 Phylogenetic studies published by Jack Garrick in 1982 and Leonard Compagno in 1988 , based on morphology , placed the bignose shark in the " obscurus group " of Carcharhinus , centered on the dusky shark ( C. obscurus ) and the Galapagos shark ( C. galapagensis ) . The group consists of large , triangular @-@ toothed sharks with a ridge between the dorsal fins . Gavin Naylor 's 1992 study , based on allozyme sequences , upheld and further resolved this " ridge @-@ backed " group . The bignose shark was found to be the sister species of the sandbar shark ( C. plumbeus ) , with the two forming one of the group 's two branches . 
