The Tethysaurinae 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, 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, i ...

. Members of the subfamily are informally and collectively known as "tethysaurines" and have been recovered from

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and

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 ...

. Only two tethysaurine genera are known, ''

Pannoniasaurus ''Pannoniasaurus'' is an extinct genus of tethysaurine mosasauroid known from the Late Cretaceous Csehbánya Formation (Santonian stage) of Hungary. It contains a single species, ''Pannoniasaurus inexpectatus'', Material was copied from this sou ...

'' and ''

Tethysaurus ''Tethysaurus'' is an extinct genus of tethysaurine mosasauroid from the Early Turonian (Late Cretaceous) period. The only species is ''Tethysaurus nopcsai''. Discovery The name means "Tethys' lizard of Nopcsa", a reference to the Greek godd ...

''. The genera ''

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 ...

'' and ''

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 ...

'' were previously considered tethysaurines until they were grouped with '' Romeosaurus'' in the new subfamily

Yaguarasaurinae The Yaguarasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "yaguarasaurines" and have been recovered from North and South America and Eu ...

. A possible member of this clade (subfamily) is a mosasaur specimen known from a maxilla fragment, found in

1960 It is also known as the "Year of Africa" because of major events—particularly the independence of seventeen African nations—that focused global attention on the continent and intensified feelings of Pan-Africanism. Events January * Ja ...

in the

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

(then

Czechoslovakia , rue, Чеськословеньско, , yi, טשעכאסלאוואקיי, , common_name = Czechoslovakia , life_span = 1918–19391945–1992 , p1 = Austria-Hungary , image_p1 ...

), in Dolní Újezd near

Litomyšl Litomyšl (; german: Leitomischl) is a town in Svitavy District in the Pardubice Region of the Czech Republic. It has about 9,900 inhabitants. It is former bishopric and Latin Catholic titular see. Litomyšl is known for the château-type castle c ...

. Like the closely related yaguarasaurines, all tethysaurines were plesiopedal (meaning primitive and not as well adapted to marine life as later mosasaurs). They generally retained relatively small sizes compared to later giant mosasaurs. The tethysaurines appeared during 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 by t ...

and went extinct in 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 ...

, possibly outcompeted by more derived mosasaurs. 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 ''Tethysaurus'' ('' Tethys'' from the

Greek goddess A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities of de ...

of the sea and ''sauros'', Greek for "lizard").

Description

Tethysaurines were primitive and comparatively small to medium-sized mosasaurs that lived during the earlier stages of mosasaur evolutionary history. ''

'' itself is approximately 3 metres long, whilst ''

'' might have reached lengths of 6 metres. They had a plesiopedal limb condition, meaning that they were not as well adapted to marine life as later mosasaurs and probably kept to shallow bodies of water. ''

'' is the only known mosasaur recovered from freshwater deposits. Makádi et al. (2012) originally diagnosed the Tethysaurinae as all mosasaurs descended from the recentmost common ancestor of '' Tethysaurus nopscai'' and '' Russellosaurus coheni''. By this definition, the

would be sunk into this subfamily since ''Russellosaurus'' is now considered a yaguarasaurine. Unambiguous character states were listed as follows: "predental rostrum absent; premaxilla-maxilla suture ends anterior to or level with the midline of the fourth maxillary tooth; nearly straight frontoparietal suture; quadrate alar concavity shallow; elongated stapedial pit (at least three times longer than wide); quadrate distal condyle saddle-shaped, upward deflection of quadrate distal condyle absent; mandibular glenoid formed mainly by articular; cervical synapophyses extend below ventral border of centrum; dorsoventrally compressed centra in precaudal vertebrae; two sacrals with large ribs/transverse processes subcircular/oval in cross-section; facet for ilium on tip of sacral transverse processes; very elongated (two times longer than wide) pontosaur-like caudal centra; anteroposteriorly narrow scapula; ilium with posterior iliac process with compressed dorsal end bearing longitudinal grooves and ridges, and spoon-shaped preacetabular process overlapping the pubis".

Phylogeny

The subfamily name is derived from ''

'' due to ''Tethysaurus'' being the best-represented genus of the subfamily and being known from multiple partial skeletons. The original definition of the Tethysaurinae was as all mosasaurs descended from the recentmost common ancestor of '' Tethysaurus nopscai'' and '' Russellosaurus coheni''. The cladogram below follows Makádi et al. (2012) and the then assumed internal relationships of the Tethysaurinae. ''

'' and ''

'' are today considered part of the

instead, which is defined as the most recent common ancestor of ''Russellosaurus'', '' Romeosaurus'', and ''Yaguarasaurus'', and all of its descendants.

Species and taxonomy

Tethysaurinae * ''

'' ** ''T. nopscai'' * ''

'' ** ''P. inexpectatus''

References

{{Taxonbar, from=Q6143599 Mosasaurs