The scalloped hammerhead shark is a well-known denizen of the U.S. East Coast. When a paper published in 1967 noted a specimen with an unusually small number of vertebrae, no one thought much about it. As often happens in science, though, subsequent specimens eventually drew ichthyologists to reexamine whether there might be more than one species. By jingo (does anyone say that anymore?), there is. The newly designated Carolina hammerhead has 83 to 91 vertebrae, while the scalloped hammerhead has 92 to 99. It's a case of cryptic species: species which look very similar on the outside but turn out to be distinct. This matters, not only to the sharks, but to conservationists who are trying to determine whether each species is healthy and how to manage their habitats.
The are over 350 species of sharks, and new ones are described every year. These are usually tiny deep-water sharks, but scientists don't doubt some big ones are out there, too. (Okay, not Megalodon - that's too much to hope for.)
A 2007-8 study in Australia confirmed - seriously - 100 new species of sharks and rays in the local waters, including a 2-meter shark with a preference for fresh water.
So, a little late for Shark Week but always timely, welcome the newest shark - 3.5 meters long, 180 kilograms or so, and living an inoffensive life (to humans) all its own.