Doraemon the Movie: Nobita's Dinosaur 2006 2-01

Nobita finds a fossilized dinosaur egg and uses Doraemon's time-cloth gadget to turn it back to it's original state. A plesiosaur is born and Nobita takes care of it until he becomes too big to stay hidden. Given the name Pii-suke, the young dinosaur must then be sent back in time to the era which he belongs.