The annelid worm Glycera dibranchiata has an oxygen binding protein with the same folding pattern as myoglobin. Myoglobins and hemoglobins occur sporadically among invertebrate phyla. It is hard to see a clear, common line of decent from a single ancestor for these species let alone annelids, insects, and vertebrates. No other known protein form has oxygen binding capability. How might these observations best be explained.