New species of hammerhead shark causes concern

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The discovery of a new species of hammerhead shark that is almost an identical twin to the Scalloped hammerhead shark (Sphyrna lewini) may hamper efforts to save both species from extinction.

The new, unnamed shark looks almost identical to the Scalloped hammerhead, and is only distinguished by its distinctive DNA (which suggested that it diverged from the Scalloped hammerhead about 4.5 million years ago) and fewer vertebrae (about 170 vs. 190).

In a study published in a recent issue of the journal Marine Biology, Danillo Pinhal and co-authors found that the new shark may be found throughout the western Atlantic, reporting on the occurrence of this species about 7,000 km from where it was first reported.

The authors contend that the new species is most likely equally prized for its fins and faces the same fishery pressure as the Scalloped hammerhead shark, which is in the midst of a stock collapse in the northern Atlantic and considered an endangered species by the IUCN.

According to co-author Mahmood Shivji: "It's a classic case of long-standing species misidentification that not only casts further uncertainty on the status of the real Scalloped hammerhead but also raises concerns about the population status of this new species."

For more information, see the paper: Pinhal, D, MS Shivji, M Vallinoto, DD Chapman, OBF Gadig and C Martins (2012) Cryptic hammerhead shark lineage occurrence in the western South Atlantic revealed by DNA analysis. Marine Biology 159, pp. 829–836.

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