Masonoceras

Masonoceras Temporal range: Early Mississippian
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Ammonoidea
Order:	Goniatitida
Suborder:	Tornoceratina
Superfamily:	Karagandocerataceae
Family:	Karagandoceratidae
Genus:	Masonoceras Work & Manger, 2002

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 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.