''Euomphaloceras'' is an early Upper Cretaceous

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) ...

genus, (Cephalopoda, Ammonoidea), included in the

Acanthoceratinae The Acanthoceratinae comprise a subfamily of ammonoid cephalopods that lived during the Late Cretaceous from the latter early Cenomanian to the late Turonian Shells are evolute, tuberculate and ribbed, with subquadrate to squarish whorl sectio ...

until established as the type genus for the

Euomphaloceratinae Euomphaloceratinae is a subfamily of Upper Cretaceous ammonites included in the Acanthoceratidae, characterized by generally evolute shells with quadrate whorl sections that are strongly ribbed. Sutures are ammonitic, but not overly complex. Gen ...

by Cooper, 1978. The shell is very evolute, all whorls exposed, and rather depressed, with prominent umbilical and ventrolateral tubercles on some or all main ribs. The Venter broad and flat with three rows of tubercles that are more numerous than the ventrolateral ones. May have shallow ventral constrictions. Derivation is from an evolute '' Acathoceras''.

References

* W.J. Arkell ''et al.'', 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology,Part L, Mollusca 4. Geological Society of America and University of Kansas Press. Acanthoceratidae Cretaceous ammonites Ammonitida genera Ammonites of North America Cenomanian life {{ammonitina-stub