Middle Cretaceous (Cenomanian)
Hajoula, Lebanon

20mm worm on 60mm slab.

Here is an unidentified marine worm from around the mid-point of the Cretaceous Period.  There are not a lot of Cretaceous sites that preserve soft-bodied animals.  It’s possible this worm is new to science. Click the bottom picture to see a video of what living polychaetes do.

Across geologic time, worms have been quite diverse and we will never know about all the forms that have existed since at least the Early Cambrian.  The ones that paleontologists do know about do not belong to the same group.  Many are only distantly related.