''Polyptychodon'' (meaning 'shaped fin tooth') is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

pliosaurid Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous ( Rhaetian to Turonian stages) of Australia, Europe, North America and South America. The family is more inclusive than the archetypa ...

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 s ...

'' in a 2016 review.

History of discovery

The

type species In 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 species that contains the biological type specimen ...

, ''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 acr ...

of southern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

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

Hythe Formation The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian stages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were ...

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 32 miles (51 km) east-south-east of London. The River Medway runs through the c ...

Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...

. (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'' ( ; meaning "lizard of Kronos") is a potentially dubious genus of extinct short-necked pliosaur. With an estimated length of , it was among the largest pliosaurs, and is named after the leader of the Greek Titans, Kronos. It ...

'' 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. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. ...

. Similar fossils of pliosaurs were found also in

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

. The species ''Polyptychodon patagonicus'' (Ameghino, 1893), discovered in

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

, has also been assigned to the genus, but it is unknown whether ''P. patagonicus'' belonged to ''Polyptychodon'' or not. According to a 2010 study, ''P. patagonicus'' is a '' nomen vanum'' and a ''

''.

Misassigned species

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

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by t ...

-age

Eagle Ford Formation The Eagle Ford Group (also called the Eagle Ford Shale) is a sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas. The Eagle Ford is predominantly compos ...

of Dallas,

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

References

External links

''Polyptychodon''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) 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

Misassigned species

See also

References

External links