What animal has a jellylike body, long tentacles, and the power to stop a person’s heart? It’s the jellyfish, and these adaptations have helped it survived over hundreds of millions of years. Readers will learn all about these living fossils–from their life cycle to their habitats–and how those traits and everything in between have changed little over the course of time. Age-appropriate text and bright images of fossils and living jellyfish give readers a sense of this animal’s ancientness. A glossary, index, and websites provide opportunities for additional learning.