''Protaconeceras'' is a deeply umbliciate, involute haploceratacean ammonite from the Lower

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

included in the oppeliid subfamily Aconeceratinae. The shell of ''Protaconeceras'' has a crunulate keel, especially in the youth. Sides are slightly convex and are covered with flexious striae or flattened ribs that extend onto the ventral surface. Sutural elements are wider and shallower than in ''

Aconeceras ''Aconeceras'' is an early Cretaceous ammonite included in the oppeliid subfamily Aconeceratidae, characterized by an involute, high-whorled, flat-sided shell that bears a finely serrate keel along the venter. Sutures have narrower and deeper ele ...

''. Stratigraphic range is confined to the

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the Va ...

References

Arkell et al., 1957 Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L. Geol Society of America and Univ Kansas Press R.C Moore (ed) 1957 {{Taxonbar, from=Q7251146 Cretaceous ammonites Ammonitida