# Simosaurus

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Extinct genus of reptiles

Not to be confused with [Siamosaurus](/source/Siamosaurus), [Simosuchus](/source/Simosuchus), or [Sinosaurus](/source/Sinosaurus).

Simosaurus Temporal range: Middle Triassic, 240–230 Ma PreꞒ Ꞓ O S D C P T J K Pg N Mounted skeleton of Simosaurus gaillardoti in the State Museum of Natural History Stuttgart Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Superorder: †Sauropterygia Order: †Nothosauroidea Suborder: †Nothosauria Family: †Simosauridae Huene, 1948 Genus: †Simosaurus Meyer, 1842 Type species †Simosaurus gaillardoti Meyer, 1842 Synonyms Nothosaurus mougeoti (Meyer, 1855) Simosaurus guilelmi Meyer, 1842 Simosaurus mougeoti Meyer, 1855

***Simosaurus*** is an [extinct](/source/Extinct) [genus](/source/Genus) of [marine reptile](/source/Marine_reptile) within the [superorder](/source/Superorder) [Sauropterygia](/source/Sauropterygia) from the [Middle Triassic](/source/Middle_Triassic) of central Europe. Fossils have been found in deposits in [France](/source/France) and [Germany](/source/Germany) that are roughly 230 million years old. It is usually classified as a [nothosaur](/source/Nothosaur),[1] but has also been considered a [pachypleurosaur](/source/Pachypleurosaur) or a more primitive sauropterygian.

## Description

Skeleton

*Simosaurus* grew from 3 to 4 metres (9.8 to 13.1 ft) in length. It has a blunt, flattened head and large openings behind its eyes called upper temporal fossae. These fossae are larger than the eye sockets but not as big as those of other nothosaurs. *Simosaurus* also differs from other nothosaurs in that it has blunt teeth that were probably used for crushing hard-shelled organisms. The jaw joint is set far back, projecting beyond the main portion of the skull.[2]

## History

The [type species](/source/Type_species) of *Simosaurus*, *S. gaillardoti*, was named by German paleontologist [Christian Erich Hermann von Meyer](/source/Christian_Erich_Hermann_von_Meyer) in 1842.[1] In the same year, von Meyer also named *S. mougeoti*. He named a third species, *S. guilelmi*, in 1855. Oscar Fraas named *S. pusillus* in 1881. A year later, however, it was reassigned to its own genus, *[Neusticosaurus](/source/Neusticosaurus)*.[3] *S. mougeoti* and *S. guilelmi* have more recently been considered junior synonyms of *S. gaillardoti*, meaning that they represent the same species.[2]

Fossils of the ammonite *[Ceratites nodosus](/source/Ceratites)* mark the first presence of *Simosaurus* in German deposits.

The first fossils of *Simosaurus*, those described by von Meyer, were found in [Lunéville](/source/Lun%C3%A9ville), France.[1] These were found in the upper [Muschelkalk](/source/Muschelkalk), which dates back to the [Ladinian](/source/Ladinian) stage of the Middle Triassic. Material found in France includes the [holotype](/source/Holotype) skull of *S. gaillardoti* and a partial mandible referred to *S. mougeoti*. Both were described by von Meyer. The skull, which served as the basis for the first description of *Simosaurus*, has since been lost. Although initially attributed to *Simosaurus*, the mandible was labeled as "*Nothosaurus mougeoti*" in one of von Meyer's later papers.

Additional remains of *Simosaurus* were found in [Franconia](/source/Franconia) and [Württemberg](/source/W%C3%BCrttemberg) in Germany. [Duke William of Württemberg](/source/Duke_William_of_W%C3%BCrttemberg) discovered a complete skull and sent it to von Meyer in 1842. Von Meyer named *S. guilelmi* on the basis of this skull, noting that it was smaller and narrower than those of the type species. A complete skeleton first referred to *S. guilelmi* has been designated the [neotype](/source/Neotype) of *Simosaurus*. Some German fossils have been found in the stratigrafically younger [Keuper](/source/Keuper) deposits, but are very rare. *Simosaurus* is present in biozones of the Muschelkalk that are distinguished by different [ammonite](/source/Ammonite) fauna. *Simosaurus* first appears in the *nodosus* biozone, where fossils of the ammonite *[Ceratites nodosus](/source/Ceratites)* are abundant. Specimens becomescommon in the slightly younger *dorsoplanus* biozone, characterized by the ammonite *Ceratites dorsoplanus*.[2]

