There are ongoing arguments among taxonomists as to which phyla represent the closest relatives of phylum Annelida. Some propose that these worms share a common ancestor with the arthropods (crabs, insects etc.). However, the majority continue to keep the annelids lumped together with the Lophotrochozoa. The reasons for this are many but probably the least disputed comes from:. a. the segmented body plan of the annelids.
b. molecular analysis.
c. metamerism.
d. schizocoelous origin of the coelom.