Engonoceratidae is a family of typically compressed, more or less flat sided and involute ammonites (cephalopod order Ammonitida

Ammonitida

The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....

) from the mid Cretaceous belonging to the Hoplitaceae. shells have flat sided outer rims ( venters), at least in some stage. Single or branching irregular ribs and variably placed tubercles may occur. Sutures have numerous auxiliary and adventive elements of similar form, in general radially arranged. Forwardly divergent saddles tend to be simple, without subdivision. Lobes, pointing apically, may be simple and undivided or may be frilled with short irregular serrations.

Some classification go so far as to put the Engonoceratidae in its own superfamily, the Engonoceratoidea (.i.e. Engonocerataceae) although its derect decendant the Placenticeratidae is retained in the Hoplitaceae.

The Engonoceratidae first appear in the lower Albian

Albian

The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...

. Origin in the Desheyesitidae has been suggested, but seems unlikely even without the Desheyesitidae being removed to the Ancyloceratina

Ancyloceratina

The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and become one of the most distinctive components of...

. Derivation from the Hoplitidae

Hoplitidae

The Hoplitidae is a family of Cretaceous ammonites that lived during the middle of the period from the late Aptian to the Cenomanian. They are part of the superfamily Hoplitaceae....

 seems more likely, from something like Cleoniceras

Cleoniceras

Cleoniceras is a rather involute, high-whorled hoplitid from the Lower to basal Middle Albian of Europe, Madagascar, and Transcaspian region...

or Aioloceras

Aioloceras

Aioloceras is an ammonite, order Ammonitida, from near the end of the Early Cretaceous. The shell is compressed with the outer whorl covering much of the previous. Sides are slightly convex, converge toward a narrowly ached venter. Inner whorls have sharp falcoid ribs, outer are smooth. Umbilical...

by simpilification and evening out of the suture.

The Engoceratidae gave rise in the Late Albian to the Placenticeratidae

Placenticeratidae

The Placenticeratidae is a family of mostly Late Cretaceous ammonites included in the superfamily Hoplitaceae, derived from the Engonoceratidae by an increase in suture complexity....

, which differ in having a more elaborate suture, before dying out in the Early Turonian

Turonian

The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...

.

References

• Arkell,et al,1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L (Ammonoidea). Geol Soc. of America and Univ. Kansas Press.

category:Ammonites
category:Ammonitida