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Temporal range: Late Permian - Recent, 260–0Ma
A Plumed Basilisk
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Neodiapsida
Infraclass: Lepidosauromorpha
Benton, 1983

Lepidosauromorpha is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (including crocodiles and birds). The only living sub-group is the Lepidosauria: extant lizards, snakes, and tuataras. The extinct lepidosauropmorphans are thought to include the plesiosaurs.

Lepidosauromorpha are distinguishable from Archosauromorphs (archosaurs) by their primitive sprawling gait, which allows for the same sinusoidal trunk and tail movement seen in fish, the sliding "joint" between the coracoids and the sternum (for a longer stride), and their pleurodont dentition. In contrast, Archosauromorphs possess a parasagittal gait, a reduction in their dermal girdle, a reduction and/or loss of the sternum, and a more thecodont dentition.

Lepidosauromorpha have retained cold blood because of their low-energy sprawling stance.