''Clypeoceras'' is a genus of

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s with an involute discoidal shell from the Lower Triassic.

Description

The shell of ''Clypeoceras'' is laterally compressed, involute, discoidal; whorls strongly embracing and deeply indented by the next inner whorl, increasing rapidly in height. Sides slightly convex, sloping outward to a rather narrow venter, which may be angular or rounded but never with keels or grooves. Surface smooth or ornamented with radial striae and folds. Body chamber short.J.P. Smith,1932. Lower Triassic Ammonoids of North America. US Geological Survey Professional Paper 167. Suture ceratitic with deep asymmetric saddles and broad serrated lobes. Sutures have a ''Meekoceras'' stage produced during early growth with broad asymmetric saddles and narrower serrated lobes, indicating a phylogenetic relationship.

Taxonomy

J.P Smith (1932) placed ''Clypeoceas'' in the Meekoceratidae, indicated by the similarity of the shell with ''

Meekoceras ''Meekoceras'' is a genus of ceratitid ammonites with a discoidal shell that lived during the Early Triassic Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular cal ...

'' and the development of the suture, produced by septa, during growth. Smith (1932) however included the Meekoceratidae in the Prolecanitoidea whereas it is considered part of the Noritaceae in the

Treatise A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ...

, which includes ''Clypeoceras'' in the Paranoritidae instead.

References

* Arkell, et al., 1957. Mesocoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L. Geological Society of America and University of Kansas Press. Meekoceratidae Triassic ammonites Ceratitida genera Triassic animals of Asia {{Ceratitida-stub