Ghost sharks, or what marine biologists call chimaeras, are a family of unusual fishes whose bodies are stiffened not by bones, but by plates and bone-like bits of cartilage. The animals may be rare, but there are about 38 species of chimaeras around the world.
Technically speaking, chimaeras are not sharks, having diverged from a common ancestor some 400 million years ago. These creatures, which are also related to rays, are veritable living fossils, confined to depths as low as 8,500 feet (2,600 meters).
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