Haploceratoidea, formerly Haplocerataceae, is an extinct superfamily of ammonoid cephalopods belonging to the

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

that unites three families, Strigoceratidae,

Oppeliidae Oppeliidae are compressed to oxyconic, sculptured Haploceratoidea, either unkeeled, unicarinate, bicarinate, or tricarinate; with sutures in great variety, but ribbing usually more or less falcoid or falcate. The Oppeliidae is the principal famil ...

, 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 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonia ...

. 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 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

; the Oppeliidae into the middle

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

, 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 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...

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 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

Bonarelli, 1894 **Subfamily Aconeceratinae (Spath, 1923) ***Genus '' Aconeceras'' 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 is a term used for a taxonomy (biology), 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, uncertainty ...

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

References

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, 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