Scientists have discovered a remarkable new species of a rare hammerhead shark in South Carolina.
Researchers found the shark, the Carolina hammerhead, which had long eluded discovery because it is outwardly indistinguishable from the common scalloped hammerhead.
Through its rarity, the new species, Sphyrna gilberti, underscores the fragility of shark diversity in the face of relentless human predation.
Ichthyologist Joe Quattro, a biology professor in University of South Carolina (USC)'s College of Arts and Sciences, and colleagues examined the genetic makeup of fish species within the ancient freshwater drainage systems.
In the process of looking at hammerheads, Quattro, his student William Driggers III and their colleagues quickly uncovered an anomaly.
The scalloped hammerheads (Sphyrna lewini) that they were collecting had two different genetic signatures, in both the mitochondrial and nuclear genomes.
Searching the literature, they found that Carter Gilbert, the renowned curator of the Florida Museum of Natural History from 1961 to 1998, had described an anomalous scalloped hammerhead in 1967 that had 10 fewer vertebrae than S lewini.
It had been caught near Charleston and, because the sample was in the National Museum of Natural History, the team was able to examine it morphologically and suggest that it constituted a cryptic species - that is, one that is physically nearly indistinguishable from the more common species.
After publishing the preliminary genetic evidence for the new, cryptic species in the journal Marine Biology in 2006, Quattro and colleagues followed up by making thorough measurements - of 54 cryptic individuals and 24 S lewini - to fully describe in journal Zootaxa the new species, S gilberti, named in Gilbert's honour.
The difference in vertebrae, 10 fewer in the cryptic species, is the defining morphological difference.
