Nothosaurs (superfamily Nothosauroidea) were

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

marine

sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosau ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s. They averaged about in length, with a long body and tail. The feet were paddle-like, and are known to have been webbed in life, to help power the animal when swimming. The neck was quite long, and the head was elongated and flattened, and relatively small in relation to the body. The margins of the long jaws were equipped with numerous sharp outward-pointing teeth, indicating a diet of

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

and

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

Taxonomy

The Nothosauroidea has been suggested to consist of two suborders, the

Pachypleurosaur Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles from the Triassic period. Pachypleurosaurs vaguely resembled aquatic lizards, with elongate forms ranging in size from , with small heads, long necks, paddle-like limbs, a ...

ia, which are small primitive forms, and the Nothosauria (including two families

Nothosauridae Nothosauridae are an extinct family (biology), family of carnivore, carnivorous aquatic sauropterygian reptiles from the Triassic time period of China, France, Germany, Israel, Italy, Netherlands, Russia, Switzerland, and northern Africa. Phyl ...

and

Simosauridae ''Simosaurus'' is an extinct genus of marine reptile within the superorder Sauropterygia from the Middle Triassic of central Europe. Fossils have been found in deposits in France and Germany that are roughly 230 million years old. It is usually ...

), which may have evolved from pachypleurosaurs. The relation of pachypleurosaurs to Nothosauroidea is uncertain, as several analyses recover the clade as basal to

Eusauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauri ...

, e.i. the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

formed by Nothosauria and Pistosauroidea, instead as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of Nothosauria. Many recent analyses have recovered the pachypleurosaurs as a basal clade of

eosauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosau ...

ns outside of the nothosauroidea. Nothosaur-like reptiles were in turn ancestral to the more completely marine

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 ...

s, which replaced them at the end of the Triassic period. In their 2024 description of ''

Dianmeisaurus mutaensis ''Dianmeisaurus'' is an extinct genus of pachypleurosaur from the Middle Triassic Guanling Formation in China. The type species is ''D. gracilis''. An additional species, ''D. mutaensis'', was named in 2024 based on a small skeleton likely belong ...

'', Hu, Li & Liu recovered the Nothosauroidea as the

to the

Pachypleurosauria Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles from the Triassic period. Pachypleurosaurs vaguely resembled aquatic lizards, with elongate forms ranging in size from , with small heads, long necks, paddle-like limbs, ...

. The results of their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

are shown in the

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

below: image:Keichousaurus BW.jpg, ''

Keichousaurus ''Keichousaurus'' (meaning " Kweichow lizard") is an extinct genus of pachypleurosaurian marine reptile from the Chialingchiang and Falang Formations of China with two known species attributed to the genus: ''K. hui'' and ''K. yuananensis''. ...

'' (a pachypleurosaur) image:Lariosaurus BW.jpg, ''

Lariosaurus ''Lariosaurus'' is an extinct genus of nothosaurid from the Middle Triassic (late Anisian to late Ladinian stage) of central and western Europe and China. With a complete specimen of ''L. xingyiensis'' measuring long and ''L. hongguoensis'' poss ...

'' image:Ceresiosaurus12.jpg, ''

Ceresiosaurus ''Ceresiosaurus'' is an extinct aquatic genus of lariosaurinae, lariosaurine nothosaurid sauropterygian known from the Middle Triassic (Anisian-Ladinian boundary) of Monte San Giorgio, southern Switzerland and northern Italy. Ceresiosaurus, meaning ...

Distribution

A 2024 description of a fossil nothosaur vertebra from the

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

indicates that nothosaurs dispersed worldwide from their region of origin in the northern Tethys much earlier than presumed, eventually reaching the southern polar region of

Panthalassa Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek "all" and "sea"), was the vast superocean that encompassed planet Earth and surrounded the supercontinent Pangaea, the latest in a series of supercontinent ...

by the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

. This vertebra is the oldest

sauropterygian Sauropterygia ("lizard Flipper (anatomy), flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the Permian–Triassic extinction event, end-Permian extinction and flourished dur ...

fossil from the Southern Hemisphere, and appears to be from a taxon related to ''

Nothosaurus ''Nothosaurus'' ('false lizard', from the Ancient Greek and ) is an extinct genus of sauropterygian reptile from the Triassic period, approximately 245–228 million years ago, with fossils being distributed throughout the former Tethys Ocean, ...

'' and ''

''.

References

Sources

* * Benton, M. J. (2004), ''Vertebrate Paleontology'', 3rd ed. Blackwell Science Ltdbr>classification
* Colbert, E. H., (1969), ''Evolution of the Vertebrates'', John Wiley & Sons Inc (2nd ed.) * Rieppel, O., (2000), Sauropterygia I, placodontia, pachypleurosauria, nothosauroidea, pistosauroidea: In: ''Handbuch der Palaoherpetologie'', part 12A, 134pp. Verlag Dr. Friedrich Pfeilbr>Table of contents
Triassic sauropterygians Taxa named by Georg Baur {{paleo-reptile-stub