Pleurosauridae, from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

πλευρά (''pleurá''), meaning "rib" or "side", and σαῦρος (''saûros''), meaning "lizard", is an extinct family of sphenodontian reptiles, known from the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

of Europe. Members of the family had long-snake like bodies with reduced limbs that were adapted for aquatic life in marine environments. It contains two genera, ''

Palaeopleurosaurus ''Palaeopleurosaurus'' (meaning "old side lizard") is an extinct genus of diapsid reptiles belonging to the group Sphenodontia.Dupret, V. (2004). The pleurosaurs: anatomy and phylogeny. ''Revue de Paléobiologie'', 9: 61-8/ref> ''Palaeopleuros ...

,'' which is known from the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic� ...

(

Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...

)

Posidonia Shale The Posidonia Shale (, also called Schistes Bitumineux in Luxembourg) geologically known as the Sachrang Formation, is an Early Jurassic (Early to Late Toarcian) geological formation in Germany, northern Switzerland, northwestern Austria, souther ...

of Germany, as well as '' Pleurosaurus'' from the Late Jurassic of Germany and France. ''Paleopleurosaurus'' is more primitive than the later ''Pleurosaurus'', with a skull similar to those of other sphenodontians, while that of ''Pleurosaurus'' is highly modified relative to other sphenodontians. They likely swam via

anguilliform locomotion Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body a ...

.Dupret, V. (2004). The pleurosaurs: anatomy and phylogeny. ''Revue de Paléobiologie'', 9: 61-8

/ref> ''

Vadasaurus ''Vadasaurus'' is an extinct genus of rhynchocephalian closely related to the aquatic pleurosaurids. Although this genus was not as specialized as the eel-like pleurosaurs for aquatic life, various skeletal features support the idea that it had ...

'' and ''

Derasmosaurus ''Derasmosaurus'' is an extinct monotypic genus of rhynchocephalian known from the Early Cretaceous (Albian) aged Pietraroja Plattenkalk of Italy. The only species in the genus is ''Derasmosaurus pietrarojae''. It was originally considered to be ...

'' from the Late Jurassic and Early Cretaceous of Europe have been placed as part of this family in some studies, but lack the body elongation that typifies the other two genera.

References

Jurassic lepidosaurs

† A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species or languages). It is one of the mo ...

Toarcian first appearances Late Jurassic extinctions Taxa named by Richard Lydekker {{paleo-reptile-stub