Tiny can't believe it when he finds out that his friend Cindy Cimolestes doesn't like fish, but she explains that she's a mammal and many mammals don't eat fish. Determined, Tiny sets out to find a mammal in the Mesozoic who likes fish, so she, Buddy, Cindy and Dad set out on a fishing trip where they run into Cassie Castrocauda, a Jurassic mammal that looks like a cross between a beaver, an otter and a platypus, who also happens to love fish!