The Land Unknown. originally planned to be in color, the movie is a lot of fun and very pulp oriented. three people crash land in an undiscovered Antarctic wilderness (quite possibly the Savage Land) and have struggle to survive against hordes... well, two giant prehistoric pests.
one is a rather stiff and lumbering tyrannosaurus rex and the other slightly more movable menace was a hungry elasmosaurus with an attitude and a penchant for being in the right place to threaten our heroes at the right time.
now, the elasmosaurus is my favorite mesozoic aquatic reptile. sadly, it's never been really well realized in movies, and these days it's been turned into a regular if weird looking animal it's even less impressive looking.
it's a tribute to the movie that even with these less than awesome monsters, it works really well as a fun prehistoric adventure. I would have loved to have seen this as a kid, since it's has all the right ingredients to re-enact on the playground.