''Masonoceras'' is a genus of Karagondoceratids from Lower Mississippian strata, the shell of which is thinly subdiscoidal to discoidal with an acute ventral margin in late ontogeny. Whorls are strongly embracing, umbilicus narrow to occluded. The mature external suture contains a wide trifid ventral lobe, the flanking prongs longer that the medial, an asymmetrically rounded lateral saddle and a deeper asymmetric pointed lateral lobe. Internal molds of the type, ''Mesoceras Kentuckiense'' show presence of a broad hyponomic sinus flanked by high rounded vantrolateral salients. ''Mesonoceras'' is similar in general form to tis probable ancestor ''

Karagandoceras ''Karagandoceras'' is an ammonoid genus belonging to the goniatid family Karagandoceratidae that lived during the early Mississippian (lower Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 ...

'' but differs primarily in its pointed asymmetric lateral lobe, that of ''Karagandoceras'' is more symmetric.

References

* ''Mesonoceras'', A New Karadondoceratid Ammonoid from the Lower Mississippian (Lower Osagean) of Kentucky. David M. Work and Walter L. Manger. Jour Paleo vol 6, no 3 May 2002. Goniatitida genera Karagandocerataceae {{Goniatitida-stub