The Psilocerataceae is a superfamily of Early Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 ammonoid cephalopods proposed by Alpheus Hyatt

Alpheus Hyatt

Alpheus Hyatt was an American zoologist and palaeontologist.- Biography :Alpheus Hyatt II was born in Washington, D.C. to Alpheus Hyatt and Harriet Randolph Hyatt...

 in 1867, assigned to the 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....

.

The Psilocerataceae are probably derived from the Ussuritidae

Ussuritidae

Ussuritidae are ancestral, Triassic, Phylloceratina characterized by generally smooth, discoidal, evolute shells with rounded venters and little or no ornamentation and by sutures with primitive monophyllitic saddles with a single terminal branch or leaflet....

, which are found in the Phylloceratida, and combine five families, the Psiloceratidae, Echioceratidae, Schlotheimiidae, Arietitidae

Arietitidae

Arietitidae is a family of true ammonites that make up part of the superfamily Psilocerataceae. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures...

, and Oxynoticeratidae

Oxynoticeratidae

Oxynoticeratidae is a family of true ammonites from the Lower Jurassic. They are part of the superfamily Psilocerataceae, characterized by mostly involute, oxyconic shells with narrow venter and compressed, lanceolate whorl section. Suture is ammonitic. Ribbing is feeble, hardly functional and...

. The Psiloceratidae, which is the ancestral and type family, provides the basic description for the group.

Families Included

• Psiloceratidae - The Psiloceratidae are evolute, smooth or with blunt primary ribbing. The venter is rounded and generally smooth, in some feebly keeled. Sutures are simple with phylloid saddle endings in some. The aptychus is single, found in sutu in Psiloceras
  Psiloceras
  Psiloceras is an extinct genus of cephalopod belonging to the ammonite subclass. Psiloceras fossils are commonly found at Lyme Regis, Dorset Coast, England. Here smooth-shelled Psiloceras planorbis are to be found as usually flattened fossils in the Blue Lias....
  
  
• Echioceratidae
• Schlotheimiidae
• Arietitdae
• Oxynoticeratidae
  Oxynoticeratidae
  Oxynoticeratidae is a family of true ammonites from the Lower Jurassic. They are part of the superfamily Psilocerataceae, characterized by mostly involute, oxyconic shells with narrow venter and compressed, lanceolate whorl section. Suture is ammonitic. Ribbing is feeble, hardly functional and...