First of all, Plesiosaurs aren't actually dinosaurs. Dinosaur is a generic term for terrestrial vertebrates of the time, it's just cooler (albeit entirely incorrect) to say dino instead of 'giant prehistoric marine reptile'.
Seen here in an artist's grody rendition just begging to attract sharks, a prehistoric plesiosaur gives live birth to its young. An occurrence that, until a recent fossil discovery, hadn't been proven to take place. Me? I already knew that (I went snorkeling on a recent time-machine vacay).
The study focused on a 78-million-year-old, 15.4-foot-long (4.7-meter-long) adult Polycotylus latippinus plesiosaur fossil found in 1987. The fossil's abdominal cavity contains tiny bones--parts of a plesiosaur that hadn't been born by the time its mother died.
The finding, detailed in this week's issue of the journal Science, is the first proof that plesiosaurs were viviparous--that they gave birth to live young.
"The fetus is too large to make an egg physiologically or mechanically feasible," study co-author Robin O'Keefe told National Geographic News. "And why carry a big egg around?"
Exaaaaactly -- why carry a big egg around? *ahem* Humpty. We left that f***er right where he fell!
"Sea Monster" Fetus Found--Proof Plesiosaurs Had Live Young? [nationalgeographic]
Thanks to Jordan, alexis and Muff, who agree a prehistoric Seaworld would be pretty sweet.