These reptiles are placodonts, a group of animal probably related to diapsids, but that look similar to the turtles.

Macroplacus, in particular, was a representative of cyamodontoidea, characterized by heavy armor and narrow snouts.

[4] Macroplacus raeticus, the only known species, possessed a relatively flat body, quite armored and similar to that of a turtle.

The teeth were present on the palate and jaw, and were round shaped, with huge molars.

Like all placodonts, Macroplacus had to swim slowly in shallow water and coastal areas, in search of shellfish that made up most of its diet.