The first flatworms, or platyhelminthes, probably evolved from something like a hydra about 550 million years ago.

How long have flatworms been around?

It has generally been thought that most bilaterians arose during a dramatic diversification of animal life (dubbed the Cambrian explosion) 540-500 million years ago. That's because the ancestors of nearly all major modern animal groups, or phyla, made an appearance in the fossil record during this period.

Where in the world are flatworms found?

Most freshwater flatworms are free-living and can be found in ponds, lakes, streams, ditches, and temporary puddles. They live under rocks, plants, and debris to avoid direct sunlight. They can be found on hard and soft substrates, but are more common on the hard surfaces.