Near São Bartolomeu de Messines, in the Castelo area, a fossil deposit from the Triassic period (252 – 201 million years ago) was discovered. During this time, the continents were joined together as one supercontinent known as Pangaea. The deposit contains remains of shells and bones from animals called placodonts, specifically from the suborder Cyamodontoidea, also known as shelled placodonts.

Although placodonts had a somewhat turtle-like appearance, they belonged to a different group of reptiles. While these animals typically lived in marine environments, the rock formations at the site suggest that the placodonts found in this deposit inhabited more continental environments, such as lagoons. This site boasts a high concentration of fossils, and further research is still ongoing. Notably, it is where placodonts were first identified in Portugal.