The occurrence of cartilage canals in shark vertebrae

Cartilage canals were found in the vertebrae of 16 species of sharks from five families. The canals variously contain blood vessels, lymph-like material, clumps of immature chondrocytes, unidentified amorphous material, or appear empty. Of 10 species examined in the family Carcharhinidae, only the dogfish, Mustelus canis, was devoid of canals. No canals were seen in the two batoid fish examined. The presence of canals may depend on the phylogenetic position or the maximum size attained by the species.