## Paleobiology

### Movement

*Simosaurus* has well-developed vertebrae and a dorsoventrally flattened trunk that would have inhibited side-to-side movement. This movement, called lateral undulation, is seen in most other nothosaurs, including *Nothosaurus*. The [humerus](/source/Humerus) has well-developed crests and the underside of the pectoral girdle is large, suggesting that the forelimbs had a powerful downstroke and provided most of the thrust required for swimming. The [scapula](/source/Scapula) is relatively small for a reptile that swims with its limbs, indicating that the upstroke of *Simosaurus* was weak. *Simosaurus* was probably a moderately powerful swimmer with a locomotion that was transitional between the lateral undulation of early sauropterygians and the strong flipper-driven swimming of plesiosaurs.[2]

### Feeding

Skull

Because it has blunt teeth, *Simosaurus* is often thought to have been [durophagous](/source/Durophagous), meaning that it ate organisms with hard shells. Durophagous reptiles usually have deep jaws and large adductor muscles that close them, but *Simosaurus* had long, slender jaws and relatively small adductor muscles. The long jaw of *Simosaurus* more closely resembles those of reptiles that have snapping bites. Long jaw muscles attach to the front of the large temporal fossae in the top of the skull and slant down to the back end of the lower jaw. These long, slanted muscles exert a forward pull on the jaw, quickly snapping it shut. Smaller muscles are located farther back in the skull, attaching to the back portion of the temporal fossae. These muscles are shorter because they are angled vertically and the skull is very low along the vertical axis. Their close proximity to the jaw joint, however, allows for more crushing power to be exerted. The combination of muscles that quickly snap the jaw shut and muscles that provide crushing power at the back of the jaw is unique to *Simosaurus*. It probably fed on moderately hard-shelled organisms such as *[Ceratites](/source/Ceratites)* and [holostean](/source/Holostean) fish.[2]

## References

1. ^ [***a***](#cite_ref-vonMeyerr42_1-0) [***b***](#cite_ref-vonMeyerr42_1-1) [***c***](#cite_ref-vonMeyerr42_1-2) H. von Meyer, (1842). *Simosaurus*, die Stumpfschnauze, ein Saurier aus dem Muschelkalke von Luneville. *Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde* 1842:184-197

1. ^ [***a***](#cite_ref-RO94_2-0) [***b***](#cite_ref-RO94_2-1) [***c***](#cite_ref-RO94_2-2) [***d***](#cite_ref-RO94_2-3) [***e***](#cite_ref-RO94_2-4) Rieppel, O. (1994). ["Osteology of *Simosaurus gaillardoti* and the relationships of stem-group Sauropterygia"](https://archive.org/details/osteologyofsimos28riep). *Fieldiana Geology*. **28**: 1–85.

1. **[^](#cite_ref-CG85_3-0)** Carroll, R.L.; Gaskill, P. (1985). ["The nothosaur *Pachypleurosaurus* and the origin of plesiosaurs"](https://doi.org/10.1098%2Frstb.1985.0091). *Philosophical Transactions of the Royal Society of London B*. **309** (1139): 343–393. [Bibcode](/source/Bibcode_(identifier)):[1985RSPTB.309..343C](https://ui.adsabs.harvard.edu/abs/1985RSPTB.309..343C). [doi](/source/Doi_(identifier)):[10.1098/rstb.1985.0091](https://doi.org/10.1098%2Frstb.1985.0091).

