Where the River Rises — Max Marlow

When Professor Geoffrey Lyon and his team of palaentologists travel to a remote village deep in the heart of the Amazon jungle, they assume that they are on a routine field trip in search of an extinct prehistoric bird. But search turns to terror as the worst storm in a century floods the river. There is, however, something else lurking in the jungle, and the paleontologists discover that nature is not his most dangerous enemy in the Amazon basin.