thalattosuchians

Thalattosuchia, commonly called thalattosuchians, are an extinct clade of marine crocodylomorphs that lived from the Early Jurassic to the Early Cretaceous. They represent one of the major lineages of marine crocodile relatives and are divided into two principal clades: Teleosauroidea, which includes long-snouted, fish-eating forms, and Metriorhynchoidea, a group that evolved full marine adaptations and open-water locomotion.

Teleosauroids typically possessed elongated jaws with conical teeth and were often associated with coastal and estuarine environments. Metriorhynchoids developed a more streamlined body, paddle-like limbs, and, in many taxa, a tail fluke for propulsion in the water. Some metriorhynchids show a reduction of bony armor, consistent with a fully marine lifestyle.

Ecology and life history: Both groups were largely marine or coastal predators feeding on fish and other vertebrates. The metriorhynchoids, in particular, are among the most derived marine crocodylomorphs, with adaptations that parallel those of later marine reptiles in locomotion and ecology.

Distribution and fossil record: Thalattosuchians have been found in Europe, Africa, and the Americas, with the richest fossil assemblages from Jurassic marine deposits in Europe. The fossil record documents their presence across tropical and temperate seas over several tens of millions of years.

Examples of genera include Teleosaurus and Steneosaurus (teleosauroids) and Metriorhynchus, Dakosaurus, and Plesiosuchus (metriorhynchoids). The group was first recognized in the 19th century and has since been refined through ongoing paleontological work.