Placodonts

Placodonts are an extinct order of marine reptiles that lived during the Triassic period, roughly 245 to 210 million years ago. They represent some of the earliest marine specialists within the broader group Sauropterygia, though they are not direct ancestors of plesiosaurs.

Two major body plans characterize placodonts. Some lineages, known as placodontids, developed broad heads and robust dental plates composed of tightly packed teeth for crushing mollusk shells, paired with compact bodies. Other lineages, notably cyamodontids, bore heavy dorsal armor formed from interlocking osteoderms, and in some forms a low, turtle-like carapace. These variations reflect different adaptations within the same overall lifestyle.

Most placodonts inhabited shallow coastal waters and were bottom dwellers. They fed on hard-shelled invertebrates such as mollusks and brachiopods, using their dental plates to crush prey on the seafloor. Their limbs were modified into paddle-like flippers for swimming, while their short necks and broad skulls supported stability in cluttered, nearshore environments.

Taxonomically, Placodontia includes several genera within families such as Placodontidae and Cyamodontidae, among others. The group first appeared in the Early to Middle Triassic and declined by the Late Triassic, becoming extinct by the end of the period. This turnover coincides with broader changes in marine ecosystems and competition with other marine reptiles.

Fossils have been found across Europe, North Africa, and Asia, with notable examples from Germany, Poland, and China. Placodonts illustrate early experimentation with armored protection and specialized dentition as adaptive strategies for life in marine environments.