Masonoceras

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, the umbilicus narrow to occlude. The mature external suture contains a wide trifid ventral lobe, the flanking prongs longer than the medial, an asymmetrically rounded lateral saddle and a deeper asymmetric pointed lateral lobe. Internal molds of the type, Mesoceras Kentuckiense show the presence of a broad hyponomic sinus flanked by high rounded vantrolateral salients.

Masonoceras
Temporal range: Early Mississippian
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: †Ammonoidea
Order: †Goniatitida
Family: †Karagandoceratidae
Genus: †Masonoceras
Work & Manger, 2002

Mesonoceras is similar in general form to this 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.


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