The simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamental layers) are the Platyhelminthes, which are the flatworms. true or false?

This statement is false. The simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamental layers) are the Platyhelminthes, however, it is not the flatworms, instead, it is the roundworms who are the simplest animals that are bilaterally symmetrical and triploblastic.