Palaeopleurosaurus

left|thumb|Restoration of the skull in lateral and dorsal view Palaeopleurosaurus (meaning "old side lizard") is an extinct genus of diapsid reptiles belonging to the group Sphenodontia.

Palaeopleurosaurus fossils were discovered in Germany (Holzmaden and Kerkhofen) from the Lower Toarcian (Early Jurassic), Posidonia Shale, dated to about 182-180 million years ago. The holotype come from the Middle Section, just under the Seagrasschiefer section (=Bifrons subzone) on both localities, probably linked with the coeval measured sea regression. Initially, Paleopleurosaurus was described to represent an intermediate morphology between Late Triassic-Lower Jurassic terrestrial sphenodontia and the late Jurassic fully aquatic Pleurosaurus. The study of a new specimen provided additional information, corroborating the existence of an early lineage of elongated sphenodontians, although with retained characters of terrestrial genera such as Kallimodon.