Thalattosauria is an extinct order of prehistoric marine reptiles that lived in the Middle to Late Triassic. Thalattosaurs were diverse in size and shape, and are divided into two superfamilies: Askeptosauroidea and Thalattosauroidea. Askeptosauroids were endemic to the Tethys Ocean, their fossils have been found in Europe and China, and they were likely semiaquatic fish eaters with straight snouts and decent terrestrial abilities. Thalattosauroids were more specialized for aquatic life and most had unusual downturned snouts and crushing dentition. Thalattosauroids lived along the coasts of both Panthalassa and the Tethys Ocean, and were most diverse in China and western North America. The largest species of thalattosaurs grew to over 4 meters (13 feet) in length, including a long, flattened tail utilized in underwater propulsion. Although thalattosaurs bore a superficial resemblance to lizards, their exact relationships are unresolved. They are widely accepted as diapsids, but experts have variously placed them on the reptile family tree among Lepidosauromorpha, Archosauromorpha, ichthyosaurs, and/or other marine reptiles.
Many 20th-century paleontologists considered thalattosaurs to be an independent offshoot of formerly terrestrial reptiles closely related to squamates (such as lizards) or rhynchocephalians (such as the tuatara, pictured)
Thalattosaurs have been proposed to be related to various reptile groups including archosauromorphs, sauropterygians, and ichthyosaurs (such as Temnodontosaurus, pictured)
Image: Anshunsaurus huangguoshuensis NTM
Image: Askeptosaurus italicus
The Triassic is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.
Early Triassic sandstone (Buntsandstein) near Stadtroda, Germany
Middle Triassic Muschelkalk (shell-bearing limestone) near Dörzbach, Germany
Late Triassic Steigerwald Formation and overlying Hassberge Formation in Schönbuch, Germany
Sydney, Australia lies on Triassic shales and sandstones. Almost all of the exposed rocks around Sydney belong to the Triassic Sydney sandstone.