v t e Sauropterygia Kingdom: Animalia Phylum: Chordata Class: Sauropsida Subclass: Diapsida Clade: Neodiapsida Sauropsida see Sauropsida Sauropterygia see below↓ Sauropterygia Sauropterygia Alexeyisaurus Atopodentatus Palatodonta? Pomolispondylus? Hanosaurus? Helveticosauridae? Eusaurosphargis? Helveticosaurus Saurosphargidae Hemilopas? Largocephalosaurus Prosaurosphargis Saurosphargis Sinosaurosphargis Stauromatodon? Placodontia Paraplacodus Pararcus Placodus Cyamodontoidea Cyamodus Glyphoderma Henodus Macroplacus Parahenodus Placochelys Protenodontosaurus Psephochelys Psephoderma Psephosauriscus Psephosaurus Sinocyamodus Eosauropterygia see below↓ Eosauropterygia Eosauropterygia Brevicaudosaurus? Corosaurus Cymatosaurus Lamprosauroides? Pachypleurosauria Anarosaurus Chusaurus Dactylosaurus Dawazisaurus? Diandongosaurus Dianmeisaurus Dianopachysaurus Hanosaurus? Honghesaurus Keichousaurus Luopingosaurus Majiashanosaurus Neusticosaurus Odoiporosaurus Prosantosaurus Panzhousaurus Qianxisaurus Serpianosaurus Wumengosaurus Nothosauroidea Hispaniasaurus? Sanchiaosaurus Simosauridae Paludidraco Simosaurus Nothosauria Brevicaudosaurus? Carinthiasaurus Ceresiosaurus Germanosaurus Lariosaurus Lijiangosaurus Metanothosaurus Nothosaurus Proneusticosaurus Silvestrosaurus Wangosaurus? Pistosauroidea Augustasaurus Bobosaurus Chinchenia Kwangsisaurus Pistosaurus Tanaisosaurus Wangosaurus? Yunguisaurus Plesiosauria see below↓ Plesiosauria Plesiosauria Anningasaura Bathyspondylus Bobosaurus? Lindwurmia Sinopliosaurus Termatosaurus? Rhomaleosauridae Anningasaura? Archaeonectrus Atychodracon Avalonnectes Bishanopliosaurus? Borealonectes Eurycleidus Lindwurmia? Macroplata Maresaurus Meyerasaurus Rhomaleosaurus Sthenarosaurus Stratesaurus Thaumatodracon Yuzhoupliosaurus? Pliosauridae Anguanax Arminisaurus Attenborosaurus Cryonectes Hauffiosaurus Marmornectes Pachycostasaurus Rhaeticosaurus Thalassiodracon Thalassophonea Eardasaurus Gallardosaurus Liopleurodon Lorrainosaurus Megalneusaurus Peloneustes "Pliosaurus" andrewsi Pliosaurus Simolestes Brachaucheninae Acostasaurus Boyacasaurus Brachauchenius Eiectus Kronosaurus Luskhan Makhaira Megacephalosaurus Monquirasaurus Polyptychodon Sachicasaurus Stenorhynchosaurus Plesiosauroidea Eoplesiosaurus Eretmosaurus Franconiasaurus Leurospondylus Plesionectes Plesiopharos Plesiopterys Plesiosaurus Westphaliasaurus Microcleididae Hydrorion Lusonectes Microcleidus Occitanosaurus Seeleyosaurus Cryptoclidia see below↓ Cryptoclidia Cryptoclididae Opallionectes Colymbosaurinae Abyssosaurus Colymbosaurus Djupedalia Pantosaurus Spitrasaurus Cryptoclidinae Cryptoclidus Kimmerosaurus Ophthalmothule Tatenectes Muraenosaurinae Muraenosaurus Picrocleidus Tricleidus? Vinialesaurus Xenopsaria Leptocleidia Hastanectes? Nichollssaura? Leptocleididae Brancasaurus Hastanectes? Leptocleidus Nichollssaura? Umoonasaurus? Vectocleidus Polycotylidae Edgarosaurus Manemergus Mauriciosaurus Thililua Palmulasaurinae Pahasapasaurus? Palmulasaurus Occultonectia Plesiopleurodon Sulcusuchus Polycotylinae Eopolycotylus Georgiasaurus Polycotylus Scalamagnus Serpentisuchops Trinacromerum Dolichorhynchia Dolichorhynchops Martinectes Unktaheela Elasmosauridae Callawayasaurus Cimoliasaurus Eromangasaurus Goniosaurus Jucha Lagenanectes Leivanectes Mauisaurus Ogmodirus Orophosaurus Plesioelasmosaurus Scanisaurus Traskasaura Wapuskanectes Woolungasaurus Euelasmosaurida Cardiocorax Libonectes Thalassomedon Elasmosaurinae Albertonectes Elasmosaurus Fluvionectes Hydrotherosaurus? Nakonanectes Styxosaurus Terminonatator Weddellonectia Aphrosaurus Chubutinectes Futabasaurus Fresnosaurus? Hydrotherosaurus? Kawanectes Marambionectes Morenosaurus Tuarangisaurus Vegasaurus Zarafasaura? Aristonectinae Alexandronectes Aristonectes Kaiwhekea Morturneria Wunyelfia

[Portal](https://en.wikipedia.org/wiki/Wikipedia:Contents/Portals):
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Taxon identifiers Simosaurus Wikidata: Q3961306 GBIF: 4575587 IRMNG: 1381204 Open Tree of Life: 4129921 Paleobiology Database: 36453

Authority control databases: National Israel

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Adapted from the Wikipedia article [Simosaurus](https://en.wikipedia.org/wiki/Simosaurus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Simosaurus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.