''Polyptychodon'' (meaning 'many-folded tooth') is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of pliosaurid found in Middle-Late Cretaceous marine deposits in southern England, France and Argentina. It has been considered a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

'' in a 2016 review.

History of discovery

The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''P. interruptus'' is known from an isolated tooth from the Late Cretaceous

Chalk Group The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur ac ...

of southern

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. Owen described a second nominal species of the genus, ''P. continuus'', from an isolated tooth collected in the Hythe Formation of

Maidstone Maidstone is the largest Town status in the United Kingdom, town in Kent, England, of which it is the county town. Maidstone is historically important and lies east-south-east of London. The River Medway runs through the centre of the town, l ...

Kent Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...

. (The macronarian sauropod '' Dinodocus'' was mistakenly thought to be conspecific with ''P. continuus'' before it was correctly recognized as a dinosaur and not a plesiosaur.) Numerous pliosaurid teeth and vertebrae from England and eastern France have been previously assigned to ''Polyptychodon'', including isolated vertebrae from France which were misidentified as a sauropod. Comparison between Albian-age isolated vertebrae from marine deposits in France and ''

Kronosaurus ''Kronosaurus'' ( ) is an extinct genus of large short-necked pliosaur that lived during the Aptian to Albian Stage (stratigraphy), stages of the Early Cretaceous in what is now Australia. The first known specimen was received in 1899 and consis ...

'' suggested a size of approximately for a ''Polyptychodon''-like brachaucheniine pliosaurid. However, a 2016 re-evaluation found ''Polyptychodon'' and its types species to be dubious, and that numerous remains from the Chalk Group in England that had been referred to the genus most likely represent different species of plesiosaurs, with some teeth possibly being referable to

Polycotylidae Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. They are known as false pliosaurs. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widesprea ...

. Similar fossils of pliosaurs were found also in

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

. The species ''Polyptychodon patagonicus'' (Ameghino, 1893), based on crocodile teeth discovered in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

, shares the same genus name. According to a 2010 study, ''P. patagonicus'' is a ''

nomen vanum This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Many of the abbreviations are ...

'' and a ''

''.

''Polyptychodon hudsoni'' (holotytpe, SMU 60313) was described from the

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

-age Eagle Ford Formation of Dallas,

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

. It probably belongs to a different genus.

References

External links

''Polyptychodon''
in the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

{{Taxonbar, from=Q572528 Late Cretaceous plesiosaurs of Europe Cenomanian genus first appearances Turonian genus extinctions Fossil taxa described in 1841 Taxa named by Richard Owen Nomina dubia Sauropterygian genera

History of discovery

See also

References

External links