1994  Pennoceras sp.nov.1 Boardman, Work, Mapes & Barrick: 62, pl.3 fig.18-20. [not pl.3 fig.15-17, = P. bennisoni].
     2007  Pennoceras heckeli Work, Boardman & Mapes: 592, fig.3.1-3.4, 3.9-3.11, 4, 5.

Nos. SUI 94702, Iowa City.