Pluridens And Halisaurus By Nick Longrich on:
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''Pluridens'' ("many teeth") is an extinct
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 ...
of marine lizard belonging to the Mosasauridae. ''Pluridens'' is placed in the subfamily Halisaurinae with the genera ''Phosphorosaurus
''Phosphorosaurus'' ("phosphate lizard") is an extinct genus of marine lizard belonging to the mosasaur family. ''Phosphorosaurus'' is classified within the Halisaurinae subfamily alongside the genera '' Pluridens'', ''Eonatator'' and ''Halisauru ...
'', ''Eonatator
''Eonatator'' is an extinct genus of marine lizard belonging to the mosasaur family. It is a close relative of ''Halisaurus'', and part of the same subfamily, the Halisaurinae. It is known from the Late Cretaceous of North America, Colombia and S ...
'' and ''Halisaurus
''Halisaurus'' is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
''.Konishi, Takuya; Caldwell, Michael W.; Nishimura, Tomohiro; Sakurai, Kazuhiko; Tanoue, Kyo (2015). "A new halisaurine mosasaur (Squamata: Halisaurinae) from Japan: the first record in the western Pacific realm and the first documented insights into binocular vision in mosasaurs". Journal of Systematic Palaeontology: 1–31. doi:10.1080/14772019.2015.1113447. Compared to related halisaurines, ''Pluridens'' had longer jaws with more teeth, and smaller eyes. It also grew large size, measuring long and perhaps over in some individuals. The jaws in some specimens are robust, and sometimes show injuries suggestive of combat. The jaws may have been used for fighting over mates or territories.
''Pluridens'' lived in the shallow seas of West Africa
West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Maurit ...
during the late Campanian-Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...
. Three species of are known, ''P. walkeri'', ''P. calabaria'', and ''P. serpentis.'' ''P. walkeri'' is known from the Maastrichtian of southwest Niger
)
, official_languages =
, languages_type = National languagesT. Lingham-Soliar. 1998. A new mosasaur ''Pluridens'' walkeri from the Upper Cretaceous, Maastrichtian of the Iullemmeden Basin, southwest Niger. Journal of Vertebrate Paleontology 18(4):709-707. whereas ''P. calabaria'' is found in slightly older (late Campanian) deposits in
''Pluridens'' was a moderately large mosasaur at roughly in length if the proportions of the dentary and the rest of the animal matches that of ''
The shallow dentary and small teeth of ''Pluridens'' was likely elongated relative to the rest of the head to allow for the massive battery of teeth. Due to force exerted by the lower jaw when biting against the upper jaw would decrease with the distance from the joint, the anterior teeth would have been ineffectual for biting and crushing. Lingham-Soliar (1998) likened the lifestyle and feeding of ''Pluridens'' with that of the
The unusually high amount of teeth present in the dentaries of both species of ''Pluridens'' initially made it difficult to immediately assign a classification on the subfamily level. Lingham-Soliar (1998) remarked that the unique combination of features (e.g. the high tooth count and a unique tooth shape) would normally result in the creation of a completely new subfamily, but did not create a new subfamily due to the rather fragmentary nature of the remains. Lindgren and Siverson (2005) considered many of the unique features of ''Pluridens'' to be shared with ''
Nigeria
Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
.Nicholas R. Longrich (2016). "A new species of ''Pluridens'' (Mosasauridae: Halisaurinae) from the upper Campanian of Southern Nigeria". Cretaceous Research. in press. doi:10.1016/j.cretres.2016.03.013. ''P. serpentis'' was found in Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...
deposits in Morocco
Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...
. ''Pluridens'' was briefly synonymized with ''Halisaurus
''Halisaurus'' is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
'' by Lindgren and Siverson (2005),Lindgren J, Siverson M. 2005.'' Halisaurus sternbergii'', a small mosasaur with an intercontinental distribution. Journal of Paleontology 79 (4): 763–773. but subsequent studies rejected the synonymy.Michael J. Polcyn, Johan Lindgren, Nathalie Bardet, Dirk Cornelissen, Louis Verding, and Anne S. Schulp (2012) Description of new specimens of ''Halisaurus arambourgi'' Bardet & Pereda Suberbiola, 2005 and the relationships of Halisaurinae. Bulletin de la Société Géologique de France 183:123-136 doi:10.2113/gssgfbull.183.2.123 http://bsgf.geoscienceworld.org/content/183/2/123.abstract
Description
''Pluridens'' was a moderately large mosasaur at roughly in length if the proportions of the dentary and the rest of the animal matches that of ''Halisaurus
''Halisaurus'' is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
''; the referred material suggests an even larger body size at more than in length. A feature that separates ''Pluridens'' not only from the rest of the Halisaurinae, but from the rest of the Mosasaur
Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...
idae at large is its unusually high tooth count, dentaries
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
assigned to the genus preserve almost twice the amount of teeth found in most other mosasaur genera. Additionally, the dentary of ''Pluridens'' also has one of the slenderest profiles among the mosasaurs; the only genus having a similarly narrow dentary being the mosasaurine
The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except ...
