click the figure number to see the cladogram)
+----- Utterbackia_peggyae
+--+
| | +-- Utterbackia_imbecillis
| +--+
--+ +-- Utterbackia_peninsularis
|
| +----- Pyganodon_lacustris
| |
+--+----- Pyganodon_grandis
|
| +-- Pyganodon_cataracta
+--+
+-- Pyganodon_fragilis