The Haploceratidae is one of the families to go to form the Haplocerataceae

Haplocerataceae

Haplocerataceae is a superfamily of ammonoid cephalopods belonging to the Ammonitida that unites three families, the Strigoceratidae, Oppeliidae, and Haploceratidae, listed below....

, a superfamily in the ammonitina

Ammonitina

The Ammonitina comprises a diverse suborder of ammonoid cephalopods that lived during the Jurassic and Cretaceous periods of the Mesozoic Era. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific geological time periods.The shells of...

; which according to Donovan et al (1981)can be derived from the Taramelliceratinae, a subfamily of the Oppeliidae

Oppeliidae

Oppeliidae are compressed to oxyconic, sculptured Haplocerataceae, either unkeeled, unicarinate, bicarinate, or tricarinate; with sutures in great variety, but ribbing usually more or less falcoid or falcate...

.

Haploceratids, (Haploceratidae) are typically small, smooth and somewhat featurelss ammonites, as described by Arkell et al, without ribbing or ventral keels and moderately undifferentiated sutures; that range from the Late Kimmeridgian

Kimmeridgian

In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

 to the Hauterivian

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 136.4 ± 2 Ma and 130 ± 1.5 Ma...

, crossing from the Jurassic into the Cretaceous.