This fossilized Polycotylus latippinus, a carnivorous marine reptile that lived 78 million years ago, contains a smaller, less developed skeleton inside of her. Scientists are therefore speculating that this creature did not lay eggs like other dinosaurs, but gave birth to live young. If true, then this dinosaur may have exhibited maternal care behavior similar to modern marine mammals, such as dolphins. This fossil is on public display at the Natural History Museum of Los Angeles, so if you live in that area, you can get a close look for yourself.
Link -via reddit | Photo: Natural History Museum of Los Angeles Count
"It makes sense that a completely marine reptile would not lay eggs."
Bwahahahahahahaha. Let me guess, Public School?
**cough** Sea Turtles **cough**
Physics and Chemistry are strong sciences since theories can be tested and create positive proof... like exploding all over the lab.
As to this whatever-it-is, it could have been eaten (as V said), fallen over on it in death, or something else.
There used to be a concept in science which said that the simplest answer is general the correct one. People are forgetting that.
Back on topic, it makes sense that a completely marine reptile (i.e. one that spends its entire life in the ocean) would not lay eggs.