Gavin Naylor, a biologist at the College of Charleston in South Carolina, and his colleagues sequenced samples from 4,283 specimens of sharks and rays as part of a major effort to fill the gaps. The team found 574 species, of which 79 are potentially new, they report in the Bulletin of the American Museum of Natural History1.
http://www.nature.com/news/shark-species-more-diverse-than-thought-1.10879
