The Tylosaurinae are a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

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,Williston, S. W. 1897. Range and distribution of the mosasaurs with remarks on synonymy. ''Kansas University Quarterly'' 4(4):177-185. 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 th ...

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 "tylosaurines" and 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 southe ...

. The subfamily includes the genera ''

Tylosaurus ''Tylosaurus'' (from the ancient Greek (') 'protuberance, knob' + Greek (') 'lizard') is a genus of mosasaur, a large, predatory marine reptile closely related to modern monitor lizards and to snakes, from the Late Cretaceous. Description A ...

'', '' Taniwhasaurus'', ''

Hainosaurus ''Tylosaurus'' (from the ancient Greek (') 'protuberance, knob' + Greek (') 'lizard') is a genus of mosasaur, a large, predatory marine reptile closely related to modern monitor lizards and to snakes, from the Late Cretaceous. Description ...

'' and ''

Kaikaifilu ''Kaikaifilu'' is a genus of mosasaur from the Late Cretaceous part of the Lopez de Bertodano Formation of Antarctica, just before the Cretaceous–Paleogene extinction event. It is thought to be among the largest members of the tylosaurines, a ...

'', although some scientists argue that only ''Tylosaurus'' and ''Taniwhasaurus'' should be included. Tylosaurines first appeared in the

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by t ...

Everhart MJ. 2005b. Earliest record of the genus ''Tylosaurus'' (Squamata; Mosasauridae) from the Fort Hays Limestone (Lower Coniacian) of western Kansas. ''Transactions'' 108 (3/4): 149-155. and gave rise to some of the largest mosasaurs within the genera ''Tylosaurus'' and ''Hainosaurus'' which came to dominate as

apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

s in

marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surf ...

s throughout the

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. The ...

and

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. Campanian s ...

, but appear to have been largely replaced by large mosasaurines, such as ''

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 ...

'', by the end of 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 interval from ...

. Nevertheless, the subfamily survived to the end of the Cretaceous, covering a period lasting approximately twenty million years. 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 Phonological chan ...

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

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 ...

''tylos'' = "knob" +

''sauros'' = "lizard").

Description

In general, tylosaurines were large-bodied marine lizards armed with sturdy, conical teeth and an elongated premaxilla and extensions of the dentaries that do not bear teeth to the very end such as is found in other genera of mosasaurs. Cope's original concept of a "battering ram" snout is not supported by fossil evidence. Stomach contents from a tylosaur recovered in

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

Martin JE, Bjork PR. 1987. Gastric residues associated with a mosasaur from the late Cretaceous (Campanian) Pierre Shale in South Dakota. ''Dakoterra'' 3:68-72. included remains of another mosasaur, a

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

, the large, flightless

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...

Hesperornis ''Hesperornis'' (meaning "western bird") is a genus of cormorant-like bird that spanned the first half of the Campanian age of the Late Cretaceous period (83.5–78 mya). One of the lesser-known discoveries of the paleontologist O. C. Marsh i ...

'', and possibly a

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

, indicating that tylosaurs were generalists. Another specimen collected by Charles Sternberg Sternberg CH. 1922. Explorations of the Permian of Texas and the chalk of Kansas, 1918. Transactions of the Kansas Academy of Science 30(1):119-120. (Papers - Fifty-first annual meeting, 1919), State Printer, Topeka. included the bones of a small

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

(see also Everhart MJ. 2004. Plesiosaurs as the food of mosasaurs; new data on the stomach contents of a ''Tylosaurus proriger'' (Squamata; Mosasauridae) from the Niobrara Formation of western Kansas. ''The Mosasaur'' 7:41-46.). Lingham-Soliar suggested that tylosaurines were not among the fastest swimming nor the strongest mosasaurids. However, they are lightly built, having greatly reduced the weight of their bodies and possessing relatively small

pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectorali ...

and

pelvic The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

girdles, fore- and hindlimbs. Their bone is highly cancellous and may have been impregnated with

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

cells during life, adding buoyancy. These traits suggest that tylosaurs may have been ambush

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s. Tylosaurs were among the largest mosasaurs, with some species of ''Tylosaurus'' and ''Hainosaurus'' reaching lengths of 9-12+ meters, making them among the largest of all marine reptiles. Russell (1967, pp. 170 Russell DA, 1967. Systematics and morphology of American mosasaurs. Peabody Museum of Natural History, Yale University, Bulletin 23.) defined the Tylosaurinae as follows: "Large

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 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 b ...

ry teeth. Twelve or more teeth in

dentary 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 tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

and

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

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

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

. No canal in basioccipital or basispehnoid for basilar artery. Suprastapedial process of quadrate moderately large, distally pointed.

Dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

edge of surangular rounded and longitudinally horizontal...Twenty nine 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 characteristic i ...

present. Length of presacral series less than that of postsacral series in ''

'',

neural spine 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 ...

s of posterior

caudal 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 characteristic ...

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 unfused to caudal centra. Appendicular elements lack smoothly finished articular surfaces."

Species and taxonomy

Tylosaurinae *''

'' **''T. proriger'' **''T. nepaeolicus'' (=''T. kansasensis)'' **''T. pembinensis'' **''T. gaudryi'' **''T. saskatchewanensis'' **''T. ivoensis'' **''T. iembeensis *''

'' (=''

''?) **''H. bernardi'' *'' Taniwhasaurus'' **''T. oweni'' (=''Tylosaurus haumuriensis'') **''T. antarcticus'' *''

'' **''K. hervei''

Description

Species and taxonomy

References

Further reading