Elpistostegalia

Elpistostegalia, also known as Panderichthyida, is a type of prehistoric fish which lived about 385 to 374 million years ago.Elpistostegidae on the Taxonomicon 

 Why they evolved 
A rise in the world's oxygen content caused predatory fish to evolve, and this fish was the most successful.

 What they evolved from 

Below is a description of their evolutionary family tree.

References

Category:Extinct fish
Category:Lobe-finned fish