''Plotosaurus
''Plotosaurus'' ("swimmer lizard") is an extinct genus of mosasaur from the Upper Cretaceous (Maastrichtian) of Fresno County, California. Originally named '' Kolposaurus'' (meaning "bay lizard") by Berkeley paleontologist Charles Lewis Camp in 1 ...
''. This combination of features indicate a feeding niche and lifestyle unique among the mosasaurs.
The shallow dentary and small teeth of ''Pluridens'' was likely elongated relative to the rest of the head to allow for the massive battery of teeth. Due to force exerted by the lower jaw when biting against the upper jaw would decrease with the distance from the joint, the anterior teeth would have been ineffectual for biting and crushing. Lingham-Soliar (1998) likened the lifestyle and feeding of ''Pluridens'' with that of the ichthyosaur
Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...
s, particularly early ichthyosaurs such as ''Temnodontosaurus
''Temnodontosaurus'' (Greek for "cutting-tooth lizard"temno, meaning "to cut", odont meaning "tooth" and sauros meaning "lizard") is an extinct genus of ichthyosaur from the Early Jurassic period. They lived between 200 and 175 million years ag ...
'' and '' Leptonectes''.
Lingham-Soliar (1998
1998 was designated as the ''International Year of the Ocean''.
Events January
* January 6 – The '' Lunar Prospector'' spacecraft is launched into orbit around the Moon, and later finds evidence for frozen water, in soil in permanently ...
) listed the following unambiguous character states for the genus: "Very long, slender dentary, anterior half cross-section almost circular extending to tip. Twenty eight-plus teeth in dentary, close-set. Tooth crowns short, no distinguishable carinae, broad, smooth anterior surface, hairline crenations posterior, slightly discernible broad facets, tips posteriorly recurved; teeth virtually uniform in size along most of the dental ramus; replacement teeth emerge medial to mature tooth crowns; resorption pits on mid-lingual side of tooth base".
Classification
The unusually high amount of teeth present in the dentaries of both species of ''Pluridens'' initially made it difficult to immediately assign a classification on the subfamily level. Lingham-Soliar (1998) remarked that the unique combination of features (e.g. the high tooth count and a unique tooth shape) would normally result in the creation of a completely new subfamily, but did not create a new subfamily due to the rather fragmentary nature of the remains. Lindgren and Siverson (2005) considered many of the unique features of ''Pluridens'' to be shared with ''Halisaurus
''Halisaurus'' is an extinct genus of marine reptile belonging to the mosasaur family. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
'' and reassigned ''P. walkeri'' as "''Halisaurus walkeri''". The genus synonymy was rejected by later authors, though similarities between the genera and the discovery of distinctly halisaurine vertebrae in Niger
)
, official_languages =
, languages_type = National languagesHalisaurinae. Thus, ''Pluridens'' is today considered a highly derived halisaurine.
Species and specimens
Three species are known, ''Pluridens walkeri'' from the early Maastrichtian of Niger, ''P. calabaria'' from the Campanian of Nigeria, and ''P. serpentis'' from the late Maastrichtian of Morocco. The type specimen of ''P. walkeri'' is BMNH R14153, an almost complete dentary recovered from the Maastrichtian Farin-Doutchi Formation near Mount Ilatarda,Niger
)
, official_languages =
, languages_type = National languagesNkporo Formation
Nkporo (Okwe ancient kingdom ) is a town in Abia State, in southeastern Nigeria, traditionally an Igbo speaking region. And it is in the Ohafia Local Government Area.
History
Nkporo is said to be one of the oldest communities among clans th ...
near Calabar in southern Nigeria
Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
, to ''P. walkeri''. The Nigerian specimen BMNH R9804 was reassigned to its own species by Longrich (2016
File:2016 Events Collage.png, From top left, clockwise: Bombed-out buildings in Ankara following the 2016 Turkish coup d'état attempt; the impeachment trial of Brazilian President Dilma Rousseff; Damaged houses during the 2016 Nagorno-Karabakh ...
) as it lacks many of the derived features that characterize ''P. walkeri'', such as a high tooth count and extreme elongation of the dentary. The Calabar dentary also lack the extreme lateral protrusion and subcircular section of the dentary and the strong transverse expansion of the dental thecae, both of which are present in BMNH R14153. Longrich (2016) dubbed the new species ''Pluridens calabaria''. It may be a direct ancestor to ''P. walkeri''.
A third species, ''Pluridens serpentis,'' was described from the late Maastrichtian phosphates of Morocco in 2021. It is the most completely known species, being represented by two skulls and a number of jaws.
Longrich, N. R., Bardet, N., Khaldoune, F., Yazami, O. K., & Jalil, N.-E. (2021). ''Pluridens serpentis'', a new mosasaurid (Mosasauridae: Halisaurinae) from the Maastrichtian of Morocco and implications for mosasaur diversity. Cretaceous Research, 104882.
References