Fossilized Shark Vertebrae

Considering that sharks are mostly made of cartilage, some assume that only their teeth fossilize. Although shark teeth are by far the most common fossils, many other parts of sharks can also fossilize—one of those being the spine. Shark skeletons are composed of cartilage, the same flexible tissue that makes up your ears and nose. Cartilage is much softer than bone and rarely survives fossilization. Because of this, entire fossilized shark skeletons are generally a rare find. However, the vertebral centra are the densest part of the shark skeleton and sometimes do fossilize. These specimens are just that. Pretty cool to think that these fossilized columns were once cartilage rather than the usual bone.