During the evolution of animals, metamerism first appeared in the phylum 

During the course of evolution, metamerism is first observed in the members of phylum Annelida. Annulus is a Latin word which means little ring. In animals like earthworm, the body is externally and internally divided into segments with a serial repetition of at least some organs. This body pattern is called metameric segmentation and the phenomenon is known as metamerism.