Wikipedia
Placodont
Placodonts (" Tablet teeth") is an extinct order of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. It is believed that they were part of Sauropterygia, the group that includes plesiosaurs. Placodonts were generally between in length, with some of the largest measuring long.
The first specimen was discovered in 1830. They have been found throughout central Europe, North Africa, the Middle East and China.
Usage examples of "placodont".
About 120 million years after the placodonts became extinct, the giant marine lizards, the mosasaurs, appeared.