1. Marie Todey Period 1

2. Twin Hammerheads When studying the DNA of what they thought was a scalloped hammerhead shark, scientists recently discovered that it was in fact a different species that looked like a hammerhead. The two species’ appearances are identical, but have a couple distinct differences: DNA differences 20 fewer vertebrae (170 vs. 190) The two species are thought to have separated about 4.5 million years ago.

3. Difficulties This new discovery makes it much more difficult to track and count shark populations, because of the similarity in appearance and the fact that this species seems to have a very wide range. With the discovery of this new species comes the thought that scalloped hammerhead populations may be lower than previous counts suggested. At least 7% of sharks around the United States once thought to be scalloped hammerheads ended up being this new species.

4. Sources http://news.discovery.com/animals/hammerhead- shark-120327.html http://news.discovery.com/animals/hammerhead- shark-120327.html http://www.csmonitor.com/Science/2012/0327/Hamm erhead-shark-twin-discovery-creates-concern-for- species http://www.csmonitor.com/Science/2012/0327/Hamm erhead-shark-twin-discovery-creates-concern-for- species http://esciencenews.com/articles/2012/03/26/hammer head.shark.double.whammy http://esciencenews.com/articles/2012/03/26/hammer head.shark.double.whammy http://www.csmonitor.com/Science/2012/0327/Hamm erhead-shark-twin-discovery-creates-concern-for- species http://www.csmonitor.com/Science/2012/0327/Hamm erhead-shark-twin-discovery-creates-concern-for- species