The Mosasaurinae are a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus Genus ( plural genera ) is a taxonomic rank used in the biological classifica ...

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 ...

s, a diverse group of Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except for

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 sou ...

. The lineage first appears in the Turonian and thrived until the K-Pg mass extinction at the end of the Maastrichtian. They ranged in size from some of the smallest known mosasaurs ('' Carinodens'', 3–3.5 meters), to medium-sized taxa ('' Clidastes'', 6+ meters), to the largest of the mosasaurs ('' Mosasaurus hoffmannii'') potentially reaching about 13 m in length. Many genera of mosasaurines were either piscivorous or generalists, preying on

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

and other marine reptiles, but one lineage, the

Globidensini The Globidensini or Globidentatini are a tribe of mosasaurine mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the tribe, known as "globidensins" or "globidensine mosasaurs", have been recovered from North America, Eu ...

, evolved specialized crushing teeth, adapting to a diet of ammonites and/or marine turtles. Though represented by relatively small forms throughout the Turonian and

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

, such as '' Clidastes'', the lineage diversified during the Campanian and had by the Maastrichtian grown into the most diverse and species-rich mosasaur subfamily. The etymology of the group derives from the genus ''Mosasaurus'' (

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''Mosa'' = " Meuse river" + Greek ''sauros'' = "lizard").

Description

Russell (1967, pp. 123–124) defined the Mosasurinae as differing from all other mosasaurs as follows: "Small rostrum present or absent anterior to

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

ry teeth. Fourteen or more teeth present in dentary and maxilla. Cranial nerves X, XI, and XII leave lateral wall of opisthotic through two foramina. No canal or groove in floor of basioccipital or basisphenoid for basilar artery. Suprastapedial process of quadrate distally expanded. Dorsal edge of surangular thin lamina of bone rising anteriorly to posterior surface of coronoid...At least 31, usually 42–45 presacral vertebrae present. Length of presacral series exceeds that of postsacral, neural spines of posterior caudal vertebrae elongated to form distinct fin. Appendicular elements with smoothly finished articular surfaces, tarsus and carpus well ossified." In his 1997 revision of the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological s ...

of the Mosasauroidea, Bell (pp. 293–332) retained the Mosasaurinae as a clade, though he reassigned Russell's tribe Prognathodontini to the Mosasaurinae and recognized a new tribe of mosasaurines, the

. The subfamily is generally recognised as containing two subdivisions, the tribes

(''

Globidens ''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 b ...

'' and its closest relatives) and Mosasaurini (''

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 sta ...

'' and its closest relatives). A third tribe, the Prognathodontini (''

Prognathodon ''Prognathodon'' 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 ''Clidastes''. ''Prognathodon'' has been recovered from de ...

'' and its closest relatives, 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 ...

''), is also used on occasion. "Clidastini" or the adjective "clidastine" is also used sometimes, but generally refers to an adaptive grade close to and containing the genus '' Clidastes'', rather than an actual clade.

Relationships

Cladogram of the Mosasaurinae modified from Simões et al. (2017):

Description

Relationships

References

Further reading