X-Ray Image of a Smalltooth Sawfish

The long toothy rostrum or “saw” gives sawfish their common name. They use the saw to dig in the sand for crustaceans or to attack prey by vigorously slashing from side to side. This smalltooth sawfish (Pristis pectinata) is endangered in the U.S. because of habitat loss as mangroves are destroyed, and because their saws are easily caught in fishing nets.

Scientists in the Division of Fishes at the Smithsonian's National Museum of Natural History use X-ray images, like the one shown, to study the complex bone structure and diversity of fish without having to dissect or damage the specimen. In 2012, the National Museum of Natural History hosted "X-Ray Vision: Fish Inside Out," a temporary exhibit that showcases fish evolution and diversity through 40 black and white X-ray images prepared for research purposes. See more photos from the exhibit.