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 botanical subfamily names with "-oideae", and zo ...

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...

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 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

marine squamates. 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 considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The subfamily includes the genera ''

Tylosaurus ''Tylosaurus'' (; "knob lizard") is a genus of Russellosaurina, russellosaurine mosasaur (an extinct group of predatory marine Squamata, lizards) that lived about 92 to 66 million years ago during the Turonian to Maastrichtian stages of the Late ...

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

s in

marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in Saline water, waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 7 ...

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 m ...

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. Campa ...

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

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

'', by the end of the

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

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

etymology Etymology ( ) is the study of the origin and evolution of words—including their constituent units of sound and meaning—across time. In the 21st century a subfield within linguistics, etymology has become a more rigorously scientific study. ...

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

Greek Greek may refer to: 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 of all kno ...

''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, 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 Dakota people, Dakota Sioux ...

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 ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

, the large, flightless

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

'' Hesperornis'', and possibly a

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

, 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 or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

(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 and

pelvic The pelvis (: pelves or pelvises) is the lower part of an anatomical 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). ...

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 specif ...

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

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

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 ** podium * 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 ...

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 mammals h ...

ry teeth. Twelve or more teeth in

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

and

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

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

foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...

. 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 The fus ...

edge of surangular rounded and longitudinally horizontal...Twenty nine presacral

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

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

'', neural spines of posterior

caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

at most only slightly elongated, do not form an appreciable fin. Haemal arches 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'' *'' Hainosaurus'' (=''

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

Description

Species and taxonomy

References

Further reading