What dinosaur did the spectacled caiman descend from?

Answer

Dear David,

Caimans belong to the order of the crocodilians. These do not descend from dinosaurs, but both groups have a common ancestor: the Archosauria, who lived as early as the Triassic period (between 250-200 million years ago). So these are fossil reptiles, but formally not dinosaurs. You can read this in detail at the Wikipedia link.