Mosasaurini is a extinct

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English language, English is in the discipline of anthropology. This definition is contested, in p ...

of mosasaurine

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 ...

s who lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

and whose fossils have been found in

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South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and

Oceania Oceania (, , ) is a region, geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern Hemisphere, Eastern and Western Hemisphere, Western hemispheres, Oceania is estimated to have a land area of ...

, with questionable occurrences in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

. They are highly derived mosasaurs, containing genera like ''

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 ...

'', having unique adaptations to fast swimming speeds, or ''

Mosasaurus ''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages o ...

'', which is among the largest known

marine reptiles Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...

Description

The Mosasaurini form a clade of derived mosasaurine. The

contains one of the largest known

species, ''

Mosasaurus hoffmannii ''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages ...

'', measuring over in length, but such a size is unusual within the tribe and even within the genus ''Mosasaurus'' in himself. Other large representatives are around long (like ''

'', ''

Eremiasaurus ''Eremiasaurus'' is a genus of extinct genus of Cretaceous marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurini tribe (within the Mosasaurinae) and is exclusively known from the Maastrichtian phosphates of t ...

'', ''Mosasaurus conodon'' and ''Mosasaurus beaugei'') while others are even smaller, in a range of around long (like ''Mosasaurus missouriensis'').

Classification

The tribe was erected by Russell in 1967, stating that it is unified by having twelve or less pygal

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e and that the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

and

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

are widely separated by a bridge of carpalia on the distal border of the antebrachial

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

. But In a 1997 study, paleontologist Gorden Bell recovered ''Plotosaurus'', which was formerly classified within another tribe called the Plotosaurini, as a sister genus to ''Mosasaurus''. This rendered the Mosasaurini

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, which meant that it now contains a descendant lineage (Plotosaurini) that is not classified under it, and made its definition defunct. Paraphylys are forbidden in

cladistics Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

and so scientists must reclassify groups in order to eliminate such discrepancies if possible. Bell proposed that the Mosasaurini should be abandoned and that all members of the tribe should be incorporated into the Plotosaurini. While other scientists agree that a tribe containing ''Mosasaurus'' should be

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

, they argue that Mosasaurini should be the valid tribe. For example, in a 2012 study, Aaron LeBlanc, Caldwell, and Bardet argued that, while it is not necessarily invalid, abandoning Mosasaurini would not follow the general principle of the type genus carrying over to all ranks in a classification hierarchy, and that the original diagnostics of the Plotosaurini is outdated. The taxa Mosasaurini has historically been more inclusive, on occasion including genera such as ''

Plesiotylosaurus ''Plesiotylosaurus'', meaning "near ''Tylosaurus''", is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Prognathodon''. The gen ...

'', ''

Liodon ''Liodon'' is a dubious genus of mosasaur from the Late Cretaceous, known from fragmentary fossils discovered in St James' Pit, England and possibly also the Ouled Abdoun Basin of Morocco. Though dubious and of uncertain phylogenetic affinities, ' ...

'' and ''

Clidastes ''Clidastes'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Prognathodon''. ''Clidastes'' is known from deposits ranging i ...

'', all of which are now seen as more basal mosasaurines. A more recently suggested definition is a branch-based definition diagnosing the Mosasaurini as the most inclusive clade containing ''

'' but not ''

Globidens dakotensis ''Globidens'' ("Globe teeth") is an extinct genus of mosasaur lizard classified as part of the Globidensini tribe in the Mosasaurinae subfamily. ''Globidens alabamaensis'' was the first species of ''Globidens'' described, in a publication by ...

''.

References

{{Taxonbar, from=Q21229977 Mosasaurines