Medlicottiidae is a family 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

Prolecanitida Prolecanitida is an order of extinct ammonoidea, 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 ...

, known from the Upper Carboniferous ( Pennsylvanian) to the Early

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

Characteristics

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

Taxonomy

Subfamilies

The Medlicottiide, established by Karpinsky in 1889, is by prevailing current perspective divided into five subfamilies. These are the Episageceratinae, Medlicottiinae, Propinacoceratinae, Sicanitinae, and Uddenitinae. 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 A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ...

, 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

Medlicottioidea The Medlicottioidea is one of two superfamilies that make up the Prolecanitida, the other being the Prolecanitoidea. The Medlicottioidea are recognized by their discoidal to thinly lenticular, and involute shells with small umbilici; flat, often ...

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

ceratitid 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 ammoni ...

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 U''ddenites''; 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''.

References

* Alpheus Hyatt and J.P. Smith, 1905. Triassic Cephalopod Genera of America. U.S. Geological Survey Professional Paper 40. * Smith, J.P., 1932. Lower Triassic Ammonoids of North America. U.S. Geological Survey Professional Paper 167 * Miller, Furnish, and Schindewolf, 1957. Paleozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L, (Ammonoidea). Geological Society of America and University of Kansas Press. pp L72-L74. *Glenister, Brian F, and Furnish, W. M. 1961. The Permian Ammonoids of Australia; Journal of Paleontology v.35, no.4, p. 673-736, July 1961.
taxonomy, GONIAT

Medlicottiidae
in Paleobiology Database. {{Taxonbar, from=Q6807232 Ammonite families Pennsylvanian first appearances Early Triassic extinctions Prolecanitida