wwwwhhhhaaatttt?

Well, maybe not that surprising. Can you imagine defending giant eggs in the ocean? Also, a close relative could do the same thing:

It is becoming increasingly clear that marine reptiles gave live birth in the oceans, and to only one offspring. It is surprising how many fossil specimens have been found with an embryo (or, in the case above, in the process of giving birth).

Marine reptiles, a cast of swimming creatures pictured above, are not dinosaurs. But they are closely related. The same goes for pterodactyls and flying reptiles - they are a separate branch of reptile goodness as well