Plioplatecarpinae is 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 Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, it ...

. Members of the subfamily are informally and collectively known as "plioplatecarpines" and have been recovered from all continents, though the occurrences in Australia remain questionable. The subfamily includes the genera '' Latoplatecarpus'', ''

Platecarpus ''Platecarpus'' ("flat wrist") is an extinct genus of aquatic lizards belonging to the mosasaur family, living around 84–81 million years ago during the middle Santonian to early Campanian, of the Late Cretaceous period. Fossils have been fo ...

'', ''

Plioplatecarpus ''Plioplatecarpus'' is a genus of mosasaur lizard. Like all mosasaurs, it lived in the late Cretaceous period, about 73-68 million years ago. Description ''Plioplatecarpus'' was a medium-sized mosasaur, measuring long and weighing . The eyes ...

'' and ''

Plesioplatecarpus ''Plesioplatecarpus'' is an extinct genus of plioplatecarpine mosasaur known from the Late Cretaceous (middle Coniacian to middle Santonian stage) of the northern Gulf of Mexico and the Western Interior Basin of North America. It was a rel ...

''. Plioplatecarpines were small to medium-sized mosasaurs that were comparatively fast and agile compared to mosasaurs of other subfamilies. The first plioplatecarpines appear in 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 b ...

and are among the oldest of mosasaurs, and the clade persists throughout the

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 inte ...

, a period of approximately 24 million years. The subfamily was seemingly heavily affected during a poorly understood middle-

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

mosasaur extinction event and its genera appear to have faced competition from mosasaurine mosasaurs during the Maastrichtian, leading to a decline in numbers and in diversity. The

etymology Etymology () The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words ...

of this group derives from the genus ''Plioplatecarpus'' (

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''pleion'' = "more" +

''plate'' = "oar" +

''karpos'' = "wrist,

carpus In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

").

Description

In general, plioplatecarpines were short-skulled, short-bodied forms and were among the strongest swimming mosasaurs . Some workers have likened them to

pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the ...

s in their agility . Most forms were likely piscivores ("fish eaters"), though

cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

s (

belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

s) evidently formed an important part of the plioplatecarpine diet. Larger forms may have also fed upon smaller marine reptiles. At least one

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

evolved sturdy crushing teeth adapted to feeding on

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environ ...

. The plioplatecarpines were medium-sized mosasaurs ranging from around 2.5 to 7.5 meters in length. Russell (1967, pp. 148Russell DA. 1967. Systematics and morphology of American mosasaurs. ''Peabody Museum of Natural History, Yale University, Bulletin'' 23.) defined the Plioplatecarpinae as follows: Small

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

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. Cranial nerves X, XI, XII leave lateral wall of opisthotic through single

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

. Canal or deep groove in floor of basioccipital and basispehnoid for basilar artery. Suprastapedial process of quadrate large, bluntly terminated and with parallel sides. Dorsal edge of surangular rounded and longitudinally horizontal...Twenty-nine or less presacral

vertebrae 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 characteristi ...

present. Length of presacral series less than that of postsacral, neural spines of posterior

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

vertebrae at most only slightly elongated, do not form an appreciable fin.

Haemal arch A haemal arch also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the hae ...

es usually unfused to caudal

centra Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the stores are all owned by individual franchisees. The chain has three different ...

. Appendicular elements lack smoothly finished articular surfaces."

Phylogeny

Russell included two tribes, the Plioplatecarpini and Prognathodontini, the latter of which has been reassigned by BellBell GL. Jr. 1997. A phylogenetic revision of North American and Adriatic Mosasauroidea. pp. 293-332 In: Callaway JM, Nicholls EL, (eds.), ''Ancient Marine Reptiles'', Academic Press, 501 pp. to the

Mosasaurinae 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 excep ...

. Polcyn and Bell (2005, p. 322Polcyn MJ, Bell GL. Jr. 2005. ''Russellosaurus coheni'' n. gen., n. sp., a 92 million-year-old mosasaur from Texas (USA), and the definition of the parafamily Russellosaurina. ''Netherlands Journal of Geosciences'' 84 (3): 321-333.) have erected a more inclusive clade, the parafamily Russellosaurina, which includes the "subfamilies Tylosaurinae and Plioplatecarpini and their sister-clade containing the genera '' Tethysaurus'', ''

Russellosaurus ''Russellosaurus'' is an extinct genus of tethysaurine mosasauroid from the Late Cretaceous of North America. The genus was described from a skull discovered in an exposure of the Arcadia Park Shale (lower Middle Turonian) at Cedar Hill, Dallas ...

'', and ''

Yaguarasaurus ''Yaguarasaurus'' is an extinct genus of mosasauroid from the Late Cretaceous (Turonian) period of Colombia, South America. The remains discovered (an articulated skull, some vertebrae and ribs) were defined as a new genus and species of mosasa ...

''." The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below follows Simões et al. (2017)

Species and taxonomy

Plioplatecarpinae * '' Angolasaurus'' ** ''A. bocagei'' * '' Ectenosaurus'' ** ''E. clidastoides'' * '' Gavialimimus'' ** ''G. almaghribensis'' * '' Selmasaurus'' ** ''S. russelli'' ** ''S. johnsoni'' * Plioplatecarpini **'' Latoplatecarpus'' ***''L. nichollsae'' ***''L. willistoni'' **''

'' ***''P. tympaniticus'' **''

'' ***''P. planifrons'' **''

'' ***''P. primaevus'' ***''P. houzeaui'' ***''P. marshii''

References

{{Taxonbar, from=Q591005 Turonian first appearances Maastrichtian extinctions