Medlicottiidae is a family of ammonoid cephalopods belonging to the Prolecanitida

Prolecanitida

The Prolecanitida are extinct ammonoid cephalopods with discoidal to thinly lenticular shells with goniatitic or ceratitic sutures and which retained the simple retrochoanitic siphuncle with backward extending septal necks. As typical for ammonoids the siphuncle is along the ventral margin...

, known from the Upper Carboniferous (Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

) to the Early Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

.

Characteristics

Medlicottidae are characterized by discoidal to thinly lenticular shells and sutures with a narrow ventral lobe and a modified first lateral saddle.

Subfamlies

The Medlicottiide, established by Karpinsky in 1889, is by prevailing current perspective divided into five subfamilies. These are the Episageceratinae

Episageceratinae

Episageceratinae is a subfamily of the Medlicottiidae, a family of prolecanitid ammonites. The Episageceratinae, proposed by Ruzhencev, 1956, is based on the genus Episageceras previously included in the subfamily Medlicottiinae and lived during Late Permian and Early Triassic times.So far only...

, Medlicottiinae

Medlicottiinae

The Medlicottiinae a subfamily of the Medlicottiidae, a family of ammonoid cephalopods included in the Prolecanitida, characterized by having discoidal to thinly lenticular shells with a retuse venter and sutures with bifid auxiliary lobes....

, Propinacoceratinae, Sicanitinae, and Uddenitinae

Uddenitinae

The Uddenitinae a subfamily of the Medlicottiidae, a family of ammonoid cephalopods included in the Prolecanitida.The Uddenitinae, proposed by Miller and Furnish, and known from the Pennsylvanian and Lower Permian, are transistional between the ancestral Pronoritidae and the more more traditional...

. The Artioceratinae and Miklukhoceratinae, sometimes included as well, are junior synonyms respectively for the Sicanitinae and Propinacoceratinae.

Previously the Medlicottiidae were divided in part L of the Treatise

Treatise on Invertebrate Paleontology

The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...

, 1957, into just two subfamilies, the Uddenitinae introduced by Miller and Furnish in 1940 and the Medlicottinae revised from Karpinsky 1889.

Higher taxa

The Medlicottiidae are included in the superfamily Medlicottiaceae

Medlicottiaceae

The Medlicottiaceae is the second of the two superfamilies that make up the Prolecanitida, the first being the Prolecanitaceae.The Medlicottiaceae are recognized by their discoidal to thinly lenticular, and involute shells with small umbilici; flat, often grooved venters, and variably complex sutures...

 which now also includes the Pronoritidae and Sundaitidae. The Sageceratidae, included in the Treatise, Part L, 1957, have been removed to the ceratitid

Ceratitida

The Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post Triassic ammonites....

 superfamily Sagecerataceae.

Alternative taxonomies

Hyatt and Smith (1905) included Medlicottia in the Pronoritidae, prior to the establishment of the Prolecanitina as a separate order by Mller and Furnish, 1954. The Pronoritidae of Hyatt and Smith were included in their suborder Pinacoceratoidea. The Pinacoceratoidea also includes the family Pinacoceratidae, which included the genus Sageceras, which later became the type genus for the Sageceratidae. The distinction between the Medlicottiidae and Sageceratidae lies mainly in the distinction of their respective sutural development.

According to Hyatt and Smith, the Pronoritidae contains Pronorites, Parapronorites, Medlicottia, (with its subgenera Episageceras, Propinacoceras, and Artinskia ), Sicanites, Uddenites, Sundaites, Daraelites, Albanites, and Cordillerites. Lanceolites was added by Smith (1932). All are confined to the Paleozoic except Episageceras which extends into the Triassic and Cordillerites and Lanceolites which are confined to the Triassic.

Smith (1932) pointed out that Medlicottia, Uddenites, and Cordillerites all have the peculiar Pronorites stage in their early development. Pronorites is recapitulated in the young of Parapronorites, Medlicottia, and Uddenites; less so in Cordillerites, and even less in the young of Daraelites.

Ruzhencev,1949 (in Glesister and Furnish 1961) included in the Medlicottiidae following genera: Akmilleria, Aktubinskia, Arctioceras, Artinskia, Daixites, Eurmedlicottia, Medlicottia, Neogastroceras, Sicanites, Synartinskia, Propinacoceras, Prouddenites, and Uddenites.