Claim: The extinct Coniasaurus has been identified from chalk deposits in the Upper Cretaceous limestone of the Late Cretaceous era, and imcomplete specimens, as a marine squamate of the largest order of reptiles.
Evidence: Coniasaurus is an extinct genus of Late Cretaceous marine squamates that range in age from Cenomanian to Santonian. It was first described by Richard Owens in 1850 from lower Cenomanian chalk deposits in southeast England. Chalk is a limestone that consists of coccolith biomicrite. Coniasaurus has only been described from incomplete specimens, but it is known to have had a relatively elongate skull with specialised teeth. Squamata Order: Squamata (/skwæˈmeɪtə/, Latin squamatus ("scaly, having scales")) is the largest order of reptiles, comprising lizards, snakes and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. Polyglyphanodontians, a distinct clade of lizards, and mosasaurs, a group of predatory marine lizards that grew to enormous sizes, also appeared in the Cretaceous.