This rare fish has been called a living fossil
A recent study in 
Nature Communications confirmed that a rare order of deep water fish called... [DOC] [TLE] Scientists find lamprey a "living fossil": 360 million-year-old fish hasn ... [PAR] Oct 25, 2006 ... Scientists find lamprey a "living fossil": 360 million-year-old fish hasn't ... this fossil 
shows that lampreys have been parasitic for at least 360 ... Because lampreys do 
not have bone or any substantial cartilage, they are extremely rare as fossils.