Haploceratoidea, formerly Haplocerataceae, is an extinct superfamily of

ammonoid 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) ...

cephalopods belonging to the

Ammonitida Ammonitida is an order of ammonoid cephalopods that lived from the Jurassic through Paleocene time periods, commonly with intricate ammonitic sutures. Ammonitida is divided into four suborders, the Phylloceratina, Lytoceratina, Ancyloceratin ...

that unites three families, Strigoceratidae, Oppeliidae, and Haploceratidae, listed below. Haploceratoidea begins with all three families in the lower

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age. Stra ...

. Strigoceratidae is limited to the Bajocian but Oppeliidae, and Haploceratidae extend through the remaining Jurassic, well into the

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 ...

; the Oppeliidae into the middle

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 113.0 ± 1.0 Ma to 100.5 ± 0 ...

, the Haplocertidae only into the

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...

Diagnosis

Haploceratoidea are typically compressed, discoidal Ammontida that may be keeled or unkeeled, tending to be oxyconic, with usually falcoid or falcate ribbing. The aptychi are paired and differ between families and have been found ''in situ'' in e.g. '' Oppelia subrudiata'' and in '' Pseudolissoceras''.

Taxonomy

The Origin of the Haploceratoidea is undetermined but it is likely all three component families have their beginnings in the

Hammatoceratidae Hammatoceratidae is a family of lower and middle Jurassic ammonites included in the superfamily Hildoceratoidea. Diagnosis Hammatoceratidae comprises genera which are characterized by ribbed evolute shells (all whorls visible), some bearing keel ...

in the middle Bajocian. None of the Haploceratoidea is thought to have given rise to any subsequent group. Superfamily Haploceratoidea Zittel, 1884 *Family Haploceratidae Zittel, 1884 **Genus '' Lissoceras'' Bayle, 1879 **Genus '' Glochiceras'' Hyatt, 1900 **Genus '' Haploceras'' Zittel, 1870 **Genus '' Neolissoceras'' Spath, 1923 *Family Oppeliidae Bonarelli, 1894 **Subfamily Aconeceratinae (Spath, 1923) ***Genus ''

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 el ...

'' Hyatt, 1903 ***Genus '' Gyaloceras'' Whitehouse, 1927 ***Genus '' Koloceras'' Riccardi ''et al.'', 1987 ***Genus '' Sanmartinoceras'' **Subfamily Hecticoceratinae Spath, 1925 ***Genus '' Hecticoceras'' Bonarelli, 1893 ***Genus '' Pseudosonninia'' Parent, 2019 **Subfamily Mazapilitinae Spath, 1928 **Subfamily Oppeliinae Bonarelli, 1894 ***Genus '' Submazapilites'' Cantu-Chapa, 1962 **Subfamily Streblitinae Spath, 1925 ***Genus '' Bornhardticeras'' Böhm & Riedel, 1933 ***Genus '' Cyrtosiceras'' Hyatt, 1900 ***Genus '' Substreblites'' Spath, 1925 ***Genus '' Uhligites'' Kilian, 1913 **Subfamily ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'' ***Genus '' Naramoceras'' McNamara, 1985 *Family Strigoceratidae Buckman, 1924 **Genus '' Oecoptychius'' **Genus '' Phlycticeras'' Hyatt, 1900 **Genus '' Strigoceras'' Quenstedt, 1886

References

* Treatise on Invertebrate Paleontology, Part L Ammonoidea, (L171), Geological Society of America and University of Kansas press, 1964. Ammonitina Ammonitida superfamilies Bajocian first appearances Early Cretaceous extinctions {{Ammonitina-stub