79 new shark, ray species discovered?

This video is called Scalloped Hammerhead Shark (Sphyrna lewini).

From Nature journal:

Shark species more diverse than thought

Genetic analysis suggests overlooked species, raises concerns about conservation.

Daniel Cressey

22 June 2012

A genetic study of thousands of specimens of sharks and rays has uncovered scores of potential new species and is fuelling biologists’ debates over the organisation of the family tree of these animals. The work also raises the possibility that some species are even more endangered than previously thought.

Sharks and rays are key predators in marine ecosystems, but the life cycles and population numbers of many species remain poorly understood. The family tree of these animals — which are part of the elasmobranch subclass — has proved similarly opaque, with little agreement among researchers over their evolutionary relationships.

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 History.

Naylor says that he was “flabbergasted” by the result, especially because the sequencing covered only around half of the roughly 1,200 species thought to exist worldwide.

The huge number of new species found raises immediate conservation concerns — the reason that some of these purported new species have gone undetected is probably their close resemblance to already-identified species. The populations of such species may, therefore, be even smaller than estimated, as what was thought to be one population may instead be several smaller populations of separate species.

For example, Naylor’s work suggests that the endangered scalloped hammerhead (Sphyrna lewini) is actually two separate species. “Scalloped hammerheads in general have taken a huge hit, so it may be even worse than has been documented if there’s more than one species out there,” he says.

Naylor is now working on a project with the US National Science Foundation to catalogue the diversity of sharks and rays and is working to assist the International Union for Conservation of Nature to map which species are where in the world.

“This will have an impact on what is considered endangered and the fragility of different organisms,” he says. “These are sentinel species of all sorts of other organisms in the sea which are probably undergoing similar or worse kinds of impacts.”

Bull sharks have the strongest bite of any shark species, scientists have discovered. Relative to their body size, bull sharks bite harder than other, larger predatory sharks: here.