Cuttlefish are mollusks that look somewhat like squid. They have an internal, hard, supportive structure with soft organs around and inside it. This resilient "cuttlebone" is made of cleverly woven strands of a biochemical material called chitin and mixed with a hard biomineral called aragonite.

Many believe that fossils represent organisms that died millions of years ago. Scientific literature, however, contains dozens of well-described original soft tissues in fossils. Since laboratory tests have shown that organic tissues decay in only thousands of years, these fossils have been at the center of much heated controversy.

Cambrian rock layers contain many strange animal fossils, and very few fossils appear in layers below them. Called the "Cambrian explosion of life," the creatures in these layers come from all the major groups of animals alive today (including fish, which represent the vertebrates), plus many more that later became extinct.

A new fossil was uncovered in China with bird bones in its ribcage—right where its stomach must have been. Researchers consider it to be a predatory dinosaur that ate an adult bird just before it died. But was it really a dinosaur?