	Authors	Year	Title
	Gordon	1960	Some American Midcontinent Carboniferous Cephalopods. Journal of Paleontology 34: 133-151, pls.27,28, 3 text-figs.,Tulsa, OK.
	Gordon	1965	Carboniferous Cephalopods of Arkansas. Professional Papers, U.S. Geological Survey, 460: 1-322, fig.1-96, pl.1-32; Washington. [imprint 1964].
	Kant	1975	Biometrische Untersuchungen an Ammonoideen-Gehäusen. Paläontologische Zeitschrift: 203-220, 19 fig., Stuttgart.
	Manger & Saunders	1980	Lower Pennsylvanian (Morrowan) ammonoids from the North American midcontinent. Journal of Paleontology, 54, Suppl.(3): 1-56, fig.1-21, pl.1-6, tab.1-10; Tulsa, Okla.
	Mather	1915	The fauna of the Morrow group of Arkansas and Oklahoma. Bull. Denison Univ. Sci. Lab., 18 (3): 59-284, pl.1-16;
	Miller & Moore	1938	Cephalopods from the Carboniferous Morrow Group of Northern Arkansas and Oklahoma. Journal of Paleontology, 12 (4): 341-374, fig.1-4, pl.43,44; Tulsa, Oklahoma.
	Quinn	1965	Reevaluation of Pygmaeoceras. Oklahoma Geology Notes, 25 (8): 228-236, fig.1-4; Norman.
	Ruan & Zhou	1987	Carboniferous cephalopods in Ningxia Hui Autonomous Region. [In Chinese, with Engl. summary]. Namurian Strata and Fossils of Ningxia, China: 55-177, 78 text-figs., 15 pls., Nanjing.
	Saunders, Manger & Gordon	1977	Upper Mississippian and lower and middle Pennsylvanian ammonoid biostratigraphy of Northern Arkansas. Oklahoma Geolological Survey Guidebook 18: 117-137, fig.1-2, tab.1-2, pl.1-6.